Glossary and index

Alow

Down near deck level or below, contrasted with aloft.

18. The Tall Triangle — Form a metal section

Aluminium alloy

Aluminium combined with other elements to give useful engineering properties.

Aluminium mast

A mast made from aluminium alloy, commonly using hollow extruded sections.

18. The Tall Triangle — Form a metal section

Ama

An ama is an outrigger hull or float in the documented usage; its immersed shell supplies support and its attachment delivers that reaction to a connecting beam.

38. Separate the Hulls — Read the names in their setting

Amidships

Amidships: middle along the vessel or middle across it as determined by context.

1. A Boat Before Sail — Directions that turn with the boat

Amidships across the boat

A handle held amidships across the boat is centred rather than offset to either side.

3. Give the Hull a Shape — Locate a part, locate another boat

Amidships along length

Between them is the middle region, amidships.

1. A Boat Before Sail — Directions that turn with the boat

Anchor

A device that grips or bears on the seabed to restrain a vessel.

31. Turn, Stop and Rebalance — Add drag at a chosen end

Anchor bitt

A strong post or paired posts for securing an anchor cable.

41. Hold the Boat to the Seabed — Give the held load its own support

Anchor bridle

A two-legged attachment sharing anchor loads between two points on the boat.

41. Hold the Boat to the Seabed — Divide the attachment between two bowside points

Anchor cable

The heavy chain or rope connecting an anchor to the vessel.

41. Hold the Boat to the Seabed — Join the anchor to the boat

Anchor drag

Movement of an anchor across the bottom instead of reliably holding.

41. Hold the Boat to the Seabed — Hold in a particular bottom

Anchor ring

A ring at an anchor’s shank for attaching its cable or connector.

41. Hold the Boat to the Seabed — Give the bottom something to resist

Anchor scope

The ratio of deployed rode length to the relevant vertical distance to the seabed; not a universal safe-setting prescription.

41. Hold the Boat to the Seabed — State both lengths before comparing them

Anchor set

The process or achieved condition of an anchor engaging the seabed.

41. Hold the Boat to the Seabed — Hold in a particular bottom

Anchor shackle

A shackle joining an anchor to its chain or another part of the rode.

41. Hold the Boat to the Seabed — Join the anchor to the boat

Anchor shank

The main lengthwise member connecting an anchor’s holding body to its cable attachment.

41. Hold the Boat to the Seabed — Give the bottom something to resist

Anchor well

A recess or locker at the bow arranged to hold an anchor or its gear.

41. Hold the Boat to the Seabed — Make room for what comes aboard

Angle of attack

The angle between a sail or foil’s chord and the local incoming flow.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Angle of incidence

An angle between a surface and a specified reference; do not automatically treat structural incidence as angle of attack.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Angle of vanishing stability / AVS

The arm reaches zero after the chosen positive range at the condition-specific angle of vanishing stability.

36. Stability Has a Range — Follow the arm beyond the first lean

Anisotropy

Having different properties in different directions, as in wood and many fibre composites.

13. Give the Sail Its Shape — Give the fibres different jobs

Anti-torsion cable

The anti-torsion cable resists twist so rotation applied at one end reaches the other through cable and terminations.

30. Reduce, Gather or Replace the Sail — Decide where the roll starts

Apparent wind

The airflow experienced by the moving boat, combining environmental wind with the effect of the boat’s own motion.

5. The Wind the Sail Actually Meets — Choose the observer

Apparent wind angle

The apparent wind’s direction relative to the boat, measured from a stated reference such as the bow.

5. The Wind the Sail Actually Meets — Choose the observer

Apron

The apron bears inside the stem and is bolted to it so forward loads can enter the added timber.

32. Build a Hull from Joined Pieces — Connect the bottom and the ends

Aramid / Kevlar / Twaron

A high-strength fibre family and associated trade names used in some sails and structures.

13. Give the Sail Its Shape — Give the fibres different jobs

Archimedes’ principle

An immersed body experiences buoyancy equal to the weight of the fluid it displaces.

2. Why a Hull Floats — Weight and the water’s support

Arm

A projecting anchor member carrying or forming a fluke.

41. Hold the Boat to the Seabed — Give the bottom something to resist

Aspect ratio

A measure of tall-and-narrow versus low-and-wide shape; for a simple foil it is span squared divided by area.

18. The Tall Triangle — Measure the surface being compared

Assisted power

A motor or actuator converts energy carried aboard into the required control movement; the person commands the action while the machine supplies some or all of the work.

37. From the Hand to the Rudder — Transmit the movement through fluid

Asymmetrical spinnaker

An unequal-sided spinnaker with distinct tack and clew, commonly set from a bowsprit or bow attachment.

29. When the Wind Moves Aft — Put a distinct tack ahead of the bow

Athwartships

Across the boat, approximately at right angles to its centreline.

3. Give the Hull a Shape — Locate a part, locate another boat

Autoclave

A pressure-and-temperature chamber used to cure some high-performance composites.

18. The Tall Triangle — Hold fibres in a rigid shape

Autopilot

A control system that senses heading or another target and drives steering to reduce deviations.

44. When Muscle Is Not Enough — Return the measured heading to the steering

Axle

The axle supports the rotating sheave between the block cheeks and transmits its bearing force into the body.

11. Trade Force for Distance — What turns inside the block

Babystay

The babystay pulls forward on a lower/intermediate mast region to influence shape and normally does not carry a headsail.

12. Hold Up the Mast — Support the mast fore and aft

Back splice

Interlocked end strands are tucked back into their own rope to resist unlaying, adding a bulky finish rather than an attachment eye.

9. Join Ropes and Make Attachments — Join the rope’s own construction

Backbone

The backbone names connected central fore-and-aft members; keel timber and keelson organise the hull while other structure shares its loads.

6. Give the Water Something to Push Against — Give the water force a surface

Backing a sail / aback

Setting a sail so wind loads its opposite side, which may help stop or turn the vessel.

31. Turn, Stop and Rebalance — Unload the sail or put pressure on its other face

Backstay

A backstay leads aft, supplying aft restraint; changing its pull can affect mast bend and forestay tension through the connected rig.

12. Hold Up the Mast — Support the mast fore and aft

Backwind

Airflow or pressure that disturbs a sail from its opposite side, often because of interaction with another sail.

31. Turn, Stop and Rebalance — Unload the sail or put pressure on its other face

Bail / bale

A curved bracket provides the incoming bearing point on a spar or fitting, with its own mounting determining the onward load path.

10. Hold the Load, Keep Control — The eye and the structure behind it

Balance (junk-sail area)

The proportion of sail area lying forward of the mast or relevant turning axis.

Related labels and senses: Balance; Other senses: Balance (yacht forces).

19. A Sail Divided by Battens — Put supporting members across the sail

Balance (yacht forces)

The relationship among sail, hull and rudder forces that determines turning tendencies and steering effort.

Related labels and senses: Balance; Other senses: Balance (junk-sail area).

7. Why the Boat Leans and Wants to Turn — Why the helm needs a correction

Balanced lug

A lug sail with part of the sail and normally its boom projecting forward of the mast; it is not dipped at each tack.

16. Sloping Yards and Diagonal Spars — Leave the yard on one side, or move it

Balanced rudder

A rudder with some blade area ahead of its turning axis, reducing the steering effort required.

37. From the Hand to the Rudder — Put the turning axis within the blade

Balanced sail

A sail with some area ahead of its mast or turning axis; specify which geometry supplies the balance.

27. Rearrange the Whole Rig — Put sail on both sides of the pivot

Balestron rig

A balanced rotating sail-support arrangement with a spar extending both forward and aft of its pivot.

27. Rearrange the Whole Rig — Put sail on both sides of the pivot

Ball terminal

A ball terminal transfers pull through its rounded end into a matching cup, with movement limited by that mating geometry.

14. Attach and Support the Sail — Break the continuous attachment into moving pieces

ball-bearing car

A sail-luff carriage running on a track with rolling balls carrying contact loads, including designs that recirculate balls as the carriage travels.

Ballast

Weight carried or positioned to improve stability or achieve a required trim.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Ballast keel

An external keel containing substantial weight as well as usually contributing underwater side area.

35. Keels, Ballast and Adjustable Draught — Put the mass inside or outside

Ballast ratio

The fraction of total displacement mass assigned to ballast leaves mass position and immersed form unspecified.

36. Stability Has a Range — Keep the ratio and move the weight

Ballast stability

Resistance to heeling gained by placing weight low enough to help oppose the tilting moment.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Balloon jib

A large, full light-weather headsail; its precise historical shape and role vary.

20. Use the Space Ahead of the Mast — Choose the forward inventory

Balsa core

A core made from lightweight balsa wood, commonly arranged with its grain through the panel thickness.

33. Change the Material, Keep the Jobs — Separate two skins and connect them

Barber hauler

A barber hauler supplements a sheet’s lead; Corsair’s line attaches to the clew, turns through a float-deck block and returns to a cockpit cleat.

37. From the Hand to the Rudder — Put the turning axis within the blade

Barn-door rudder

An informal name for a broad, relatively simple slab-like rudder.

Barque / bark

Barque or bark retains square rig on all principal masts except the aftermost, with at least three masts in the chosen convention.

26. Read the Whole Square or Mixed Rig — Change the allocation on selected masts

Barquentine / barkentine

Barquentine or barkentine keeps square rig only forward, with fore-and-aft rig on the remaining principal masts, three or more in total.

26. Read the Whole Square or Mixed Rig — Change the allocation on selected masts

Baseline

A fixed reference line or plane from which design heights are measured.

43. Draw It, Measure It, Compare It — Locate one point on the hull

Batten

A strip or rod supporting part of a sail’s shape.

13. Give the Sail Its Shape — The edge is part of the shape

Batten box

A fitting receiving and locating the end of a sail batten.

14. Attach and Support the Sail — Support an edge, then span the sail

Batten downhaul

A line helping pull a batten and its sail panel into a lowered or reefed position.

19. A Sail Divided by Battens — Pull down a reluctant member

Batten parrel

A restraint connecting a junk-sail batten around the mast.

19. A Sail Divided by Battens — Keep the sail beside its mast

Batten pocket

A sleeve in a sail that holds a batten.

14. Attach and Support the Sail — Support an edge, then span the sail

Batten receptacle

A fitting accepting a batten end and transferring its loads into the sail or mast-car system.

14. Attach and Support the Sail — Support an edge, then span the sail

Batten rise

The upward slope of a batten from its forward to after end.

19. A Sail Divided by Battens — Put supporting members across the sail

Batten stagger

The fore-and-aft offset between batten ends when they settle into a lowered sail bundle.

19. A Sail Divided by Battens — Receive the lowered sail

Beam

The boat’s width; say where and how it is measured when precision matters.

3. Give the Hull a Shape — Measure the same hull in several ways

Beam knee

A beam knee braces a deck beam to adjacent hull structure through its two fastened arms.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Beam reach

Sailing with the wind approximately across the boat.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Beam shelf

The beam shelf is a lengthwise ledge bearing beneath deck-beam ends and fastening to side frames.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Bear up

A traditional expression commonly meaning bear away; teach the convention rather than guessing from the ordinary word up.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Bearding line

The bearding line locates the fitted planking’s inner-face intersection with the backbone in the selected rabbet.

32. Build a Hull from Joined Pieces — Transfer the shape into the timber

Bearing

Mechanical bearing: support/contact carrying load while permitting motion; navigational direction is a separate contextual sense, not assessed by this example.

1. A Boat Before Sail — Give the oar somewhere to bear

Bearing away / bearing off

Turning the bow farther away from the wind’s source.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Beating / working to windward

Making progress towards the wind by sailing alternate close-hauled legs.

6. Give the Water Something to Push Against — The other moving fluid

Becket

The block becket receives the pull of a fixed rope end separately from the sheave pin’s contact loads.

11. Trade Force for Distance — What turns inside the block

Becket bend

The sheet-bend path surrounds an existing attachment eye instead of an open receiving rope bight.

10. Hold the Load, Keep Control — Let the hands leave the rope

Belay

Securing at a pin or cleat transfers the loaded line from the crew’s hand to a supported fastening.

Belaying pin

Upper and lower exposed portions receive alternating wraps and carry their pull into the supporting rail.

10. Hold the Load, Keep Control — Let the hands leave the rope

Bend (rope connection)

Joining two rope ends establishes the receiving bight and the continuing tensile path before the particular sheet bend is named.

14. Attach and Support the Sail — Guide an edge along a stay

Bend on

Attach a sail to its spars, stay or fittings, not necessarily curve it.

Bending

Deformation in which a member curves under load.

19. A Sail Divided by Battens — Form the curve between battens

Bendy batten

A flexible batten designed to bend into a useful sail-section curve.

Bent frame

A bent frame obtains its transverse curve by bending a piece whose grain follows the support.

32. Build a Hull from Joined Pieces — Make a frame follow the hull

Bermuda schooner

Bermuda triangular mast-supported principal sails combined with schooner mast distribution.

24. Spread the Work Across a Schooner — Keep the sail support separate from the mast arrangement

Bermudan / Bermuda rig

A rig using a triangular fore-and-aft sail rising along a mast, without a gaff supporting an upper edge.

18. The Tall Triangle

Bias

A direction diagonally across woven fabric, along which it commonly distorts differently from the yarn directions.

13. Give the Sail Its Shape — Turn the cloth towards the load

Biaxial reinforcement

Reinforcement with fibres arranged in two principal directions.

33. Change the Material, Keep the Jobs — Place fibres where the load must travel

Bibbs

Traditional supporting pieces attached near a mast’s cheeks to help carry the trestletrees.

25. Build Height, Divide Sail — Give the upper mast a seat

Bight

A doubled middle curve is formed without threading an end, providing the receiving geometry for later eyes and bends.

8. What a Rope Is Made to Do — Which part of the rope moves?

Bilge

The lower region where hull sides meet the bottom; inside the boat, also the low space where unwanted water collects.

3. Give the Hull a Shape — Read a slice through the hull

Bilge as inner low space

Inside the boat, bilge also names the low space where unwanted water collects.

3. Give the Hull a Shape — Read a slice through the hull

Bilge as outer side-bottom region

The region where the side turns towards the bottom is the bilge.

3. Give the Hull a Shape — Read a slice through the hull

Bilge keel

A fin near the bilge. It may be one of a sailing boat’s twin grounding keels or a ship’s smaller roll-damping fins.

35. Keels, Ballast and Adjustable Draught — Put supports to either side

Bilge pump

The selected bilge pump uses handle, pivoted fork and diaphragm with separate inlet/outlet valves; alternate volume changes admit and expel water.

40. A Deck with Openings — Collect water without joining every compartment

Bilge strake

The bilge strake locates a course near the hull’s lower turn.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Bilge stringer

A bilge stringer fastens along successive frames at their lower curved regions.

32. Build a Hull from Joined Pieces — Make a frame follow the hull

Bill / bill point

The pointed end of an anchor fluke that first enters the seabed.

41. Hold the Boat to the Seabed — Give the bottom something to resist

Bitt

The paired mooring bitts have upright bodies, retaining lips, a common base and receiving structure below deck; the line bears on the posts and pulls that connected support.

41. Hold the Boat to the Seabed — Give the held load its own support

Bitter end

The inboard end of an anchor cable or rope, traditionally the end secured aboard; distinguish it from a loose working end.

41. Hold the Boat to the Seabed — Make room for what comes aboard

Bitter pin

A securing pin associated with the inboard end of an anchor cable; arrangement varies.

41. Hold the Boat to the Seabed — Retain the last connection

Blackwall hitch

The loaded standing part traps the short end against the hook body; loss of load explains its insecure temporary character.

9. Join Ropes and Make Attachments — Bind the object and retain the end

Block

A housing containing one or more grooved wheels that guide a line; blocks can change pull direction or form a tackle.

4. One Mast, One Sail — Raise the head, control the clew

Block and tackle

Block and tackle names the connected rope-and-block hauling arrangement whose reeving determines movement and tensions.

11. Trade Force for Distance — Make the block move with the load

Block coefficient

Displaced volume divided by a reference box of length, beam and draught: a measure of overall underwater fullness.

43. Draw It, Measure It, Compare It — Give fullness a denominator

Blooper

A specialised light offwind sail once used alongside a spinnaker; retain as a design-context example rather than racing narrative.

29. When the Wind Moves Aft — Choose the shape as well as the name

Boat

Boat as a watercraft; conventional relationship to ship.

42. Hold the Boat Alongside — Retrieve a mooring connection

Boathook

A boathook transmits hand push or pull through a pole to a shaped end that reaches, catches or pushes an object beyond the hand.

Bobstay

A support running down from the outer bowsprit towards the bow, opposing the upward pull of headsail rigging.

21. Move the Sail Beyond the Bow — Hold the inner end and restrain the outer one

Bobstay fitting

The attachment carrying a bobstay load into the hull or bowsprit.

21. Move the Sail Beyond the Bow — Hold the inner end and restrain the outer one

Body plan

A drawing showing transverse hull sections as viewed from ahead or astern.

43. Draw It, Measure It, Compare It — Locate one point on the hull

Bollard

The shore bollard transfers line contact through its body and base into grout, hold-down bolts and the foundation.

42. Hold the Boat Alongside — Carry the pull beyond the post

Bollard pull

Bollard pull is measured towing force transmitted through a connected towline at zero speed through the water, with the cited trial using a measured load route and stated conditions.

42. Hold the Boat Alongside — Release a connection and interpret a quoted pull

Bolt rope

A rope attached along a sail edge to reinforce it or engage a groove.

14. Attach and Support the Sail — Finish and reinforce an edge

Bonjean curve

A curve showing immersed cross-sectional area against water level at a hull station, used in hydrostatic calculations.

43. Draw It, Measure It, Compare It — Add the immersed slices

Boom

A spar usually controlling the lower edge or clew of a fore-and-aft sail.

4. One Mast, One Sail — Corners, edges and a moving boom

Boom brake

A device resisting or controlling boom movement during a gybe; it is not identical to a fixed preventer.

31. Turn, Stop and Rebalance — Give the boom a deliberate restraint

Boom end

The outboard end of a boom, away from the mast.

4. One Mast, One Sail — Corners, edges and a moving boom

Boom heel

The inboard end of a boom, nearest its mast or pivot.

4. One Mast, One Sail — Corners, edges and a moving boom

Boom jaws

Forked or curved pieces at a traditional boom’s forward end that bear around the mast.

17. What the Gaff Adds — Retain the inner end without fixing it

Boom parrel

A restraint holding the junk sail’s boom near the mast.

19. A Sail Divided by Battens — Keep the sail beside its mast

Boom vang

The boom vang’s diagonal tackle pulls an under-boom fitting towards a lower mast fitting, restraining rise and loading the boom towards the gooseneck.

28. Shape Is a Control — Give boom rise its own restraint

Boomed sail

A sail controlled or supported by a boom.

4. One Mast, One Sail — One mast and one principal sail

Boomkin / bumpkin

A short projecting spar, commonly aft, providing an outboard attachment for a sheet, stay or other rigging.

21. Move the Sail Beyond the Bow — Retain the job, change the exposure

Boomless sail

A sail worked without a conventional boom.

4. One Mast, One Sail — One mast and one principal sail

Bottle screw

Bottle screw is an overlapping name for the threaded adjuster; opposite-handed ends let body rotation change effective length.

12. Hold Up the Mast — Turn the adjuster while letting the joint align

Bottom

The lower external surface of the hull.

3. Give the Hull a Shape — Follow the outside from bow to stern

Bottom-up furling

The code sail’s tack and lower cable terminal turn first, wrapping upwards along a cable sewn into the luff or a torsionally stiff panel.

30. Reduce, Gather or Replace the Sail — Decide where the roll starts

Boundary layer

Near the hull, velocity changes from the wall value to the outer flow; viscous effects create a boundary layer and wall shear.

34. Why Hull Shapes Behave Differently — Follow the flow next to the surface

Bow

The forward end of the boat, whether or not the boat is moving forwards.

42. Hold the Boat Alongside — Give each line a direction

Bow line

The bow line runs from the forward part of the boat to a shore attachment ahead; its forward pull opposes the boat’s movement astern.

Bow roller

A roller at the bow supporting and guiding an anchor or rode.

41. Hold the Boat to the Seabed — Bring the rode across the bow

Bow shackle

The wider rounded body provides room for attachments to settle while retaining limits on permitted pull direction.

10. Hold the Load, Keep Control — Close the link without fixing every movement

Bower anchor

A principal anchor carried ready for ordinary anchoring service.

41. Hold the Boat to the Seabed — Use the holding point to move the boat

Bowline

The small loop nips the two returning portions while an encircling collar retains them, fixing the large eye’s size.

9. Join Ropes and Make Attachments — Make an eye that stays the same size

Bowline on a bight

A doubled middle portion supplies two eyes when its projected bight is opened back around the whole knot.

9. Join Ropes and Make Attachments — Make an eye that stays the same size

Bowsprit

A spar projecting forward from the bow, extending sail or rigging attachments beyond the hull.

21. Move the Sail Beyond the Bow

Bowsprit cap

A fitting at a bowsprit’s outer end that supports or locates a jibboom.

21. Move the Sail Beyond the Bow — Extend the projection in stages

Bowsprit end

The outer end of a bowsprit, carrying sail or rigging attachments.

21. Move the Sail Beyond the Bow — Hold the inner end and restrain the outer one

Bowsprit guy

A line restraining or positioning a bowsprit sideways; naming depends on whether it is fixed or adjustable.

21. Move the Sail Beyond the Bow — Hold the inner end and restrain the outer one

Bowsprit heel

The inboard end of a bowsprit where its loads are supported by the hull.

21. Move the Sail Beyond the Bow — Hold the inner end and restrain the outer one

Bowsprit heel fitting

The support or fastening holding the inboard end of a bowsprit.

21. Move the Sail Beyond the Bow — Hold the inner end and restrain the outer one

Bowsprit shroud

A side support restraining the bowsprit against lateral loads.

21. Move the Sail Beyond the Bow — Hold the inner end and restrain the outer one

Brace

A line that turns a yard horizontally to change the angle of its square sail.

15. A Sail on a Yard — Turn the yard, then place the corners

Brace up

Turn square-sail yards towards a more oblique setting, commonly for sailing closer to the wind.

15. A Sail on a Yard — Turn the yard, then place the corners

Braided rope

Opposed travelling strands interweave and produce flexibility without a laid rope’s one-direction twist.

8. What a Rope Is Made to Do — From fibres to a working line

Brail

A line gathering a sail towards a mast or spar so it can be reduced or stowed.

16. Sloping Yards and Diagonal Spars — Gather the cloth towards the mast

Brail / brailing

Gathering a sail towards its mast or spar using brail lines rather than rolling it around a foil.

16. Sloping Yards and Diagonal Spars — Gather the cloth towards the mast

brail line

A line led to gather sailcloth towards its supporting mast or spar; its attachments and leads determine the gathering path.

16. Sloping Yards and Diagonal Spars — Gather the cloth towards the mast

Brail up

Gather a sail using its brails.

16. Sloping Yards and Diagonal Spars — Gather the cloth towards the mast

brailing action

Gathering a sail towards its mast or spar by hauling the relevant brail lines.

16. Sloping Yards and Diagonal Spars — Gather the cloth towards the mast

Brailing line

A line performing the sail-gathering job called brailing.

16. Sloping Yards and Diagonal Spars — Gather the cloth towards the mast

Brails

Lines gathering a sail towards its supporting mast or spar.

16. Sloping Yards and Diagonal Spars — Gather the cloth towards the mast

Breast line

A breast line crosses the gap approximately athwartships, pulling the boat towards the berth as it moves away.

42. Hold the Boat Alongside — Give each line a direction

Breast rope

Breast rope is given as an alias for the transverse mooring line crossing from boat to berth.

42. Hold the Boat Alongside — Give each line a direction

Breasthook

The breasthook’s arms fasten into the converging bow sides or stringers and tie them across the bow.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Bridge deck

A multihull bridge deck spans the hulls; its surface carries crew load through panels/supports into beams and hulls.

38. Separate the Hulls — Put a working surface across the gap

Bridge deck — cockpit-to-companionway separation

This bridge deck is a raised separation between the cockpit and entrance below; water must rise over its level while the crew steps across it.

38. Separate the Hulls — Put a working surface across the gap

Bridge deck: multihull platform

This specific bridge-deck sense is the working platform spanning multihull hulls and carrying surface loads to its structural supports.

38. Separate the Hulls — Put a working surface across the gap

Bridgedeck clearance

Bridgedeck clearance is the gap from the actual water surface to the particular spanning underside; load and relative water/boat motion alter that gap.

38. Separate the Hulls — Leave space for moving water

Bridle

Multiple legs distribute attachment locations, while wider splay increases each required tension because sideways components cancel.

10. Hold the Load, Keep Control — The eye and the structure behind it

Brig

A brig repeats a square-rigged fore and main unit on two principal masts.

26. Read the Whole Square or Mixed Rig — Repeat the square-rigged mast

Brigantine

The selected modern brigantine has square fore and fore-and-aft main; dated usage can retain upper main squares.

26. Read the Whole Square or Mixed Rig — Change the allocation on selected masts

Broach

An uncontrolled turn, often across the wind and waves, accompanied by loss of normal steering control.

31. Turn, Stop and Rebalance — When the intended balance is lost

Broad reach

Sailing with the wind from behind the beam but not directly astern.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Broad strake

The broad strake is located by the explicitly stated builder’s convention beside the garboard.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Broadseam

A deliberately shaped seam joining sail panels so that the finished sail gains three-dimensional curvature.

13. Give the Sail Its Shape — Join flat pieces into a curved surface

Bronze

A copper-alloy family used for castings, bearings and traditional marine fittings; composition matters.

33. Change the Material, Keep the Jobs — Join plates into a supported shell

Buckling

Buckling is loss of stability as compression amplifies a slender member’s sideways departure, distinct from ordinary bending or crushing.

12. Hold Up the Mast — Restrain a slender member between its ends

Built-up mast

A mast assembled from several pieces rather than one unbroken trunk or tube.

18. The Tall Triangle — Build a long spar from wood

Bulb keel

A keel with a concentrated, enlarged ballast body near its lower end.

35. Keels, Ballast and Adjustable Draught — Give depth a stated condition

Bulkhead

An internal wall dividing the hull; some bulkheads also carry major structural loads.

4. One Mast, One Sail — Bring the loads into the hull

Bullseye

The bullseye’s fixed smooth hole guides a line while its surrounding strop supports it; it has no sheave.

12. Hold Up the Mast — Adjust a connection made from rope and iron

Bulwark

A bulwark continues a solid hull-side boundary above the deck; supported panels or planks connect into deck and hull.

21. Move the Sail Beyond the Bow — Give the downward support a better angle

Bunt

The central body or gathered belly of a sail.

15. A Sail on a Yard — Gather different parts of the sail

Buntline

A line hauling up the central body of a square sail towards its yard.

15. A Sail on a Yard — Gather different parts of the sail

Buntline hitch

A clove hitch around the standing part progresses towards the attachment, seating a compact gathering-line connection.

9. Join Ropes and Make Attachments — Bind the object and retain the end

Buoyancy

The upward force exerted by displaced water on an immersed body.

2. Why a Hull Floats — Weight and the water’s support

Butt block

A butt block bridges meeting plank ends; each plank fastens into the common backing.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Butt joint

A butt joint meets plank ends directly; a backing and its fasteners connect their loads.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Buttock

A curve formed by a vertical fore-and-aft plane cutting the hull.

43. Draw It, Measure It, Compare It — Locate one point on the hull

By the lee

Sailing with wind approaching from the same side as the boom, near the conditions for an unintended gybe.

31. Turn, Stop and Rebalance — Move the boom while it can still be loaded

C-foil

A curved board producing both sideways and upward force when deployed.

39. Move Mass, Add Foils — Let the curve decide what emerges from the case

Cabin trunk

The cabin trunk projects above the surrounding deck, with sides and roof enclosing extra height and passages alongside.

40. A Deck with Openings — Walk around the raised enclosure

Cable

A substantial rope or chain; in traditional anchoring language it need not mean an electrical cable.

41. Hold the Boat to the Seabed — Join the anchor to the boat

Cable-laid

Three laid ropes form another helix, adding a construction stage whose settling affects extension.

8. What a Rope Is Made to Do — From fibres to a working line

Cam cleat

Offset pivoted jaws are initially closed by springs and then driven into grip by the rope’s reverse pull.

10. Hold the Load, Keep Control — Grip the line between surfaces

Camber

The curvature of a sail or foil section; not simply the two-dimensional outline.

13. Give the Sail Its Shape — Give the curve a reference

Cambered junk sail

A junk sail whose panels are deliberately shaped to develop curvature rather than cut as wholly flat panels.

19. A Sail Divided by Battens — Form the curve between battens

Canoe stern

A stern tapering towards a rounded or pointed end, giving the boat a canoe-like outline from above.

3. Give the Hull a Shape — Several ways to finish the hull

Canting keel

A ballast keel that tilts sideways to move its weight towards the windward side.

39. Move Mass, Add Foils — Move the lead sideways

Canvas

A strong woven cloth; in sailing, also a traditional collective word for sails, even when modern material is used.

13. Give the Sail Its Shape — Join flat pieces into a curved surface

Cap rail

The cap rail finishes the top of a bulwark or similar edge; in the timber box-gunwale example it closes the supported assembly’s top.

40. A Deck with Openings — Follow the upper hull edge

Cap shroud

The cap shroud supports the upper mast and commonly passes over spreader tips on its route to the hull.

12. Hold Up the Mast — Restrain a slender member between its ends

Capsize

Overturning far enough to lose normal upright operation is distinguished from a temporary severe lean and complete inversion.

36. Stability Has a Range — Distinguish overturning from recovery

Capstan

A capstan hauls by a vertical-axis drum, traditionally driven by crew pushing long bars around it.

11. Trade Force for Distance — The drum still needs a tail

Capstan winch versus captive winch

One handles line around a friction drum with a free tail; the other stores and manages the working line as part of the machine.

11. Trade Force for Distance — The drum still needs a tail

Capstan winch versus captive winch

Captive versus free-tail identifies what happens to the rope at the winch; manual versus powered independently identifies where the input energy comes from.

11. Trade Force for Distance — The drum still needs a tail

Capstan/free-tail friction drum

A rotating friction drum that transmits hauling force through rope turns while the line has a free tail rather than being stored on a dedicated captive reel.

11. Trade Force for Distance — The drum still needs a tail

Captive storage

A captive reel winch keeps and stores its dedicated line on its drum while the line is led to the controlled sail, spar or appendage.

11. Trade Force for Distance — The drum still needs a tail

Captive winch

A powered line-handling winch that stores and controls its working line internally.

44. When Muscle Is Not Enough — Give the retrieved rope a home

Caravel

Caravel is a smaller trading/voyaging vessel family, represented by the Berlin c1450 Portuguese model with three lateen sails.

26. Read the Whole Square or Mixed Rig — Separate the boat’s work from its rig

Carbon reinforcement

Carbon fibres used to add stiffness and strength to a composite structure.

18. The Tall Triangle — Hold fibres in a rigid shape

Carbon-fibre mast

A mast made with carbon-fibre composite, allowing designers to tailor stiffness and reduce weight aloft.

18. The Tall Triangle — Hold fibres in a rigid shape

Carbon-fibre-reinforced polymer / CFRP

A composite of carbon fibres in a polymer matrix.

33. Change the Material, Keep the Jobs — Specify the structure, then make it

Carlin / carling

The carlin runs along a deck opening between full beams and receives shortened beam ends.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Carrack

Carrack is explained through MadreDeus’s named long-distance trade and a modern model’s deep cargo hull and square fore/main plus lateen after supports.

26. Read the Whole Square or Mixed Rig — Separate the boat’s work from its rig

Carrick bend

The explicit over/under route interlocks two loops, with opposite tails and a different loaded shape from the flat arrangement.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Carvel planking

Carvel planks meet edge to edge, held by frame fastenings and connected hull structure.

Cascade

One complete purchase hauls the working end of another, multiplying the ideal force and travel ratios.

11. Trade Force for Distance — Make one purchase haul another

Cascade purchase

Cascade purchase names linked stages in which one purchase acts on another’s hauling end.

11. Trade Force for Distance — Make one purchase haul another

Cast off

To cast off is to release a securing connection, removing that line’s restraint and changing what the remaining connections must do.

10. Hold the Load, Keep Control — Let the hands leave the rope

Cat rig

A single-mast, single-principal-sail arrangement without a conventional headsail, usually with the mast well forward.

4. One Mast, One Sail — One mast and one principal sail

Cat tackle

The tackle lifting an anchor towards the cathead.

41. Hold the Boat to the Seabed — Lift the two ends of a traditional anchor

Cat-ketch

Cat-style forward main plus a smaller mizzen ahead of the rudder stock, with no ordinary headsails.

23. Put a Smaller Sail Aft — Combine two masts with the cat arrangement

Cat-yawl

Cat-style forward main plus a small far-aft mizzen under the yawl rudder-stock convention.

23. Put a Smaller Sail Aft — Combine two masts with the cat arrangement

Catamaran

A vessel with two principal hulls.

22. One Mast, Several Sail Plans — Begin with the one-sail boat

Catboat

A boat carrying a cat rig; many traditional catboats also have distinctive broad hulls, which are not the rig’s definition.

Catenary

The sagging curve of a hanging line or chain under its own weight.

41. Hold the Boat to the Seabed — Support the weight hanging between the ends

Catharpin

A transverse lashing or supporting connection drawing opposing lower rigging inward near a traditional masthead.

Related labels and senses: Catharpins.

25. Build Height, Divide Sail — Continue the pull below the platform

Cathead

A projecting timber or beam at the bow of a traditional ship used in handling a heavy anchor.

21. Move the Sail Beyond the Bow — Give the downward support a better angle

Caulking

Caulking works fibrous packing into the prepared wooden seam.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Caulking cotton

Caulking cotton supplies fibres packed and compressed into a seam.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Caulking seam

A caulking seam is shaped between planks to receive compressed packing.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Cavitation

Vapour cavities forming where water pressure becomes sufficiently low; different from air being drawn down from the surface.

39. Move Mass, Add Foils — Keep the water in the comparison

Ceiling

Ceiling is inner planking fastened to the hull frames; the outer shell, frame and inner face are located, with substantial ceiling contributing to the connected structure.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Centre of buoyancy

The centre of the underwater displaced volume, through which the resultant buoyancy force acts.

2. Why a Hull Floats — Weight and the water’s support

Centre of effort / CE

A reference point representing the combined action of sail forces; the real resultant changes with sail trim and flow.

Related labels and senses: Centre of effort.

7. Why the Boat Leans and Wants to Turn — Force needs a place to act

Centre of gravity

The point representing the combined position of all the boat’s weight.

2. Why a Hull Floats — Weight and the water’s support

Centre of lateral resistance / CLR

A useful approximate location for the resultant underwater sideways force; it is not a permanently fixed geometric point.

7. Why the Boat Leans and Wants to Turn — Locate the combined water force

Centre of pressure

The effective location of a resultant pressure force; it changes with shape and flow conditions.

43. Draw It, Measure It, Compare It — Separate an outline from its force

Centreboard / centerboard

A board, usually pivoting, lowered from a hull case to provide side area and raised for shallower water.

6. Give the Water Something to Push Against — Give the water force a surface

Centreboard case / trunk

The watertight-sided box that houses a centreboard and passes through the hull.

6. Give the Water Something to Push Against — Give the water force a surface

Centreboard pennant

The line or cable used to raise or control a centreboard; spelling also appears as pendant.

39. Move Mass, Add Foils — Haul a board without making its line the hinge

Centreboard pin

The pin carrying a centreboard at its pivot.

6. Give the Water Something to Push Against — Give the water force a surface

Centreboard pivot

The point or axis about which a centreboard swings.

6. Give the Water Something to Push Against — Give the water force a surface

Centreline

The fore-and-aft line or plane dividing the vessel into port and starboard halves.

1. A Boat Before Sail — Directions that turn with the boat

Chafe

Repeated loaded rubbing removes fibres at a guide or internally, establishing the problem later coverings address.

8. What a Rope Is Made to Do — Keep the line able to run

Chafe protection

The replaceable sleeve surrounds the rope at a wear contact; its closure holds it round the line while separate position-retaining attachments keep it at the intended contact.

41. Hold the Boat to the Seabed — Divide the attachment between two bowside points

Chain

Linked chain transfers tension through successive metal contacts; the traditional chains may name a wider attachment assembly.

12. Hold Up the Mast — Adjust a connection made from rope and iron

Chain — linked metal elements

Each metal chain link bears against its neighbours to carry tension through the joined length.

12. Hold Up the Mast — Adjust a connection made from rope and iron

Chain — traditional attachment assembly

Metal members beneath the lower deadeye carry its upward pull down into the hull, while the channel preserves outboard geometry.

12. Hold Up the Mast — Adjust a connection made from rope and iron

Chain hook

A hook shaped to engage a chain link for holding or attaching a snubber.

41. Hold the Boat to the Seabed — Let part of the connection extend

Chain link

One individual interlocking element of a chain.

41. Hold the Boat to the Seabed — Join the anchor to the boat

Chain locker

The compartment in which anchor chain is stored.

41. Hold the Boat to the Seabed — Make room for what comes aboard

Chain pipe / spurling pipe

The pipe leading anchor chain from the deck machinery into the chain locker.

Related labels and senses: Spurling pipe / chain pipe.

41. Hold the Boat to the Seabed — Make room for what comes aboard

Chain stopper

A fitting securing chain so the full anchoring load need not remain on the windlass.

41. Hold the Boat to the Seabed — Give the held load its own support

Chainplate

A strong hull attachment transferring a stay or shroud load into the boat’s structure.

Related labels and senses: Chainplates.

4. One Mast, One Sail — Bring the loads into the hull

Chainplate bolt

A fastening securing a chainplate or its supporting structure.

4. One Mast, One Sail — Bring the loads into the hull

Chainplate bulkhead

A bulkhead receiving and spreading loads from standing-rigging attachments.

4. One Mast, One Sail — Bring the loads into the hull

Chainplate knee

The chainplate knee braces the concentrated entry into adjacent frame, deck or bulkhead structure, resisting their relative distortion.

12. Hold Up the Mast — Continue the load beyond the fitting

Chainplate laminate

The reinforced composite structure receiving loads at a chainplate or equivalent rigging attachment.

33. Change the Material, Keep the Jobs — Bond the interior into the hull

Channel / chainwale

The channel or chainwale projects the lower shroud attachment outboard; iron members continue the pull into the hull below.

Related labels and senses: Channels.

12. Hold Up the Mast — Adjust a connection made from rope and iron

Checkstay

A checkstay pulls aft on an intermediate region and controls its bending or repeated motion, rather than merely supporting the masthead.

12. Hold Up the Mast — Support the mast fore and aft

Cheek

Cheeks flank the sheave and support the axle, passing its load into the body and attachment.

11. Trade Force for Distance — What turns inside the block

Cheek block

A cheek block mounts one side to a supporting surface so its sheave redirects a line beside that surface.

11. Trade Force for Distance — Lead the rope where it is useful

Cheeks

Paired side pieces supporting or guiding a fitting, as around mast hardware or a sheave.

25. Build Height, Divide Sail — Give the upper mast a seat

Chine

A lengthwise change of angle where parts of a hull surface meet, commonly between its bottom and sides.

3. Give the Hull a Shape — Read a slice through the hull

Chock

A chock presents a shaped bearing surface where a mooring line changes direction before continuing to its securing point.

31. Turn, Stop and Rebalance — Add drag at a chosen end

Chopped-strand mat

A sheet of short, randomly arranged reinforcing fibres held together before lamination.

33. Change the Material, Keep the Jobs — Place fibres where the load must travel

Chord

A straight reference line between the leading and trailing edges of a foil or sail section.

5. The Wind the Sail Actually Meets — Follow the air, then the force

chronological sequence

The ordering of dated events, records or forms; dates locate evidence but do not by themselves explain mechanisms, descent or the order in which a learner needs concepts.

43. Draw It, Measure It, Compare It — Put causes beside the dates

Clam cleat

The commonly used style name is linked to the branded ridged groove, without treating the trade name as a universal rated specification.

10. Hold the Load, Keep Control — Grip the line between surfaces

Clamp

A permanent hull clamp links side frames near beam level; its particular geometry establishes the load route.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Claw anchor

An anchor with a curved, claw-like holding body.

41. Hold the Boat to the Seabed — Change the part that turns into the ground

Cleat

The securing fitting takes the line’s pull and transmits its reaction to its mounting, freeing the hand.

10. Hold the Load, Keep Control — Let the hands leave the rope

Clench nail

The clench nail crosses the lap and its point turns back into the inner timber.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Clevis

The clevis places a mating fitting between two forked sides, transmitting pull through their shared pin and bearing contacts.

12. Hold Up the Mast — Turn the adjuster while letting the joint align

Clevis pin

The clevis pin spans both fork sides and the enclosed fitting, carrying shear/bearing load with a separate withdrawal retainer.

12. Hold Up the Mast — Turn the adjuster while letting the joint align

Clew

The lower after corner of a fore-and-aft sail; square and symmetrical sails have two lower clews.

4. One Mast, One Sail — Corners, edges and a moving boom

Clew height

The height of a sail’s clew above a stated deck or waterline reference.

20. Use the Space Ahead of the Mast — Measure the sail that extends aft

Clew outhaul

The clew outhaul connects an internal boom purchase through the aft sheave to the rear of a car whose front carries the sail clew.

30. Reduce, Gather or Replace the Sail — Route the reef controls

Clew reef line

The boom-secured line passes through the new leech cringle and down to an after slider block, drawing the corner down and aft.

Clew up

Haul a square sail’s lower corners upwards for reduction or furling.

15. A Sail on a Yard — Gather different parts of the sail

Clewline

A line hauling a square sail’s lower corner upwards towards the yard.

15. A Sail on a Yard — Gather different parts of the sail

Clinker / lapstrake planking

Clinker or lapstrake overlaps neighbouring edges and connects their bearing land with fasteners or a specified bond.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Clipper

Cutty Sark’s 1869 speed-oriented tea-trade purpose combines a fine hull, stated composite construction and an identified three-masted ship rig.

34. Why Hull Shapes Behave Differently — Put speed back into the purpose

Close reach

Sailing with the wind forward of the beam but farther off the wind than close-hauled.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Close-hauled

Sailing as close to the wind as the boat can usefully manage.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Closed chock

The closed chock surrounds the line with a bounded aperture, whose upper part retains it against lifting out.

31. Turn, Stop and Rebalance — Add drag at a chosen end

Clove hitch

Two encircling turns and a diagonal crossing trap the end against the support; shifting load can slip or bind it.

9. Join Ropes and Make Attachments — Fasten to something solid

Club / jib club

A short spar supporting or controlling the foot or clew of a jib.

20. Use the Space Ahead of the Mast — Give each unit its own controls

Club boom

A short boom associated with a sail such as a self-tending jib; terminology is rig-specific.

20. Use the Space Ahead of the Mast — Give each unit its own controls

Club topsail

A topsail using a short supporting spar or club; distinguish the particular rig’s naming from jackyard variants.

17. What the Gaff Adds — Fill the space above the gaff

Coachroof

The coachroof is the raised cabin’s roof above its enclosing sides, with the surrounding deck beside it.

40. A Deck with Openings — Walk around the raised enclosure

Coaming

A coaming is a raised rim around an opening; its height and continuity make water climb before entry.

40. A Deck with Openings — Step from the cockpit into the cabin

Cockpit

The working or seating area from which a small yacht is commonly steered and its sails controlled.

3. Give the Hull a Shape — A working surface and ways through it

Cockpit coaming

The cockpit coaming borders the cockpit and can support a back or fittings; its raised edge interrupts the route from surrounding deck to well.

40. A Deck with Openings — Step from the cockpit into the cabin

Cockpit sole

The cockpit sole is the foot-supporting surface at the bottom of the well; its level relative to outside water affects gravity drainage.

40. A Deck with Openings — Step from the cockpit into the cabin

Cockpit well / footwell

The cockpit well or footwell is the lower open recess occupied by feet and standing crew, above its sole.

40. A Deck with Openings — Step from the cockpit into the cabin

Code sail

A purpose-designed sail for a particular range of reaching angles and wind strengths; naming varies with maker and rule.

29. When the Wind Moves Aft — Choose the shape as well as the name

Code Zero

A light-air reaching sail with an asymmetric outline; its precise geometry is not defined by one universal everyday standard.

29. When the Wind Moves Aft — Choose the shape as well as the name

Cog

Cog refers to a medieval northern-European cargo-vessel tradition; Bremen1380’s high-sided hull, bottom, side planks and stern rudder are specified.

26. Read the Whole Square or Mixed Rig — Separate the boat’s work from its rig

Coil

Loops arrange the rope for storage while preserving its lay and avoiding added twist or trapped crossings.

8. What a Rope Is Made to Do — Keep the line able to run

Coir rope

Coconut-husk cordage trades bulk and wear behaviour against useful flotation, spring and regional availability.

8. What a Rope Is Made to Do — Different fibres, different useful properties

Cold moulding / cold molding

Cold moulding bonds thin wood layers over a form with the necessary contact pressure during cure.

32. Build a Hull from Joined Pieces — Make thin layers work together

Collision bulkhead

The collision bulkhead is a forward watertight division isolating a bow volume, with a complete supported boundary and controlled openings.

40. A Deck with Openings — Preserve the intended water boundary

Companion

A companion in the selected historical usage is the hooded entrance structure above access to a small vessel’s cabin.

40. A Deck with Openings — Step from the cockpit into the cabin

Companionway

The entrance and steps leading from deck level into accommodation below.

3. Give the Hull a Shape — A working surface and ways through it

Companionway sill

The companionway sill is the fixed raised lower entrance edge remaining after boards are removed; water must reach its level or arrive over it.

40. A Deck with Openings — Close the lid and the entrance

Compression

A pushing load tending to shorten or buckle a member.

12. Hold Up the Mast — Support the heel and restrain the spar

Compression post

The compression post continues the mast seating’s downward force from deck to lower hull structure, requiring support at each end.

Computational fluid dynamics / CFD

Numerical modelling of fluid flow around sails, hulls or foils.

43. Draw It, Measure It, Compare It — Compute a flow, then predict a sailing state

Constrictor knot

Interlocked ends lie beneath the loaded crossing against a curved support, producing a persistent binding.

9. Join Ropes and Make Attachments — Bind the object and retain the end

Constructional stretch

Loaded yarns, strands and crossings settle, so a line can retain extra length even when the fibre itself has little elastic extension.

8. What a Rope Is Made to Do — Equal strength, different movement

Continuous-line furler

A continuous-line furler circulates an endless rope round a gripping wheel while the stationary body returns the torque reaction to its attachment.

30. Reduce, Gather or Replace the Sail — Decide where the roll starts

Control line

A general name for a line used to adjust a sail, spar or mechanism.

4. One Mast, One Sail — Raise the head, control the clew

Controlled gybe

A planned gybe in which the crew manages the boom, sheets and boat’s turn.

31. Turn, Stop and Rebalance — Move the boom while it can still be loaded

Copper rivet

The copper rivet spans the joined pieces with a head outside and an end peened over the inner rove.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Cordage

The collective family includes working rope and small cord, while an individual line receives its shipboard job name.

8. What a Rope Is Made to Do — From fibres to a working line

Core (composite panel)

The middle layer between structural skins in a sandwich panel.

Related labels and senses: Core; Other senses: Core (rope).

33. Change the Material, Keep the Jobs — Separate two skins and connect them

Core (rope)

The inner braided structure can carry the principal tension even when its condition is concealed by a sound outer cover.

Related labels and senses: Core; Other senses: Core (composite panel).

8. What a Rope Is Made to Do — From fibres to a working line

Core bond

The adhesive connection between a sandwich panel’s core and its skin.

33. Change the Material, Keep the Jobs — Separate two skins and connect them

Core crushing

Local compression damage to a sandwich core under concentrated load.

33. Change the Material, Keep the Jobs — Receive a concentrated fastening load

Core shear

Shearing action within a sandwich core, where adjacent material tends to slide past itself under load.

33. Change the Material, Keep the Jobs — Separate two skins and connect them

Corner patch

Extra reinforcing material spreading loads away from a sail corner.

14. Attach and Support the Sail — Spread the pull beyond the hole

Corner ring

A load-spreading ring at a sail corner.

14. Attach and Support the Sail — Spread the pull beyond the hole

Corrosion

Conducting salt water at stainless/aluminium contact can promote loss of aluminium; environmental reaction differs from chafe and fatigue.

12. Hold Up the Mast — Inspect the connected support

Cotter pin / split pin

Bent split legs stop a substantial pin withdrawing; the smaller retainer does not replace the pin’s transverse load-bearing section.

10. Hold the Load, Keep Control — Close the link without fixing every movement

Cotton sailcloth

Woven cotton used for sails before and alongside modern synthetic materials.

13. Give the Sail Its Shape — Give the fibres different jobs

Counter

The projecting part of a stern above and behind the after end of the waterline.

3. Give the Hull a Shape — Several ways to finish the hull

Counter stern

A stern with an overhang behind the waterline, creating a projecting counter.

3. Give the Hull a Shape — Several ways to finish the hull

Counter timber

Counter timbers bear by their heels in the wing transom and continue aft/up into the counter and upper stern.

32. Build a Hull from Joined Pieces — Give the projecting stern its own supports

Couple

Two opposite forces separated by a distance, producing a turning effect without a net straight-line force.

7. Why the Boat Leans and Wants to Turn — Force needs a place to act

Course

The lowest principal square sail on a mast; this is a different sense from the direction a vessel intends to travel.

25. Build Height, Divide Sail — Put the sails between their supports

Course (direction)

The direction a vessel intends or is directed to follow; distinguish heading, track and the square sail called a course.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Course over ground / COG

The direction of movement relative to the Earth, including the effect of current.

6. Give the Water Something to Push Against — Where the boat points and where it goes

Cover

The outer sheath provides contact and protection and may share the tensile load, depending on the specified double braid.

8. What a Rope Is Made to Do — From fibres to a working line

Covering board

The covering board lies over the frame-head region and finishes the upper hull-side edge.

32. Build a Hull from Joined Pieces — Close the deck without fragile ends

Cow hitch

A bight encircles the support and receives both exiting lengths, so their loading controls how it seats.

9. Join Ropes and Make Attachments — Fasten to something solid

Crab-claw rig

A sail family with two principal spars supporting converging sail edges, associated with Oceanic traditions; forms and handling differ.

16. Sloping Yards and Diagonal Spars — Look beyond the triangular outline

Crane

The rigging crane projects an attachment beyond a spar, creating clearance and an offset turning demand at its mounting.

12. Hold Up the Mast — Describe the mast’s shape precisely

Cranse iron

A ring-like end fitting on a bowsprit, with eyes for attaching stays and other rigging.

21. Move the Sail Beyond the Bow — Hold the inner end and restrain the outer one

Creep

Sustained loading produces time-dependent, largely permanent extension distinguished from bedding and immediate or delayed recovery.

8. What a Rope Is Made to Do — Equal strength, different movement

Crevice corrosion

Localised corrosion in restricted, poorly aerated spaces, relevant to certain stainless-steel fittings.

33. Change the Material, Keep the Jobs — Follow the environment into the connection

Crew workload

Crew workload combines effort, travel, time, rope handling and coordination in the chosen equipment.

11. Trade Force for Distance — More pull changes the crew’s job

Cringle

A reinforced eye at a sail edge or corner through which a line or fitting attaches.

14. Attach and Support the Sail — Spread the pull beyond the hole

Cross curves of stability

Separate heel-angle curves tabulate a reference arm against displacement under declared density, trim and G conventions.

36. Stability Has a Range — Keep the ratio and move the weight

Crossbeam

The crossbeam connects separated hulls and transmits their reactions; unequal fore/aft and side loads produce bending, shear and twisting demands in the connected platform.

38. Separate the Hulls — Give the separated support a route home

Crosscut

A sail-panel layout with seams running broadly across the sail.

13. Give the Sail Its Shape — Turn the cloth towards the load

Crossjack

The lower transverse yard on a square-rigged vessel’s mizzenmast; this is a yard, not a mast component.

25. Build Height, Divide Sail — Add area beside and beneath the main supports

Crosstrees

Transverse members at a traditional masthead spreading upper rigging or supporting a top.

25. Build Height, Divide Sail — Give the upper mast a seat

Crown

The central region where an anchor’s arms or flukes meet the shank.

41. Hold the Boat to the Seabed — Give the bottom something to resist

Cruiser stern

A rounded stern form that carries the hull shape around the rear rather than ending in a flat transom; forms vary.

3. Give the Hull a Shape — Several ways to finish the hull

cruising priorities

A cruising design brief ranks intended passages, payload, accommodation, crew workload, access, serviceability and performance for a particular use rather than maximising speed alone.

43. Draw It, Measure It, Compare It — Change the objective without changing the question’s scale

Cruising versus racing optimisation

Different priorities for comfort, endurance, crew effort, cost and performance, not a simple good-versus-bad hierarchy.

43. Draw It, Measure It, Compare It — Change the objective without changing the question’s scale

Cunningham

The Cunningham pulls down through a reinforced eye above the tack, with the Navy line retained at a horn and its tail in a below-boom purchase.

14. Attach and Support the Sail — Give different attachments their own reinforcement

Cunningham cringle

The reinforced eye near a sail’s tack through which a Cunningham control applies tension.

Cure

The chemical hardening process of a resin or adhesive.

18. The Tall Triangle — Hold fibres in a rigid shape

Current

Movement of the surrounding water relative to the Earth.

5. The Wind the Sail Actually Meets — Choose the observer

Cutter

In yacht-rig usage, a one-masted arrangement designed to work with separated inner and outer headsails; the word has other vessel-type meanings.

22. One Mast, Several Sail Plans — Divide the forward area again

Cutter (service vessel)

A vessel designation based on service or tradition, which does not necessarily mean a cutter sail plan.

20. Use the Space Ahead of the Mast — Read the work as well as the rig

Cutter stay

An inner forward stay carrying a cutter’s staysail; its position and support requirements must be shown.

20. Use the Space Ahead of the Mast — Put a separate sail on the forward support

Cutter staysail

The inner working headsail of a cutter arrangement.

20. Use the Space Ahead of the Mast — Put a separate sail on the forward support

Cutter versus Solent

A comparison between working separated inner-and-outer headsails and closely spaced alternative headsails; real hybrids require qualification.

22. One Mast, Several Sail Plans — Carry alternatives close together

Cutter-rigged sloop

A descriptive, not uniformly defined label for a sloop equipped to use an additional inner headsail.

22. One Mast, Several Sail Plans — Read the compound names in context

Cutwater

The leading edge of the bow structure where it meets and parts the water.

3. Give the Hull a Shape — Follow the outside from bow to stern

D-shackle

Narrow, relatively straight sides lead to a closing pin and suit a chiefly aligned connection.

10. Hold the Load, Keep Control — Close the link without fixing every movement

Dagger knee

The dagger knee takes an oblique side route towards an adjacent beam in Thompson’s assembly.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Daggerboard

A board that slides approximately vertically through a case to provide underwater side area.

6. Give the Water Something to Push Against — Give the water force a surface

Daggerboard case

The housing guiding a daggerboard and transferring its loads into the hull.

6. Give the Water Something to Push Against — Give the water force a surface

Damping

Energy leaves the released model’s oscillation through wave radiation and viscous losses, reducing successive excursions.

36. Stability Has a Range — Return, overshoot and settle

Dead run

Sailing with the wind directly astern.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Deadeye

Paired deadeyes use fixed holes for repeated lanyard reeving; hauling brings the eyes closer while friction affects tension sharing.

Related labels and senses: Deadeyes.

12. Hold Up the Mast — Adjust a connection made from rope and iron

Deadrise

The angle by which a hull’s bottom rises away from its centreline, measured at a stated location.

3. Give the Hull a Shape — Read a slice through the hull

Deadwood

Joined deadwood fills the narrowing wedge and gives backbone members contact and fastening space.

32. Build a Hull from Joined Pieces — Connect the bottom and the ends

Debonding

Failure of an adhesive connection between parts or between a core and skin.

33. Change the Material, Keep the Jobs — Receive a concentrated fastening load

Deck

A platform forming the boat’s upper working surface or separating levels inside a larger vessel.

3. Give the Hull a Shape — A working surface and ways through it

Deck beam

A deck beam spans across beneath the deck and connects to the sides; reinforcement routes loads around an interrupted mast opening.

12. Hold Up the Mast — Continue the load beyond the fitting

Deck eye

Location on deck can encompass several eye constructions, each dependent on fasteners and support beneath it.

10. Hold the Load, Keep Control — The eye and the structure behind it

Deck organizer

A deck organizer gives several separate lines their own sheaves in one common mounting.

11. Trade Force for Distance — Lead the rope where it is useful

Deck plank

A deck plank spans supports as part of the fitted deck surface.

32. Build a Hull from Joined Pieces — Close the deck without fragile ends

Deck-stepped mast

A deck-stepped heel bears at deck level and its compression passes through reinforcement or a post into the hull.

12. Hold Up the Mast — Support the heel and restrain the spar

Deckhead

The deckhead is the underside of the deck overhead, which an interior headliner can conceal.

40. A Deck with Openings — Step from the cockpit into the cabin

Deckhouse

A deckhouse is an enclosed structure built on deck, with sides, roof and entrances and possibly a protected working position.

36. Stability Has a Range — Distinguish overturning from recovery

Deep-V

A hull with comparatively large deadrise, commonly trading low-speed stability and efficiency for impact behaviour at speed.

3. Give the Hull a Shape — Read a slice through the hull

Delamination

Separation between bonded layers of a composite.

33. Change the Material, Keep the Jobs — Receive a concentrated fastening load

Density

Mass per unit volume, helping explain why equal-sized materials can have very different weights.

7. Why the Boat Leans and Wants to Turn — Reduce the load, then change the wind side

Depower

Reduce a rig’s effective heeling or driving load by changing sail area, shape or angle.

Design brief

The intended purpose, conditions and priorities against which design choices are judged.

43. Draw It, Measure It, Compare It — Give two cruisers different jobs

Design trade-off

A choice that improves one property while accepting costs or limitations elsewhere.

Design waterline / DWL

The waterline at which a designer expects the boat to float in a specified loading condition.

Related labels and senses: Design waterline.

2. Why a Hull Floats — Loading changes the waterline

Development class

A class allowing design changes within defined limits.

43. Draw It, Measure It, Compare It — Let the rule change what is rewarded

Devil’s claw

A claw-like fitting gripping anchor chain as part of a securing or tensioning arrangement.

41. Hold the Boat to the Seabed — Give the held load its own support

Dhow

A broad English label for several regional vessel traditions, not one precise hull or sail design.

16. Sloping Yards and Diagonal Spars — Suspend a long sloping edge

Diagonal

An oblique reference slice used to examine or fair hull shape.

43. Draw It, Measure It, Compare It — Locate one point on the hull

Diagonal planking

Diagonal planking lays wooden material at a slant to the hull’s length.

32. Build a Hull from Joined Pieces — Make thin layers work together

Diamond stay

A diamond stay returns wire to mast attachments around offset struts, bracing a selected region through tension and compression.

12. Hold Up the Mast — Support the mast fore and aft

Dipping lug

A lug sail whose yard is moved around the mast when tacking to set the sail on the new leeward side.

16. Sloping Yards and Diagonal Spars — Leave the yard on one side, or move it

Displaced volume

The volume of water occupied by the immersed part of the vessel.

2. Why a Hull Floats — Weight and the water’s support

Displacement

The mass of water displaced by a floating boat, equal to the boat’s total mass in that condition; volume is another stated form.

2. Why a Hull Floats — Loading changes the waterline

Displacement as mass

The term displacement commonly gives the mass of the water displaced, equal to the boat’s total mass when it floats at rest.

2. Why a Hull Floats — Loading changes the waterline

Displacement curve

A graph showing how displaced volume or mass changes with draught or another defined condition.

43. Draw It, Measure It, Compare It — Add the immersed slices

Displacement hull

A displacement hull operates chiefly with buoyant support while motion still changes pressure and attitude.

34. Why Hull Shapes Behave Differently — Change the way the water supports the hull

displacement mass/volume

For a floating yacht, the mass of displaced water equals the yacht’s mass; specifications commonly call the yacht mass displacement, while displaced volume is a different quantity requiring water density.

2. Why a Hull Floats — Loading changes the waterline

Displacement stated as volume

A description can instead state displacement as a volume, here 250 litres under the stated fresh-water assumption.

2. Why a Hull Floats — Loading changes the waterline

Displacement-length ratio

A conventional comparison of displacement with waterline length; units and the chosen formula must be stated.

43. Draw It, Measure It, Compare It — Recalculate the same boat with more aboard

Dolphin-striker

A downward-projecting strut beneath a bowsprit or jibboom that improves the angle of supporting rigging.

21. Move the Sail Beyond the Bow — Give the downward support a better angle

Dory

A boat family associated with particular flat-bottomed, flared-side forms, not a rig category.

3. Give the Hull a Shape — Read a slice through the hull

Double block

A double block contains two sheaves, commonly side by side, providing separate reeving passages.

11. Trade Force for Distance — What turns inside the block

Double braid

One braid encloses another; conventional and core-dependent versions assign the two layers different loads.

8. What a Rope Is Made to Do — From fibres to a working line

Double diagonal

Double diagonal puts two connected layers on opposed slants.

32. Build a Hull from Joined Pieces — Make thin layers work together

Double sheet bend

A second circuit increases contact around the receiving bight without implying twice the strength.

3. Give the Hull a Shape — Several ways to finish the hull

Double-ended hull / double-ender

A hull tapering at both ends rather than having a broad transom; the ends need not be identical.

Double-luff tackle

The chosen double-luff arrangement uses two double blocks, a fixed upper end and four supporting rope parts.

11. Trade Force for Distance — Add parts, then follow every one

Doubling

The overlap between lower and upper mast sections.

25. Build Height, Divide Sail — Give the upper mast a seat

Downflooding

Heel or waves bring a specified open sea-to-interior route into contact with water, admitting it into a dry space.

36. Stability Has a Range — Let liquid move and follow the water entry

Downflooding angle

The angle belongs to the specified opening’s immersion and water admission under actual loading, trim and closure conditions.

36. Stability Has a Range — Let liquid move and follow the water entry

Downhaul

A line pulling a sail or spar down; its exact purpose depends on the attachment.

16. Sloping Yards and Diagonal Spars — Leave the yard on one side, or move it

Downwash

The deflection of flow behind a lifting surface associated with its production of lift.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Draft depth

How far a sail section curves away from a straight chord, often expressed as a fraction of chord length.

13. Give the Sail Its Shape — Give the curve a reference

Draft position

Where the deepest part of a sail section lies between its leading and trailing edges.

13. Give the Sail Its Shape — Give the curve a reference

Draft stripe

A visible stripe across a sail helping the reader or sailor judge its curvature.

14. Attach and Support the Sail — Observe what the surface is doing

Drag

The component of fluid force acting along the relative flow, opposing a body’s motion through that fluid.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Drag link

A rigid connecting rod transmitting steering movement between levers.

37. From the Hand to the Rudder — Wind a rope or move a rigid link

Drain limber

Drain limber is the drainage-purpose name for the passage through or past bottom members towards a collection point.

40. A Deck with Openings — Collect water without joining every compartment

Drift bolt

A drift bolt is tightly driven through aligned holes so its shank grips and bears in substantial timbers.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Drifter

A lightweight, often large headsail intended for very light winds.

20. Use the Space Ahead of the Mast — Choose the forward inventory

Driving force

The useful forward component of the forces acting on the vessel.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Drogue

A drag device streamed in the water to reduce speed or improve behaviour in difficult conditions.

31. Turn, Stop and Rebalance — Add drag at a chosen end

Drop keel

A keel lowered from a case or housing, usually by vertical movement; the name alone does not specify ballast.

39. Move Mass, Add Foils — Change depth by a different motion

Dropboards

Dropboards are removable entrance panels lowered into the Tanzer guide’s vertical grooves; side guides, lower seat and upper restraint define their closure.

40. A Deck with Openings — Close the lid and the entrance

Dugout / logboat

A hull formed mainly by hollowing a tree trunk.

27. Rearrange the Whole Rig — Rotate the square-sail stack as a unit

DynaRig

A modern square-rig system using rotating unstayed masts with fixed curved yards and sails that stow into the mast.

Dyneema / Spectra

The trade names identify high-performance polyethylene fibre products without specifying a grade’s creep or termination behaviour.

8. What a Rope Is Made to Do — Different fibres, different useful properties

E

A mainsail-foot reference measurement along the boom, commonly between defined limit marks.

43. Draw It, Measure It, Compare It — Measure the space for the sails

Earing

A short line securing a sail corner to a yard or gaff, including a reef corner when reducing sail.

Related labels and senses: Earring.

4. One Mast, One Sail — One mast and one principal sail

Earliest surviving object

The oldest presently known surviving example in the archaeological record, whose survival and discovery do not establish when the craft or mechanism was invented.

Ease / sheet out

Let a loaded control line out in a controlled way.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Elastic stretch

The substantially recoverable extension is identified by unloading, independent of the sample’s stiffness ranking.

8. What a Rope Is Made to Do — Equal strength, different movement

Elasticity

Unloading distinguishes recovery from how much extension occurred at the original pull.

8. What a Rope Is Made to Do — Equal strength, different movement

Electric winch

A winch driven by an electric motor, with controls and power demands beyond the drum itself.

44. When Muscle Is Not Enough — Turn the familiar drum with a motor

Emergency / jury rig

Colman’s repaired boom, adapted supporting rigging, secured base and reduced cloth rebuilt an improvised sail-carrying structure after dismasting.

30. Reduce, Gather or Replace the Sail — Restore a support after damage

Emergency tiller

A separate tiller arrangement used if the normal steering connection fails.

37. From the Hand to the Rudder — Give a failed connection another route

Energy

The capacity to do mechanical work; sailing draws energy from relative air-and-water motion rather than creating it in a sail.

1. A Boat Before Sail — Energy and effort

Entrance

The immersed forward region widens from cutwater and forefoot, directing approaching water aside and below.

34. Why Hull Shapes Behave Differently — Follow the water from the bow to the stern

Entry

The shape and orientation of the forward part of a sail section where airflow arrives.

13. Give the Sail Its Shape — Give the curve a reference

Epoxy

A resin family used for adhesives, coatings and structural composites.

18. The Tall Triangle — Hold fibres in a rigid shape

Equilibrium

A condition with no net change caused by unbalanced forces or turning moments; steady motion can still occur.

7. Why the Boat Leans and Wants to Turn — Steady motion and changing motion

Euphroe

A multi-hole friction fitting distributing and controlling lines in a traditional sheeting arrangement.

19. A Sail Divided by Battens — Change a retaining or sheeting route

Exit

The shape and orientation of the after part of a sail section where airflow leaves.

13. Give the Sail Its Shape — Give the curve a reference

Experimental reconstruction

A new object built to test an interpretation of historical evidence; it is not automatically identical to the original.

43. Draw It, Measure It, Compare It — Test an interpretation of the past

External ballast

Ballast carried outside the main hull shell, commonly in a keel or bulb.

35. Keels, Ballast and Adjustable Draught — Put the mass inside or outside

Extrusion

A process forming material through a shaped opening to make a continuous section such as an aluminium mast.

18. The Tall Triangle — Form a metal section

Eye

An enclosed attachment opening gives the connected object a place to bear and can be tied or permanently prepared.

8. What a Rope Is Made to Do — Which part of the rope moves?

Eye splice

The returned leg of a fixed eye transfers its pull into the continuing rope through separate strand tucks.

9. Join Ropes and Make Attachments — Join the rope’s own construction

Eye strap

A raised strip forms an opening whose load reaches the surface through its two fastened ends.

10. Hold the Load, Keep Control — The eye and the structure behind it

Eye terminal

An eye terminal ends in a closed opening receiving a pin or shackle so the member’s pull can cross the attachment.

10. Hold the Load, Keep Control — The eye and the structure behind it

Eyebolt

The pull enters the eye at the bolt head and reaches the supporting material through the shank and fastening.

Eyelet

A small reinforced hole receiving a line, fastening or lacing.

14. Attach and Support the Sail — Spread the pull beyond the hole

Failure mode

The particular way something can stop performing its intended job.

33. Change the Material, Keep the Jobs — Keep the load path usable and reachable

Fairlead

A fairlead guides a rope through the intended route using smooth sliding contact or a moving guide.

11. Trade Force for Distance — Lead the rope where it is useful

Fall

The fall is the rope reeved through the tackle, carrying the tensions between its blocks and attachments.

11. Trade Force for Distance — Make the block move with the load

False keel

A false keel takes wear beneath the main timber and passes the contact reaction through its fastenings.

32. Build a Hull from Joined Pieces — Connect the bottom and the ends

Fan-up

Unwanted upward spreading or rotation of spars that disturbs a junk sail’s intended arrangement.

19. A Sail Divided by Battens — Pull down a reluctant member

Fanned sail

A sail whose battens spread at differing angles, giving a fan-like outline or panel arrangement.

19. A Sail Divided by Battens — Put supporting members across the sail

Fashion piece

Fashion pieces give after planking terminating width in the small-vessel arrangement and shape the end boundary in the separately identified older stern.

32. Build a Hull from Joined Pieces — Give the projecting stern its own supports

Fathead

An informal name for a mainsail with substantial area near its broad upper end.

13. Give the Sail Its Shape — The edge is part of the shape

Fathom

A traditional depth unit of six feet.

41. Hold the Boat to the Seabed — State both lengths before comparing them

Fatigue

Fatigue accumulates material damage through repeated loads, including loads below a single breaking event, rather than one overload.

10. Hold the Load, Keep Control — A sudden stop changes the load

Feathering

Briefly easing the effective angle of attack, often by heading up slightly, to reduce load.

31. Turn, Stop and Rebalance — Unload the sail or put pressure on its other face

Feedback

Information about a system’s actual response returned to its controller.

27. Rearrange the Whole Rig — Ask for movement, measure the result

Felucca

A regional traditional sailing-vessel designation, commonly associated with lateen sails; avoid treating it as one universal rig.

16. Sloping Yards and Diagonal Spars — Suspend a long sloping edge

Fender

The fender’s yielding body sits between hull and berth; in the inflatable example its flexible wall and compressed air deform while its rope eye and suspension locate it.

42. Hold the Boat Alongside — Cushion the surfaces that can still meet

Ferrule

A compressed sleeve grips adjacent wire lengths behind a thimble eye, transferring the returned length’s force.

10. Hold the Load, Keep Control — Close the link without fixing every movement

Fibre orientation

The directions in which reinforcing fibres are laid, affecting which loads the composite carries most effectively.

13. Give the Sail Its Shape — Give the fibres different jobs

Fid (splicing tool)

A tapered tool opens strands or carries a buried end, then leaves the splice rather than becoming a working structural member.

9. Join Ropes and Make Attachments — Join the rope’s own construction

Fid (topmast support)

A removable key or bar supporting the heel of a topmast in its working position; distinct from the rope-splicing tool.

Related labels and senses: Fid.

25. Build Height, Divide Sail — Give the upper mast a seat

Fiddle block

A fiddle block arranges two sheaves along its length, often unequal in size to provide lead clearance.

11. Trade Force for Distance — What turns inside the block

Figure-eight knot

The end’s route around the standing part and back through the first loop creates two adjacent lobes that obstruct a smaller opening.

9. Join Ropes and Make Attachments — Make the end too large to pass

Fin keel

A relatively short fore-and-aft underwater fin providing side-force, commonly with ballast in or below it.

35. Keels, Ballast and Adjustable Draught — Spread the keel along the boat or concentrate it

Fineness

Slenderness and taper need a stated reference; the illustrative loaded LWL/maximum-waterline-beam ratios compare 5 with 4.

34. Why Hull Shapes Behave Differently — Follow the water from the bow to the stern

First attestation versus invention

The earliest known record of a word or object does not establish when it was invented.

4. One Mast, One Sail — One mast and one principal sail

First linguistic attestation

The earliest located and dated use of a word in the surviving linguistic record, which dates evidence of usage rather than invention of the object or necessarily first use of the word.

4. One Mast, One Sail — One mast and one principal sail

Fish tackle

A tackle supporting and lifting an anchor’s outer body or fluke end into its stowed position.

41. Hold the Boat to the Seabed — Lift the two ends of a traditional anchor

Fisherman

Fisherman is the shortened name for the additional upper inter-mast sail in this cloth-and-hoists context.

24. Spread the Work Across a Schooner — Add cloth high between the masts

Fisherman / Admiralty-pattern anchor

A traditional stock anchor with two arms and a crosswise stock helping one fluke take hold.

41. Hold the Boat to the Seabed — Give the bottom something to resist

Fisherman staysail

The sail sense identifies Delphinus’s four-cornered upper inter-mast fisherman with two hoists and lower controls.

24. Spread the Work Across a Schooner — Add cloth high between the masts

Fisherman staysail

The representative fisherman staysail has four corners in the upper gap between foremast and mainmast.

24. Spread the Work Across a Schooner — Add cloth high between the masts

Fisherman’s bend / anchor bend

The securing tuck passes under the encircling turns before the added half-hitch, locking the round turn at its support.

9. Join Ropes and Make Attachments — Fasten to something solid

Fishing smack

A historical working-vessel designation whose exact hull and rig vary.

20. Use the Space Ahead of the Mast — Read the work as well as the rig

Flake a line

Ordered folds place the next departing length where it can run without a crossing trapping it.

8. What a Rope Is Made to Do — Keep the line able to run

Flake a sail

Flaking lays the sail in orderly folds above the boom as the attached luff fittings descend and stack.

30. Reduce, Gather or Replace the Sail — Catch the lowered sail

Flare

The outward widening of the hull sides as they rise, often increasing buoyancy and deflecting spray near the bow.

3. Give the Hull a Shape — Read a slice through the hull

Flat-bottom hull

A hull with a comparatively flat bottom across much of its width.

3. Give the Hull a Shape — Read a slice through the hull

Flogging

Repeated violent flapping of a loose sail, which can damage cloth and fittings.

31. Turn, Stop and Rebalance — Unload the sail or put pressure on its other face

Flooding

Unwanted water entering spaces that are intended to remain dry.

2. Why a Hull Floats — Loading changes the waterline

Floor

The structural floor crosses the bottom and ties framing into the keel assembly, independently of the cabin walking surface.

12. Hold Up the Mast — Continue the load beyond the fitting

Floor / floor timber

A floor timber ties lower framing across the centreline into the keel region and receives structural load beneath the sole.

12. Hold Up the Mast — Continue the load beyond the fitting

Floor grid

A grid of lower-hull supports; distinguish the load-carrying structure from the walking surface above.

33. Change the Material, Keep the Jobs — Bond the interior into the hull

Flotation

The condition or capability of remaining supported at the water surface.

1. A Boat Before Sail

Flow attachment

A condition in which fluid follows a surface without large-scale separation.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Flow separation

A condition in which the flow leaves the surface and creates a separated region.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Fluid

A substance that flows; both air and water are fluids.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Fluke

The part of an anchor designed to dig into or grip the seabed.

41. Hold the Boat to the Seabed — Give the bottom something to resist

Fluke anchor

A name commonly used for a pivoting flat-fluke anchor type, though flukes are parts of many anchor designs.

41. Hold the Boat to the Seabed — Change the part that turns into the ground

Flush deck

A flush deck continues the principal deck without a major raised cabin, as in the selected Thistle layout.

40. A Deck with Openings — Walk around the raised enclosure

Flying jib

A forward headsail set outside the ordinary jib in traditional rigs; the term does not by itself mean unsupported by a stay.

21. Move the Sail Beyond the Bow — Extend the projection in stages

Flying jibboom

An additional spar extending beyond a jibboom for outer headsails on some traditional rigs.

21. Move the Sail Beyond the Bow — Extend the projection in stages

Flying-jib stay

The stay serving an outer flying jib on a traditional rig.

21. Move the Sail Beyond the Bow — Extend the projection in stages

Foam core

A cellular plastic core used between composite skins.

33. Change the Material, Keep the Jobs — Separate two skins and connect them

Foil cant / rake

Two distinct foil adjustments: sideways tilt and fore-and-aft inclination; show their axes.

39. Move Mass, Add Foils — Tilt about a named axis

Foil cant: sideways tilt

Foil cant is sideways inclination about a stated, generally fore-and-aft axis. In the AC75 rule’s 2022 arm drawing, a hydraulic cylinder connects an inboard hull mounting to the upper foil arm near its longitudinal bearing axis. Changing cylinder length rotates the arm across the boat. The arm bearing and cylinder mount carry reactions into the hull while the foil changes position and inclination.

39. Move Mass, Add Foils — Tilt about a named axis

Foil flap

A movable trailing-edge surface adjusting a foil’s force.

39. Move Mass, Add Foils — Give the foil a shape we can describe

Foil rake: fore-and-aft inclination

Foil rake is fore-and-aft inclination, involving rotation about a generally transverse axis. In side view, the foil tilts forwards or aft instead of swinging across the boat. This mounting angle differs from its instantaneous angle of attack to locally approaching water. Pitch, heave and waves can change that local flow even when the crew leaves the rake setting alone.

39. Move Mass, Add Foils — Tilt about a named axis

Foil section

The cross-sectional shape of a keel, rudder or lifting foil.

39. Move Mass, Add Foils — Give the foil a shape we can describe

Foil span

The tip-to-tip or root-to-tip extent of a foil, according to the stated geometry.

35. Keels, Ballast and Adjustable Draught — Spread the keel along the boat or concentrate it

Foil-assisted sailing

Using hydrofoils to reduce hull loading or heel without necessarily lifting the whole vessel clear.

39. Move Mass, Add Foils — Share the weight between hull and wings

Foil-control wand

A mechanical surface-sensing device used on some foilers to adjust a foil flap.

39. Move Mass, Add Foils — Give the flap a measurement and a connection

Foiling

Sailing with hydrofoils carrying enough upward load to lift much or all of the hull clear of the water.

39. Move Mass, Add Foils — Share the weight between hull and wings

Foot

The lower edge of a sail.

4. One Mast, One Sail — Corners, edges and a moving boom

Foot block

A foot block leads a descending line towards its next route, commonly at the mast foot or another low turn.

11. Trade Force for Distance — Lead the rope where it is useful

Foot length

The measured length of a sail’s lower edge under a stated method.

13. Give the Sail Its Shape — Say what was measured

Foot rope

A rope reinforcing a sail’s lower edge; distinguish this from the crew footrope suspended below a yard.

14. Attach and Support the Sail — Finish and reinforce an edge

Foot round

Extra curved material along the foot of a sail contributing to its shape.

13. Give the Sail Its Shape — The edge is part of the shape

Foot tape

A reinforcing strip along a sail’s lower edge.

14. Attach and Support the Sail — Finish and reinforce an edge

Foot tension

The tension along a sail’s lower edge.

13. Give the Sail Its Shape — The edge is part of the shape

Footing

Sailing slightly farther from the wind to gain speed rather than maximum pointing angle.

31. Turn, Stop and Rebalance — Unload the sail or put pressure on its other face

Footrope

A rope suspended below a yard on which crew stand while working aloft; distinct from a sail’s reinforcing foot rope.

25. Build Height, Divide Sail — Bring the cloth to the people

Force

Pushes and pulls can move or deform familiar objects.

1. A Boat Before Sail — A hand, a blade and a direction

Force component

One part of a force resolved along a chosen direction, such as forward or sideways.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Fore / forward

Towards the bow, or located in the vessel’s forward part.

1. A Boat Before Sail — Directions that turn with the boat

Fore and aft

Along the boat’s length.

1. A Boat Before Sail — Directions that turn with the boat

Fore course

The lowest principal square sail on the foremast.

25. Build Height, Divide Sail — Put the sails between their supports

Fore topmast

The topmast above the lower foremast.

25. Build Height, Divide Sail — Extend and name the upper stages

Fore-and-aft rig

A rig whose principal sails are arranged along the vessel’s length rather than primarily across it.

14. Attach and Support the Sail — Read one property at a time

Fore-reaching

Continuing to move slowly ahead, sometimes while hove to or under greatly reduced sail.

31. Turn, Stop and Rebalance — Arrange a slow balance

Foredeck

The forward area of the deck.

3. Give the Hull a Shape — A working surface and ways through it

Forefoot

The lower forward region where the bow curves or slopes into the bottom of the hull.

3. Give the Hull a Shape — Follow the outside from bow to stern

Foreguy

A line led forward and down to restrain the spinnaker pole.

29. When the Wind Moves Aft — Hold the windward corner away from the mast

Foremast

The foremast is ahead of the mainmast and carries its own principal foresail in the selected schooner.

24. Spread the Work Across a Schooner — Put the foremast ahead of the main

Forepeak

The forepeak is the narrowing forward-end space within the converging bow boundaries.

40. A Deck with Openings — Step from the cockpit into the cabin

Foresail

On a sloop, often the headsail; on a schooner or square-rigger, a principal sail of the foremast. Context is essential.

20. Use the Space Ahead of the Mast — Put a separate sail on the forward support

Foresail — headsail sense

Foresail used for a sloop headsail.

20. Use the Space Ahead of the Mast — Put a separate sail on the forward support

Foresail — schooner

Foresail identifies the principal gaff-supported sail carried on the schooner’s foremast.

24. Spread the Work Across a Schooner — Keep the sail support separate from the mast arrangement

Foresail — square-course sense

Principal lower square sail on the foremast.

25. Build Height, Divide Sail — Put the sails between their supports

Forestay

The forestay leads from mast towards bow, supplying forward restraint and sometimes a separate headsail-supporting job.

12. Hold Up the Mast — Support the mast fore and aft

forestay sag

With fixed endpoints and the same transverse sail load, higher stay tension can oppose that load with less directional deflection.

28. Shape Is a Control — Change the supporting curve

Forestay sag versus sail draft

Forestay sag changes the leading support, while sail draft is measured through a local cloth section against its chord.

28. Shape Is a Control — Change the supporting curve

Foretriangle

The triangular reference space ahead of the mast, commonly defined by the mast and principal forestay geometry.

20. Use the Space Ahead of the Mast — Measure the sail that extends aft

Fork terminal

A fork terminal surrounds its mating fitting with two sides and transmits the pull through a transverse pin.

34. Why Hull Shapes Behave Differently — Let pressure recover and account for the waves

Form drag

The chapter bounds form drag to viscous shape/separation and its resulting pressure contribution.

Form stability

Resistance to heeling arising from hull shape and how buoyancy moves as the boat tilts.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Forward lift

A line supporting the forward part of a junk sail’s lowered spars and bundle.

19. A Sail Divided by Battens — Receive the lowered sail

Forward lower

The forward lower leads to a hull point ahead of the mast, adding forward restraint to its lower-region side support.

12. Hold Up the Mast — Restrain a slender member between its ends

Forward overhang

The bow’s projection forward of the front end of the waterline.

3. Give the Hull a Shape — Several ways to finish the hull

Forward spring

Under the stated Navy lead convention, a forward spring leads forward from its boat attachment and opposes movement astern.

42. Hold the Boat Alongside — Give each line a direction

Foul / snag

A catch stops travel, distinguishing obstruction from abrasion even though subsequent loading can cause both.

8. What a Rope Is Made to Do — Keep the line able to run

Four-masted schooner

Four principal mast positions; Santa Maria Manuela’s2023 rig has gaff lower sails and gaff topsails at each plus forward headsails.

24. Spread the Work Across a Schooner — Extend the distribution along the hull

Fractional rig

A rig whose principal headsail stay attaches below the masthead; this describes stay geometry, not the number of masts.

22. One Mast, Several Sail Plans — Move the upper attachment

Fractional sloop

A sloop whose principal headsail stay attaches below the masthead.

22. One Mast, Several Sail Plans — Move the upper attachment

Frame

A frame follows and supports a transverse shell section; adjoining planking and lengthwise members carry its loads farther.

6. Give the Water Something to Push Against — Give the water force a surface

Frame timber

A frame timber is an individual wooden piece making all or part of a transverse frame.

32. Build a Hull from Joined Pieces — Make a frame follow the hull

Free-standing rig

A rig whose mast or masts stand without conventional external supporting stays and shrouds.

36. Stability Has a Range — Let liquid move and follow the water entry

Free-surface effect

Liquid redistributes towards the lowered side of a partly filled space, reducing the effective restoring separation.

Freeboard

The vertical distance from the waterline to a specified deck edge or other defined reference on the hull.

2. Why a Hull Floats — Loading changes the waterline

Freeing port

A freeing port is a low bulwark opening through which substantial shipped water can escape; a grid or flap must preserve that route.

40. A Deck with Openings — Give exposed water a route out

Friction

Friction at contacting solids, including useful grip; internal fluid resistance is a related but separately explained sense.

4. One Mast, One Sail — Raise the head, control the clew

Friction: fluid surface shear

Friction between moving air and the surface adds a load along the surface, called viscous shear. This is the fluid-surface form of friction, related to the way layers of fluid and the surface move relative to each other.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Friction: solid contact

There is friction, resistance to relative motion, where contacting surfaces rub. A turning sheave lets the rope travel without simply scraping around a fixed corner, although the rope bends and the wheel’s bearing still has losses.

4. One Mast, One Sail — Raise the head, control the clew

Froude number

Speed divided by the square root of gravity times chosen length gives a unitless gravity/inertia comparison; the stated example is about 0.303.

34. Why Hull Shapes Behave Differently — Compare speed with length

Fulcrum / pivot

The support or axis about which a lever turns.

1. A Boat Before Sail — Give the oar somewhere to bear

full furl/stow

All cloth wrapped around the support has reached the stowed state, with the line, foil and swivel transmitting the required motion.

30. Reduce, Gather or Replace the Sail — Roll a supported edge

Full keel

A keel extending along much of the hull’s underwater length, often blended into the hull and historically associated with an attached rudder.

35. Keels, Ballast and Adjustable Draught — Spread the keel along the boat or concentrate it

Full-batten

Describes a sail using battens spanning essentially from luff to leech.

14. Attach and Support the Sail — Support an edge, then span the sail

Full-length batten

A batten running essentially all the way from the luff to the leech.

14. Attach and Support the Sail — Support an edge, then span the sail

Full-rigged ship / ship rig

Ship rig applies square rig to each of three or more principal masts under the selected modern convention.

26. Read the Whole Square or Mixed Rig — Repeat the square-rigged mast

Fully submerged foil

A foil operating below the surface, usually requiring another means of controlling flight height.

39. Move Mass, Add Foils — Separate the lifting wing from the surface crossing

Furl

Gather or roll a sail into a secured, non-working state.

7. Why the Boat Leans and Wants to Turn — Reduce the load, then change the wind side

Furling drum

The Furlex drum stores operating-line turns and converts an unwinding pull into foil rotation.

30. Reduce, Gather or Replace the Sail — Roll a supported edge

Furling foil

The grooved extrusion surrounds the wire stay and receives the luff tape, so its rotation carries the attached sail edge.

30. Reduce, Gather or Replace the Sail — Roll a supported edge

Furling line

Pulling the line off the Furlex drum rotates the connected foil and wraps its attached luff; deployment reverses the motion and restores drum turns.

30. Reduce, Gather or Replace the Sail — Roll a supported edge

Furling swivel

The bearing connects a sail-side rotating lower attachment to the halyard-side upper attachment while carrying tension.

30. Reduce, Gather or Replace the Sail — Roll a supported edge

Furling versus reefing

Full gathering into storage and a supported smaller working sail are separate outcomes whose mechanisms can overlap only where designed to do so.

30. Reduce, Gather or Replace the Sail — Roll a supported edge

Futtock

A futtock supplies one segment between the floor region and the frame’s upper portion.

32. Build a Hull from Joined Pieces — Make a frame follow the hull

Futtock plate

A metal connection transferring loads from upper shrouds or deadeyes into the futtock-shroud arrangement.

25. Build Height, Divide Sail — Continue the pull below the platform

Futtock shroud

A short support carrying the outer edge of a traditional mast-top platform’s rigging loads down towards the lower mast.

Related labels and senses: Futtock shrouds.

25. Build Height, Divide Sail — Continue the pull below the platform

Gaff

The sloping spar supporting the upper edge of a four-sided fore-and-aft sail.

17. What the Gaff Adds

Gaff jaws

The forked or curved fitting at a gaff’s inner end that fits around the mast.

17. What the Gaff Adds — Retain the inner end without fixing it

Gaff rig

A rig using a four-sided fore-and-aft sail with its upper edge supported by a gaff.

17. What the Gaff Adds

Gaff saddle

A bearing arrangement supporting the gaff at the mast while allowing the required movement.

24. Spread the Work Across a Schooner — Keep the sail support separate from the mast arrangement

Gaff schooner

Gaffs support the heads of the schooner’s principal fore-and-aft sails.

Gaff topsail

A sail filling space above a gaff sail.

17. What the Gaff Adds — Fill the space above the gaff

Gaff topsail

If the mast extends above the gaff’s throat, another sail can occupy the opening between that upper mast and the sloping gaff. This is a gaff topsail: a topsail in the fore-and-aft, above-the-gaff sense. It is a separate surface, with its own head, tack and clew. A square topsail instead spreads on a transverse yard above a lower square sail. That supported stack will need its own explanation later.

17. What the Gaff Adds — Fill the space above the gaff

Gaff vang

A line controlling a gaff’s lateral movement, rather than the lower boom’s rise.

26. Read the Whole Square or Mixed Rig — Separate the boat’s work from its rig

Galleon

Galleon is a dated trading/war vessel family with the selected elongated hull and square fore/main, lateen mizzen arrangement.

Galley

A vessel type relying substantially on banks of oars, often also carrying sails.

33. Change the Material, Keep the Jobs — Follow the environment into the connection

Galvanic corrosion

Accelerated corrosion associated with electrically connected dissimilar metals in an electrolyte such as seawater.

Gammon iron

A metal fitting doing the securing job otherwise performed by bowsprit lashings.

21. Move the Sail Beyond the Bow — Hold the inner end and restrain the outer one

Gammoning

Lashings securing a traditional bowsprit down to the bow structure.

21. Move the Sail Beyond the Bow — Hold the inner end and restrain the outer one

Garboard / garboard strake

The garboard or garboard strake is the shell course immediately beside the keel.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Gasket

A sail gasket binds the gathered cloth to its spar so the compact bundle stays contained.

30. Reduce, Gather or Replace the Sail — Secure the bundle and the loose lines

Gelcoat

A resin-rich outer finish applied to a moulded composite surface.

33. Change the Material, Keep the Jobs — Specify the structure, then make it

Gennaker

A commercial or informal name for an asymmetric downwind or reaching sail; not a single universally standardised design.

29. When the Wind Moves Aft — Choose the shape as well as the name

Genoa

An overlapping headsail whose clew extends aft of the mast region; percentage overlap needs a defined foretriangle reference.

20. Use the Space Ahead of the Mast — Measure the sail that extends aft

Genoa halyard

The line or tackle that raises and lowers a genoa.

20. Use the Space Ahead of the Mast — Give each unit its own controls

Genoa sheet

A line controlling a genoa’s clew and sail setting.

20. Use the Space Ahead of the Mast — Give each unit its own controls

Genoa track

The genoa track guides and retains the car carrying the genoa sheet’s first block, with reactions transmitted through track fastenings.

20. Use the Space Ahead of the Mast — Choose the forward inventory

Ghoster

A very light-weather sail, commonly a lightweight headsail; usage overlaps drifter.

Girder

A substantial beam supporting structure or spreading concentrated loads.

33. Change the Material, Keep the Jobs — Join plates into a supported shell

Glass cloth

Woven glass-fibre fabric used as composite reinforcement.

33. Change the Material, Keep the Jobs — Place fibres where the load must travel

Glass-reinforced plastic / GRP / fibreglass

A composite made from glass fibres in a resin matrix.

33. Change the Material, Keep the Jobs — Specify the structure, then make it

Gnav

The RS500 gnav is an above-boom strut between a mast bracket and a forward-hauled boom slider; its compression produces a downward reaction on that slider.

28. Shape Is a Control — Give boom rise its own restraint

Gollywobbler

A large light inter-mast sail; Mayan’s2015 example has a foremast-foot tack and two masthead hoists.

24. Spread the Work Across a Schooner — Add cloth high between the masts

Gooseneck

The articulated connection between boom and mast.

4. One Mast, One Sail — Corners, edges and a moving boom

Gooseneck fitting

The joint connecting a boom to a mast while allowing required movement.

4. One Mast, One Sail — Corners, edges and a moving boom

Goosewinged / wing-and-wing

Sailing downwind with principal sails spread to opposite sides.

29. When the Wind Moves Aft — Hold an ordinary headsail out instead

Grapnel

An anchor or grappling device with several projecting hooks or arms.

41. Hold the Boat to the Seabed — Change the part that turns into the ground

Gravity

Gravity and the everyday downward weight of a held object.

36. Stability Has a Range — Describe the motion and the sea separately

Green water

A body of water comes aboard and applies weight and moving-water loads to the deck and its boundaries.

Grommet

Initial N01 rope-ring sense; reinforcing-hole-eye sense explicitly retained for the later N12B owner.

1. A Boat Before Sail — Give the oar somewhere to bear

Grommet — reinforced eye

A small reinforced opening is commonly called an eyelet. Grommet can identify the reinforcement surrounding such a hole, especially a fitted metal eye. In that arrangement the line bears on the smooth inner metal surface, the fitting bears on its surrounding reinforced cloth, and the cloth transfers the pull farther into the sail. The hole is the passage; its grommet is the local reinforcing fitting.

14. Attach and Support the Sail — Spread the pull beyond the hole

Grommet as rope ring

A ring made from rope is a grommet.

1. A Boat Before Sail — Give the oar somewhere to bear

Ground tackle

The anchor, its chain or rope, and the fittings used to connect, handle and secure them.

41. Hold the Boat to the Seabed

Grounding

Contact between the vessel and the seabed or another submerged surface.

35. Keels, Ballast and Adjustable Draught — Change the direction of the load

Grounding load path

The route by which impact at a keel or hull contact is transferred into the supporting structure.

35. Keels, Ballast and Adjustable Draught — Change the direction of the load

Gudgeon

A socket or eye in a hinge fitting that receives a pintle.

6. Give the Water Something to Push Against — A blade that can turn the boat

Gun tackle

The selected gun tackle uses one moving and one fixed single block to obtain two supporting tensions with a downward haul.

11. Trade Force for Distance — Make the block move with the load

Gunter rig

A rig with a near-vertical upper spar that raises the sail above the lower mast, often allowing shorter spars when lowered.

17. What the Gaff Adds — Raise the upper spar nearer upright

Gunter yard

The near-vertical upper spar of a gunter rig.

17. What the Gaff Adds — Raise the upper spar nearer upright

Gunwale / gunnel

Gunwale or gunnel denotes the upper hull-side edge or its reinforcing member, receiving local loads at an otherwise flexible open shell.

1. A Boat Before Sail — Give the oar somewhere to bear

Gust

A temporary increase in wind speed that can increase sail load before the crew has changed any controls.

5. The Wind the Sail Actually Meets — When the wind changes

Gybe / jibe

A change in which side carries the sail as the wind passes across the stern, unlike a tack through the bow.

7. Why the Boat Leans and Wants to Turn — Reduce the load, then change the wind side

Gypsy

The pocketed wheel of a windlass that engages anchor-chain links.

41. Hold the Boat to the Seabed — Turn a wheel that matches the chain

Half beam

A half beam stops at the carlin beside an opening rather than crossing the entire hull.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Half-breadth plan

A plan view showing one half of a hull’s symmetrical width and its waterlines.

43. Draw It, Measure It, Compare It — Locate one point on the hull

Halyard / halliard

A line or tackle used to hoist and lower a sail or supporting spar.

4. One Mast, One Sail — Raise the head, control the clew

Halyard exit

The opening where an internally led halyard leaves the mast.

14. Attach and Support the Sail — Enter the groove and manage the opening

Halyard sheave

A grooved wheel guiding a sail-hoisting line, commonly at the masthead.

14. Attach and Support the Sail — Enter the groove and manage the opening

Hand a sail

A traditional expression for taking in and securing a sail.

15. A Sail on a Yard — Gather different parts of the sail

Handedness of thread

Thread handedness makes matched left and right threads advance in opposite senses; opposed ends move together as the body turns.

12. Hold Up the Mast — Turn the adjuster while letting the joint align

Handy billy

A handy billy is a portable tackle attached temporarily where an extra pull is needed.

11. Trade Force for Distance — Add parts, then follow every one

Hanging knee

The hanging knee bolts one arm beneath the beam and another down the side.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Hank

A clip or ring attaching a headsail’s luff to a stay.

14. Attach and Support the Sail — Guide an edge along a stay

Hard chine

A sharply defined change of angle between adjacent hull surfaces.

3. Give the Hull a Shape — Read a slice through the hull

Hatch

A closable opening, commonly in a deck or roof, providing access, light or ventilation.

3. Give the Hull a Shape — A working surface and ways through it

Hatch coaming

A hatch coaming is the raised frame above the supporting hatchway structure, providing the rim against which a closure can fit.

40. A Deck with Openings — Close the lid and the entrance

Hatchway

The opening and passage served by a hatch.

3. Give the Hull a Shape — A working surface and ways through it

Hauling part

The hauling part is the free working length on which the crew pull, drawing rope through the selected route.

11. Trade Force for Distance — Make the block move with the load

Hawsehole

An opening through which an anchor cable or other heavy line passes.

41. Hold the Boat to the Seabed — Bring the rode across the bow

Hawsepipe

A lined passage carrying an anchor chain or cable through the hull or deck structure.

41. Hold the Boat to the Seabed — Bring the rode across the bow

Hawser

The hawser is the substantial working rope used here for mooring or towing; its size and load-bearing role explain why a lighter line may be sent first.

42. Hold the Boat Alongside — Bring a manageable line to the attachment

Head

The upper corner of a triangular sail; on a four-sided sail, its upper edge. The meaning follows the sail’s geometry.

4. One Mast, One Sail — Corners, edges and a moving boom

Head — four-sided sail

The square sail’s head is its upper edge, extending along the yard. On the earlier triangular sail, head identified its upper corner; this four-sided sail has an upper edge between two corners. The two side edges are its leeches; the bottom remains the foot, and the two lower corners are clews. On an oblique course, the windward side edge can act as the sail’s leading edge. The names describe parts of this supported surface without requiring the sail to keep facing directly aft.

4. One Mast, One Sail — Corners, edges and a moving boom

Head: triangular corner

Upper corner of a triangular sail.

Headboard

A stiff reinforcement at the head of a sail, spreading the halyard load.

14. Attach and Support the Sail — Give different attachments their own reinforcement

A wind shift that makes a given sailing heading closer to the wind, often making an upwind course less favourable.

5. The Wind the Sail Actually Meets — When the wind changes

Headfoil

A grooved foil around the headstay for hoisting and supporting a headsail.

14. Attach and Support the Sail — Guide an edge along a stay

Heading

The direction in which the bow points.

5. The Wind the Sail Actually Meets — Choose the observer

Heading up / luffing up

Turning the bow closer towards the direction from which the wind comes.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Headsail

A sail set forward of the principal mast, commonly a jib, genoa or staysail.

20. Use the Space Ahead of the Mast — Put a separate sail on the forward support

Headstay

Headstay is the stated overlapping name for the principal forward forestay, especially when it also supports a headsail.

12. Hold Up the Mast — Support the mast fore and aft

Headstay furler

The headstay furler combines a lower drive, rotating foil around the forestay and upper swivel to gather the attached headsail.

30. Reduce, Gather or Replace the Sail — Roll a supported edge

Headstay sag

Headstay sag is the loaded forestay’s sideways/aft displacement from its endpoint reference line.

28. Shape Is a Control — Change the supporting curve

Heave

The hull translates up and down while a pure heave leaves its angle unchanged.

36. Stability Has a Range — Describe the motion and the sea separately

Heave to / hove to

Set sails and steering to maintain a slow, relatively steady drifting condition; suitable arrangements differ between boats.

31. Turn, Stop and Rebalance — Arrange a slow balance

Heaving line

The heaving line is a lighter line that can be sent across the gap and used to draw over a heavier working rope or intermediate messenger.

42. Hold the Boat Alongside — Bring a manageable line to the attachment

Heel

The boat’s sideways tilt, commonly under wind load; distinguish it from a persistent list caused by weight distribution.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Heel fitting

A fitting supporting or locating the lower end of a rudder or other upright component.

18. The Tall Triangle — Compare a material, then its finished mast

Heeling force

The part of the wind’s loading that contributes to tilting the boat when acting above its opposing underwater force.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Helm

The steering equipment, steering station or person steering, depending on context.

6. Give the Water Something to Push Against — A blade that can turn the boat

Helm: equipment

The steering control/equipment being operated.

6. Give the Water Something to Push Against — A blade that can turn the boat

Helm: person

The person operating the steering.

6. Give the Water Something to Push Against — A blade that can turn the boat

Helm: station

The place from which the boat is steered.

6. Give the Water Something to Push Against — A blade that can turn the boat

Hem

A folded and secured fabric edge preventing fraying and adding local strength.

14. Attach and Support the Sail — Finish and reinforce an edge

Hemp cordage

Stem fibres and their preparation supplied a historical cordage material; the later construction comparison holds lay fixed while changing fibre.

8. What a Rope Is Made to Do — Different fibres, different useful properties

Hermaphrodite brig / schooner brig

Hermaphrodite brig and schooner brig combine the square forward unit with a schooner’s after fore-and-aft rig in the specified dated sources.

26. Read the Whole Square or Mixed Rig — Read a period description in its own terms

High-peaked gaff

A gaff set at a steep angle, giving a taller sail outline; the distinction from gunter is not simply a universal angle.

17. What the Gaff Adds — Raise the upper spar nearer upright

Hiking

Moving crew weight outboard while remaining supported by the boat to oppose heel.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Hinged batten

A batten built in jointed sections whose controlled angles help create sail camber.

19. A Sail Divided by Battens — Form the curve between battens

Hitch

The object is part of the fastening’s working contact, explaining why removal of that support can collapse the arrangement.

9. Join Ropes and Make Attachments — Fasten to something solid

Hog / hog timber

The hog lies above the keel and receives lower frames across its wider surface.

32. Build a Hull from Joined Pieces — Connect the bottom and the ends

Hogging

Lengthwise bending that raises a hull’s middle relative to its ends.

32. Build a Hull from Joined Pieces — Connect the bottom and the ends

Hoist

Raise a sail or spar.

4. One Mast, One Sail — Raise the head, control the clew

Holding ground

The seabed material and condition in which an anchor must grip.

41. Hold the Boat to the Seabed — Hold in a particular bottom

Hollow wooden mast

A wooden mast with an internal cavity, reducing weight compared with a solid section of similar outside size.

18. The Tall Triangle — Build a long spar from wood

Hong Kong parrel

A diagonal inter-batten restraint used to control junk-sail panel alignment; its loads and details need rig-specific explanation.

19. A Sail Divided by Battens — Locate the yard and the panel diagonals

Hood end

A hood end is the terminating plank end seated and fastened into the stem or sternpost rabbet in the selected example.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Hook

The attached eye bears deep in an open curved body; slack and altered direction can move it towards the unclosed mouth.

10. Hold the Load, Keep Control — Retain the opening, then decide how it releases

Horn cleat

Base contact, crossed horn turns and a retaining hitch transfer load away from the hand in distinct stages.

10. Hold the Load, Keep Control — Let the hands leave the rope

Horn timber

The horn timber projects aft over the sternpost/deadwood from a supported forward region.

32. Build a Hull from Joined Pieces — Give the projecting stern its own supports

Horse / sheet horse

Smyth’s sheet horse is a transverse iron bar secured at its ends, with the sheet attachment travelling along it; his foresheet uses a ring.

28. Shape Is a Control — Choose a route and share its load

Hounds

The region or fittings near an upper mast attachment where major rigging bears or is secured.

25. Build Height, Divide Sail — Give the upper mast a seat

Hull

The boat’s main body: the structure that keeps the water out and carries people, equipment and loads.

1. A Boat Before Sail

Hull draft / draught (depth)

The vertical distance from the waterline to the lowest included point of the boat.

Related labels and senses: Draft / draught; Other senses: Sail draft / draught (shape).

2. Why a Hull Floats — Loading changes the waterline

Hull liner

An inner moulded component lining the hull; it may be decorative, structural or both.

33. Change the Material, Keep the Jobs — Bond the interior into the hull

Hull resistance

Water opposition to hull advance combines surface-force contributions; at steady speed driving and opposing components balance.

34. Why Hull Shapes Behave Differently — Follow the flow next to the surface

Hull skin

Hull skin names the outer structural shell; the wooden example’s planking participates in load transfer rather than merely enclosing air.

12. Hold Up the Mast — Continue the load beyond the fitting

Hull speed

The conventional reference sets deep-water gravity wavelength equal to LWL, giving about 7.7 knots for 10 metres and the familiar feet/knots coefficient.

34. Why Hull Shapes Behave Differently — Compare speed with length

Human effort and purchase

A person supplies mechanical work directly or through leverage, gearing and purchase; reduced input force requires more motion and does not supply free energy.

11. Trade Force for Distance — Make the block move with the load

Human power versus assisted power

A comparison of who supplies the energy; a purchase reduces effort but is not a substitute for a motor’s energy source.

37. From the Hand to the Rudder — Transmit the movement through fluid

Hydraulic accumulator

A device storing pressurised fluid energy for later demand.

44. When Muscle Is Not Enough — Store energy as well as rope

Hydraulic pump

A device moving liquid and supplying energy to a hydraulic circuit.

37. From the Hand to the Rudder — Transmit the movement through fluid

Hydraulic ram / cylinder

An actuator that converts liquid pressure into straight-line push or pull.

27. Rearrange the Whole Rig — Give the aerodynamic surface thickness

Hydraulic steering

A steering connection transmitting wheel or control movement through pressurised fluid.

37. From the Hand to the Rudder — Transmit the movement through fluid

Hydraulic system

A power system transmitting force through pressurised liquid to an actuator.

37. From the Hand to the Rudder — Transmit the movement through fluid

Hydraulic winch

A winch driven by a hydraulic motor rather than only by hand.

44. When Muscle Is Not Enough — Carry the work through liquid

Hydrofoil

A shaped surface producing useful force in water, whether sideways resistance or upward support.

6. Give the Water Something to Push Against — The other moving fluid

Hydrolysis

Chemical breakdown involving water, relevant to some polymers and resins.

33. Change the Material, Keep the Jobs — Follow the environment into the connection

Hydrostatics

The study of fluid at rest and the buoyancy and balance of floating bodies.

43. Draw It, Measure It, Compare It — Add the immersed slices

I

A vertical foretriangle measurement used in rig drawings and rating systems; its exact endpoints depend on the convention.

43. Draw It, Measure It, Compare It — Measure the space for the sails

In irons

Stopped or nearly stopped with the bow too close to the wind for the sails to drive the boat normally.

31. Turn, Stop and Rebalance — When the tack does not complete

In-boom furling

A bearing-supported horizontal mandrel within the stationary boom receives the foot boltrope and winds the cloth while the halyard lowers its head.

30. Reduce, Gather or Replace the Sail — Roll a supported edge

In-line spreader

An in-line spreader’s root-to-tip direction is approximately athwartships; the shroud’s remaining route completes its restraint geometry.

12. Hold Up the Mast — Restrain a slender member between its ends

In-mast furling

A vertical extrusion in the mast’s after compartment turns the attached luff while the clew outhaul deploys cloth through the slot.

30. Reduce, Gather or Replace the Sail — Roll a supported edge

Inboard

Inboard: towards centreline and within the hull, assessed separately in the diagnosis.

3. Give the Hull a Shape — Locate a part, locate another boat

Inboard as direction

inboard, towards that centreline

3. Give the Hull a Shape — Locate a part, locate another boat

Inboard as hull-boundary location

The same words can describe whether something is within the hull or outside it.

3. Give the Hull a Shape — Locate a part, locate another boat

Induced drag

Drag associated with producing lift on a finite-span foil, including its three-dimensional wake and tip-flow effects.

18. The Tall Triangle — Follow the flow around the end

Inertia

The tendency of a mass to resist changes in its motion.

7. Why the Boat Leans and Wants to Turn — Steady motion and changing motion

Inhauler

An inhauler draws a movable sheet guide inboard on a separately hauled and retained line while the sheet runs through it.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Initial stability

Resistance to small departures from upright, not a complete description of capsize resistance.

Inner forestay

A forward stay positioned inside the principal outer forestay.

20. Use the Space Ahead of the Mast — Put a separate sail on the forward support

Inner skin

The inside structural layer of a sandwich panel.

33. Change the Material, Keep the Jobs — Separate two skins and connect them

Inner staysail

A staysail set inside an outer headsail.

20. Use the Space Ahead of the Mast — Put a separate sail on the forward support

Intermediate shroud

The intermediate shroud restrains an intermediate mast region; its endpoints identify the length supported.

12. Hold Up the Mast — Restrain a slender member between its ends

Internal ballast

Ballast carried within the hull rather than in an external appendage.

35. Keels, Ballast and Adjustable Draught — Put the mass inside or outside

Invention distinction

An invention claim concerns the creation of an arrangement; a surviving object or recorded name supplies bounded evidence and may be much later than that creation.

36. Stability Has a Range — Follow the arm beyond the first lean

Inversion / turtling

The upside-down orientation places the rig beneath the hull and is called turtling in small-sailing-boat usage.

Inwale

An inwale reinforces the inside of the upper hull edge; CLC’s spaced blocks and bonded contacts tie the strip to the side panel.

40. A Deck with Openings — Follow the upper hull edge

Iron (ballast metal)

A metal used for ballast castings; distinguish its properties and volume from lead.

35. Keels, Ballast and Adjustable Draught — Put the mass inside or outside

Iron keel

A ballast keel made largely from iron, often cast; its volume and corrosion behaviour differ from lead.

35. Keels, Ballast and Adjustable Draught — Put the mass inside or outside

J

The horizontal foretriangle base measurement between mast and forward tack or stay reference under a stated convention.

20. Use the Space Ahead of the Mast — Measure the sail that extends aft

J-foil

A curved foil combining lateral and vertical force components.

39. Move Mass, Add Foils — Let the curve decide what emerges from the case

Jackstay (deck safety)

A deck-safety jackstay carries the moving tether connection along its working length; webbing tension reaches actual end loops or adjuster and deck fittings.

Related labels and senses: Jackstay; Other senses: Jackstay (spar fitting).

Jackstay (spar fitting)

A rod or line along a spar used to attach sails or fittings; distinct from a modern deck-safety line.

Related labels and senses: Jackstay; Other senses: Jackstay (deck safety).

17. What the Gaff Adds — Fill the space above the gaff

Jackyard

A light spar used to extend a topsail beyond the support otherwise available; traditional arrangements differ.

Jackyard topsail

A topsail extended by additional light spar support beyond the ordinary gaff-and-mast opening.

17. What the Gaff Adds — Fill the space above the gaff

Jam cleat

A narrowing groove wedges the rope between stationary gripping surfaces until it is lifted clear.

10. Hold the Load, Keep Control — Grip the line between surfaces

Jammer

In the specified manufacturer’s distinction, another device must take the load before the gripping parts can release.

10. Hold the Load, Keep Control — Grip the line between surfaces

Jaw rope

A rope closing the open side of traditional spar jaws around the mast.

17. What the Gaff Adds — Retain the inner end without fixing it

Jib

A forward sail, usually triangular and supported along its luff by a stay; distinguish its geometry from overlapping genoas.

20. Use the Space Ahead of the Mast — Put a separate sail on the forward support

Jib halyard

The line or tackle that raises and lowers a jib.

20. Use the Space Ahead of the Mast — Give each unit its own controls

Jib inhaul

A line bringing a jib attachment inward for handling or adjustment.

21. Move the Sail Beyond the Bow — Move the attachment, or move the whole spar

Jib outhaul

A line moving a jib attachment outward, such as towards the end of a bowsprit.

21. Move the Sail Beyond the Bow — Move the attachment, or move the whole spar

Jib sheet

A line controlling the jib’s clew and its setting relative to the wind.

20. Use the Space Ahead of the Mast — Give each unit its own controls

Jib topsail

A light upper or outer headsail in some traditional yacht rigs; identify its actual attachment points.

21. Move the Sail Beyond the Bow — Distinguish the sail above from the sail below

Jib track

A jib track guides the adjustable first lead for the smaller headsail’s sheet; the Navy route uses a forward car before its aft turning car.

21. Move the Sail Beyond the Bow — Move the attachment, or move the whole spar

Jib traveller

A moving ring or fitting on a bowsprit used to position a jib’s attachment.

Jibboom / jib-boom

A spar extending forward beyond a traditional bowsprit to carry further headsail attachments.

Related labels and senses: Jibboom.

21. Move the Sail Beyond the Bow — Extend the projection in stages

Jibboom guy

A lateral support controlling or restraining a jibboom.

21. Move the Sail Beyond the Bow — Spread the side restraints

Jibstay

The stay carrying or supporting a jib.

21. Move the Sail Beyond the Bow — Extend the projection in stages

Jiffy reefing

Jiffy reefing is the Catalina manual’s name for a readily operated slab arrangement, not a prescribed one-tail route.

30. Reduce, Gather or Replace the Sail — Route the reef controls

Joining shackle

A connector used to join chain lengths or associated fittings.

41. Hold the Boat to the Seabed — Join the anchor to the boat

Jumper stay

The jumper stay’s wire runs from an upper mast point over a strut and back towards a lower point, pulling against the compressed offset support.

12. Hold Up the Mast — Support the mast fore and aft

Jumper strut

A jumper strut maintains an upper wire’s offset in compression, so the tensioned returning wire braces a mast region.

12. Hold Up the Mast — Support the mast fore and aft

Junk (vessel)

A broad historical vessel designation, distinct from the junk-rig sail system that can be fitted to other hulls.

19. A Sail Divided by Battens

Junk ketch / junk schooner

Junk ketch combines battened sails with forward main/after smaller mizzen; junk schooner combines them with smaller fore/larger after main.

24. Spread the Work Across a Schooner — Put the battened sail on either arrangement

Junk rig

A rig with fully battened sails and sheets distributed to several battens; mast count is a separate classification.

19. A Sail Divided by Battens

Junk sail

A fully battened sail whose sheets distribute control to several battens along the leech.

19. A Sail Divided by Battens

Kedge / kedge anchor

A smaller anchor used to help move, position or supplement the holding of a vessel.

41. Hold the Boat to the Seabed — Use the holding point to move the boat

Kedging

Using an anchor laid away from the boat to help pull or reposition the vessel.

41. Hold the Boat to the Seabed — Use the holding point to move the boat

Keel

Either the hull’s main lengthwise backbone or an underwater appendage providing side-force and sometimes ballast. These jobs must be distinguished.

6. Give the Water Something to Push Against — Give the water force a surface

Keel attachment integrity

The condition of fastenings and surrounding structure that together keep an external keel attached.

35. Keels, Ballast and Adjustable Draught — Keep the complete attachment capable

Keel bolt

A fastening connecting an external keel to the hull structure; several usually share the loads.

35. Keels, Ballast and Adjustable Draught — Follow the fastening into timber

Keel box

The structural housing supporting or enclosing a moving keel and its loads.

39. Move Mass, Add Foils — Change depth by a different motion

Keel case

The case into which a movable keel retracts, with structure to contain water and transmit load.

39. Move Mass, Add Foils — Change depth by a different motion

Keel floor

The keel floor crosses the keel region and connects lower framing, distinct from the cabin walking sole.

12. Hold Up the Mast — Continue the load beyond the fitting

Keel grid

A reinforcing grid specifically arranged to spread keel loads.

33. Change the Material, Keep the Jobs — Bond the interior into the hull

Keel matrix

A connected grid of reinforcing members spreading keel loads into the surrounding hull.

35. Keels, Ballast and Adjustable Draught — Spread a shorter root through the hull

Keel shoe

The keel shoe presents a protective wooden or metal contact piece beneath the keel.

32. Build a Hull from Joined Pieces — Connect the bottom and the ends

Keel stub

The short hull projection to which an external keel may be attached.

35. Keels, Ballast and Adjustable Draught — Spread a shorter root through the hull

Keel sump

A deep local recess at the keel region, often collecting bilge water; construction and terminology vary.

35. Keels, Ballast and Adjustable Draught — Spread a shorter root through the hull

Keel timber

The keel timber is the principal bottom centreline timber forming the structural keel in this wooden example.

12. Hold Up the Mast — Continue the load beyond the fitting

Keel-hung rudder

A rudder hinged or supported along the after end of a keel.

37. From the Hand to the Rudder — Hang the blade where the hull can carry it

Keel-stepped mast

A keel-stepped spar passes through the deck to a lower step, with partners supplying separate lateral restraint above.

12. Hold Up the Mast — Support the heel and restrain the spar

Keel: lateral-force appendage

Projection below the hull that supplies sideways water force and may carry ballast.

6. Give the Water Something to Push Against — Give the water force a surface

Keel: structural backbone

Bottom-centreline lengthwise structural member.

6. Give the Water Something to Push Against — Give the water force a surface

Keelson

The internal keelson runs above the keel and connects the bottom structure along the boat; its presence varies by construction.

12. Hold Up the Mast — Continue the load beyond the fitting

Ketch

Taller forward mainmast and smaller after mizzenmast, ahead of the rudder stock under the stated convention.

23. Put a Smaller Sail Aft — Name the two arrangements

Kicker

Kicker is the British usage for the described boom-vang control restraining boom rise.

28. Shape Is a Control — Give boom rise its own restraint

Kicking strap

Kicking strap names the described under-boom restraining control, including a rope tackle arrangement.

28. Shape Is a Control — Give boom rise its own restraint

King plank

A king plank lies along the deck centreline and can receive adjacent plank ends.

32. Build a Hull from Joined Pieces — Close the deck without fragile ends

Knee

A knee’s two connected arms spread fastenings away from the junction and resist changing angle.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Knockdown

A severe often temporary heel towards horizontal identifies a knockdown without asserting complete inversion.

36. Stability Has a Range — Distinguish overturning from recovery

Knot (rope)

Own-rope bends and contacts provide holding, joining, binding or stopping action; different load paths tighten different contacts.

9. Join Ropes and Make Attachments

Knot (speed)

One nautical mile per hour; unrelated to the tied-rope meaning of knot.

5. The Wind the Sail Actually Meets — Choose the observer

L-foil

A foil with a bent or angled lower portion providing both side-force and upward lift.

39. Move Mass, Add Foils — Let the curve decide what emerges from the case

Laminar flow

Laminar flow has orderly neighbouring layers with relatively limited cross-layer mixing.

34. Why Hull Shapes Behave Differently — Follow the flow next to the surface

Laminate

A material built from bonded layers; in boats, often reinforcing fibres held in resin.

13. Give the Sail Its Shape — Bond a surface around reinforcement

Laminate schedule

The specification of a laminate’s layers, materials, orientations and amounts.

33. Change the Material, Keep the Jobs — Specify the structure, then make it

Landing

The land or landing is the width of bearing contact in the plank overlap.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Lanyard

The lanyard is a short securing/tensioning line that repeatedly crosses between deadeye holes and is hauled then secured.

Related labels and senses: Lanyards.

12. Hold Up the Mast — Adjust a connection made from rope and iron

Lap

The lap is the physical overlap between adjacent clinker planks.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Large-angle stability

Substantial heel changes the immersed geometry and the resulting restoring or overturning arm.

36. Stability Has a Range — Follow the arm beyond the first lean

Lark’s head

The common alternate name is tied to the cow-hitch bight-through-bight geometry and the role of both outgoing parts.

9. Join Ropes and Make Attachments — Fasten to something solid

Lashing

Repeated rope turns hold the components over their contact, with end retention and unequal turn tensions still affecting the attachment.

10. Hold the Load, Keep Control — The eye and the structure behind it

Lateen rig

A rig with a triangular sail carried on a long sloping yard; its history should not be reduced to one unsupported origin story.

16. Sloping Yards and Diagonal Spars — Suspend a long sloping edge

Lateen sail

A triangular sail carried by a long sloping yard.

16. Sloping Yards and Diagonal Spars — Suspend a long sloping edge

Lateen yard

The long sloping yard carrying a lateen sail.

16. Sloping Yards and Diagonal Spars — Suspend a long sloping edge

Lateral plane

The underwater side-view area contributing to sideways resistance; projected area is only a simplification of real flow.

6. Give the Water Something to Push Against — Give the water force a surface

Lay

The strand helix and alternating manufacturing twists give the assembled rope a stable arrangement.

8. What a Rope Is Made to Do — From fibres to a working line

Lazarette

A lazarette in the selected modern yacht usage is an after storage compartment commonly reached from deck or cockpit.

40. A Deck with Openings — Step from the cockpit into the cabin

Lazy guy

The currently unloaded guy, ready to become the working line after a gybe.

29. When the Wind Moves Aft — Hold the windward corner away from the mast

Lazy sheet

The sheet currently unloaded on a sail with two sheets.

29. When the Wind Moves Aft — Hold the windward corner away from the mast

Lazyjack

Upper mast-supported lines and lower branches to separated boom positions form a cradle on each side of descending cloth.

30. Reduce, Gather or Replace the Sail — Catch the lowered sail

Lead (ballast metal)

A dense metal used to concentrate ballast weight in a relatively small volume.

35. Keels, Ballast and Adjustable Draught — Put the mass inside or outside

Lead (geometric offset)

The fore-and-aft separation of chosen sail and underwater-force centres; distinct from the metal pronounced led.

Related labels and senses: Lead.

7. Why the Boat Leans and Wants to Turn — Locate the combined water force

Lead angle

Lead angle specifies the direction along which the control pulls against an identified reference, with across-boat and downward components in this example.

28. Shape Is a Control — Trace the mainsheet to the boat

Lead block

A lead block redirects a working line towards a useful position.

11. Trade Force for Distance — Lead the rope where it is useful

Lead car

The lead car holds the sheet block on the track, retained by a pin or by a separately controlled purchase.

35. Keels, Ballast and Adjustable Draught — Put the mass inside or outside

Lead keel

A ballast keel using lead for much of its weight; its supporting and attaching structure must also be understood.

Leading edge

The edge of a foil first meeting the relative flow.

39. Move Mass, Add Foils — Give the foil a shape we can describe

Lee helm

A tendency for the boat to turn away from the wind, requiring corrective steering.

7. Why the Boat Leans and Wants to Turn — Why the helm needs a correction

Lee shore

A shore towards which wind is blowing the vessel, reducing room to recover from loss of control.

31. Turn, Stop and Rebalance — Reach the other tack by another route

Leeboard

A board fitted outside a hull’s side to provide lateral resistance, commonly lowered on the leeward side.

6. Give the Water Something to Push Against — Give the water force a surface

Leeboard bracket

The mounting that attaches and supports a leeboard at the hull side.

6. Give the Water Something to Push Against — Give the water force a surface

Leeboard tackle

The rope-and-block arrangement used to raise, lower or restrain a leeboard.

39. Move Mass, Add Foils — Haul a board without making its line the hinge

Leech

The after edge of a fore-and-aft sail; a square sail has two side leeches.

4. One Mast, One Sail — Corners, edges and a moving boom

Leech — square sail

14. Attach and Support the Sail — Support an edge, then span the sail

Leech batten

A shorter batten supporting the after edge of a sail.

Leech hollow

An inward curve cut into a sail’s after edge rather than projecting outward as roach.

13. Give the Sail Its Shape — The edge is part of the shape

Leech length

The measured length of a sail’s after edge under a stated method.

13. Give the Sail Its Shape — Say what was measured

Leech line / leech cord

The leech line or cord lies inside the trailing edge and is retained by a small cleat; the chosen return runs around the clew.

14. Attach and Support the Sail — Finish and reinforce an edge

Leech tape

A reinforcing strip along a sail’s after edge.

Leech tension

The tension acting along a sail’s after edge, influencing its shape and twist.

13. Give the Sail Its Shape — The edge is part of the shape

Leech: after edge

After edge of a fore-and-aft sail.

4. One Mast, One Sail — Corners, edges and a moving boom

Leechline

A line gathering the side of a square sail upwards; distinguish it from the small anti-flutter cord in a modern sail edge.

15. A Sail on a Yard — Gather different parts of the sail

Leeward

The side or direction away from the wind.

5. The Wind the Sail Actually Meets — Give the wind a side

Leeway

Sideways displacement through the water relative to the boat’s heading, usually towards the leeward side.

6. Give the Water Something to Push Against — Where the boat points and where it goes

Left-hand lay

Reversing the visible helix identifies a different construction direction that matters when opening or arranging the rope.

8. What a Rope Is Made to Do — From fibres to a working line

Leg-of-mutton sail

A triangular sail whose outline suggests a leg of mutton; it can occur in different spar arrangements.

16. Sloping Yards and Diagonal Spars — Look beyond the triangular outline

Length between perpendiculars / LBP

Length between defined forward and after reference lines used in ship measurement, not simply the boat’s maximum length.

3. Give the Hull a Shape — Measure the same hull in several ways

Length on deck / LOD

Length measured along the deck-level hull, normally excluding projecting spars; the exact endpoints must be stated.

3. Give the Hull a Shape — Measure the same hull in several ways

Length overall / LOA

Overall length measured under a stated convention; bowsprits, platforms and other projections are not treated identically by all schemes.

3. Give the Hull a Shape — Measure the same hull in several ways

Length waterline / LWL

The length of the hull where it intersects a particular waterline.

3. Give the Hull a Shape — Measure the same hull in several ways

Lever

A rigid member that turns about a support, allowing force and movement to be exchanged.

1. A Boat Before Sail — Give the oar somewhere to bear

Lever arm

The perpendicular distance between a turning axis and a force’s line of action.

7. Why the Boat Leans and Wants to Turn — Force needs a place to act

Lie ahull

Drift without working sail, with the vessel’s response depending on hull, wind and sea.

31. Turn, Stop and Rebalance — Arrange a slow balance

Lifeline / guardwire

A lifeline or guardwire spans between supports as part of the perimeter barrier; deflection increases line tension and transfers reactions to guides, ends and bases.

40. A Deck with Openings — Give the crew supports with identifiable connections

Lift (aerodynamic or hydrodynamic)

The force component perpendicular to local incoming flow; sideways force on a keel is therefore a form of lift.

Related labels and senses: Lift; Other senses: Lift (supporting line).

5. The Wind the Sail Actually Meets — Follow the air, then the force

Lift (supporting line)

A rigging line holding up a yard, boom or other spar.

Related labels and senses: Lift; Other senses: Lift (aerodynamic or hydrodynamic).

15. A Sail on a Yard — Raise it and keep it near the mast

Lift (wind shift)

A wind shift that lets an upwind boat head nearer its destination while keeping the same useful angle to the wind.

5. The Wind the Sail Actually Meets — When the wind changes

Lift-to-drag ratio

Useful perpendicular fluid force divided by force along the flow, under a stated condition.

18. The Tall Triangle — Follow the flow around the end

Lift: aerodynamic component

The component of the sail’s aerodynamic resultant perpendicular to the incoming apparent airflow, which need not point vertically or directly forward.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Lift: hydrodynamic component

Water-force component perpendicular to local incoming flow.

6. Give the Water Something to Push Against — The other moving fluid

Lifting keel

A keel that can be raised to reduce draught; identify whether it lifts ballast, side area or both.

39. Move Mass, Add Foils — Change depth by a different motion

Light displacement

The boat’s displacement in a defined light condition; included equipment, liquids and stores must be specified.

2. Why a Hull Floats — Loading changes the waterline

Limber

A limber is a continuous drainage passage through or past bottom structure; successive aligned openings let internal water reach collection.

40. A Deck with Openings — Collect water without joining every compartment

Limber hole

A limber hole is the opening through a frame or floor that continues the drainage route; the bored and under-floor examples identify the local interface.

40. A Deck with Openings — Collect water without joining every compartment

Line

A general working name for rope used aboard; not evidence that the word rope becomes forbidden on a boat.

4. One Mast, One Sail — Raise the head, control the clew

Linen / flax sailcloth

Sailcloth made from flax fibres, used in various historical contexts.

13. Give the Sail Its Shape — Give the fibres different jobs

Lines plan

A set of drawings describing a hull’s three-dimensional shape through coordinated views and sections.

43. Draw It, Measure It, Compare It — Locate one point on the hull

List

A persistent lean can follow off-centre loading, with a shifted liquid distribution also changing equilibrium and response.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Load cell

A sensor measuring force, useful for monitoring rig and sail-handling loads.

42. Hold the Boat Alongside — Release a connection and interpret a quoted pull

Load path

The route by which a force passes from one component through its connections into the rest of the boat.

2. Why a Hull Floats — Loading changes the waterline

Load waterline

The waterline corresponding to a stated loaded condition; distinguish it from regulatory load-line marks.

load-induced draft migration

A change in the position of a sail’s deepest section caused by its current loading, cloth extension, luff tension and support geometry.

13. Give the Sail Its Shape — Change the load, then repeat the comparison

Load-path sail

A sail with reinforcing fibres arranged to follow anticipated force paths through the cloth or membrane.

13. Give the Sail Its Shape — Arrange reinforcement for the whole sail

Loaded displacement

The total displacement in a stated loaded condition, including the relevant crew, equipment, stores and liquids.

2. Why a Hull Floats — Loading changes the waterline

Loaded waterline

The waterline when the vessel carries a stated load; it changes as weight and trim change.

2. Why a Hull Floats — Loading changes the waterline

Locker

A locker is an enclosed storage space, from an interior cabinet to a compartment accessed through a seat or deck.

40. A Deck with Openings — Step from the cockpit into the cabin

Lodging knee

The lodging knee lies approximately horizontally with arms along beam and side.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Lofting

Laying out a hull’s shape at full size or accurately in a digital equivalent to derive fair construction geometry.

43. Draw It, Measure It, Compare It — Carry the lines into the workshop

Long keel

A keel with a long fore-and-aft footprint; usage overlaps with full keel rather than marking one universal boundary.

35. Keels, Ballast and Adjustable Draught — Spread the keel along the boat or concentrate it

Long splice

Opposite strands occupy vacated helical grooves and finish at staggered positions, distributing the join without one short swelling.

9. Join Ropes and Make Attachments — Join the rope’s own construction

Long ton

A mass of 2,240 pounds, used in some older British marine measurements.

Longitudinal

Longitudinal identifies a fore-and-aft structural member; stringer and keelson are particular members in that orientation.

12. Hold Up the Mast — Continue the load beyond the fitting

Longitudinal stiffener

A lengthwise reinforcement preventing a plate or shell panel from bending excessively.

33. Change the Material, Keep the Jobs — Join plates into a supported shell

Longship

The longship is a long narrow sail-and-oar vessel associated with warrior transport; Skuldelev 2 supplies a dated clinker example.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Loop

Crossing the sides of a curved rope encloses an opening, distinguished locally from an unsecured doubled bight.

8. What a Rope Is Made to Do — Which part of the rope moves?

Loose-footed sail

A sail whose foot is not attached continuously to a boom, although its tack and clew may still be secured to one.

14. Attach and Support the Sail — Finish and reinforce an edge

Low-friction ring

The ring presents a rounded fixed passage for the moving rope, with its outer groove receiving the support.

11. Trade Force for Distance — Lead the rope where it is useful

Lower / strike a sail

Bring a sail down from its working position.

4. One Mast, One Sail — Raise the head, control the clew

Lower mast

The principal lower section of a mast built in separate vertical stages.

25. Build Height, Divide Sail — Give the upper mast a seat

Lower shroud

The lower shroud pulls from a lower or middle mast attachment, restraining that region rather than only the top.

12. Hold Up the Mast — Restrain a slender member between its ends

Lower topsail

The lower of two sails dividing the traditional topsail area.

25. Build Height, Divide Sail — Divide the largest upper sail

LP / luff perpendicular

The shortest distance from a headsail clew to its luff, used to describe headsail size and overlap.

20. Use the Space Ahead of the Mast — Measure the sail that extends aft

Luff

The leading edge of a fore-and-aft sail. To luff also means to head towards the wind or let the sail’s leading edge flutter.

4. One Mast, One Sail — Corners, edges and a moving boom

Luff car

A car supporting the leading edge of a sail on its track.

14. Attach and Support the Sail — Break the continuous attachment into moving pieces

Luff foil

A grooved support at a sail’s luff that retains the beaded luff tape while allowing it to slide. The headfoil surrounding a headstay is the taught example. Guiding the sail and rotating as part of a furling system are distinct capabilities.

14. Attach and Support the Sail — Guide an edge along a stay

Luff groove

A groove guiding the leading edge of a sail in a mast or headsail foil.

14. Attach and Support the Sail — Keep the luff close while letting it rise

Luff hauling parrel

An adjustable line drawing the luff region towards its intended position relative to the mast.

19. A Sail Divided by Battens — Keep the sail beside its mast

Luff length

The measured length of a sail’s leading edge under a stated method.

13. Give the Sail Its Shape — Say what was measured

Luff parrel

A line constraining the sail’s forward region relative to the mast.

19. A Sail Divided by Battens — Keep the sail beside its mast

Luff rope

A reinforcing or attachment rope along the leading edge of a sail.

14. Attach and Support the Sail — Finish and reinforce an edge

Luff round

Extra curved material along a sail’s luff, used with mast or stay geometry to help develop the intended three-dimensional shape.

13. Give the Sail Its Shape — The edge is part of the shape

Luff tackle

The chosen luff tackle secures the standing end at the moving block and reeves one lower and two upper sheaves.

11. Trade Force for Distance — Add parts, then follow every one

Luff tape

A narrow reinforced strip along a sail’s luff, often carrying the bead that slides into a foil groove.

14. Attach and Support the Sail — Finish and reinforce an edge

Luff tension

The tension along a sail’s leading edge, influencing wrinkles and draft position.

13. Give the Sail Its Shape — The edge is part of the shape

Luff: forward edge

Leading edge of a fore-and-aft sail.

4. One Mast, One Sail — Corners, edges and a moving boom

Luff: turn or flutter

Action: head towards the wind or let the leading edge flutter.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Luffing

The leading region of a sail fluttering or losing its normal filled shape; also used for turning the boat towards the wind.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Lug

In rig discussion, short for a lug sail or its arrangement; elsewhere a lug may simply mean a projecting attachment tab.

16. Sloping Yards and Diagonal Spars — Leave the yard on one side, or move it

Lug — projecting attachment tab

A lug in this sense is a projecting attachment tab whose hole receives the connection; the later lug sail is a different sense.

12. Hold Up the Mast — Turn the adjuster while letting the joint align

Lug — sail

A lugsail, also called a lug in the sail sense, is a four-sided sail hanging from a sloping yard which crosses the mast, with part of the yard and sail ahead of it. Its lug yard supports the head; the halyard lifts at a sling point along that yard. A lug rig uses this arrangement. Lug here is the sail name. An attachment lug on a metal fitting is a different object.

16. Sloping Yards and Diagonal Spars — Leave the yard on one side, or move it

Lug rig

A rig using a four-sided sail suspended from an angled yard that projects forward of the mast.

16. Sloping Yards and Diagonal Spars — Leave the yard on one side, or move it

Lug yard

The sloping spar carrying the upper edge of a lug sail.

16. Sloping Yards and Diagonal Spars — Leave the yard on one side, or move it

Lugger

A vessel carrying lug sails, with the mast number and local hull type needing separate description.

16. Sloping Yards and Diagonal Spars — Leave the yard on one side, or move it

Lugsail

A four-sided sail carried by an angled yard with part of the yard and sail forward of the mast.

16. Sloping Yards and Diagonal Spars — Leave the yard on one side, or move it

Lull

A temporary reduction in wind speed, often requiring a different sail setting or course to keep the boat moving.

5. The Wind the Sail Actually Meets — When the wind changes

Main boom

The main boom joins the mainmast, holds the mainsail clew and transmits sheet restraint to the hull.

24. Spread the Work Across a Schooner — Put the foremast ahead of the main

Main halyard

The line or tackle that raises and lowers the mainsail.

4. One Mast, One Sail — Raise the head, control the clew

Main topmast

The topmast above the lower mainmast.

25. Build Height, Divide Sail — Extend and name the upper stages

Mainmast

The mast designated as carrying the principal mainsail; its position depends on the sail plan.

22. One Mast, Several Sail Plans

Mainsail / main

The principal sail associated with the mainmast; it is not necessarily the largest sail carried in every condition.

4. One Mast, One Sail — Corners, edges and a moving boom

Mainsheet

The line or tackle controlling the mainsail’s boom position and, through its downward pull, aspects of sail shape.

4. One Mast, One Sail — Raise the head, control the clew

Mainsheet traveller versus sheet tension

Traveller position changes the lower attachment; changing paid-out mainsheet length at a fixed car changes the restraint towards that attachment.

28. Shape Is a Control — Trace the mainsheet to the boat

Maintainability

How readily a component can be inspected, repaired or replaced.

33. Change the Material, Keep the Jobs — Keep the load path usable and reachable

Make fast

A line or object is secured to remain in place; the worked line requires a continuous load path before the hand leaves it.

10. Hold the Load, Keep Control — Let the hands leave the rope

Manila rope

Abaca’s plant identity distinguishes manila from botanical hemp and relates named cordage to its source material.

8. What a Rope Is Made to Do — Different fibres, different useful properties

Manual override

A means of controlling equipment when the normal powered or automatic method is unavailable.

44. When Muscle Is Not Enough — Find the actual manual connection

Marconi rig

A name often used for tall triangular Bermuda rigs; historical usage and the associated mast-bracing analogy need explicit context.

18. The Tall Triangle — Put the developments in time

Margin plank

A margin plank borders the deck or an opening and receives neighbouring fitted ends where specified.

32. Build a Hull from Joined Pieces — Close the deck without fragile ends

Marline

Small usually two-strand cord provides binding and protection rather than the main line’s load-carrying length.

8. What a Rope Is Made to Do — Keep the line able to run

Marline hitch

An overhand arrangement encloses the bundle and can repeat along it, leaving overhand knots if the bundle is removed.

9. Join Ropes and Make Attachments — Bind the object and retain the end

Martingale

Traditional bowsprit-support terminology, commonly for rigging led via a downward strut; usage can overlap the strut’s own name.

21. Move the Sail Beyond the Bow — Give the downward support a better angle

Martingale backrope

A return support running aft from a martingale or dolphin-striker arrangement.

21. Move the Sail Beyond the Bow — Give the downward support a better angle

Martingale guy

A supporting line in a martingale assembly; show its exact load path rather than relying on the name alone.

21. Move the Sail Beyond the Bow — Give the downward support a better angle

Martingale stay

A stay led through or to a downward strut to support a bowsprit or jibboom.

21. Move the Sail Beyond the Bow — Give the downward support a better angle

Mass

The quantity measuring an object’s inertia, distinct from the gravitational force called weight.

Mast

The principal upright spar carrying sails and transmitting their loads into the hull.

12. Hold Up the Mast — Describe the mast’s shape precisely

Mast bend

Mast bend is curvature of the mast axis, contrasted with whole-axis inclination and an initial deliberately set curve.

Mast boot

The flexible mast boot joins spar to penetration boundary and excludes water while accommodating allowed movement; partners carry restraint.

12. Hold Up the Mast — Support the heel and restrain the spar

Mast bury

Mast bury is the supported portion below the upper lateral restraint; separated bearing reactions can supply a resisting moment.

12. Hold Up the Mast — Support the heel and restrain the spar

Mast cap

A fitting or traditional timber connecting and locating overlapping mast sections.

25. Build Height, Divide Sail — Give the upper mast a seat

Mast collar

A mast collar surrounds the spar; its material and installation decide whether it seals, locates or provides bearing contact.

12. Hold Up the Mast — Support the heel and restrain the spar

Mast collar — seal

The flexible sealing collar closes the deck-penetration gap and remains distinct from structural partners and bearing reactions.

12. Hold Up the Mast — Support the heel and restrain the spar

Mast collar — support

Seldén’s collar wear pad builds up mast width at the gate, receiving bearing pressure and passing it to the mast.

12. Hold Up the Mast — Support the heel and restrain the spar

Mast foot

The bottom of the mast or its base fitting.

4. One Mast, One Sail — Bring the loads into the hull

Mast gate

A closure or opening controlling access to a mast’s sail groove, or a retaining arrangement at a small boat’s mast support.

14. Attach and Support the Sail — Enter the groove and manage the opening

Mast gate — mast support

The RS Venture gate closes the open-sided upper mast support while the heel is located separately in its lower step.

12. Hold Up the Mast — Support the heel and restrain the spar

Mast gate — sail groove

Spaced slides can enter through a widened opening in the mast groove. A mast gate, in this sail-groove sense, closes or manages that opening once they have been inserted. In Seldén’s documented gate arrangement, the fitted closure restores the retaining passage so slides can move past the loading region as the sail is lowered, remaining in the groove instead of spilling out through the gap. Opening it again permits their removal.

14. Attach and Support the Sail — Enter the groove and manage the opening

Mast heel

The lower end of a mast where it bears on its support.

4. One Mast, One Sail — Bring the loads into the hull

Mast hoop

A ring around a traditional mast attaching and guiding a sail’s luff.

14. Attach and Support the Sail — Keep the luff close while letting it rise

Mast partners

Partners restrain the spar laterally at the deck opening through chocks or bearing contact into surrounding structure; compression enters below.

12. Hold Up the Mast — Support the heel and restrain the spar

Mast prebend versus rake

Mast prebend describes initial curvature while rake describes overall inclination; their independent comparisons precede coupled real adjustments.

12. Hold Up the Mast — Describe the mast’s shape precisely

Mast prebend versus rake

The same overall axis can have different curvature, and a straight mast can tilt, so neither measurement uniquely determines the other.

12. Hold Up the Mast — Describe the mast’s shape precisely

Mast pumping

Mast pumping is repeated fore-and-aft or sideways oscillation under changing loads, with support, stiffness and excitation all relevant.

12. Hold Up the Mast — Describe the mast’s shape precisely

Mast rake

Mast rake is overall fore-and-aft inclination against a stated upright reference, here perpendicular to design waterline.

12. Hold Up the Mast — Describe the mast’s shape precisely

Mast rake

The heel-to-head reference line’s inclination is compared with an upright perpendicular to design waterline, independently of curvature.

12. Hold Up the Mast — Describe the mast’s shape precisely

Mast section

Mast section describes cross-sectional shape and dimensions, whose material distribution affects directional bending response.

12. Hold Up the Mast — Describe the mast’s shape precisely

Mast step

The structural seat supporting the mast’s lower end and transferring its load into the boat.

4. One Mast, One Sail — Bring the loads into the hull

Mast tang

The mast tang receives rigging pull at a projecting hole and transfers it through its material and fastenings into the mast wall.

12. Hold Up the Mast — Turn the adjuster while letting the joint align

Mast track

A rail or groove on the mast guiding sail slides or cars.

14. Attach and Support the Sail — Break the continuous attachment into moving pieces

Mast wall

The mast wall surrounds the hollow interior; wall thickness differs from overall section size and affects local stability and connections.

12. Hold Up the Mast — Describe the mast’s shape precisely

Mast-aft rig

A rig concept placing the main support mast unusually far aft and carrying substantial sail area ahead of it.

27. Rearrange the Whole Rig — Change where the support stands

The masthead is the top region containing the selected halyard and structural attachments, each located by its actual connection.

12. Hold Up the Mast — Describe the mast’s shape precisely

A masthead crane offsets a top attachment to provide clearance, while its projection creates a moment at the mounting.

12. Hold Up the Mast — Describe the mast’s shape precisely

A rig whose principal headsail stay reaches the masthead or its principal top attachment.

22. One Mast, Several Sail Plans — Move the upper attachment

A sloop whose principal headsail stay reaches the masthead.

22. One Mast, Several Sail Plans — Move the upper attachment

Matrix / resin matrix

The material surrounding reinforcing fibres and transferring loads between them.

13. Give the Sail Its Shape — Bond a surface around reinforcement

Maximum beam

The greatest width of the hull, under the measurement convention being used.

3. Give the Hull a Shape — Measure the same hull in several ways

Mechanical advantage

Mechanical advantage compares useful output force with input force in the stated model.

11. Trade Force for Distance — Make the block move with the load

Mechanical terminal

The selected Sta-Lok terminal confines wire strands around a tapered wedge and core, transferring pull through assembled gripping parts.

13. Give the Sail Its Shape — Arrange reinforcement for the whole sail

Membrane sail

A sail using engineered sheets, films or bonded fibre structures rather than only conventional woven panels.

Metacentre

The limiting intersection of neighbouring buoyancy-force lines supplies a geometric reference near upright.

36. Stability Has a Range — Look closely at the first few degrees

Metacentric height / GM

The upright separation from G to the transverse metacentre describes the initial restoring geometry.

36. Stability Has a Range — Look closely at the first few degrees

Midship coefficient

Immersed midship-section area divided by its reference beam-and-draught rectangle.

43. Draw It, Measure It, Compare It — Give fullness a denominator

Midship section

A cross-section at the vessel’s defined midship position; it need not be the section with the greatest area.

3. Give the Hull a Shape — Read a slice through the hull

Miss stays

Fail to complete a tack, especially in traditional sailing usage.

31. Turn, Stop and Rebalance — When the tack does not complete

Mizzen

Mizzen can denote the after mast or its sail, distinguished by the described attachment or action.

23. Put a Smaller Sail Aft — Give the after sail its own support

Mizzen — mast

Mizzen denotes the physical after mast in Knight’s curved-tiller clearance passage.

23. Put a Smaller Sail Aft — Give the after sail its own support

Mizzen — sail

Mizzen denotes the independently selectable cloth carried by the after mast.

23. Put a Smaller Sail Aft — Give the after sail its own support

Mizzen boom

The mizzen boom swings at the mast joint, holds the after clew and receives restraint from its own sheet.

23. Put a Smaller Sail Aft — Give the after sail its own support

Mizzen sail

The mizzen sail is the cloth carried on the smaller aftermast in the selected two-mast arrangement.

23. Put a Smaller Sail Aft — Give the after sail its own support

Mizzen sail

The explicit mizzen-sail phrase identifies the same cloth as the bare sail sense of mizzen.

23. Put a Smaller Sail Aft — Give the after sail its own support

Mizzen staysail

An additional light sail ahead of the mizzenmast, with WAXWING’s separate head, forward tack and after clew routes.

23. Put a Smaller Sail Aft — Use the space ahead of the mizzen

Mizzen topmast

The topmast above the lower mizzenmast.

25. Build Height, Divide Sail — Extend and name the upper stages

Mizzenmast

The mizzenmast stands aft of the mainmast and separately supports the smaller group in this prototype.

23. Put a Smaller Sail Aft — Give the after sail its own support

Moment / torque

The turning effect of a force acting at a distance from an axis.

7. Why the Boat Leans and Wants to Turn — Force needs a place to act

Moment: turning effect

Force multiplied by its perpendicular arm about an axis.

7. Why the Boat Leans and Wants to Turn — Force needs a place to act

Momentum

Mass multiplied by velocity, describing how much motion a moving body carries.

7. Why the Boat Leans and Wants to Turn — Steady motion and changing motion

Monkey’s fist

Three perpendicular groups of turns lock into a rope ball, giving a light throwing-line end bulk and mass.

9. Join Ropes and Make Attachments — Make the end too large to pass

Monocoque

A structure whose shell carries much of the load rather than relying only on a separate frame.

33. Change the Material, Keep the Jobs — Give the shell a structural job

Monohull

A vessel with one principal hull.

25. Build Height, Divide Sail — Put the sails between their supports

Moonraker

A name for an exceptionally high additional sail on certain historical rigs; rare and usage-dependent.

Mooring bridle

The mooring bridle receives a common pull through its shared connector and divides it into two rope legs attached to separate boat-side supports.

42. Hold the Boat Alongside — Return the bridle to a different holding point

Mooring eye

The mooring eye is the prepared loop whose curved part bears on a post or connector and passes pull into its two legs and the continuing rope.

42. Hold the Boat Alongside — Prepare an eye and preserve a clear passage

Mooring line

The mooring line carries tension between the boat attachment and berth connection, restraining movement through the direction of its pull.

42. Hold the Boat Alongside

Mooring ring

The selected mooring ring pivots in a fixed receiving eye on a plate bolted to a pontoon; a rope eye or connector bears on the ring.

42. Hold the Boat Alongside — Retrieve a mooring connection

Mould / mold

A timber mould or template transfers an outline to stock or supports pieces against a required form.

32. Build a Hull from Joined Pieces — Transfer the shape into the timber

Mould / mold

Production mould receiving composite shell material

33. Change the Material, Keep the Jobs — Specify the structure, then make it

Mould / mold — timber frame/form template

The frame-template sense uses a recorded edge to mark the timber’s required curve.

32. Build a Hull from Joined Pieces — Transfer the shape into the timber

Mould loft

The space or workshop where full-size ship lines are traditionally laid out.

43. Draw It, Measure It, Compare It — Carry the lines into the workshop

Moulded breadth

Moulded breadth measures the hull across specified structural reference surfaces; Curtis uses the outside of frames.

32. Build a Hull from Joined Pieces — Transfer the shape into the timber

Moulded dimension

A dimension taken to defined construction reference surfaces, not automatically the outer finished surface.

43. Draw It, Measure It, Compare It — Carry the lines into the workshop

Mousing

Small line bridges and binds the hook opening as secondary retention while the seated eye loads the main body.

10. Hold the Load, Keep Control — Retain the opening, then decide how it releases

Movable ballast

Weight that can be shifted to change the boat’s balance or righting moment.

6. Give the Water Something to Push Against — Give the water force a surface

Movement ahead/astern

Push the boat backwards and it moves astern while its bow continues to point towards the branch ahead.

1. A Boat Before Sail — Directions that turn with the boat

Multi-masted schooner

Several principal fore-and-aft units extend along the hull with the named vessel’s actual sail allocation stated.

24. Spread the Work Across a Schooner — Extend the distribution along the hull

Multichine

A hull formed with several lengthwise chines, often allowing flat panels to approximate a rounded shape.

3. Give the Hull a Shape — Read a slice through the hull

Multihull

A vessel with more than one principal hull.

5. The Wind the Sail Actually Meets — Choose the observer

Nautical mile

A distance of exactly 1,852 metres in modern usage.

Negative stability

The weight and buoyancy force lines create an overturning action away from upright in the chosen heel direction.

36. Stability Has a Range — Follow the arm beyond the first lean

Nib

A nib is the short blunt shaped termination of a deck plank.

32. Build a Hull from Joined Pieces — Close the deck without fragile ends

Nibbing

Nibbing shapes the blunt end and matching recess in its bordering plank.

32. Build a Hull from Joined Pieces — Close the deck without fragile ends

No-go zone

The range of headings too close to the wind for a particular boat to sustain useful sailing.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

No. 1 jib

A numbered headsail designation, generally the largest in a particular working inventory; numbers are not universal dimensions.

20. Use the Space Ahead of the Mast — Choose the forward inventory

No. 2 jib

A middle-sized headsail within a boat’s numbered inventory; its exact area and wind range depend on that boat.

20. Use the Space Ahead of the Mast — Choose the forward inventory

No. 3 jib

A smaller working headsail in a numbered inventory; the number alone does not define a universal shape or size.

20. Use the Space Ahead of the Mast — Choose the forward inventory

Nylon / polyamide

Polyamide’s recoverable extension can cushion a moving boat, while wet properties and precise halyard control impose different demands.

8. What a Rope Is Made to Do — Different fibres, different useful properties

Oakum

Oakum supplies loose rope-derived fibres, commonly tarred, for packing the wooden seam.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Oar

A blade and shaft worked against a support on the boat, allowing the rower to apply leverage through the hull.

1. A Boat Before Sail — Give the oar somewhere to bear

Oar blade

The broad end of an oar that pushes against the water.

1. A Boat Before Sail — Give the oar somewhere to bear

Oar collar / button

A collar preventing an oar from sliding too far through its support.

1. A Boat Before Sail — Give the oar somewhere to bear

Oar handle / grip

The end of an oar held by the rower.

1. A Boat Before Sail — Give the oar somewhere to bear

Oar leather

A protective wrapping where an oar bears on its rowlock or thole arrangement.

1. A Boat Before Sail — Give the oar somewhere to bear

Oar loom / shaft

The long body of an oar between its handle and blade.

1. A Boat Before Sail — Give the oar somewhere to bear

Offset

A measured distance from a reference line or plane to a point defining the hull.

43. Draw It, Measure It, Compare It — Locate one point on the hull

One-design

A class concept limiting boats to a common design, with specific permitted variations.

43. Draw It, Measure It, Compare It — Let the rule change what is rewarded

Open chock

An open chock has a gap above its bearing surface through which the line can be laid or lifted.

42. Hold the Boat Alongside — Guide the line across the edge

Osmotic blistering

Blister formation associated with water movement and soluble substances within certain coating or laminate systems.

33. Change the Material, Keep the Jobs — Follow the environment into the connection

Outboard

Outboard: away from centreline; outside hull; removable propulsion-motor noun.

3. Give the Hull a Shape — Locate a part, locate another boat

Outboard as direction

a seat moved outboard can still remain inside

3. Give the Hull a Shape — Locate a part, locate another boat

Outboard as external location

A blade worked outboard of the hull is outside the side

3. Give the Hull a Shape — Locate a part, locate another boat

Outboard motor

A self-contained outboard propulsion motor.

37. From the Hand to the Rudder — Turn the thrust itself

Outer forestay

The farther-forward of a rig’s forward supporting stays.

20. Use the Space Ahead of the Mast — Put a separate sail on the forward support

Outer skin

The outside structural layer of a sandwich panel.

33. Change the Material, Keep the Jobs — Separate two skins and connect them

Outhaul

Outhaul is the outward-drawing job; N25 gives the mainsail clew/car/boom version after earlier topsail and jib examples.

Outrigger

A side float or its supporting assembly that increases a craft’s resistance to rolling.

40. A Deck with Openings — Follow the upper hull edge

Outwale

An outwale runs along the outside of the upper hull edge; its contact with the panel complements the inner strip and connections.

Overhang

A part of the hull extending beyond the waterline length at the bow or stern.

3. Give the Hull a Shape — Measure the same hull in several ways

Overlap

The extent to which a headsail extends aft relative to its foretriangle or mast reference.

20. Use the Space Ahead of the Mast — Measure the sail that extends aft

Overload protection

A device or control that limits damage when loads exceed an intended level.

44. When Muscle Is Not Enough — Give a limit a particular action

Override

An override is a rope turn crossing and trapping another turn on the drum under load.

11. Trade Force for Distance — The drum still needs a tail

P

A mainsail-hoist reference measurement along the mast, commonly between defined limit marks.

43. Draw It, Measure It, Compare It — Measure the space for the sails

Paddle

A hand-held blade and shaft used to push against water without a fixed pivot on the boat.

1. A Boat Before Sail — A hand, a blade and a direction

Paddling

Propelling or steering with hand-held paddles rather than pivot-supported oars.

1. A Boat Before Sail — A hand, a blade and a direction

Padeye

A base-supported structural eye receives the connector and distributes the load into its actual mounting.

10. Hold the Load, Keep Control — The eye and the structure behind it

Painter

A painter attaches at a small boat’s bow for holding, handling or towing, with the described period example following the pull through a stem ringbolt and thimble.

42. Hold the Boat Alongside — Retrieve a mooring connection

Palm

The broad face of a traditional anchor fluke.

41. Hold the Boat to the Seabed — Give the bottom something to resist

Panel

One shaped piece of material making up part of a sail.

13. Give the Sail Its Shape — Join flat pieces into a curved surface

Panel seam

The joint connecting adjoining sail panels.

13. Give the Sail Its Shape — Join flat pieces into a curved surface

Parallelogram sail

A junk-sail form with largely parallel battens and a broadly parallelogram-shaped lower portion.

19. A Sail Divided by Battens — Put supporting members across the sail

Parcelling

Protective strips wrap the rounded surface between the groove-filling worming and retaining serving.

8. What a Rope Is Made to Do — Keep the line able to run

Parrel / parral

A rope or fitting holding a yard or other spar against a mast while allowing the intended movement.

Related labels and senses: Parrel.

17. What the Gaff Adds — Retain the inner end without fixing it

Parrel beads

Beads threaded onto a parrel rope to reduce rubbing and help it move around the mast.

17. What the Gaff Adds — Retain the inner end without fixing it

Parrel rope

The rope passing around the mast as part of a parrel.

17. What the Gaff Adds — Retain the inner end without fixing it

Pawl

The pawl is a one-way pivoting catch whose contact with teeth arrests reverse movement.

11. Trade Force for Distance — Put the travel into a handle

Paying

Paying applies the covering or sealing compound after the seam’s packing.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Peak

The upper outer corner of a gaff or spritsail.

17. What the Gaff Adds — Raise two ends of one spar

Peak bridle

A multi-point attachment sharing peak-halyard loads along the gaff.

Peak downhaul

A line used to pull down or restrain the outer end of a gaff.

17. What the Gaff Adds — Raise two ends of one spar

Peak halyard

The hoisting control supporting the outer end of a gaff and setting its angle.

Peak purchase

A tackle multiplying the effort applied to a gaff’s peak-hoisting control.

Peak span

A length of rigging spreading support along a gaff near its outer region.

33. Change the Material, Keep the Jobs — Receive a concentrated fastening load

Peel load

A load tending to lift an adhesive joint from an edge, often less favourable than distributed shear.

Pelican hook

A retained hinged opening allows an eye to leave; the documented keeper/body load placement explains different release effort.

10. Hold the Load, Keep Control — Retain the opening, then decide how it releases

Pendant / pennant

A short tension link moves the working attachment away from the rigid deck point while retaining two end connections.

10. Hold the Load, Keep Control — The eye and the structure behind it

Permanent backstay

The permanent backstay normally remains connected through a tack, even though its tension can change or be adjusted.

12. Hold Up the Mast — Support the mast fore and aft

Pickup line

Launer’s pickup line connects a reachable buoy to the free end of the loaded pendant; pulling it brings the working eye to hand, while the pendant’s other end joins the chain.

42. Hold the Boat Alongside — Retrieve a mooring connection

Pilot cutter

A vessel used for pilotage service, often cutter-rigged historically; service role and sail plan are different classifications.

20. Use the Space Ahead of the Mast — Read the work as well as the rig

Pinching

Sailing too close to the wind for efficient forward progress, or deliberately feathering close to that limit.

31. Turn, Stop and Rebalance — Unload the sail or put pressure on its other face

Pinrail

A pierced structural rail supports the belaying pins and transmits the force from their wraps into the boat.

10. Hold the Load, Keep Control — Let the hands leave the rope

Pintle

A projecting hinge pin fitting into a gudgeon to support a rudder or similar component.

6. Give the Water Something to Push Against — A blade that can turn the boat

Piston hank

A headsail hank with a spring-loaded plunger closing its opening.

14. Attach and Support the Sail — Guide an edge along a stay

Pitch (motion)

The bow and stern alternately rising and falling as the boat rotates about a transverse axis.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Pitch (sealing compound)

Pitch is the historical tar/resinous sealing substance applied over the packed seam.

Related labels and senses: Pitch.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Pitting

Localised corrosion creating small deep cavities rather than evenly thinning a surface.

33. Change the Material, Keep the Jobs — Follow the environment into the connection

Planform

The two-dimensional outline of a sail or foil seen from a specified direction.

43. Draw It, Measure It, Compare It — Separate an outline from its force

Planing

Flow-related pressure supplies substantial upward support and changes running immersion and wetted contact.

34. Why Hull Shapes Behave Differently — Change the way the water supports the hull

Planking

Planking is the joined collection of shell boards, carrying water pressure and sharing distortion loads through its fastenings.

3. Give the Hull a Shape — Follow the outside from bow to stern

Plate strake

A lengthwise course of metal hull plates.

33. Change the Material, Keep the Jobs — Join plates into a supported shell

Plough anchor

An anchor with a plough-like fluke shape intended to bury in the seabed.

41. Hold the Boat to the Seabed — Change the part that turns into the ground

Plumb bow

The plumb stem is approximately vertical in profile, allowing waterline length to reach forward within a fixed overall hull length.

34. Why Hull Shapes Behave Differently — Read the bow in more than one view

Plywood

Plywood is a sheet of bonded veneers with crossed adjacent principal grain directions.

32. Build a Hull from Joined Pieces — Make thin layers work together

Point of sail

A boat’s direction of travel relative to the wind, such as close-hauled, reaching or running.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Pointing ability

How close to the wind a boat can sail usefully; heading without speed and leeway is insufficient evidence.

43. Draw It, Measure It, Compare It — Measure progress towards something

Polacre / polacca

Smyth’s polacre/polacca comparison includes continuous masts without tops/crosstrees and a Mediterranean vessel tradition.

26. Read the Whole Square or Mixed Rig — Change the mast construction as well

Polar diagram

A graph of predicted or measured boat speed for different wind angles and wind strengths.

43. Draw It, Measure It, Compare It — Measure progress towards something

Pole / punting pole

A long pole pushed against the bottom to propel or manoeuvre a boat in shallow water.

1. A Boat Before Sail — A hand, a blade and a direction

Pole downhaul

A line restraining a pole from rising.

29. When the Wind Moves Aft — Hold the windward corner away from the mast

Pole lift

A line supporting and setting the height of a spinnaker pole.

29. When the Wind Moves Aft — Hold the windward corner away from the mast

Pole mast

A mast without a separately stepped topmast, though it may be made from joined material.

18. The Tall Triangle — Build a long spar from wood

Pole uphaul

A line lifting a pole, normally another name for its lift.

29. When the Wind Moves Aft — Hold the windward corner away from the mast

Polyester / Dacron

A synthetic fibre widely used in sails and ropes; Dacron is a trade name, not a different basic fibre.

13. Give the Sail Its Shape — Give the fibres different jobs

Polyester film / Mylar

A thin film used in some laminated sails; Mylar is a trade name.

13. Give the Sail Its Shape — Bond a surface around reinforcement

Polyester resin

A resin family widely used in glass-fibre hull construction.

33. Change the Material, Keep the Jobs — Place fibres where the load must travel

Polypropylene rope

Low density allows flotation, with heat, creep and grip limiting the use of particular constructions.

8. What a Rope Is Made to Do — Different fibres, different useful properties

Port

The vessel’s left side when facing its bow, independent of which way a person aboard is facing.

1. A Boat Before Sail — Directions that turn with the boat

Port tack

Sailing with the wind coming over the port side under the relevant sailing convention.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Position ahead/astern

Ahead and astern can describe positions: a floating branch lies ahead of the bow, another astern of the stern.

1. A Boat Before Sail — Directions that turn with the boat

Positive stability

The separated weight and buoyancy lines create a moment tending back towards upright.

36. Stability Has a Range — Follow the arm beyond the first lean

Power

The rate at which work is done or energy is transferred.

1. A Boat Before Sail — Energy and effort

Power-assisted steering

Steering in which an external power source helps move or control the rudder.

37. From the Hand to the Rudder — Transmit the movement through fluid

Powered furling

A sail-furling system driven by an electric or hydraulic actuator.

44. When Muscle Is Not Enough — Move cloth through its supported store

Prebend

Prebend is the deliberate initial mast curvature before changing sailing load, distinct from subsequent working bend.

12. Hold Up the Mast — Describe the mast’s shape precisely

Prebend

The deliberately bowed initial mast is distinguished from the later working bend under sail load at a stated overall inclination.

12. Hold Up the Mast — Describe the mast’s shape precisely

Prepreg

Reinforcing fibre supplied already impregnated with a controlled resin system, normally cured under specified conditions.

33. Change the Material, Keep the Jobs — Use a pressure difference

Pressure

Force spread over an area; pressure differences over a sail or hull can produce a resultant force.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Preventer

A restraint arranged to oppose an unintended boom swing across the boat; its loads and safe use require separate explanation.

31. Turn, Stop and Rebalance — Give the boom a deliberate restraint

Preventer stay

The preventer stay supplements a principal support; its actual endpoints establish its reinforcing or backup direction.

12. Hold Up the Mast — Support the mast fore and aft

Prismatic coefficient

Displaced volume divided by a prism of the same waterline length and maximum immersed section: a measure of lengthwise fullness.

43. Draw It, Measure It, Compare It — Give fullness a denominator

Proa

The selected CHamoru proa has asymmetric main-hull/float geometry and keeps the float windward while sail and steering functions exchange ends during a shunt.

38. Separate the Hulls — Let the two ends exchange jobs

Projected sail area

The area a sail presents when projected onto a stated plane, not necessarily the cloth’s actual surface area.

29. When the Wind Moves Aft — Present the area to the air

Propulsion

Producing useful force to move a boat relative to the surrounding water.

1. A Boat Before Sail — A hand, a blade and a direction

Pulley

A grooved wheel that guides a rope; aboard, it is commonly the sheave within a block.

4. One Mast, One Sail — Raise the head, control the clew

Pulpit

A pulpit is the rigid protective rail at the bow; its legs deliver forces to bases and its fittings can receive lifeline ends.

40. A Deck with Openings — Give the crew supports with identifiable connections

Purchase

A purchase exchanges greater working-end movement for greater useful load force through connected tensioned parts.

9. Join Ropes and Make Attachments — A connection can help with the pull

Purchase ratio

Purchase ratio expresses the selected arrangement’s ideal output/input force relationship and corresponding travel exchange.

11. Trade Force for Distance — Make the block move with the load

Pushpit

A pushpit or stern pulpit is the rigid rail at the stern, with legs, bases and possible lifeline-end contacts.

40. A Deck with Openings — Give the crew supports with identifiable connections

Quadrant

A curved sector attached to a rudder stock, around which steering cables pull.

37. From the Hand to the Rudder — Turn a wheel, then follow both cable legs

Quarter (direction)

A direction towards one side of the stern, between directly abeam and directly astern.

3. Give the Hull a Shape — Locate a part, locate another boat

Quarter knee

A quarter knee ties the transom’s corner to the side stringer with bolts entering the connected members.

32. Build a Hull from Joined Pieces — Give the projecting stern its own supports

Quarter rudder

A steering blade mounted near one side of the stern rather than on the centreline.

6. Give the Water Something to Push Against — A blade that can turn the boat

Quarter timber

Quarter timbers occupy the outer quarters of the older upper stern framing.

32. Build a Hull from Joined Pieces — Give the projecting stern its own supports

Quarterdeck

Quarterdeck identifies an after upper-deck region; Smyth’s 1867 convention places it from mainmast towards stern.

40. A Deck with Openings — Walk around the raised enclosure

Rabbet / rebate

A rabbet or rebate receives the plank’s fitted edge or end against shaped faces.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Rabbet line

A drawing line locating the groove where planking meets a backbone member.

43. Draw It, Measure It, Compare It — Carry the lines into the workshop

racing priorities and comparison

A racing brief seeks useful performance under specified course, conditions and class/rating rules; compare its chosen compromises with a stated cruising brief rather than with an invented generic cruiser.

43. Draw It, Measure It, Compare It — Change the objective without changing the question’s scale

Rack-and-pinion steering

Steering using a toothed gear and matching straight or curved rack to transmit motion.

37. From the Hand to the Rudder — Wind a rope or move a rigid link

Racking

Distortion that changes the angle of a frame or structural box.

35. Keels, Ballast and Adjustable Draught — Let the whole hull bend and distort

Radial

In steering, a circular or part-circular cable-driving fitting attached to the rudder stock; product usage varies.

37. From the Hand to the Rudder — Turn a wheel, then follow both cable legs

Radial cut

A sail-panel layout spreading out from loaded corners.

13. Give the Sail Its Shape — Turn the cloth towards the load

Radial patch

A corner reinforcement arranged with strips or fibres spreading out along likely load directions.

14. Attach and Support the Sail — Spread the pull beyond the hole

Raft

A floating structure made from connected buoyant elements or a broad platform, rather than necessarily a hollow hull.

40. A Deck with Openings — Walk around the raised enclosure

Raised deck

A raised deck lifts a deck area above the adjoining main deck; Erin’s elevated forward area steps down aft.

Raked bow

The selected forward-raked stem slopes so its upper end lies farther forwards, creating overhang above the loaded waterline.

34. Why Hull Shapes Behave Differently — Read the bow in more than one view

Ram’s horn

A ram’s horn is the paired curved hooked fitting at the inner boom region, offering a hook on each side for the reef tack connection.

30. Reduce, Gather or Replace the Sail — Route the reef controls

Ratchet block

A one-way catch holds the sheave against paying-out rotation so its surface helps the operator resist loaded rope by friction.

11. Trade Force for Distance — Lead the rope where it is useful

Rating rule

A method of measuring or handicapping boats that can influence design; technical effects matter here more than race chronology.

43. Draw It, Measure It, Compare It — Let the rule change what is rewarded

Ratline

One of the small horizontal lines between shrouds forming steps for climbing.

Related labels and senses: Ratlines.

25. Build Height, Divide Sail — Continue the pull below the platform

Reach / reaching

Sailing across or obliquely across the wind between close-hauled and running.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Reacher

A sail intended primarily for sailing with the wind across the boat rather than close-hauled or directly behind.

29. When the Wind Moves Aft — Choose the shape as well as the name

Reaching strut

A short projecting spar keeping a loaded line clear of rigging or improving its lead when reaching.

29. When the Wind Moves Aft — Change the lead without losing the corner

Redundancy

An alternative means of preserving a function if one component or path fails.

44. When Muscle Is Not Enough — Preserve a function through a different path

Reed boat

A craft using bundled reeds as buoyant or structural material.

7. Why the Boat Leans and Wants to Turn — Reduce the load, then change the wind side

Reef

A reduction in exposed working sail area, made while retaining a usable sail shape.

Reef band

A reef band reinforces a strip across the sail at the chosen level, supporting intermediate local attachments.

30. Reduce, Gather or Replace the Sail — Give the loose cloth a different job

Reef clew

The reinforced after attachment above the ordinary clew becomes the working lower after corner when the sail is lowered and secured.

30. Reduce, Gather or Replace the Sail — Put the load on new corners

Reef cringle

The reinforced corner eye receives the line or hook contact and transfers its concentrated pull through the surrounding patch.

30. Reduce, Gather or Replace the Sail — Put the load on new corners

Reef earing

An earing that holds a square sail’s reef corner to the yard when the sail is shortened.

Related labels and senses: Reef earring.

15. A Sail on a Yard — Establish a smaller working sail

Reef gasket

The gathering gasket encloses surplus cloth in the slab comparison; the 2022 vessel handbook separately identifies corner lashings and intermediate bindings.

30. Reduce, Gather or Replace the Sail — Give the loose cloth a different job

Reef hook

The reef hook receives a forward reef cringle and transfers its upward sail pull into the gooseneck-region mounting.

30. Reduce, Gather or Replace the Sail — Route the reef controls

Reef knot / square knot

Opposite half-knots form a binding over gathered material; changing independent line pulls can distort this into an unreliable bend.

9. Join Ropes and Make Attachments — Bind the object and retain the end

Reef line

Reef line names the control securing or tensioning a working reduced sail, with actual after and forward routes then distinguished.

30. Reduce, Gather or Replace the Sail — Route the reef controls

Reef nettle

Nettle is a traditional name for the short tie at an intermediate reef eye, binding the unused cloth into a bundle.

30. Reduce, Gather or Replace the Sail — Give the loose cloth a different job

Reef patch

The reef patch spreads the corner attachment’s concentrated force through additional material into a wider sail region.

30. Reduce, Gather or Replace the Sail — Put the load on new corners

Reef pendant

Reef pendant is the alternate spelling for the corner-hauling pennant in the chosen boom reef route.

30. Reduce, Gather or Replace the Sail — Route the reef controls

Reef pennant

The pennant is the line drawing a reinforced working corner into place through the described lower leads.

30. Reduce, Gather or Replace the Sail — Route the reef controls

Reef point

Intermediate reef points are short ties through the reinforced row which gather the loose cloth beneath the new working foot.

30. Reduce, Gather or Replace the Sail — Give the loose cloth a different job

reef points

The short intermediate ties pass through local eyes in the reinforced row and gather cloth beneath the reef.

30. Reduce, Gather or Replace the Sail — Give the loose cloth a different job

Reef tack

The reinforced luff attachment above the ordinary tack becomes the smaller sail’s forward lower corner.

30. Reduce, Gather or Replace the Sail — Put the load on new corners

Reef tackle

A reef tackle introduces moving-versus-fixed rope contacts to haul the working reef corner through a purchase.

30. Reduce, Gather or Replace the Sail — Route the reef controls

Reefed sail

The reefed sail remains set with less available cloth exposed between new corners and its lowered head.

30. Reduce, Gather or Replace the Sail — Put the load on new corners

Reefing

Reducing the working area of a sail to suit wind, balance or handling conditions.

7. Why the Boat Leans and Wants to Turn — Reduce the load, then change the wind side

Reefing horn

The reefing horn is the projecting hooked part holding the reinforced tack connection near the gooseneck.

30. Reduce, Gather or Replace the Sail — Route the reef controls

Reefing line

Reefing line names a control securing or tensioning the sail’s reduced setting; the subsequent single-line route serves both corners.

30. Reduce, Gather or Replace the Sail — Route the reef controls

Reefing points versus corner loads

The slab’s working corner controls and patches take the sailing load while the intermediate ties contain only surplus fabric.

30. Reduce, Gather or Replace the Sail — Give the loose cloth a different job

Reeve / rove

Reeve means threading rope through the selected openings and round sheaves; rove describes the threaded state.

11. Trade Force for Distance — Make the block move with the load

Reinforcement

Fibres or other material added to carry load within a composite.

13. Give the Sail Its Shape — Bond a surface around reinforcement

Reinforcement patch

Additional material strengthening a locally loaded area of a sail.

13. Give the Sail Its Shape — Concentrate the same pull into less material

Relative motion

Movement measured with respect to a specified reference, essential when comparing wind, water and boat speeds.

5. The Wind the Sail Actually Meets — Choose the observer

Reserve buoyancy

Watertight volume above the current waterline available to provide further buoyancy as immersion increases.

2. Why a Hull Floats — Loading changes the waterline

Resin infusion

Drawing resin through dry reinforcement in a controlled moulding process.

33. Change the Material, Keep the Jobs — Use a pressure difference

Resultant force

The single force representing the combined effect of several forces.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Retractable keel

A keel that can withdraw partly or wholly into the boat; mechanisms differ.

39. Move Mass, Add Foils — Change depth by a different motion

Retrieval line / dousing line

A line pulling a sail into a sock, chute or gathered position.

29. When the Wind Moves Aft — Bring the cloth under control

Reverse bow

A reverse stem’s upper region lies aft of its lower region in side view.

34. Why Hull Shapes Behave Differently — Read the bow in more than one view

Reynolds number

Speed times chosen length divided by kinematic viscosity gives the inertia/viscosity ratio; the stated example is 30 million.

34. Why Hull Shapes Behave Differently — Follow the flow next to the surface

Rib

A rib is a curved transverse support, commonly a relatively slender one.

32. Build a Hull from Joined Pieces — Make a frame follow the hull

Ride height

The hull’s height above the water when foil-supported.

39. Move Mass, Add Foils — Separate the lifting wing from the surface crossing

Riding sail

A small sail set to help steady a boat’s heading while at anchor, not primarily to drive it ahead.

41. Hold the Boat to the Seabed — Let the water level and the boat change position

Rig

The arrangement of sails, supporting spars and rigging that lets a boat use the wind.

12. Hold Up the Mast — Support the mast fore and aft

Rig tension

Rig tension may refer to the initial setting or working loads; preload precedes sail force and later loads redistribute.

Rigging inspection

Inspection follows wire, terminals and attachments into hull structure, with access limits preventing a visual check proving hidden residual strength.

12. Hold Up the Mast — Inspect the connected support

Rigging screw

The rigging screw changes end separation through opposed threads in a rotating body, taking up slack and then altering rig tension.

12. Hold Up the Mast — Turn the adjuster while letting the joint align

Right-hand lay

A right-handed screw and the near-face slope identify the actual direction rather than an observer’s chosen rope end.

8. What a Rope Is Made to Do — From fibres to a working line

Righting arm / GZ

The horizontal separation of weight and buoyancy force lines at a stated heel angle, providing a restoring or overturning lever.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Righting moment

The turning effect that tends to bring a heeled boat upright; it depends on displacement and the righting arm.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Righting-arm curve

A graph plots righting arm against heel angle for one specified hull, load and water-exclusion condition.

36. Stability Has a Range — Follow the arm beyond the first lean

Rigid vang

The gas-spring Rodkicker example uses telescoping tubes, end forks and pins, with a purchase shortening the assembly against its supporting spring force.

28. Shape Is a Control — Give boom rise its own restraint

Rigid wingsail

A sail formed as a rigid aerofoil structure rather than freely flexible cloth.

27. Rearrange the Whole Rig — Give the aerodynamic surface thickness

Ring cotter

Coiled spring wire passes through a cross-hole and forms an obstruction to withdrawal of the larger pin.

10. Hold the Load, Keep Control — Close the link without fixing every movement

Ringbolt

A separate ring articulates within the bolt’s head eye before transmitting its load down the bolt.

10. Hold the Load, Keep Control — The eye and the structure behind it

Ringtail

An additional light-weather sail extending the area beyond the after edge of another sail, commonly a spanker.

25. Build Height, Divide Sail — Add area beside and beneath the main supports

Roach

Sail area projecting outside the straight line between the head and clew, usually along the leech.

13. Give the Sail Its Shape — The edge is part of the shape

Rocker

The fore-and-aft curvature of the hull bottom when seen from the side.

3. Give the Hull a Shape — Read a slice through the hull

Rocker versus deadrise

Rocker describes fore-and-aft bottom curvature; deadrise describes the bottom’s crosswise slope.

3. Give the Hull a Shape — Read a slice through the hull

Rod rigging

Solid rod carries the standing tension and uses formed ends with matching seats, distinct from a stranded wire cable and swaged socket.

8. What a Rope Is Made to Do — From fibres to a working line

Rode

The chain, rope or combination connecting the boat to its anchor.

31. Turn, Stop and Rebalance — Add drag at a chosen end

Roll

Side-to-side rotation of the boat.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Roller fairlead

A roller fairlead supports a changing rope lead on turning rollers at the contact surfaces.

11. Trade Force for Distance — Lead the rope where it is useful

Roller furling

Roller furling wraps the complete sail around its rotating support into a non-working stored state.

30. Reduce, Gather or Replace the Sail — Roll a supported edge

Roller reefing

Roller reefing leaves part of a suitable sail working while part wraps around its support, changing the roll thickness, clew and lead.

30. Reduce, Gather or Replace the Sail — Roll a supported edge

Rolling hitch

Extra turns towards the pull grip a spar; the rope variant adds a bend in the supporting line to resist lengthwise travel.

9. Join Ropes and Make Attachments — Fasten to something solid

Rope

A flexible length made by twisting or braiding fibres or wires together; aboard it often gains a name from its job.

1. A Boat Before Sail — A hand, a blade and a direction

Rope clutch

A lever-operated gripping body holds reverse pull and transfers the hauling equipment’s load into its mounting.

10. Hold the Load, Keep Control — Grip the line between surfaces

Rot

Rot is fungal consumption of wood’s structural constituents under enabling moisture, temperature and oxygen conditions.

32. Build a Hull from Joined Pieces — Keep the material capable of carrying the load

Rotating mast

A mast designed to turn about its lengthwise axis to improve sail alignment or airflow.

27. Rearrange the Whole Rig — Turn the mast without losing its support

Round bilge

A hull section with a smooth curved transition from bottom to side rather than a sharp chine.

3. Give the Hull a Shape — Read a slice through the hull

Round turn

The added circuit around a post supplies more contact than an initial return bend and reduces required held-end tension through friction.

8. What a Rope Is Made to Do — Which part of the rope moves?

Round turn and two half-hitches

Post contact takes the main change in direction while two same-direction half-hitches retain the returning end.

9. Join Ropes and Make Attachments — Fasten to something solid

Round up

Turn towards the wind, deliberately or because sail load overwhelms the boat’s balance.

31. Turn, Stop and Rebalance — When the intended balance is lost

Round-bottom hull

A hull with rounded transverse underwater sections.

3. Give the Hull a Shape — Read a slice through the hull

Rove

The rove bears on the inner timber beneath a rivet’s peened end.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Rowing

Propelling a boat by working oars against supports on the hull.

1. A Boat Before Sail — Give the oar somewhere to bear

Rowlock / oarlock

The fitting supporting an oar at the boat’s side and allowing it to pivot while the rower pulls.

Rowlock socket

The fitting in the hull or gunwale that receives the stem of a swivelling rowlock.

1. A Boat Before Sail — Give the oar somewhere to bear

Royal

A small upper square sail above the topgallant sail, or its associated yard.

25. Build Height, Divide Sail — Put the sails between their supports

Royal — sail sense

Royal square sail above topgallant.

25. Build Height, Divide Sail — Put the sails between their supports

Royal — yard sense

Royal yard supporting that sail.

25. Build Height, Divide Sail — Extend and name the upper stages

Royal mast

The upper mast stage supporting royal-sail gear.

25. Build Height, Divide Sail — Extend and name the upper stages

Rubbing strake

The rubbing strake presents an exposed plank course or added strip to abrasion and contact.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Rudder

A movable underwater surface producing a turning force when water flows past it.

3. Give the Hull a Shape — Measure the same hull in several ways

Rudder blade

The water-working surface of the rudder.

6. Give the Water Something to Push Against — A blade that can turn the boat

Rudder head

The upper part of a rudder or its stock where steering fittings attach.

6. Give the Water Something to Push Against — A blade that can turn the boat

Rudder post

In the opening’s usage, the moving rudder shaft, distinct from the fixed sternpost and the helm position. Some technical references also use rudderpost for a fixed member supporting the rudder; identify the intended arrangement before assigning its load.

6. Give the Water Something to Push Against — A blade that can turn the boat

Rudder shaft

Another name for the rudder stock.

6. Give the Water Something to Push Against — A blade that can turn the boat

Rudder stock

The shaft transmitting steering motion and load to the rudder blade.

6. Give the Water Something to Push Against — A blade that can turn the boat

Rudder stop

A physical limit preventing the rudder from turning farther than intended.

37. From the Hand to the Rudder — Bound the movement and follow the immersion

Rudder tube / trunk

The housing around a rudder stock where it passes through the hull.

6. Give the Water Something to Push Against — A blade that can turn the boat

Run

The submerged afterbody narrows or rises towards the stern and shapes the departing water route.

34. Why Hull Shapes Behave Differently — Follow the water from the bow to the stern

Run / running downwind

Sailing with the wind coming broadly from behind; distinct from the underwater run of a hull.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Runner

Runner is the shortened name for the worked aft support, whose windward tension and leeward easing clear the moving sail.

12. Hold Up the Mast — Support the mast fore and aft

Running backstay

A running backstay provides adjustable aft restraint with sides commonly exchanged through a tack to clear the sail.

12. Hold Up the Mast — Support the mast fore and aft

Running bowline

The fixed eye becomes a guide for its own standing part, allowing the larger surrounding loop to close.

9. Join Ropes and Make Attachments — Make an eye that stays the same size

Running rigging

Lines primarily used to raise, lower, position and shape sails or move their spars.

4. One Mast, One Sail — Raise the head, control the clew

Running spanline

An adjustable line linking a junk-sail sheet to batten spans, often through a friction block.

19. A Sail Divided by Battens — Change a retaining or sheeting route

Running tack parrel

An adjustable restraint that changes the lower sail’s fore-and-aft position relative to the mast.

19. A Sail Divided by Battens — Change a retaining or sheeting route

Sacrificial anode

A deliberately more readily corroded metal component used to protect connected metal parts.

33. Change the Material, Keep the Jobs — Follow the environment into the connection

Sacrificial strip / UV strip

A replaceable protective strip shielding the exposed edge of a furled sail from sunlight.

14. Attach and Support the Sail — Finish and reinforce an edge

Safety factor

A design allowance relating specified strength to expected loads under a defined engineering method.

33. Change the Material, Keep the Jobs — Keep the load path usable and reachable

Sagging

Lengthwise bending that lowers a hull’s middle relative to its ends.

35. Keels, Ballast and Adjustable Draught — Let the whole hull bend and distort

Sail

A supported surface arranged to turn wind loading into useful force on a vessel.

13. Give the Sail Its Shape — Change the load, then repeat the comparison

Sail ageing / draft migration

Loss or change of designed shape as materials stretch, degrade or settle under repeated loads.

Sail area

The area of sail under a stated measurement convention and sail configuration.

13. Give the Sail Its Shape — Say what was measured

Sail bundle

The stack of sailcloth and spars gathered when a junk sail is lowered or reefed.

19. A Sail Divided by Battens — Receive the lowered sail

Sail car

A sliding or rolling carriage attaching a sail to a track.

14. Attach and Support the Sail — Break the continuous attachment into moving pieces

Sail draft / draught (shape)

The curved depth of a sail section, distinct from a boat’s immersion depth.

Related labels and senses: Draft; Draft / draught; Other senses: Hull draft / draught (depth).

13. Give the Sail Its Shape — Give the curve a reference

sail draft and comparison

Equal cut cloth on differently sagged luff supports can acquire different entry and depth, each still measured against its local chord.

28. Shape Is a Control — Change the supporting curve

Sail feeder

A guide helping a sail’s luff tape enter a foil or mast groove.

14. Attach and Support the Sail — Enter the groove and manage the opening

Sail gatherer

Lines or a fabric support collecting lowered sailcloth and spars into a controlled bundle.

19. A Sail Divided by Battens — Change a retaining or sheeting route

Sail groove

A slot accepting a sail’s rope edge, tape or sliders.

14. Attach and Support the Sail — Keep the luff close while letting it rise

Sail interactions

The way nearby sails alter each other’s airflow and loads; two sails cannot always be understood as isolated wings.

20. Use the Space Ahead of the Mast — Let the two sails share the air

Sail inventory

The complete selection of sails carried to suit different wind strengths and directions.

24. Spread the Work Across a Schooner — Add cloth high between the masts

Sail lacing

A line attaching a sail edge to a spar through repeated turns or eyes.

14. Attach and Support the Sail — Keep the luff close while letting it rise

Sail plan

The arrangement, shape and relative positions of a vessel’s sails, or the drawing showing them.

14. Attach and Support the Sail — Read one property at a time

Sail shape versus mast arrangement

Independent classifications: gaff or Bermuda describes sail support, while sloop, ketch or schooner describes the overall arrangement.

14. Attach and Support the Sail — Read one property at a time

Sail slide

A small fitting that travels along a mast track or groove while attaching the sail.

14. Attach and Support the Sail — Break the continuous attachment into moving pieces

sail slug

A small luff attachment retained inside a mast groove and able to slide along it as the sail is raised or lowered.

14. Attach and Support the Sail — Break the continuous attachment into moving pieces

Sail slug versus ball-bearing car

Two ways of guiding a sail along a mast, trading simplicity against friction and load capacity.

14. Attach and Support the Sail — Break the continuous attachment into moving pieces

Sail slug versus ball-bearing car

The same luff-guidance problem solved by a groove-retained sliding slug or a track-running ball-bearing car, with different contact, load and complexity tradeoffs.

14. Attach and Support the Sail — Break the continuous attachment into moving pieces

Sail trim

Adjustment of sail angle and shape to suit wind, course and desired behaviour.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Sail window

A transparent panel allowing sight through a sail.

14. Attach and Support the Sail — Observe what the surface is doing

Sail-area/displacement ratio

A conventional comparison of sail area with displacement, used as a broad power-to-weight indicator rather than a performance guarantee.

43. Draw It, Measure It, Compare It — Recalculate the same boat with more aboard

Sailcloth

The fabric or sheet material forming the wind-working surface of a sail.

13. Give the Sail Its Shape — Join flat pieces into a curved surface

Sailing barge

A cargo-oriented vessel family, useful for explaining shallow draught, leeboards and manageable rigs.

3. Give the Hull a Shape — Read a slice through the hull

Sailing yacht

A yacht designed to use sails as a principal means of propulsion.

42. Hold the Boat Alongside — Carry the pull beyond the post

Samson post

Kathryn’s Samson post extends from its exposed head through the foredeck to a foot mortised into the stem knee; pull on the upper part reaches this deeper assembly.

Sandwich construction

A light core held between two structural skins, creating a stiff panel without making it solid and heavy throughout.

33. Change the Material, Keep the Jobs — Separate two skins and connect them

Sawn frame

A sawn frame receives its outline by cutting suitable timber to shape.

32. Build a Hull from Joined Pieces — Make a frame follow the hull

Scale model

A smaller physical representation used to study shape or performance, requiring care with scaling laws.

43. Draw It, Measure It, Compare It — Make a smaller boat, then control the test

Scaling of loads

How forces and structural demands change with size, rather than assuming every dimension can simply be enlarged together.

44. When Muscle Is Not Enough — Compare the scale of the actual job

Scantling

Scantlings give the sizes of the structural members rather than only their drawn outlines.

Related labels and senses: Scantlings.

32. Build a Hull from Joined Pieces — Transfer the shape into the timber

Scarf / scarph

A scarf or scarph joins shaped ends through extended overlapping contact and its fasteners or bond.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Schooner

The familiar two-mast schooner has a foremast ahead of an equal or taller mainmast and substantial fore-and-aft area at both.

24. Spread the Work Across a Schooner — Put the foremast ahead of the main

Schooner versus ketch

Schooner fore/main positions contrast with the known ketch main/mizzen positions and relative heights.

24. Spread the Work Across a Schooner — Put the foremast ahead of the main

Scow bow

A scow bow carries breadth well forward in a broad rounded or squared form, changing the entrance, volume and bottom area.

34. Why Hull Shapes Behave Differently — Read the bow in more than one view

Screecher

A reaching sail commonly associated with multihulls; cut, luff support and intended angles vary.

29. When the Wind Moves Aft — Choose the shape as well as the name

Scrim

An open reinforcing network incorporated into a sail laminate.

13. Give the Sail Its Shape — Bond a surface around reinforcement

Sculling

Sculling: single stern oar sweeping; two oars per rower in rowing sport.

Sculling with one stern oar

One oar worked over the stern sweeps from side to side.

Sculling with two oars per rower

A rower using a pair, one in each hand, is sculling.

40. A Deck with Openings — Give exposed water a route out

Scupper

A scupper carries water from an exposed area through an outlet or connected inlet/pipe/hose route outside.

Sea anchor

A water-deployed drag device, commonly used from the bow to help control drift and heading, not a seabed anchor.

31. Turn, Stop and Rebalance — Add drag at a chosen end

Sea state

The surface-wave condition is described by wave geometry, direction and timing, including swell.

36. Stability Has a Range — Describe the motion and the sea separately

Seacock

The seacock’s handle and driver turn a bored ball against seats to open or close the through-hull water passage; flange and backing support its body.

40. A Deck with Openings — Distinguish the hull fitting from its valve

Seam

The joint between adjacent planks, plates or pieces of sailcloth; its sealing or joining method depends on the material.

13. Give the Sail Its Shape — Join flat pieces into a curved surface

Seam

Joint between metal plates

33. Change the Material, Keep the Jobs — Join plates into a supported shell

Seam — sailcloth

One shaped piece cut from the stock material is a panel. A panel seam joins it to its neighbour. Seam is the general name for the joint between adjoining pieces; here the pieces are sail material, rather than the planks joined along a wooden hull. Stitching can carry load between overlapped cloth edges. Bonded joints transfer load through their adhered contact, often with stitching or other details appropriate to the construction.

13. Give the Sail Its Shape — Join flat pieces into a curved surface

Seam — wooden planks

The wooden seam is the interface between neighbouring planks with material-specific fastening and sealing jobs.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Seaworthiness

Fitness for the intended conditions depends on the complete vessel, equipment, loading and operation.

36. Stability Has a Range — Describe the motion and the sea separately

Secondary bonding

Joining composite parts after an earlier laminate has already cured.

33. Change the Material, Keep the Jobs — Bond the interior into the hull

Section

A slice through a hull or component, used to show its shape and internal arrangement.

3. Give the Hull a Shape — Read a slice through the hull

Seizing

Small cord grips adjacent rope parts and their neck, preserving the larger loaded strop’s intended geometry.

10. Hold the Load, Keep Control — The eye and the structure behind it

Self-draining cockpit

A self-draining cockpit separates its exposed well from hull space and drains overboard under intended load and heel; the stated upright water-level difference supplies driving pressure.

40. A Deck with Openings — Give exposed water a route out

Self-righting

Return towards upright after overturning requires a specified range, configuration and retained buoyant boundary.

36. Stability Has a Range — Distinguish overturning from recovery

Self-tacking jib

A jib with a sheet arrangement that crosses the boat during a tack without changing separately worked sheets.

20. Use the Space Ahead of the Mast — Give each unit its own controls

Self-tailer

Self-tailing jaws grip the outgoing rope and carry it to a stripping guide, replacing the person’s tailing grip.

11. Trade Force for Distance — The drum still needs a tail

Self-tending sail

A sail arranged to change sides with little or no separate adjustment during a tack.

20. Use the Space Ahead of the Mast — Give each unit its own controls

Semi-balanced rudder

A rudder with only part of its area ahead of the axis, often with support along an upper portion.

37. From the Hand to the Rudder — Put the turning axis within the blade

Semi-displacement / semi-planing

Semi-displacement and semi-planing describe a mixed operating region between primarily buoyant and strongly motion-dependent support.

34. Why Hull Shapes Behave Differently — Change the way the water supports the hull

Sensor

A device measuring a physical quantity such as angle, speed or load.

27. Rearrange the Whole Rig — Ask for movement, measure the result

Serviceability

Whether a structure remains functional and acceptably stiff, separate from whether it has actually broken.

33. Change the Material, Keep the Jobs — Keep the load path usable and reachable

Serving

Close small-cord turns bind the covering and receive external wear, with the winding direction distinguished from the lower layers.

8. What a Rope Is Made to Do — Keep the line able to run

Servo-pendulum gear

A self-steering mechanism using water force on a swinging blade to amplify a windvane’s small movement.

44. When Muscle Is Not Enough — Let the wind set the reference

Set a sail

Put a sail into its working position and trim.

4. One Mast, One Sail — Raise the head, control the clew

Settee sail

A lateen-related four-sided sail with a short forward edge rather than a single lower-forward point.

16. Sloping Yards and Diagonal Spars — Suspend a long sloping edge

Shackle

The curved body and removable closing pin form the detachable load-bearing boundary between two attachments.

10. Hold the Load, Keep Control — Close the link without fixing every movement

Sharpie

A generally narrow, shallow, flat-bottomed boat family; particular rig arrangements vary.

3. Give the Hull a Shape — Read a slice through the hull

Shear

Opposed link and fork forces tend to slide adjacent pin sections at their interfaces; hole bearing and offset bending remain distinct.

10. Hold the Load, Keep Control — Give the force a route into the boat

Sheave

The grooved rotating wheel inside a block.

4. One Mast, One Sail — Raise the head, control the clew

Sheave box

A housing containing the grooved wheel over which a line runs.

14. Attach and Support the Sail — Enter the groove and manage the opening

Sheave pin

The sheave pin is the axle carrying the sheave’s bearing load between the cheeks.

11. Trade Force for Distance — What turns inside the block

Sheer

The rise and fall of the deck edge along the boat when viewed from the side.

3. Give the Hull a Shape — Read a slice through the hull

Sheer clamp

The sheer clamp runs along the upper hull and receives notched bonded beam ends in the selected wooden construction.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Sheer plan / profile

The side-view portion of a hull drawing.

43. Draw It, Measure It, Compare It — Locate one point on the hull

Sheer pole

A bar across the lower shrouds helping maintain their alignment and spacing.

25. Build Height, Divide Sail — Continue the pull below the platform

Sheerline

The line tracing the deck edge in side view and showing its sheer.

Related labels and senses: Sheer line.

3. Give the Hull a Shape — Read a slice through the hull

Sheerstrake

The sheerstrake is the uppermost principal hull-side plank course.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Sheet

A line controlling a sail’s lower corner or its supporting boom; the precise job differs between fore-and-aft and square sails.

4. One Mast, One Sail — Raise the head, control the clew

Sheet bend

The smaller rope goes through and around both bight legs, then beneath itself so the loaded geometry traps the tail.

28. Shape Is a Control — Choose a route and share its load

Sheet bridle

The RS500 strop divides sheet-block load between legs ending at the two rear quarters.

Sheet hauling span

A term for the adjustable connecting line in some junk-sail sheeting systems.

19. A Sail Divided by Battens — Change a retaining or sheeting route

Sheet in / haul in

Pull a sheet to bring a sail or its boom towards its tighter setting.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Sheet lead

The sheet lead is its physical route from the controlled corner through the first guide and onward to the hauling point, acting through the boom on the chosen main.

28. Shape Is a Control — Trace the mainsheet to the boat

Sheet span

A line distributing a junk sail’s sheet load between two or more batten ends.

19. A Sail Divided by Battens — Bring one sheet to several heights

sheet tension and comparison

At the same stated line tension, different directions give different force components; real sheet tension then changes with rig and air-load response.

28. Shape Is a Control — Trace the mainsheet to the boat

Sheeting angle

Sheeting angle is measured against a stated reference: here a plan centreline angle is separated from a vertical deck-relative slope.

28. Shape Is a Control — Trace the mainsheet to the boat

Sheetlet

A small part of a junk sheeting system; authors differ over whether they mean a fixed span or a running connecting line.

19. A Sail Divided by Battens — Change a retaining or sheeting route

Shelf

Shelf is the shortened hull-context name for the beam-supporting lengthwise ledge.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Shell

The shell encloses the block’s sheave and support and passes load into its attachment or surrounding strop.

11. Trade Force for Distance — What turns inside the block

Shell plating

The metal plates forming a vessel’s outer hull shell.

33. Change the Material, Keep the Jobs — Join plates into a supported shell

Shoal water

Shallow water that may restrict the hull or its appendages.

41. Hold the Boat to the Seabed — Hold in a particular bottom

Shock load

A moving boat takes up slack and must stop quickly, producing a rapidly rising line force unlike the steady holding pull.

10. Hold the Load, Keep Control — A sudden stop changes the load

Short splice

Intermeshed ends tuck into the opposite intact rope, transferring load locally while increasing diameter.

9. Join Ropes and Make Attachments — Join the rope’s own construction

Short ton

A mass of 2,000 pounds, found in some American measurements.

Shroud

A side support running from the mast towards the hull or deck.

12. Hold Up the Mast — Support the mast fore and aft

Shroud tension

Shroud tension is the pulling load in a selected side support and changes with the connected mast, hull and external loads.

Shunting

Changing a craft’s direction so bow and stern exchange roles, used by some proas rather than conventional tacking.

16. Sloping Yards and Diagonal Spars — Look beyond the triangular outline

Shutter plank

The shutter plank closes the remaining gap between two planking fronts.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Side deck

The side deck is the passage beside the raised cabin, bounded by hull edge, enclosure and interfering fittings.

40. A Deck with Openings — Walk around the raised enclosure

Side force

The force component acting across the vessel rather than directly along its length.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Sided dimension

Sided dimension measures an identified axis across the timber: fore-and-aft on a deck beam, transverse on a keel.

32. Build a Hull from Joined Pieces — Transfer the shape into the timber

Single block

A single block has one sheave providing one rope turning passage.

11. Trade Force for Distance — What turns inside the block

Single braid

A single interwoven structure can have an opening centre and narrow when lengthwise tension is applied.

8. What a Rope Is Made to Do — From fibres to a working line

Single-line reefing

The Harken 430 route couples clew and tack cringles to one tail via boom, mast and deck turns while the halyard remains separate.

30. Reduce, Gather or Replace the Sail — Route the reef controls

Sister block

The historical sister block has two separated sheave openings in one elongated shell, seized between shrouds in the cited example.

11. Trade Force for Distance — What turns inside the block

Skeg

A fixed underwater projection, often ahead of a rudder to provide support, protection or directional stability.

35. Keels, Ballast and Adjustable Draught — Spread the keel along the boat or concentrate it

Skeg-hung rudder

A rudder attached to or supported by a fixed skeg ahead of it.

37. From the Hand to the Rudder — Separate the steering surface from the keel

Skin-friction resistance

Viscous shear integrated over the actual wetted surface produces skin-friction resistance, with speed, roughness and local flow affecting the result.

6. Give the Water Something to Push Against — Friction has a surface to act on

Skin-on-frame

A watertight covering stretched over a supporting framework.

25. Build Height, Divide Sail — Put the sails between their supports

Skysail

A very high light-weather square sail above a royal on some large rigs.

Slab reefing

Lowering the sail brings a higher prepared tack and clew to the boom, leaving surplus below a smaller working surface.

30. Reduce, Gather or Replace the Sail — Put the load on new corners

Slamming

An emerged hull region re-enters the water at relative speed, imposing an impact on shell and supporting structure.

36. Stability Has a Range — Describe the motion and the sea separately

Sliding gunter

A gunter arrangement in which the upper spar is guided alongside the mast as it is raised or lowered.

17. What the Gaff Adds — Raise the upper spar nearer upright

Sliding hatch

A sliding hatch moves on fixed guides; its bearing strips constrain movement and carry contact while it covers overhead access.

40. A Deck with Openings — Close the lid and the entrance

Sling point

The point on a yard where its halyard or supporting sling carries it.

16. Sloping Yards and Diagonal Spars — Suspend a long sloping edge

Sloop

A one-masted fore-and-aft sail plan normally carrying a mainsail and one principal working headsail.

22. One Mast, Several Sail Plans — Add one working headsail

Sloop of war

Sloop of war is a period service classification;1854Constellation is the three-square-mast example.

26. Read the Whole Square or Mixed Rig — Separate the boat’s work from its rig

Slot

The space between neighbouring sails, where their interacting flow matters; it is not a guaranteed Venturi nozzle.

20. Use the Space Ahead of the Mast — Let the two sails share the air

Slot effect

The aerodynamic interaction between adjacent sails; explain the coupled flow rather than claiming that a narrow gap simply accelerates everything.

20. Use the Space Ahead of the Mast — Let the two sails share the air

Slug

A compact sail slider designed to run inside a groove.

14. Attach and Support the Sail — Break the continuous attachment into moving pieces

Slutter

An informal label for a sloop/cutter hybrid, often with an inner stay; it is not a precise universal classification.

22. One Mast, Several Sail Plans — Read the compound names in context

Small stuff

The collective small-cordage category is located in protective and binding work on larger rope.

8. What a Rope Is Made to Do — Keep the line able to run

Snap shackle

A spring-loaded plunger or latch retains an opening member that can move when that release is operated.

10. Hold the Load, Keep Control — Retain the opening, then decide how it releases

Snatch block

The snatch block’s opening side admits a bight while both rope ends remain connected.

11. Trade Force for Distance — Lead the rope where it is useful

Snotter

The line or tackle supporting and tensioning the lower or inboard end of a sprit.

16. Sloping Yards and Diagonal Spars — Prop the outer corner from below

Snow

Snow denotes the selected two principal square-mast rig with a small separate after trysail support.

26. Read the Whole Square or Mixed Rig — Give the after sail a separate track

Snubber

An elastic line or device sharing anchor loads and reducing shock, commonly used with an all-chain rode.

41. Hold the Boat to the Seabed — Let part of the connection extend

Snuffer / spinnaker sock

A sleeve drawn over a spinnaker to contain it during setting or lowering.

29. When the Wind Moves Aft — Bring the cloth under control

Snuffer hoop

The opening at the bottom of a sail sock that gathers the sail as it moves down.

29. When the Wind Moves Aft — Bring the cloth under control

Soft chine

A rounded transition between hull surfaces rather than a sharp corner; terminology varies between designers.

3. Give the Hull a Shape — Read a slice through the hull

Soft shackle

The closing eye seats beneath a prepared stopper while the flexible HMPE body encloses the attachments.

10. Hold the Load, Keep Control — Retain the opening, then decide how it releases

Soft wingsail

A flexible or semi-flexible sail arrangement forming a wing-like section, often with internal support.

27. Rearrange the Whole Rig — Give the aerodynamic surface thickness

Sole

The sole is the supported walking surface; removable boards or panels can give access beneath it.

12. Hold Up the Mast — Continue the load beyond the fitting

Solent rig

A one-masted arrangement with two closely spaced forward stays, normally allowing a choice of headsail rather than two working together.

22. One Mast, Several Sail Plans — Carry alternatives close together

Solent stay

A second forward stay close to the principal forestay, used for an alternative headsail.

22. One Mast, Several Sail Plans — Carry alternatives close together

Spade rudder

A rudder supported primarily through its stock without a full-length keel or skeg supporting its leading edge.

37. From the Hand to the Rudder — Separate the steering surface from the keel

Spanker

A fore-and-aft sail set at the aftermost mast of many square-rigged vessels.

25. Build Height, Divide Sail — Add area beside and beneath the main supports

Spar

A pole-like structural member used to support or control a sail, including masts, booms, yards and gaffs.

18. The Tall Triangle — Compare a material, then its finished mast

Specific stiffness

Stiffness compared with mass or density, relevant when reducing structural weight.

Specific strength

Strength compared with mass or density, relevant to lightweight design.

18. The Tall Triangle — Compare a material, then its finished mast

Speed over ground / SOG

The boat’s speed relative to the Earth.

6. Give the Water Something to Push Against — Where the boat points and where it goes

Speed through water / STW

The boat’s speed relative to the surrounding water.

5. The Wind the Sail Actually Meets — Choose the observer

Spiling

Spiling records the required boundaries on a flexible batten and transfers them to wider cutting stock.

Related labels and senses: Spiling / spilling.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Spill wind

Allow part of a sail to unload rather than remain fully powered; unrelated to spiling a wooden plank.

31. Turn, Stop and Rebalance — Unload the sail or put pressure on its other face

Spinnaker

A large, full sail used principally off the wind, set ahead of the boat’s usual working sails.

29. When the Wind Moves Aft — Support a full sail at its corners

Spinnaker chute

A tube or opening through which a spinnaker is retrieved and stored.

29. When the Wind Moves Aft — Bring the cloth under control

Spinnaker guy

The line controlling the windward lower corner of a conventional symmetrical spinnaker through the pole arrangement.

29. When the Wind Moves Aft — Hold the windward corner away from the mast

Spinnaker halyard

The line or tackle that raises and lowers a spinnaker.

29. When the Wind Moves Aft — Support a full sail at its corners

Spinnaker pole

A spar holding a spinnaker’s windward lower corner away from the mast.

29. When the Wind Moves Aft — Hold the windward corner away from the mast

Spinnaker sheet

The line controlling the leeward lower corner of a spinnaker.

29. When the Wind Moves Aft — Hold the windward corner away from the mast

Spitfire jib

Smyth’s 1867 spitfire-jib is the small heavy-canvas storm jib associated with cutters; spitfire is retained as the short name.

30. Reduce, Gather or Replace the Sail — Set a sail made smaller

Splice

Strand interweaving or a suitable buried end transfers pull through interacting construction rather than only compact whole-rope bends.

9. Join Ropes and Make Attachments — Join the rope’s own construction

Splining

Splining inserts a timber strip into a prepared groove or seam, with a bond where specified.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Split backstay

A split backstay has one common upper member branching into two lower legs towards separate deck points.

12. Hold Up the Mast — Support the mast fore and aft

Split junk rig

A junk-rig variant dividing sail panels around a slot near the mast.

19. A Sail Divided by Battens — Leave room beside the mast

Split topsails

A large topsail divided into upper and lower sails to make handling and reduction more manageable.

25. Build Height, Divide Sail — Divide the largest upper sail

Spreader

A spreader displaces the shroud outward; its tip keeps the wire offset and its compressed root transfers the resulting reaction into the mast.

12. Hold Up the Mast — Restrain a slender member between its ends

Spreader root

The spreader root is the inner end transmitting the strut’s compressive reaction into its socket or mast attachment.

12. Hold Up the Mast — Restrain a slender member between its ends

Spreader socket

The spreader socket receives and locates the root, transferring the strut load into the mast.

12. Hold Up the Mast — Restrain a slender member between its ends

Spreader tip

The spreader tip retains the shroud at the chosen offset and receives the force produced by its changed direction.

12. Hold Up the Mast — Restrain a slender member between its ends

Spring line

A spring line has a useful fore-and-aft lead between boat and berth, so its tension restrains longitudinal movement.

42. Hold the Boat Alongside — Give each line a direction

Sprit

A spar placed diagonally across a sail to support an outer corner; distinguish it from the bowsprit.

16. Sloping Yards and Diagonal Spars — Prop the outer corner from below

Sprit boom

A boom-like spar reaching across a sail to its clew rather than following the foot.

16. Sloping Yards and Diagonal Spars — Push the clew out instead

Sprit heel

The lower or inboard end of a sprit, commonly supported by a snotter.

16. Sloping Yards and Diagonal Spars — Prop the outer corner from below

Sprit-boom rig

A rig whose sail is controlled by a spar running across it towards the clew, rather than a conventional boom along the foot.

16. Sloping Yards and Diagonal Spars — Push the clew out instead

Spritsail

A fore-and-aft sail supported by a diagonal sprit; historically also a different square sail set beneath a bowsprit.

16. Sloping Yards and Diagonal Spars — Prop the outer corner from below

Spritsail — bowsprit-square sense

Historical square sail beneath a bowsprit.

21. Move the Sail Beyond the Bow — Distinguish the sail above from the sail below

Spritsail — diagonal sprit

There is another way to hold a four-sided sail’s upper outer corner out. Hoist its forward upper corner, retain its leading edge near the mast, then push the outer upper corner up and away with a diagonal spar. That spar is a sprit. A fore-and-aft sail extended this way is a spritsail, and its arrangement is a spritsail rig. The later square sail carried beneath a bowsprit, the spar projecting from the bow, uses another sense of spritsail.

16. Sloping Yards and Diagonal Spars — Prop the outer corner from below

Spritsail rig

A rig in which a diagonal sprit supports the upper outer corner of a fore-and-aft sail.

16. Sloping Yards and Diagonal Spars — Prop the outer corner from below

Sprocket

A toothed wheel engaging a chain.

37. From the Hand to the Rudder — Turn a wheel, then follow both cable legs

Spun yarn

Twisted small cord used for serving/bindings is distinguished from the constituent yarns within a strand.

8. What a Rope Is Made to Do — Keep the line able to run

Square rig

A rig carrying principal sails on transverse yards; the yards rotate to set the sails, and the cloth need not be geometrically square.

15. A Sail on a Yard

Square the yards

Turn yards nearer the athwartships position, commonly for a following wind.

15. A Sail on a Yard — Turn the yard, then place the corners

Square topsail

A transverse-yard sail above a lower square sail.

25. Build Height, Divide Sail — Put the sails between their supports

Square-rigged yacht

Square-rigged yacht combines significant square sail with recreational use; SeaCloud’s four-mast barque is the selected conventional example.

26. Read the Whole Square or Mixed Rig — Separate the boat’s work from its rig

Square-top

A mainsail with a broad, approximately horizontal upper region instead of a narrow triangular head.

13. Give the Sail Its Shape — The edge is part of the shape

Stack pack / lazy bag

The Doyle assembly combines boom-mounted cover, cover-support battens and mast-supported adjustable lines to receive and enclose a lowered attached sail.

30. Reduce, Gather or Replace the Sail — Catch the lowered sail

Stainless steel

A steel family formulated for corrosion resistance; it is not immune to every marine corrosion mechanism.

33. Change the Material, Keep the Jobs — Join plates into a supported shell

Stall

A substantial loss of a foil’s useful lift performance associated with extensive flow separation, often at excessive angle of attack.

5. The Wind the Sail Actually Meets — Follow the air, then the force

Stanchion

A stanchion supports the perimeter line at intervals; sideways reaction creates bending transmitted through socket, base feet, bolts, backing and deck.

40. A Deck with Openings — Give the crew supports with identifiable connections

Standing lift

Steel’s fixed-in-use lift joins the spritsail yard to a bowsprit strap with a setup lanyard, carrying spar weight without a running adjustment tail.

30. Reduce, Gather or Replace the Sail — Catch the lowered sail

Standing luff parrel

A fixed-length line controlling the forward sail region’s position.

19. A Sail Divided by Battens — Change a retaining or sheeting route

Standing lug

A lug sail whose yard stays on the same side of the mast when tacking, with its tack normally near the mast.

16. Sloping Yards and Diagonal Spars — Leave the yard on one side, or move it

Standing lug versus dipping lug

The standing yard remains on one mast side through a tack; the dipping yard is moved around the mast.

16. Sloping Yards and Diagonal Spars — Leave the yard on one side, or move it

Standing part

The main length leading away from the connection contrasts with the end being manipulated; a fixed tackle part is a contextual use.

8. What a Rope Is Made to Do — Which part of the rope moves?

Standing rigging

The stays and shrouds primarily supporting spars, rather than the lines used to set and handle sails.

19. A Sail Divided by Battens — Change a retaining or sheeting route

Standing yard parrel

A fixed-length parrel restraining the yard’s position.

Standing-rigging preload

Standing-rigging preload is deliberately set initial tension, not a claim of equal or unchanged port/starboard loads under sail.

12. Hold Up the Mast — Support the mast fore and aft

Starboard

The vessel’s right side when facing its bow.

1. A Boat Before Sail — Directions that turn with the boat

Starboard tack

Sailing with the wind coming over the starboard side under the relevant sailing convention.

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Station

A defined fore-and-aft position at which a hull section is drawn or measured.

43. Draw It, Measure It, Compare It — Locate one point on the hull

Stay

A rigging member supporting a spar, commonly in the fore-and-aft direction.

28. Shape Is a Control — Change the supporting curve

Stay sag

Stay sag is the deflection of a tensioned support from the straight line between its end attachments under transverse loading.

Stayed versus unstayed

Whether a mast relies on external supporting stays and shrouds; neither choice defines its sail count.

20. Use the Space Ahead of the Mast — Put a separate sail on the forward support

Staysail

A sail supported by a stay; it may be forward of a mast or between masts.

Staysail halyard

The line or tackle that raises and lowers a staysail.

20. Use the Space Ahead of the Mast — Give each unit its own controls

Staysail schooner

A main staysail occupies a selected lower inter-mast space in place of a conventional foresail, with an after main retained.

24. Spread the Work Across a Schooner — Support a sail between the masts

Staysail sheet

A line controlling a staysail’s clew and sail setting.

20. Use the Space Ahead of the Mast — Give each unit its own controls

Staysail stay

A stay on which a staysail is carried.

20. Use the Space Ahead of the Mast — Put a separate sail on the forward support

Stealer

A stealer adds a plank or partial course where increasing girth needs more width.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Steam-bent frame

Steam supplies heat and moisture to a suitable timber before it is bent and held to shape.

32. Build a Hull from Joined Pieces — Make a frame follow the hull

Steel

An iron-based alloy used for hulls, fittings, wire and other highly loaded components.

33. Change the Material, Keep the Jobs — Join plates into a supported shell

Steering

Steering means controlling direction.

1. A Boat Before Sail — A hand, a blade and a direction

Steering cable

A flexible load-carrying cable transmitting steering movement to the rudder mechanism.

37. From the Hand to the Rudder — Turn a wheel, then follow both cable legs

Steering chain

A chain transmitting movement from a wheel’s sprocket into a steering system.

37. From the Hand to the Rudder — Turn a wheel, then follow both cable legs

Steering drum

A drum winding steering lines or cables as the wheel turns.

37. From the Hand to the Rudder — Wind a rope or move a rigid link

Steering oar

An oar used chiefly to turn or hold the direction of a vessel.

1. A Boat Before Sail — Directions that turn with the boat

Steering pedestal

The upright support carrying a yacht’s wheel and associated steering mechanism.

37. From the Hand to the Rudder — Turn a wheel, then follow both cable legs

Steering sheave

A grooved wheel guiding a steering cable.

37. From the Hand to the Rudder — Turn a wheel, then follow both cable legs

Stem

The member or formed leading structure at the bow where the two sides of the hull meet.

3. Give the Hull a Shape — Follow the outside from bow to stern

Stemhead

The upper end of the stem, near the bow’s deck edge.

3. Give the Hull a Shape — Follow the outside from bow to stern

Stemhead fitting

The metal or composite attachment at the top of the bow carrying stays, tack loads or related hardware.

21. Move the Sail Beyond the Bow — Hold the inner end and restrain the outer one

Stemhead roller

An anchor or line roller fitted at the top of the stem.

41. Hold the Boat to the Seabed — Bring the rode across the bow

Stern

The rear end of the boat, opposite the bow.

42. Hold the Boat Alongside — Give each line a direction

Stern line

The stern line runs from the after part of the boat to a berth attachment abaft, with aft-directed pull opposing ahead movement.

Sternpost

An upright or sloping structural member at the stern; on some boats it also carries rudder fittings.

3. Give the Hull a Shape — Follow the outside from bow to stern

Stevedore knot

Two full circuits before re-entry enlarge the selected stopper form; the text distinguishes its geometry from inconsistent variant names.

9. Join Ropes and Make Attachments — Make the end too large to pass

Stiff (stability)

Relatively strong resistance to the first few degrees of heel describes a stiff stability response.

36. Stability Has a Range — Look closely at the first few degrees

Stiffness

Equal-length, equal-diameter samples at the same force distinguish resistance to extension from strength and bending flexibility.

8. What a Rope Is Made to Do — Equal strength, different movement

Stirrup

A short support suspending a yard’s footrope.

25. Build Height, Divide Sail — Bring the cloth to the people

Stitch-and-glue

Stitch-and-glue temporarily ties shaped panels before a thickened-epoxy fillet and resin-wetted glass tape make the permanent corner.

32. Build a Hull from Joined Pieces — Make thin layers work together

Stock

The cross-member helping a stock anchor lie so one fluke can bite.

41. Hold the Boat to the Seabed — Give the bottom something to resist

Stock anchor

An anchor with a transverse stock helping orient its flukes on the bottom.

41. Hold the Boat to the Seabed — Give the bottom something to resist

Stockless anchor

An anchor without a separate transverse stock, generally with a pivoting arm-and-fluke assembly.

41. Hold the Boat to the Seabed — Change the part that turns into the ground

Stopper

The stopping job is distinguished among obstructing knots, a separate temporary holding line and a mechanical grip.

10. Hold the Load, Keep Control — Grip the line between surfaces

Stopper knot

Local bulk arrests the end only when the encountered opening is smaller than the tightened knot.

9. Join Ropes and Make Attachments — Make the end too large to pass

Stored energy

Energy held in a stretched line, pressurised system or raised load that can be released suddenly.

8. What a Rope Is Made to Do — Equal strength, different movement

Storm jib

A storm jib is a separate small robust forward sail; the Navy example hanks onto its inner stay with its allocated hoist and sheets.

30. Reduce, Gather or Replace the Sail — Set a sail made smaller

Storm staysail

The storm staysail is the small robust surface on the inner or staysail support in Hasse’s convention.

30. Reduce, Gather or Replace the Sail — Set a sail made smaller

Storm trysail

The separate storm sail uses a dedicated mast track, a freed main halyard, lower tack line and independent stern-led clew sheets in the Navy arrangement.

30. Reduce, Gather or Replace the Sail — Set a sail made smaller

Stow

Put equipment or a sail away and secure it for the intended conditions.

4. One Mast, One Sail — Raise the head, control the clew

Strain

Extension divided by original length makes the two- and four-metre examples comparable despite different absolute elongations.

8. What a Rope Is Made to Do — Equal strength, different movement

Strake

A strake is one fore-and-aft course which may comprise several joined plank lengths.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Strand

A major spiral in laid rope contains smaller yarns; this locates the load-carrying stage between fibre bundles and whole rope.

8. What a Rope Is Made to Do — From fibres to a working line

Stream anchor

A traditional lighter anchor used in currents or supplementary moorings; distinguish the particular vessel’s practice.

41. Hold the Boat to the Seabed — Use the holding point to move the boat

Strength

Loading to specified failure distinguishes the supported force limit from extension at ordinary working load.

8. What a Rope Is Made to Do — Equal strength, different movement

Stress

Internal force intensity within a material, related to the area carrying the load.

13. Give the Sail Its Shape — Concentrate the same pull into less material

Stress concentration

A local rise in stress around a hole, corner, defect or abrupt change of section.

33. Change the Material, Keep the Jobs — Keep the load path usable and reachable

Stringer

A stringer follows the hull lengthwise and connects successive transverse supports so a local frame load can spread.

12. Hold Up the Mast — Continue the load beyond the fitting

Strip planking

Strip planking bonds narrow lengthwise pieces which can remain as the shell and substrate for crossed veneers.

32. Build a Hull from Joined Pieces — Make thin layers work together

Strop

A closed band surrounds a traditional block and carries its guide reaction to the support.

10. Hold the Load, Keep Control — The eye and the structure behind it

Structural bulkhead

A bulkhead designed to strengthen the hull or carry loads from equipment and rigging.

4. One Mast, One Sail — Bring the loads into the hull

Structural grid

An interconnected network of members spreading loads through the hull.

33. Change the Material, Keep the Jobs — Bond the interior into the hull

Studding sail / stunsail

An extra light-weather sail set beyond the sides of a square sail on extending spars.

25. Build Height, Divide Sail — Add area beside and beneath the main supports

Studding-sail boom

A spar extending from a yard to support an additional studding sail.

25. Build Height, Divide Sail — Add area beside and beneath the main supports

Surface-piercing foil

A foil intersecting the water surface, with immersed area changing as the boat rises.

39. Move Mass, Add Foils — Separate the lifting wing from the surface crossing

Surge

Fore-and-aft translation is described relative to the travelling boat’s mean advance and position.

36. Stability Has a Range — Describe the motion and the sea separately

Swage

Swaging compresses the terminal body into its specified grip on wire; the formed result may also be called a swage.

Swaged terminal

A swaged terminal transfers wire tension through its compressed socket and must match the wire and forming process.

2. Why a Hull Floats — Loading changes the waterline

Swamping

Water filling an open or low-freeboard boat enough to impair its normal flotation or operation.

Sway

Sideways translation moves the boat across its mean track without itself changing heading.

36. Stability Has a Range — Describe the motion and the sea separately

Sweat a halyard

Sweating a halyard uses sideways deflection of a tensioned span and retention of the gain at its hauling end.

11. Trade Force for Distance — Make one purchase haul another

Sweep as long oar

In broader boat usage, a sweep can also mean a long oar.

Sweep in rowing sport

a rower with one oar is sweep rowing; that oar is a sweep oar.

Sweep oar

Sweep oar: long oar; rowing-sport single oar per person.

36. Stability Has a Range — Describe the motion and the sea separately

Swell

Wind-generated waves continue beyond their generating area and can arrive after local wind has fallen.

Swept spreader

An aft-swept spreader places its tip aft as well as outboard, changing the shroud’s fore-and-aft contribution.

12. Hold Up the Mast — Restrain a slender member between its ends

Swing keel

A keel that changes depth by pivoting rather than sliding straight up.

39. Move Mass, Add Foils — Change depth by a different motion

Swinging circle

The area a moored or anchored boat may sweep as wind or current changes.

41. Hold the Boat to the Seabed — Let the water level and the boat change position

Swivel

Loaded bearing surfaces permit rotation between the connected ends, reducing the twist demanded of the attached line.

10. Hold the Load, Keep Control — Close the link without fixing every movement

Symmetrical spinnaker

A spinnaker with a broadly symmetrical outline, normally worked with a pole on its windward side.

29. When the Wind Moves Aft — Hold the windward corner away from the mast

Synthetic standing rigging

The selected braided-HMPE stay transfers pull through a spliced eye into a broad curved end fitting and onward connection.

39. Move Mass, Add Foils — Let the curve decide what emerges from the case

T-foil

A foil arrangement with a transverse lifting surface near the end of a vertical support.

T-terminal

A T-terminal seats its cross-head behind a matching socket/backing fitting so contact transfers rig pull into the mast.

33. Change the Material, Keep the Jobs — Bond the interior into the hull

Tabbing

Strips of bonded reinforcement joining a bulkhead, frame or other part to the hull or deck.

Tabernacle

A tabernacle provides a pivot axis for controlled mast lowering while its base, seating and retained upright arrangement carry their own loads.

12. Hold Up the Mast — Support the heel and restrain the spar

Table of offsets

A numerical table of distances locating points on a hull’s designed surface.

43. Draw It, Measure It, Compare It — Locate one point on the hull

Tabling

A folded or added reinforcing border around a sail edge.

14. Attach and Support the Sail — Finish and reinforce an edge

Tack (leg)

A stretch of sailing with the wind on one side before changing to the other.

Related labels and senses: Tack; Other senses: Tack (sail corner), Tack (square-sail line), Tack (manoeuvre), Tack (wind side).

6. Give the Water Something to Push Against — The other moving fluid

Tack (manoeuvre)

Turn so the bow passes through the wind and the wind changes from one side of the boat to the other.

Related labels and senses: Tack; Other senses: Tack (sail corner), Tack (square-sail line), Tack (wind side), Tack (leg).

6. Give the Water Something to Push Against — The other moving fluid

Tack (sail corner)

The lower forward corner of a fore-and-aft sail, secured near the mast or forward attachment.

Related labels and senses: Tack; Other senses: Tack (square-sail line), Tack (manoeuvre), Tack (wind side), Tack (leg).

4. One Mast, One Sail — Corners, edges and a moving boom

Tack (square-sail line)

A control holding down or positioning a square course’s windward lower corner.

Related labels and senses: Tack; Other senses: Tack (sail corner), Tack (manoeuvre), Tack (wind side), Tack (leg).

15. A Sail on a Yard — Turn the yard, then place the corners

Tack (wind side)

A designation based on which side the wind comes from, as in port tack or starboard tack.

Related labels and senses: Tack; Other senses: Tack (sail corner), Tack (square-sail line), Tack (manoeuvre), Tack (leg).

5. The Wind the Sail Actually Meets — Point the boat, set the sail

Tack downhaul

A line pulling a sail’s tack downward to restrain it or tension the sail.

16. Sloping Yards and Diagonal Spars — Leave the yard on one side, or move it

Tack line

A line holding or adjusting a sail’s tack, often on an asymmetric spinnaker.

17. What the Gaff Adds — Fill the space above the gaff

Tack parrel

A restraint controlling the sail’s tack region relative to the mast.

19. A Sail Divided by Battens — Keep the sail beside its mast

Tack reef line

The tack reef line passes from a lower attachment through the luff reef cringle and down to its control, opposing the halyard’s upward pull.

30. Reduce, Gather or Replace the Sail — Route the reef controls

Tack swivel

The GX lower ring lets the tack rotate independently while the cable transmits the lower drive’s rotation to the sail’s head.

30. Reduce, Gather or Replace the Sail — Decide where the roll starts

Tackle

A tackle is the connected block-and-rope assembly in which reeving establishes the force and movement relationship.

11. Trade Force for Distance — Make the block move with the load

Taffeta

A woven protective layer used on some laminated sails.

13. Give the Sail Its Shape — Bond a surface around reinforcement

Tail a winch

Tailing maintains outgoing rope tension and removes the emerging rope while the drum hauls.

11. Trade Force for Distance — The drum still needs a tail

Take a turn

Wrapping at the cleat deliberately adds contact and friction before the final end fastening is made.

10. Hold the Load, Keep Control — Let the hands leave the rope

Taking the ground / drying out

Resting on the seabed as the water falls, possible only with suitable hull support and conditions.

35. Keels, Ballast and Adjustable Draught — Put supports to either side

Tall ship

Tall ship is a broad traditional large-sailing-vessel usage, illustrated by a barque and contrasted with ship rig.

26. Read the Whole Square or Mixed Rig — Separate the boat’s work from its rig

Tang

The projecting tang and its hole receive rigging pull and transmit it through the plate’s fastening to parent structure.

12. Hold Up the Mast — Turn the adjuster while letting the joint align

Tanja sail

A canted quadrilateral sail supported by upper and lower spars in Southeast Asian sailing traditions; not simply another name for lateen.

16. Sloping Yards and Diagonal Spars — Look beyond the triangular outline

Taper

Gradually reducing returned material avoids one abrupt change of thickness and flexibility at the splice end.

9. Join Ropes and Make Attachments — Join the rope’s own construction

technical causal history

An account explaining how particular needs, constraints, mechanisms and documented changes relate, without treating an earlier craft as an inevitable step towards a yacht.

43. Draw It, Measure It, Compare It — Put causes beside the dates

Technical history versus chronology

An editorial subject linking a design to its problem and alternatives without forcing teaching order to follow dates.

43. Draw It, Measure It, Compare It — Put causes beside the dates

Tell-tale

A small ribbon or tuft showing local airflow on or behind a sail.

14. Attach and Support the Sail — Observe what the surface is doing

Tender (service boat)

A smaller craft serving a larger vessel, unrelated to the stability adjective tender.

1. A Boat Before Sail — Give the oar somewhere to bear

Tender (stability)

A boat heels readily under a comparable initial load or breeze in the stability sense of tender.

36. Stability Has a Range — Look closely at the first few degrees

Tension

A pulling load tending to stretch a rope, stay or structural member.

40. A Deck with Openings — Connect a person to a working route

Tether

A tether connects the person’s harness to a fixed attachment or a deck jackstay through its end connectors; load continues into supporting boat structure.

Thermoplastic

A polymer family that softens with heat and can be formed by suitable processes.

33. Change the Material, Keep the Jobs — Use a pressure difference

Thermoset

A polymer that cures into a network and does not simply melt back into its original uncured state.

18. The Tall Triangle — Hold fibres in a rigid shape

Thimble

A grooved insert supports the rope eye around a prepared curve and receives the metal connector inside it.

10. Hold the Load, Keep Control — Close the link without fixing every movement

Thole / thole pin

A peg, often used in a pair, against which an oar bears instead of a modern forked rowlock.

1. A Boat Before Sail — Give the oar somewhere to bear

Three-masted schooner

Three principal fore-and-aft mast units; Trinovante names fore, main and mizzen and carries gaff lower sails at each.

24. Spread the Work Across a Schooner — Extend the distribution along the hull

Three-strand

Three strands wind around a common centre, with successive twist directions helping the construction stay together.

8. What a Rope Is Made to Do — From fibres to a working line

Throat

The upper forward corner of a four-sided fore-and-aft sail, near the mast.

17. What the Gaff Adds — Raise two ends of one spar

Throat halyard

The hoisting control raising the inner end of a gaff near the mast.

17. What the Gaff Adds — Raise two ends of one spar

Throat hauling parrel

A control positioning the throat or upper-forward sail region to improve the set of a junk sail.

19. A Sail Divided by Battens — Keep the sail beside its mast

Through-hull fitting

A through-hull fitting passes through the shell; TruDesign’s hollow threaded body is clamped by an outer flange and inner washer/nut with bedding outside the bore.

40. A Deck with Openings — Distinguish the hull fitting from its valve

Thwart

A crosswise seat or structural member in an open boat.

41. Hold the Boat to the Seabed — Let the water level and the boat change position

Tidal stream

Water movement associated with the tide; different from the rise and fall of water level.

Tide

The periodic rise and fall of sea level, affecting depth and the ability to dry out.

41. Hold the Boat to the Seabed — Let the water level and the boat change position

Tiller

The lever attached to a rudder head or stock and moved to steer the boat.

6. Give the Water Something to Push Against — A blade that can turn the boat

Tiller arm

A lever on the rudder stock receiving steering-system or autopilot force.

37. From the Hand to the Rudder — Bound the movement and follow the immersion

Tiller extension

A jointed extension allowing the helmsperson to operate the tiller from farther away.

37. From the Hand to the Rudder — Reach the tiller from another position

Tiller head

The fitting joining a tiller to the rudder or rudder stock.

6. Give the Water Something to Push Against — A blade that can turn the boat

Timber hitch

Repeated twists around the returning leg are trapped against the timber by the loaded surrounding loop.

9. Join Ropes and Make Attachments — Bind the object and retain the end

Tip vortex

Rotating flow near a lifting surface’s end associated with pressure differences across it.

39. Move Mass, Add Foils — Give the foil a shape we can describe

Toe rail

A toe rail is a low raised deck-edge strip against which a foot can bear; its attachment carries that local force.

30. Reduce, Gather or Replace the Sail — Set a sail made smaller

Toggle

A toggle supplies articulation through linked pivots so parts align with the pull, distinct from length adjustment by threads.

12. Hold Up the Mast — Turn the adjuster while letting the joint align

tonnage measure

A named measurement or rating quantity defined by a particular tonnage system; it must not be assumed to be the vessel’s mass merely because its name resembles a mass unit.

43. Draw It, Measure It, Compare It — Separate tonnage from displacement

Tonnage versus displacement

Tonnage often describes a volume-based measure; displacement describes floating mass or displaced volume. The measures are not interchangeable.

43. Draw It, Measure It, Compare It — Separate tonnage from displacement

Tonnage versus displacement

Displacement reports a flotation-linked mass or explicitly specified displaced volume; tonnage follows a named measurement convention and may represent a different purpose and quantity.

43. Draw It, Measure It, Compare It — Separate tonnage from displacement

Tonne / metric ton

A mass of 1,000 kilograms.

Top

A platform around the head of a traditional lower mast, supporting access and aspects of the upper rigging.

25. Build Height, Divide Sail — Give the upper mast a seat

Top timber

A top timber supplies the upper region of an assembled frame near the deck side.

32. Build a Hull from Joined Pieces — Make a frame follow the hull

Top-down furling

The drive turns the cable and attached head while the independently swivelling tack can lag, initiating wrapping at the head.

30. Reduce, Gather or Replace the Sail — Decide where the roll starts

Topgallant

A sail, yard or mast stage above the topsail or topmast level; name the component explicitly.

25. Build Height, Divide Sail — Put the sails between their supports

Topgallant — mast sense

Topgallant mast stage above the topmast.

25. Build Height, Divide Sail — Extend and name the upper stages

Topgallant — sail sense

Topgallant sail above a topsail.

25. Build Height, Divide Sail — Put the sails between their supports

Topgallant — yard sense

Yard supporting the topgallant sail.

25. Build Height, Divide Sail — Extend and name the upper stages

Topgallant mast

The mast stage above a topmast in a traditional divided mast.

25. Build Height, Divide Sail — Extend and name the upper stages

Topmast

An upper mast section carried above and overlapping a lower mast.

25. Build Height, Divide Sail — Give the upper mast a seat

Topmast backstay

An aft-running stay supporting a topmast.

Related labels and senses: Topmast backstays.

25. Build Height, Divide Sail — Continue the pull below the platform

Topmast heel

The lower end of a separate topmast where it overlaps and bears on its supporting structure.

25. Build Height, Divide Sail — Give the upper mast a seat

Topmast shroud

A shroud supporting a separate topmast.

Related labels and senses: Topmast shrouds.

25. Build Height, Divide Sail — Continue the pull below the platform

Topping lift

The line from aloft supports the boom’s outer end in tension; an adjustable lower control sets height while the mast receives the upper reaction.

30. Reduce, Gather or Replace the Sail — Catch the lowered sail

Topsail

A sail above a lower sail; specify whether it is square, gaff or another topsail form.

17. What the Gaff Adds — Fill the space above the gaff

Topsail — square sense

Square sail above a lower course.

25. Build Height, Divide Sail — Put the sails between their supports

Topsail halyard

The line or tackle that raises and lowers a topsail or its supporting yard.

17. What the Gaff Adds — Fill the space above the gaff

Topsail outhaul

A line drawing a fore-and-aft topsail’s clew outward to its working position.

17. What the Gaff Adds — Fill the space above the gaff

Topsail schooner

A schooner retains its principal lower fore-and-aft distribution and adds square topsail machinery on the foremast.

24. Spread the Work Across a Schooner — Add a square sail above the foremast

Topsail sheet

The sheet controlling a topsail’s clew; distinguish gaff-topsail and square-topsail arrangements.

17. What the Gaff Adds — Fill the space above the gaff

Topsail sheet — gaff topsail

Knight gives a definite sheet lead for his yarded topsail. From the clew the sheet leads through a sheave at the gaff’s peak, then through a block below the throat and down to the deck. Hauling moves the clew towards the outer sheave; the sheave and inner block transfer the line’s turning forces into the gaff. The crew can therefore trim a corner high above them from a working position below.

17. What the Gaff Adds — Fill the space above the gaff

Topsail sheet — square sense

Sheet hauling a square topsail clew to its lower support.

25. Build Height, Divide Sail — Bring the cloth to the people

Topsail tack

The lower forward attachment of a fore-and-aft topsail, or the line securing it.

17. What the Gaff Adds — Fill the space above the gaff

Topsail tack — corner

Begin with the simple triangular topsail described by A. J. Kenealy in 1903. A topsail halyard lifts its head towards an upper mast attachment. The lower forward corner is the topsail tack, and its securing or downhauling line is also called the topsail tack, or tack line. The corner is part of the sail; the line pulls that corner down against the halyard’s upward support. Kenealy’s example uses a purchase for this downward tension.

17. What the Gaff Adds — Fill the space above the gaff

Topsail tack — line

17. What the Gaff Adds — Fill the space above the gaff

Topsail yard

A yard carrying a topsail above a lower sail.

25. Build Height, Divide Sail — Put the sails between their supports

Topsides

The outside of the hull above the waterline and below the deck edge, not the deck itself.

3. Give the Hull a Shape — Follow the outside from bow to stern

Torque: shaft turning load

Turning moment transmitted as twisting load through the rudder shaft.

7. Why the Boat Leans and Wants to Turn — Force needs a place to act

Torsion

Torsion transmits a twist between a torqued and restrained region; internal deformation differs from bodily rotation of the spar.

12. Hold Up the Mast — Restrain a slender member between its ends

Tow-tank test

A controlled test moving a hull or appendage through water to measure behaviour.

43. Draw It, Measure It, Compare It — Make a smaller boat, then control the test

Towline

A line through which another boat or a shore-based pull moves a vessel.

1. A Boat Before Sail — A hand, a blade and a direction

Track through the water

The actual path through the surrounding water, which may differ from heading because of leeway.

6. Give the Water Something to Push Against — Where the boat points and where it goes

Trailing edge

The edge of a foil from which the flow leaves.

39. Move Mass, Add Foils — Give the foil a shape we can describe

Trampoline

A trampoline/net is a tensioned mesh, webbing or suitable fabric surface; downward crew load becomes surface and edge tension transmitted into supporting lines, beams or hulls.

38. Separate the Hulls — Put a working surface across the gap

Transom

A surface or structural assembly closing the stern across the boat, rather than bringing the sides to a point.

3. Give the Hull a Shape — Several ways to finish the hull

Transom knee

The transom knee fastens the transom to the horn timber with arms along both members.

32. Build a Hull from Joined Pieces — Give the projecting stern its own supports

Transom-hung rudder

A rudder mounted outside the boat on its transom.

37. From the Hand to the Rudder — Hang the blade where the hull can carry it

Trapeze

A wire-supported system allowing a sailor to stand farther outboard and increase righting moment.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Traveller / traveler

The traveller changes the sheet’s lower attachment along a track; the Navy 44 has two joined cars and lower blocks operated by a separate control.

28. Shape Is a Control — Trace the mainsheet to the boat

Traveller car

The traveller car is the sliding or rolling carriage carrying the lower sheet blocks on their transverse track.

28. Shape Is a Control — Trace the mainsheet to the boat

Traveller control

The traveller control is the separate rope through tackle and guides that moves and retains the lower sheet-block car assembly along its track.

28. Shape Is a Control — Trace the mainsheet to the boat

traveller position

The first comparison retains the mainsheet between secured ends while the car moves leeward, changing the lower attachment and permitted boom position.

28. Shape Is a Control — Trace the mainsheet to the boat

Traveller ring

A ring able to slide along a spar or stay while carrying an attachment.

21. Move the Sail Beyond the Bow — Move the attachment, or move the whole spar

Treenail / trunnel

A treenail or trunnel is a driven wooden pin whose sides bear across joined timber interfaces.

32. Build a Hull from Joined Pieces — Make the joint carry force and close the seam

Trestletrees

Fore-and-aft timbers near a traditional masthead that support the cross-members and top.

25. Build Height, Divide Sail — Give the upper mast a seat

Tri-radial

A panel layout arranged radially from three sail corners.

13. Give the Sail Its Shape — Turn the cloth towards the load

Triatic stay

The triatic stay connects upper foremast and mainmast attachments in tension.

24. Spread the Work Across a Schooner — Put the foremast ahead of the main

Triaxial reinforcement

Reinforcement with fibres arranged in three principal directions.

33. Change the Material, Keep the Jobs — Place fibres where the load must travel

Trigger shackle

A trigger operates the retaining mechanism; its release job is distinguished from an independent swivel’s rotational job.

10. Hold the Load, Keep Control — Retain the opening, then decide how it releases

Trim (hull attitude)

The fore-and-aft attitude of a floating boat, often expressed through differences in bow and stern draught.

2. Why a Hull Floats — Loading changes the waterline

Trimaran

A vessel with one main hull and two smaller side hulls or floats.

11. Trade Force for Distance — What turns inside the block

Triple block

A triple or treble block contains three sheaves with separate passages.

Truck

A small cap or disc at a mast’s top, sometimes carrying flag-halyard sheaves; not a road vehicle.

25. Build Height, Divide Sail — Extend and name the upper stages

Truckers’ hitch

A fixed intermediate eye and return around the second attachment create a temporary purchase, with sliding contact consuming advantage.

9. Join Ropes and Make Attachments — A connection can help with the pull

True wind

Wind expressed relative to a stated reference, commonly the water for sailing performance; distinguish it from ground-referenced wind.

5. The Wind the Sail Actually Meets — Choose the observer

True wind angle

The angle between the boat’s heading and the defined true-wind direction.

5. The Wind the Sail Actually Meets — Choose the observer

Truss

A fitting or rigging arrangement holding a yard to its mast while allowing the required turning movement.

15. A Sail on a Yard — Raise it and keep it near the mast

Trysail

Trysail in the present storm-use sense replaces the mainsail with a reduced robust sail whose track and sheets are traced separately.

30. Reduce, Gather or Replace the Sail — Set a sail made smaller

Trysail — historical fore-and-aft

Trysail here denotes the historical fore-and-aft gaff working sail, separately from a dedicated storm replacement.

26. Read the Whole Square or Mixed Rig — Give the after sail a separate track

Trysail — storm replacement

The storm replacement travels on its own port mast track and is sheeted from its clew to after blocks, leaving the secured main boom out of that route.

30. Reduce, Gather or Replace the Sail — Set a sail made smaller

Trysail mast

The trysail mast is a small separate support abaft the mainmast, with a deck foot and upper attachment at the main top in Falconer.

26. Read the Whole Square or Mixed Rig — Give the after sail a separate track

Tuck

A traditional term for the way the after planking turns or terminates beneath the stern; precise usage varies by construction.

3. Give the Hull a Shape — Several ways to finish the hull

Tumblehome

Hull sides that slope inward as they rise above their widest region.

3. Give the Hull a Shape — Read a slice through the hull

Turbulent flow

Turbulent flow contains fluctuating motion and cross-stream mixing within a possible steady mean direction.

34. Why Hull Shapes Behave Differently — Follow the flow next to the surface

Turn

The working end passes around a post, placing the loaded rope against a support and beginning the holding contact.

8. What a Rope Is Made to Do — Which part of the rope moves?

Turn of the bilge

The curved transition between the bottom and the side of a rounded hull.

3. Give the Hull a Shape — Read a slice through the hull

Turnbuckle

The turnbuckle’s opposite thread hands let a body rotation shorten or lengthen the connection without twisting the stay.

12. Hold Up the Mast — Turn the adjuster while letting the joint align

Turning block

A turning block changes the direction of a working line and passes the rope’s reaction into its mounting.

11. Trade Force for Distance — Lead the rope where it is useful

Turtle (sail bag)

A bag arranged for storing and deploying a spinnaker; not the inverted-boat meaning.

29. When the Wind Moves Aft — Bring the cloth under control

Tweaker

A tweaker is the supplementary control pulling a small sheet guide towards a deck block, changing the working line’s lead.

12. Hold Up the Mast — Support the mast fore and aft

Twin backstays

Twin backstays retain two separate mast-to-deck members, unlike two legs sharing a split backstay’s single upper section.

Twin keel

A sailing arrangement with two keels, commonly one on either side, often allowing the boat to stand when the tide falls.

35. Keels, Ballast and Adjustable Draught — Put supports to either side

Twin-skin mainsail

A mainsail using two skins to create a controllable thicker aerodynamic section.

27. Rearrange the Whole Rig — Give the aerodynamic surface thickness

Twing

A line-and-ring or block control drawing a spinnaker sheet or guy downward.

29. When the Wind Moves Aft — Change the lead without losing the corner

Twist

The change in a sail’s angle from lower sections to upper sections.

13. Give the Sail Its Shape — Give the curve a reference

Two-line reefing

Two-line reefing uses independently controlled tack and clew lines for the same reef, with each retained through its own leads.

30. Reduce, Gather or Replace the Sail — Route the reef controls

U-bolt

The curved exposed member receives the connection and its two threaded legs carry the pull into nuts and backing.

10. Hold the Load, Keep Control — The eye and the structure behind it

UHMWPE / HMPE

Expanded family names connect low mass and low extension to the need for suitable bends, grip and grade-specific creep control.

8. What a Rope Is Made to Do — Different fibres, different useful properties

Una rig

A single-mast, single-sail arrangement; usage overlaps cat rig and should not be presented as exclusively modern.

4. One Mast, One Sail — One mast and one principal sail

Unbalanced rudder

A rudder whose effective blade area lies behind its turning axis.

37. From the Hand to the Rudder — Put the turning axis within the blade

Unbend

Detach a sail from its rigging attachments.

14. Attach and Support the Sail — Guide an edge along a stay

Underbody

The portion of the hull below the waterline; specify whether appendages are included in a drawing or measurement.

3. Give the Hull a Shape — Follow the outside from bow to stern

Unidirectional reinforcement

Reinforcing fibres mainly aligned in one direction to carry loads efficiently that way.

33. Change the Material, Keep the Jobs — Place fibres where the load must travel

Unstayed rig

A rig whose mast stands without supporting stays or shrouds, carrying its bending loads through the mast and its hull support.

Related labels and senses: Una-stayed / unstayed rig.

12. Hold Up the Mast — Restrain a slender member between its ends

Upper shroud

Upper shroud identifies support of an upper region and may overlap cap shroud in the selected naming convention.

Upper topsail

The upper of two sails dividing the traditional topsail area.

25. Build Height, Divide Sail — Divide the largest upper sail

Upwash

An upward or windward deflection of flow ahead of a lifting surface, depending on the chosen viewing frame.

5. The Wind the Sail Actually Meets — Follow the air, then the force

UV degradation

Damage caused by sunlight’s ultraviolet component, relevant to sails, ropes and coatings.

33. Change the Material, Keep the Jobs — Follow the environment into the connection

V-bottom hull

A hull whose bottom rises to either side of the centreline, creating a V-shaped section.

3. Give the Hull a Shape — Read a slice through the hull

Vacuum bagging

Using a sealed bag and pressure difference to consolidate a laminate.

33. Change the Material, Keep the Jobs — Use a pressure difference

Vaka

Vaka identifies the central main hull in the selected contemporary trimaran usage, contributing buoyancy, carrying space and the structure receiving the connecting beam reactions.

38. Separate the Hulls — Read the names in their setting

Vector

A quantity with both size and direction, useful for showing wind, speed and forces.

5. The Wind the Sail Actually Meets — Choose the observer

Vectran / liquid-crystal polymer fibre

LCP’s low extension and creep suit an inner load member while a polyester cover supplies exposure protection and handling contact.

8. What a Rope Is Made to Do — Different fibres, different useful properties

Velocity made good / VMG

The component of speed towards a specified direction or target, such as directly upwind.

43. Draw It, Measure It, Compare It — Measure progress towards something

Velocity prediction program / VPP

A model estimating sailing performance by balancing aerodynamic, hydrodynamic and stability relationships.

43. Draw It, Measure It, Compare It — Compute a flow, then predict a sailing state

Ventilation

Air being drawn onto an immersed foil, potentially reducing its useful force.

39. Move Mass, Add Foils — Keep the water in the comparison

Vessel

A general term for a craft used on water, avoiding an unnecessary boat-versus-ship distinction.

33. Change the Material, Keep the Jobs — Place fibres where the load must travel

Vinylester resin

A resin family used in composites where its particular processing and durability properties are useful.

Volume

Length, width, area, volume and basic arithmetic with familiar units.

6. Give the Water Something to Push Against — Where the boat points and where it goes

Wake

The disturbed trail of water left by a moving vessel.

Wale

A wale is a thicker external longitudinal band or strake fastened into the traditional hull.

32. Build a Hull from Joined Pieces — Fit planks around the curve

Warp (cloth)

The lengthwise yarns of woven fabric.

Related labels and senses: Warp; Other senses: Warp (handling line).

13. Give the Sail Its Shape — Turn the cloth towards the load

Warp (handling line)

A handling warp is a line used to pull or position the boat; hauling it towards a fixed attachment brings external effort into the boat’s movement.

Related labels and senses: Warp; Other senses: Warp (cloth).

13. Give the Sail Its Shape — Turn the cloth towards the load

Washboards

Washboards close the vertical entrance; in Fram guides locate them and two bridge-deck lever latches lift them behind the lower sliding-hatch grabrail.

40. A Deck with Openings — Close the lid and the entrance

Water ballast

Water deliberately carried in tanks to alter stability, trim or displacement.

39. Move Mass, Add Foils — Carry water, then decide where it belongs

Water ingress

Unwanted water entering a structure, core, compartment or fitting.

33. Change the Material, Keep the Jobs — Follow the environment into the connection

Waterline

The line where hull and water meet; in a lines plan, also a horizontal reference slice through the hull.

2. Why a Hull Floats — Loading changes the waterline

Waterline beam

The hull’s width at a stated waterline, often its maximum width at that waterline.

3. Give the Hull a Shape — Measure the same hull in several ways

Waterplane

The flat shape made by slicing the floating hull at the water surface.

3. Give the Hull a Shape — Read a slice through the hull

Waterplane area

The area enclosed by that water-surface slice of the hull.

3. Give the Hull a Shape — Read a slice through the hull

Waterplane coefficient

Waterplane area divided by its reference length-and-beam rectangle.

43. Draw It, Measure It, Compare It — Give fullness a denominator

Watersail

A supplementary sail set low beneath another sail or spar to add area in light weather.

25. Build Height, Divide Sail — Add area beside and beneath the main supports

Watertight

Watertight identifies prevention of water passage under specified pressure and operating conditions, exemplified by a complete compartment boundary under a water head.

40. A Deck with Openings — Preserve the intended water boundary

Watertight bulkhead

A watertight bulkhead combines a pressure-carrying panel, continuous hull/deck connections and controlled doors or penetrations to isolate spaces under stated conditions.

40. A Deck with Openings — Preserve the intended water boundary

Watertight versus weathertight

Watertight and weathertight specify different water-exclusion conditions; the bulkhead pressure boundary and exposed hatch route make each testable claim identifiable.

40. A Deck with Openings — Preserve the intended water boundary

Watertight versus weathertight

The comparison follows water across a hatch cover/frame/seal versus through a bulkhead panel/edges/penetrations under separately stated conditions.

40. A Deck with Openings — Preserve the intended water boundary

Waterway

A waterway is the substantial deck-edge plank or channel guiding water towards drainage openings.

32. Build a Hull from Joined Pieces — Close the deck without fragile ends

Wave-making resistance

Generating the moving hull’s free-surface wave system carries energy away and creates wave-making resistance.

34. Why Hull Shapes Behave Differently — Let pressure recover and account for the waves

Wave-piercing bow

Reduced growth of upper-bow volume limits the additional buoyant support and wave excitation as the bow enters waves.

34. Why Hull Shapes Behave Differently — Read the bow in more than one view

Wearing ship

Turning a square-rigged vessel away from the wind and around through a downwind course to change tack.

31. Turn, Stop and Rebalance — Reach the other tack by another route

Weather helm

A tendency for the boat to turn towards the wind, requiring corrective steering.

7. Why the Boat Leans and Wants to Turn — Why the helm needs a correction

Weather side / lee side

Traditional terms for the windward and leeward sides of a boat.

5. The Wind the Sail Actually Meets — Give the wind a side

Weathertight

Weathertight identifies exclusion in specified weather and sea exposure; the deck hatch supplies cover, seal and retention in their intended state.

40. A Deck with Openings — Preserve the intended water boundary

Web

The relatively thin connecting part of a beam, frame or girder that helps carry shear and separates its flanges.

12. Hold Up the Mast — Continue the load beyond the fitting

Web frame

A web frame has a stronger transverse support role; Doris records additional oak loops inside the ceiling and under the beams.

32. Build a Hull from Joined Pieces — Tie the deck into the sides

Weft / fill

The crosswise yarns woven through a cloth’s lengthwise warp.

13. Give the Sail Its Shape — Turn the cloth towards the load

Weigh anchor

Raise an anchor from the seabed and recover it.

41. Hold the Boat to the Seabed — Release the ground, then support the anchor

Weight

The force exerted by gravity on a mass.

18. The Tall Triangle — Account for mass at height

Weight aloft

Weight carried high above the water, affecting stability and motions more than the same weight placed low.

Wetted surface

The area of the hull and any included appendages actually in contact with water.

6. Give the Water Something to Push Against — Friction has a surface to act on

Whaleboat

A boat developed for whaling service, often double-ended and capable under oars and sail; context is its technical purpose.

3. Give the Hull a Shape — Several ways to finish the hull

Wheel

A circular steering control connected mechanically, hydraulically or electrically to the rudder system.

23. Put a Smaller Sail Aft — Name the two arrangements

Whipping

A secured band around the cut end restrains the strands or sheath from opening.

8. What a Rope Is Made to Do — Keep the line able to run

Whipstaff

A historical upright lever acting on a tiller below, allowing steering from a higher working position.

37. From the Hand to the Rudder — Reach the tiller from another position

Whisker pole

A spar holding a headsail’s clew out to one side, commonly when sailing downwind.

29. When the Wind Moves Aft — Hold an ordinary headsail out instead

Whisker stay

A side-supporting stay in the bowsprit or jibboom arrangement; identify its endpoints on the actual rig.

21. Move the Sail Beyond the Bow — Spread the side restraints

Wildcat

Another name for a chain-engaging windlass wheel, particularly in American usage.

41. Hold the Boat to the Seabed — Turn a wheel that matches the chain

Winch

The manual winch uses a driven drum, handle and transmission to haul a wrapped rope past the machine.

10. Hold the Load, Keep Control — Grip the line between surfaces

Winch drum

The winch drum is the rotating surface transferring pull to the loaded rope through wrap friction.

11. Trade Force for Distance — Put the travel into a handle

Winch gear

Meshing toothed wheels transmit rotation between handle and drum and can trade speed for turning effect.

11. Trade Force for Distance — Put the travel into a handle

Winch handle

The inserted handle applies torque to the drive at a radius greater than the selected drum radius.

11. Trade Force for Distance — Put the travel into a handle

Winch pawl

The winch pawl engages rotating teeth, yielding in the allowed direction and carrying reverse reaction against a tooth.

11. Trade Force for Distance — Put the travel into a handle

Wind gradient

A change in wind speed or direction with height, helping explain why different heights of one sail may need different angles.

5. The Wind the Sail Actually Meets — When the wind changes

Wind shadow

A region of disturbed or weakened airflow behind an obstruction or another sail; not necessarily a sharply bounded wind-free zone.

29. When the Wind Moves Aft — Present the area to the air

Wind shift

A change in the wind’s direction, which changes the boat’s angle to the wind even before the boat turns.

5. The Wind the Sail Actually Meets — When the wind changes

Wind-tunnel test

A controlled airflow test studying aerodynamic forces and flow.

43. Draw It, Measure It, Compare It — Make a smaller boat, then control the test

Windlass

Machinery for hauling an anchor rode, using a chain wheel, rope drum or both.

11. Trade Force for Distance — The drum still needs a tail

Windlass brake

A mechanism restraining rotation of the anchor-handling machinery.

41. Hold the Boat to the Seabed — Turn a wheel that matches the chain

Windlass clutch

A coupling allowing parts of a windlass to be engaged, disengaged or controlled.

41. Hold the Boat to the Seabed — Turn a wheel that matches the chain

Windvane self-steering

A system using a wind-responsive vane to control steering without relying on an electronic heading reference.

44. When Muscle Is Not Enough — Let the wind set the reference

Windward

The side or direction from which the wind comes.

5. The Wind the Sail Actually Meets — Give the wind a side

Wing keel

A keel with sideways-projecting wings, which alter ballast placement and water flow.

35. Keels, Ballast and Adjustable Draught — Add wings to a keel

Wing mast

A mast with an aerofoil-like section that itself contributes significantly to the aerodynamic surface.

27. Rearrange the Whole Rig — Turn the mast without losing its support

Wing transom

The wing or main transom is the older stern’s principal upper cross-member receiving counter-timber heels.

32. Build a Hull from Joined Pieces — Give the projecting stern its own supports

Wire rope

Wire rope assembles small metal wires into a cable whose elements permit bending; its termination must gather their pull.

8. What a Rope Is Made to Do — From fibres to a working line

Wishbone boom

A forked, curved boom arrangement passing on both sides of a sail.

27. Rearrange the Whole Rig — Take the boom around both sides

Wishbone rig

A description centred on wishbone-shaped sail-control spars, not a unique mast-count sail plan.

27. Rearrange the Whole Rig — Take the boom around both sides

Wooden spar

A mast or other spar made from wood, solid or built up from glued or fastened pieces.

18. The Tall Triangle — Build a long spar from wood

Work

Energy transferred when a force moves something through a distance in its direction.

1. A Boat Before Sail — Energy and effort

working corners

The new tack is retained near the mast and the clew down and aft, with their cringles and patches returning sail loads into hook, line and boom.

30. Reduce, Gather or Replace the Sail — Put the load on new corners

Working end

The actively manipulated end creates the connection while the standing part leads away from it.

8. What a Rope Is Made to Do — Which part of the rope moves?

Working jib

A jib intended for ordinary useful sailing conditions rather than an unusually light or storm-specific sail.

20. Use the Space Ahead of the Mast — Choose the forward inventory

Working sheet

The sheet currently carrying the sail’s load.

29. When the Wind Moves Aft — Hold the windward corner away from the mast

working-area reef and comparison

Partial rolling changes the exposed remnant’s leading-edge thickness, corner location and sheet direction while it remains loaded.

30. Reduce, Gather or Replace the Sail — Roll a supported edge

Worm steering

A steering arrangement using a screw-like gear engaging another gear to provide reduction.

37. From the Hand to the Rudder — Obtain reduction from a screw

Worming

Small cord fills the valleys between laid strands, giving the later covering a more rounded surface.

8. What a Rope Is Made to Do — Keep the line able to run

Woven roving

A comparatively coarse woven reinforcement made from bundles of continuous fibres.

33. Change the Material, Keep the Jobs — Place fibres where the load must travel

Yacht

Yacht as a purpose/use category, with historical qualifications.

20. Use the Space Ahead of the Mast — Measure the sail that extends aft

Yankee

A relatively high-clewed headsail, often used as the outer sail of a cutter arrangement.

Yard

A spar from which a sail is suspended, typically across or obliquely across a mast.

15. A Sail on a Yard

Yard angle

The yard’s inclination to a stated reference, commonly the horizontal in a rig’s side view.

19. A Sail Divided by Battens — Put supporting members across the sail

Yard downhaul

A line helping pull a yard down when the sail is lowered.

19. A Sail Divided by Battens — Pull down a reluctant member

Yard halyard

The line or tackle raising and lowering a yard.

15. A Sail on a Yard — Raise it and keep it near the mast

Yard hauling parrel

An adjustable parrel controlling the yard’s position relative to the mast.

19. A Sail Divided by Battens — Locate the yard and the panel diagonals

Yard heel

The lower or inboard end of an oblique yard in a rig that distinguishes it from the peak.

16. Sloping Yards and Diagonal Spars — Suspend a long sloping edge

Yard parrel

A restraint locating the yard relative to the mast.

19. A Sail Divided by Battens — Locate the yard and the panel diagonals

Yard peak

The upper outer end of a sloping yard.

16. Sloping Yards and Diagonal Spars — Suspend a long sloping edge

Yard tackle

A tackle attached to or serving a yard for lifting or handling loads.

15. A Sail on a Yard — Use the supported yard for another load

Yardarm

One end portion of a yard.

15. A Sail on a Yard

Yarn

Spun, overlapping fibres make the continuous smaller bundles that are assembled into a strand.

8. What a Rope Is Made to Do — From fibres to a working line

Yaw

Rotation that changes the direction in which the bow points.

7. Why the Boat Leans and Wants to Turn — When weight and buoyancy gain leverage

Yawl

Taller forward mainmast and smaller far-aft mizzenmast, aft of the rudder stock under the stated convention.

23. Put a Smaller Sail Aft — Name the two arrangements

Yawl versus ketch

The comparison uses already established mast heights, rudder-stock positions and the actual after-sail scale.

23. Put a Smaller Sail Aft — Name the two arrangements

Yoke

A cross-piece connected to a rudder, with lines or links pulling at its ends to steer.

37. From the Hand to the Rudder — Reach the tiller from another position

Yuloh / yuloh sculling oar

A shaped stern sculling oar used with an oscillating action; its support and lanyard help manage the stroke.