Hold Up the Mast

Pulling a halyard tight puts the sail where it can work. The pull also reaches the mast through the block and the sail’s attachment. Add the sail force and the standing rigging, and the mast receives loads from several directions at once.

The opening chapters gave us the essential arrangement: a mast in compression and bending, with shrouds and stays restraining it in tension. We can now follow each connection closely enough to understand what holds the assembly in shape. Begin at the bottom, where its forces enter the boat.

Continue the load beyond the fitting

Imagine the port shroud restraining a mast pushed towards starboard. At its upper end, the shroud pulls the mast down and towards port. At its lower end, it pulls its chainplate up and towards the mast. The chainplate’s fastenings transfer that load into the hull. The mast’s downward load enters elsewhere, through its step. Connected structure must carry the forces between these regions and into the rest of the boat.

To follow that connection, look inside a traditional timber hull. Its hull skin is the outer shell. In this example the shell consists of planking, the joined collection of planks enclosing the hull. The planks carry water pressure and participate in resisting distortion; their fastenings let them transfer load into neighbouring planks and the structure inside.

Inside the planking, a frame follows the shell across the boat, helping that transverse section retain its shape. At the bottom, a floor, or floor timber, crosses the centreline and ties the lower framing into the keel region. Keel floor identifies a floor doing that job around the keel. The cabin’s walking surface is the sole. Structural floors can lie beneath it, carrying loads whether anyone stands above them or not.

Along the bottom centreline runs the keel timber, the principal lengthwise timber forming the structural keel in this wooden arrangement. Above it, an internal keelson connects the bottom structure along the boat. Together with connected fore-and-aft members, these form what builders call the backbone. The word describes their central organising role. Planking and structure farther from the centreline also share the hull’s loads.

At the top, a deck beam spans across the boat beneath the deck. Its ends connect into the sides; its upper face supports deck material. A mast opening interrupts that span, so beams and reinforcement around the opening must take the load around it. A structural bulkhead can supply another connected route across the hull, provided its edges and attachments are built for that job.

The frames also need connections along the boat. A longitudinal is a structural member running fore and aft. A stringer is one such member, following the hull and joining successive transverse supports. Local force entering a frame can then spread along the stringer and shell into other frames. Keelson, stringer and deck structure contribute different parts of the lengthwise connection.

Follow the chainplate again. In a selected timber arrangement, its fastenings engage a frame and surrounding planking. A chainplate knee provides an internal brace that spreads the concentrated pull into adjoining structure, such as the deck region, a frame or a bulkhead. Its angled shape connects parts that would otherwise tend to change their relationship under load. The lower network of floors, keelson and keel timber connects towards the mast step, while other routes run through the sides and deck.

This is a branching network, not one indispensable line through identical timbers in every yacht. Builders vary the number and form of the members, and some hulls have no separate keelson. The invariant is that joints must transfer force if adjoining members are to act together. A strong metal chainplate attached to an isolated weak patch leaves that requirement unanswered.

The network carries shear as well as direct pulls. Picture a patch of planking between two frames: one frame is pulled upwards by a rig attachment while the adjacent structure resists that movement. The patch tends to distort as one edge moves along relative to the other. Shear within the material, and shear and bearing at its fastenings, transmit force across that patch. A floor similarly carries forces between its loaded centreline region and connections farther out. A connecting sheet or relatively thin portion of a structural member is often called a web; its shearing action helps joined parts act together. This extends the pin’s local shear lesson to connected regions of the hull.

Herreshoff’s 1927 wooden-yacht rules made the connection explicit. They described extra support at mast partners and steps, with additional timbers or straps connecting chainplate regions beneath the mast step in large racing yachts. The dimensions belonged to that practice; the linked structural jobs remain recognisable in other materials and periods.

Support the heel and restrain the spar

On a deck-stepped mast, the heel ends at deck level. Its step locates the heel and receives the downward compression. Reinforcement beneath the deck must carry that concentrated force onwards. One solution is a compression post, an internal support running from beneath the mast seating to lower hull structure. A strong post still needs sound support at both ends; otherwise it merely moves the concentrated load to another weak surface.

A keel-stepped mast passes through the deck to a lower step near the keel region. Its heel bears there, with compression transferred into the connected bottom structure. The mast partners restrain it at the deck opening. In a traditional arrangement, substantial timbers surround that opening; wedges or chocks fill the appropriate gaps between spar and support. Lateral force can then pass from the mast through the bearing contact into the deck structure.

The separated deck restraint and lower support can oppose the mast’s tendency to tilt. Mast bury is the portion or supported depth below the upper lateral restraint. With a greater separation between the bearing reactions, the same resisting moment can generally be supplied by smaller opposing forces, other things equal. The mast, bearings and intervening structure still have to carry those forces. Bury is a geometrical part of the support arrangement, not a standalone guarantee of strength.

On the seventeenth-century warship Vasa, the mainmast step lies in the keelson, surrounded by substantial timber. That preserved interface makes the lower bearing concrete. It shows where a large spar was seated; it cannot reveal every load that the complete rig once put through the ship.

Supporting the mast leaves another job at the deck opening: keeping water out. A mast boot is a flexible covering joining the mast to the edge of the opening, excluding water while accommodating the movement permitted by the installation. A mast collar is a surrounding fitting whose job depends on its form. A flexible sealing collar closes the gap; it does not take over the partners’ structural restraint.

Other collars locate and protect the spar at a bearing. Seldén’s collar-type wear pad, for example, fits around a dinghy mast at its gate, increasing the local width and providing the contact surface. The pad receives local bearing pressure from the support and passes it to the mast. The collar’s material and position tell us its job; the shared name does not turn a flexible water seal into a structural bearing.

A small boat can have an open-sided upper support that allows the mast to be put into position. Its mast gate closes that opening and retains the mast. In the RS Venture S/SE arrangement, the heel is first located in the step and the gate is closed at the upper support. The lower step and upper retainer are separate parts of the restraint. We will later meet a gate that closes an opening in a sail track; that other fitting serves the moving sail attachment.

A tabernacle adds a pivoting support so the mast can be lowered under controlled conditions. Side cheeks rise from a strong base, with a transverse pin or bolt providing the mast’s turning axis. In the upright state, the heel seating and the specified retaining arrangement must carry sailing loads; during lowering, the mast rotates about the pivot and its weight must be controlled. A hinge provides a possible movement. It does not by itself supply the restraint or lifting machinery needed throughout that movement.

Restrain a slender member between its ends

A mast can bend elastically under a sideways force, returning when the force is removed. Compression introduces another problem. Take a slender supported spar with a small sideways departure from straight. An endwise compressive force can increase that departure; the increased bend then makes the force’s turning effect larger. At a sufficient load, the slightly bent form ceases to be stable and the member can bow much farther. This loss of stability is buckling.

Buckling can occur before the material is simply crushed by the end pressure. The unsupported length, section, material stiffness and end restraint all matter. Adding effective restraint partway along a mast shortens the length free to depart sideways. It also creates a new place where force must pass through a fitting into something capable of answering it.

The mast can carry a twist as well. If an attachment applies a turning moment, or torque, to one region while another region is restrained, the material between them transmits that twisting action. Torsion is this internal twisting load and deformation. Turning the complete mast bodily through an angle is a different motion: a spar may rotate with little internal twist, or be held at its base while twisting above it.

Bending changes lengths across a section. In a simple initially straight member bent without an additional endwise force, material on the outside of the curve lengthens in tension while material on the inside shortens in compression. Its bending stiffness determines how much curvature results from the applied moment. The working mast also has endwise compression from the rig, superimposed on this bending response; that can leave even the less-compressed side in compression. The same combination of lengthwise loads and bending occurs in hull members, whose connected section and material determine their resistance to deformation.

Shrouds provide lateral restraint through pulling members. A lower shroud attaches to a lower or middle mast region, often near the first spreader level. A cap shroud supports the upper mast, commonly running over spreader tips on its way down to the hull. Upper shroud can mean the same principal member or another shroud serving an upper region, depending on the rig’s naming convention. An intermediate shroud restrains a region between the lower supports and the top of the mast. Following its endpoints establishes the particular mast length it supports.

A spreader is a strut projecting from the mast to hold a shroud farther out. At its outer spreader tip, the shroud bears on a seat or fitting that maintains this offset. The spreader root is the inner end; a spreader socket receives and locates it at the mast. The shroud’s change of direction pushes the strut towards its root, placing it mainly in compression and passing that reaction into the mast through the socket.

Moving the shroud outwards gives its upper part a more useful sideways angle to the mast. A very nearly vertical line needs a large tension to provide a modest sideways force. The spreader can improve that geometry, while adding compression and attachment reactions of its own. Its tip must keep the shroud in its intended place, and its root must transmit the strut’s force; a spreader floating alongside the wire would do neither job.

An in-line spreader projects approximately athwartships. On an aft-swept spreader, the tip lies aft of the root as well as outboard. The connected shroud then contributes fore-and-aft restraint as well as transverse restraint. Its effect depends on the full route down to the chainplate. The root-to-tip direction is a useful clue, but it cannot reveal the complete support arrangement by itself.

Two lower shrouds can divide the directional job. A forward lower runs from its mast attachment to a hull attachment ahead of the mast. An aft lower leads to one abaft it. Each pulls outwards and downwards, with an additional forward or aft component. Together they can restrain the lower mast’s fore-and-aft movement as well as its sideways departure.

Support the mast fore and aft

The forestay runs from the mast towards the bow, restraining aft movement of its mast attachment. Headstay is another name commonly used for the principal forward stay, especially where it also supports a headsail. That sail’s separate attachment and control will come later. Here the stay’s structural contribution is its forward pull.

A backstay runs aft from the mast and provides a corresponding aft pull. In a particular rig, changing that pull can affect mast bend and the tension of the forestay through the connected structure. A permanent backstay normally remains connected and working through a tack, although its tension can change and it may have an adjuster.

Two lower ends at the deck can belong to quite different arrangements. A split backstay has one upper member that divides into two lower legs approaching separate deck attachments. Twin backstays are two distinct members running from their mast attachments down to their own lower attachments. Follow the pair upwards: in the split arrangement they meet at a junction; in the twin arrangement they remain separate for their full length.

The split lower connection acts as a bridle. Its two leg tensions combine at the junction to answer the upper member’s pull; spreading the lower attachments farther apart changes the useful component supplied by each leg. A short pendant can instead extend one connection to place an attachment or adjuster within reach. It lengthens a single load route, whereas the bridle divides that route between separate points.

An aft support can also need to move out of the sail’s way. A running backstay, usually shortened to runner, is adjustable and commonly supplied on both sides. In the representative arrangement, the windward runner is tensioned while the leeward one is eased so the sail can extend past it. Changing tack exchanges those roles. Its support has to be coordinated with the sail’s movement; the name running describes that worked arrangement without changing its mast-supporting purpose.

An adjustable checkstay pulls aft on an intermediate mast region, controlling its bending or repeated movement. A babystay pulls forward on a relatively low or intermediate region to help control the mast’s shape; it is not normally intended to carry a headsail. An additional preventer stay supplements or backs up another support. Its actual endpoints tell us which movement it can restrain. These are particular answers to particular regions of a spar, not equipment that every mast must carry.

Local bracing can close its triangle on the mast itself. A jumper strut holds a supporting wire away from an upper mast region. The jumper stay runs from an upper mast attachment over the projecting support and back towards a lower attachment on the mast. The wire pulls in tension while the strut maintains the offset in compression. Their combined action braces that upper length, with reactions returning at the mast attachments.

A diamond stay similarly uses mast-mounted struts and wire returning to the mast to brace a selected length in a diamond-like arrangement. The offset and the plane in which it lies determine the useful restraint. Jumper and diamond systems can support a local mast region without every wire continuing independently to the deck. Their lower reactions still enter the rest of the mast and its supporting system.

Before sail force arrives, the standing rig usually already carries tension. Standing-rigging preload, also called pretension, is the tension deliberately established in that initial condition. Rig tension can refer to this setting or the loads in the working rig; shroud tension identifies the pulling load in a particular side support. Under sail, mast bending, hull movement and external forces change their distribution. A tension member that becomes slack cannot push the mast back. Whether and when that happens must be established for the designed rig, rather than assumed for every leeward shroud.

Adjust a connection made from rope and iron

The desired initial setting requires a way to alter the connection’s effective length. Traditional standing rigging often uses a pair of deadeyes: solid, usually round fittings with several holes but no turning sheaves. One deadeye is held at the shroud’s lower end. Another is attached to the hull. A lanyard, a short securing or tensioning line, passes repeatedly between their holes.

Hauling the lanyard draws rope through the fixed holes and brings the deadeyes closer together, taking up the connection. Successive parts share the pulling job, while friction at the holes makes their actual tensions unequal. The end is then secured. The upper shroud, upper deadeye, lanyard, lower deadeye and hull attachment form a continuous route. The paired fittings let a comparatively manageable rope adjust a much larger standing member.

At a traditional rope shroud’s end, the rope can embrace the deadeye in its outer groove and return alongside itself, with seizings binding the returned part to the standing member. Those bindings preserve the eye around the loaded fitting. The lower deadeye can be held by an iron strop following its outer groove and continuing to the hull connection. Here the strop receives the deadeye’s outward bearing; the seizing keeps adjacent rope parts in their intended relationship. Both now serve the standing load rather than a freely moving tackle.

A bullseye has a smooth central hole through which a line passes, commonly with a groove outside for its supporting strop. Its fixed surface guides the line. The deadeye’s several holes serve repeated tensioning reeving; the bullseye’s single passage serves its selected lead or connection. Neither fitting contains the rotating sheave that reduced sliding contact in a block.

On a traditional ship, a channel, or chainwale, is a projecting shelf along the hull that carries the lower shroud connection farther outboard. This widens the support geometry and clears the side. Iron straps or linked members pass the pull from beneath the lower deadeye into fastenings farther down the hull; the shelf maintains the outboard position while those members carry the upward pull onwards.

Here a chain in the material sense consists of joined metal links: each loaded link bears against its neighbours and transmits tension through those contacts. Period rigging language can also call the attachment assembly beneath the deadeyes the chains, even where long straps or other formed members do much of the work. Some sources extend chains to the associated channel region. We need to identify the actual linked material, iron attachment or projecting shelf meant by the sentence.

E. F. Knight’s 1889 account of small yachts described rope lanyards through deadeyes alongside iron screw adjusters. The two arrangements already coexisted. A threaded fitting offered a different way to set effective length; it did not make the shroud’s lower structural connection unnecessary, nor did every vessel abandon its rope adjustment at the same moment.

Turn the adjuster while letting the joint align

The rigging screw, turnbuckle and bottle screw are overlapping names for threaded rigging adjusters. In a common arrangement, two threaded end fittings enter opposite ends of a central body. One has a right-hand thread and the other a left-hand thread. This handedness of thread means that matching threads advance in opposite directions for the same sense of rotation.

With both end fittings held against rotation, turning the body draws both ends in, or moves both out, together. The stay itself need not twist as the distance between its connections changes.

Shortening that connection takes up slack and then increases tension as the rig and supporting structure respond. The thread travel supplies adjustment; the connected members’ stiffness and geometry determine the resulting load.

At one end, a clevis puts a mating fitting between two forked sides. A clevis pin crosses their aligned holes. The familiar shear and bearing contacts pass the pull from the central fitting into the fork, while a split pin or other specified retainer prevents withdrawal. This connection permits movement about its pin axis. It does not permit unlimited movement in every direction.

A ring cotter can provide that secondary retention on a suitable pin instead of spread split-pin legs. Neither small retainer replaces the main pin’s loaded section. Rig movement can bring a rope or adjacent fitting against it, so the complete arrangement has to preserve retention through its allowed range of movement.

A toggle adds articulation so the connected fittings can align with the pull. In a common link, two pins with differently oriented axes permit movement in two planes. The load passes through the link and its bearing contacts while the members change angle. That freedom reduces unwanted bending at a connection intended to carry tension. The toggle supplies alignment; the threaded body supplies length adjustment.

A swivel supplies a different freedom: rotation about the connection’s lengthwise axis. That can let an attached part turn without forcing the standing member to take the same twist. A swivel’s presence does not establish that the connection can also bend to the required angle. The actual axes of movement must fit the changing rig geometry.

At the mast, a tang, or mast tang, provides a projecting plate or fitting with a hole for the connected rigging. Pull enters through the pin or shackle, passes through the projecting material and its fastening, then reaches the mast wall. Lug can also mean a projecting attachment tab of this sort. The later lug sail uses the same short word for a different object.

A projecting bail offers a curved bracket for a connection instead of a plate tab. If a shackle joins the rigging eye to that bracket, its body and closing pin must seat through the permitted angles without levering against an edge. A narrow D-shackle and a wider bow shackle offer different room for the connected parts to settle. The wider body does not remove the need to check where the changing pull bears.

At the deck, the eye fittings already examined offer different ways to receive that moving connection. A ringbolt adds movement at its ring; a fixed padeye must give the connector enough room to align. An eyebolt, U-bolt or eye strap passes the pull into a different arrangement of shanks or fastened ends. For this shroud, follow the changing pull through the selected fitting and its backing into the hull, including any bending caused when the connector reaches the end of its freedom.

The visible polished adjuster is therefore several working contacts in sequence. Wire or fibre enters a terminal, the terminal connects to an adjuster or link, pins permit the intended movement, and the chainplate carries the pull into the hull.

End the wire, rod or fibre

Wire rope consists of metal wires arranged into strands or a stranded cable. It combines many small elements into a tension member that can bend along a permitted radius. A fitting at its end must collect their pull without letting the cable withdraw or concentrating it at a damaging edge.

To swage a fitting is to compress its metal body into the intended grip; the resulting formed connection may also be called a swage. A swaged terminal has its socket compressed around the wire so the contacting metal transfers the cable’s tension into the terminal. The wire, socket dimensions and forming process must be matched. Its appearance alone does not establish whether the concealed grip is sound.

A mechanical terminal uses assembled internal parts to grip the wire. In Sta-Lok’s documented design, the outer strands surround a tapered wedge over the core, inside a confining socket. The end fitting and former complete the grip. The parts’ contact transfers the wire load into the terminal without the external machine compression used for a swage. Other mechanical terminals must be understood through their own construction.

Another wire-end arrangement turns the cable around a thimble and secures the returned length beside the standing part with a properly formed ferrule. The thimble provides the bearing curve at the eye; the ferrule grips the two adjacent wire lengths behind it. Under a changing stay angle, the eye still needs an articulated mating connection so the cable does not repeatedly bend at an unsuitable point beside its termination. The eye’s protection and the end’s grip solve different parts of that problem.

The gripping method and the external attachment shape are separate choices. An eye terminal ends in a closed eye for a pin or shackle. A fork terminal surrounds its mating fitting with two sides and a transverse pin. A T-terminal has a cross-headed end that seats behind a matching mast socket or backing fitting, spreading its pull into the receiving contact. A ball terminal uses a rounded end seated in a corresponding cup. The mating shape determines how force crosses the contact and what angular movement is possible.

Rod rigging carries the standing load in solid metal rod rather than stranded cable. Its ends can be formed into heads that bear in matching terminal seats. Hayn/NAVTEC’s tapered stemball arrangement is one documented example of a rounded seated rod connection with controlled articulation. The formed head and matching seat carry the pull while allowing the specified angular movement.

Synthetic standing rigging uses engineered fibres or fibre composites for the supporting tension members. One form uses braided HMPE stays with prepared spliced eyes bearing around shaped end fittings. The buried eye splice transfers the returned eye leg’s pull into the standing braid, while the fitting supplies an appropriate bearing curve and a connection to the adjuster or hull attachment. Other fibre constructions use different terminations, which must be considered with the member they serve.

Colligo’s documented fibre-stay arrangement connects a shaped upper end fitting to a lower distributor by separated lashing passes; the distributor is pinned to the lower attachment. Hauling and securing the lashing sets that connection while its several parts carry the pull onwards. A soft shackle would change the interface again: its fibre body and closing eye would need compatible bearing surfaces and room for the stopper, unlike a metal shackle pin. Substituting one connector material therefore requires the whole contact and closure to be reconsidered, even when the quoted straight-pull strength is high.

The rope chapter’s distinctions now have a structural consequence. Elastic extension lets a loaded stay lengthen as the mast moves, then substantially recover as that load eases. Constructional stretch can leave a newly bedded-in stay longer, changing its initial tension. Creep can continue changing length under sustained load. The same altered mast position can therefore call for different explanations depending on the load history and time involved.

For HMPE products, including Dyneema and Spectra fibres, and LCP products such as Vectran, sustained loading makes the selected grade’s creep behaviour particularly important. Chafe or heat at a terminal can also damage the member where its pull is concentrated. Changing wire to fibre therefore changes the questions about length stability, end construction and inspection as well as weight. The complete support must keep the mast within its intended movement under the conditions it actually meets.

Describe the mast’s shape precisely

At the masthead, the upper end or top region, the forestay, cap shrouds and halyard fittings reach their chosen attachments. A crane in rigging is a projecting arm that offsets a connection. A masthead crane carries that arm beyond the top of the mast, for example to keep a backstay clear of a sail edge. The clearance is useful, while the offset makes its pull impose a turning effect on the crane and its mounting.

Take an imaginary cut across a hollow mast. Its mast section is the cross-sectional shape and size: perhaps nearly circular, perhaps longer fore and aft. The mast wall is the material around the hollow interior. Outside dimensions and wall thickness are different measurements. Moving material farther from the middle can improve bending stiffness for a given amount of material, while thin walls introduce their own local stability and connection demands. Shape also makes the response differ between bending directions.

Now look along the spar. Mast rake is its overall fore-and-aft lean relative to a stated upright reference. For this comparison, use a reference perpendicular to the yacht’s design waterline and describe the overall line from heel to masthead. A straight mast can lean aft. Tilting that straight line changes rake without making it curved.

Mast bend is curvature along the mast. Hold the same overall heel-to-head inclination and bow the middle forwards: curvature has changed while the reference line’s rake remains the same. Prebend is the deliberate initial curve established before the changing sailing load is applied. The loaded rig may then bend more, less or differently from that initial shape.

This is the distinction in mast prebend versus rake: one describes an initial curvature, the other overall inclination. In a real connected rig, one adjustment may affect both, but neither quantity uniquely determines the other. Seeing the masthead move is insufficient evidence to say which changed; the shape and the reference need to be known.

Repeated movement is another description. Mast pumping is oscillation fore and aft or sideways under changing loads. Intermediate support, mast stiffness and the motion exciting it influence that movement. A checkstay can restrain a particular bending region, but the fact that it exists does not establish a universal cure or setting.

A free-standing mast accepts more of the bending job through its own section and separated lower supports. A stayed mast distributes that job through its tension members and their hull attachments. Both need a complete route for forces and moments. Stayed or free-standing describes mast support; neither name tells us how many sails the vessel carries or which form they take.

Rig descriptions also need a date. Tally Ho’s original design, her enlarged 1927 rig and the rig developed during the modern rebuild are separate configurations. The Albert Strange Association’s account records the older alteration but gives inconsistent area figures and marks its drawn reconstruction conjectural. Sampson Boat Co documented new sail-plan work in 2021 and mast stepping in 2023. These records show changed arrangements; they do not make the present spar an unchanged survivor or supply a dependable calculation of the earlier loads.

Inspect the connected support

Every joint in this route also has a condition. Fatigue is progressive material damage caused by repeated loading, sometimes at loads below those that would break the part in one application. A fitting loaded and unloaded through many sailing cycles can develop damage at a highly stressed region. That accumulation differs from one excessive load overwhelming it at once.

Corrosion is chemical or electrochemical deterioration of metal through its environment. A stainless-steel fitting in electrical contact with an aluminium mast, wetted by conducting salt water, can promote loss of the aluminium at that connection. Insulating the contact and limiting retained water address parts of that environment. Materials, isolation and exposure therefore matter at a mast fitting as well as its nominal strength. We will examine those material processes in more detail later.

Chafe removes or damages material through rubbing. Corrosion changes it through environmental reaction. Fatigue accumulates through repeated loading. A connection can experience more than one, so a visible rubbed patch or an intact outer surface is only part of the evidence.

Rigging inspection follows the known route through supporting members, terminals, pins, tangs, chainplates and receiving hull structure, looking for deterioration and changes. Access matters: a concealed socket or covered lower chainplate can hide a critical contact. The Maritime and Coastguard Agency’s rigging guidance makes that limitation explicit. A visual check cannot establish the remaining strength of every hidden part, and this explanatory account supplies no universal inspection interval or rigging lifetime.

We now have an upright structure whose members can be named by what they restrain and where their forces go. Its movement also changes the geometry offered to the sail. The next task is to give the flexible surface a useful shape, then connect it to the supporting spars without losing that shape under load.