When the Wind Moves Aft

As a conventional yacht bears away, its apparent wind commonly moves farther aft. The mainsail is eased, and the forward sail needs a different setting too. If the boat accelerates substantially, its motion can bring the apparent wind forwards again. Course and speed together determine the wind experienced aboard.

A working headsail has limited freedom. Its luff follows the forestay, its tack remains at the lower attachment and its clew can move only as far as the sheet, deck lead and neighbouring rig permit. Moving a lead helps, but eventually the chosen sail’s shape and position become the limitation. Another surface can use the available air differently.

Present the area to the air

Hold a flat card in front of you. Viewed squarely, it presents a broad rectangle; turned edge-on, it presents almost none. The card has retained the same surface area. What changed is its projection onto a plane perpendicular to your line of sight.

Projected sail area makes the same distinction. For this comparison, use a plane perpendicular to the incoming apparent airflow: the projection is the outline presented when looking along that flow. A curved sail can contain more cloth than this outline suggests. Depth, folds and orientation all affect how much of its surface appears in that projection.

Broadly presented area can be useful when sailing downwind, but it is only part of the force problem. The relatively edge-on sails of our upwind explanation still developed useful lift by turning the air. On reaches, a full sail can also develop a substantial lifting force; farther downwind, separated flow and drag can contribute more of the drive. Shape and orientation change those contributions together. The distinction is continuous, rather than a switch from an aerofoil to a bag at a particular angle.

The air reaching the sail matters as well. Behind the mainsail lies a wind shadow: a region where the upstream sail has altered the airflow’s speed, direction and steadiness. A forward sail caught in that disturbed air can lose useful loading or fill irregularly. This is the blanketing problem. Its extent changes with the sails and the boat’s motion; it has no fixed boundary at which all wind disappears. The slot interaction already examined is part of the same wider fact that neighbouring sails alter one another’s flow.

We can therefore change two things: the surface presented to the air and the location of that surface relative to the rest of the rig.

Support a full sail at its corners

A spinnaker is a large, full sail used principally for reaching and downwind work ahead of the ordinary working sails. Its head is hoisted, and lines control its two lower corners. Pressure and tension spread the cloth between those supports, giving it the deep working form that a flat triangle laid on the floor would conceal.

In the arrangements here it is set flying: no sail edge is attached to the rig. Its corners remain firmly connected. The head’s upward restraint, the lower-corner pulls and tension through the cloth establish a supported surface with considerable freedom to change shape and position.

The spinnaker halyard raises the head and holds its height. On the Navy 44 used for our preceding control examples, the halyard turns at the forward masthead, runs down inside the mast and passes through a mast-base turning block to a cabin-top winch. Its head connection takes the sail’s pull into the rope; the upper turn, mast and deck-mounted control return that load into the boat. Easing this halyard permits the head to descend. It does not itself receive the loose cloth below.

The two lower corners can now be arranged in different ways. One solution gives them broadly interchangeable roles and holds the windward one out to the side. Another gives the sail a permanent forward tack and a distinct after clew. These are different supported geometries within the spinnaker family.

Hold the windward corner away from the mast

A symmetrical spinnaker has broadly matching side edges and lower corners when considered in its designed flat shape. Under sail, one lower corner is to windward and the other to leeward. The inflated surface need not remain perfectly symmetrical: the wind, rig, heel and controls impose unequal conditions on it.

The spinnaker pole holds the windward lower corner away from the mast. Its inboard end, or heel, connects to a fitting on the mast; its outer end guides the line attached to that corner. Hauling the line brings the corner towards the pole end. The spar can then carry compression between its mast attachment and the restrained corner, keeping the cloth spread across a space that an unsupported rope alone could not maintain.

On the Navy 44, the heel socket connects to a car on a track along the mast’s forward face. This car locates the inner end and permits its height to be adjusted. The outer jaw closes around the spinnaker guy, the line controlling the windward corner through the pole arrangement. The jaw retains and guides the rope; the corner’s attachment remains beyond it.

This guy leads aft and is therefore also called the afterguy. Its forward snap shackle clips to an attachment on the sheet’s connector at the sail corner. From there it passes through the pole jaw and aft, outside the side rigging, to a block behind the shrouds and then into the cockpit. Tension in that aft-led line restrains the outer end’s forward movement and adjusts the pole’s position. It carries a tensile load while the spar carries compression.

The opposite, leeward corner has a spinnaker sheet. In this arrangement its route passes outside the rig to a stern-quarter block, turns inboard through a further rail-mounted block and reaches a cabin-top winch. Hauling or easing it changes the leeward corner’s position and the sail’s working shape. Its aft deck lead performs a different job from the pole’s mast attachment, even though both contribute to spreading the same sail.

Two more directions require control. A pole lift, also called a pole uphaul or, in this manual, the pole’s topping lift, supports its outer end from above. The line runs from that end to a sheave on the mast’s forward face, then down inside the mast through its lower turning block and control. Its tension supports weight and sets height. This is the pole’s lift, distinct from the mainsail boom’s topping lift.

A pole downhaul restrains the spar from rising. The Navy 44’s foreguy supplies a downward and forward restraint: its two-sided line runs from a cabin-side cleat to a foredeck block, up to the underside of the pole’s outer end and back down the other side of the boat. Hauling it opposes the lift and the sail’s upward pull. Foreguy specifies the forward lead in this arrangement; downhaul identifies its downward restraining job. The afterguy, foreguy and lift together control different directions around the compressed spar. The Navy 44’s equipment and rigging account gives their actual connections.

The system must also work on the other side. Each lower corner carries a sheet and a guy. While the windward guy and leeward sheet carry their working loads, the other guy is the lazy guy and the other sheet the lazy sheet: each is currently unloaded, ready for the changed arrangement. The working sheet is the one presently taking the sail’s sheet load.

During a gybe the lower corners exchange windward and leeward roles. The formerly lazy guy becomes the windward control through the pole; the formerly lazy sheet becomes the leeward working sheet. The old working lines are eased. These names describe the current job and loading, rather than a permanent property of a coloured rope. The pole and its supports must be transferred as part of that change, while the sail still needs control.

Smaller systems can reduce the number of separate lines. Seldén documents a pole with matching end fittings that is turned end-for-end during the change of sides. One pair of ropes serves both jobs: the rope on the pole side acts as guy, and the one on the other side acts as sheet. Its larger arrangement instead retains the heel at the mast and dips the outer end past the forestay to receive the new guy. These are distinct documented systems, each with its own connections and handling demands.

Change the lead without losing the corner

An afterguy’s useful pull depends on its direction. When the pole lies far forward, a line led almost straight back towards the mast region supplies a poor sideways restraint. It may also bear against the posts supporting the deck-edge guard wires.

The Navy 44’s reaching strut addresses that geometry. This short spar projects sideways from a fitting on the mast. Its outer fitting guides the afterguy farther outboard, clear of those posts. The altered lead gives the tension a more useful component for holding the forward-positioned pole away from the forestay. The guy still reaches the same sail corner through the pole’s jaw; the strut changes its intervening route. Reaction at the guide enters the strut and then the mast.

A smaller guide can change a rope’s vertical lead. Pass a spinnaker sheet or guy through a block carried by a separate control line. Lead that control down through a deck block and back to a cleat. Hauling it draws the first block down, so the loaded spinnaker line approaches the boat at a different angle. This is a twing, a particular flying-sail application of the tweaker already encountered.

Harken’s spinnaker arrangement places such a guide near the boat’s widest part. When the guy is drawn down there, its changed lead adds downward restraint to the pole-side system. Applied to the leeward sheet, the same kind of guide increases the downward component of the pull from the sail’s clew and changes the leech’s restraint. The result depends on which line passes through it and where its attachment lies. Harken’s actual sheet-and-guy diagrams, page 269, distinguish these controls from the separate paired-line system.

This continues the previous chapter’s lesson about first leads. A genoa track or jib track guides a lead car along the deck; a traveller control moves its car and attached sheet block. A sheet horse lets the sheet attachment move along a transverse bar. An inhauler draws a guide inboard, while the Corsair barber hauler adds an outboard pull. Each changes a particular force direction through its own contact with the sheet or clew. Here the twing moves a guide down towards the deck. The name alone cannot tell us the effect without that route.

Seldén’s small-pole drawing also shows an optional two-leg bridle supporting the pole. Its legs spread a lift or downhaul load into the spar. The mainsheet bridle in our preceding chapter instead supported a sheet block between two hull attachments. Following what each bridle carries keeps these different uses intelligible; the Navy 44’s separate corner sheets and guys do not become a sheet bridle merely because two ropes reach one corner.

Put a distinct tack ahead of the bow

An asymmetrical spinnaker has unequal side edges and distinct tack and clew. Its luff runs from head to forward tack; its leech runs from head to after clew. A bow attachment or projecting bowsprit locates the tack, while the sheet controls the clew. The forward corner keeps its tack role as the sail changes sides.

Take the arrangement in Corsair Marine’s 2014 manual. A tack line connects to the sail’s tack, passes through a block at the end of the projecting bow pole and returns along the main deck to a cleat on the cabin roof. Hauling it draws the tack towards that outer guide. Easing it allows the corner more freedom and changes the luff’s tension and position. The head remains held by its halyard, and the after clew by its sheet. The three adjustments interact through the cloth.

The clew sheets lead aft to blocks near the floats’ after crossbeam. Corsair also describes a block carried on a strap around that beam; moving the strap in or out changes the sheet’s first lead. The broad platform provides a different range of lead positions from a narrow monohull deck, but the same rule applies: resolve the pull along the line from clew to guide. The dated Corsair manual supplies this arrangement, including distinct routes for inside and outside gybes.

With an inside route, the lazy sheet passes through the space ahead of the forestay or inner rolled sail and behind the flying sail’s tack. With an outside route it passes around the tack as well. Those routes allow different paths for the clew’s side change. They cannot be interchanged casually: a rope led on the wrong side of a support can restrain the very movement the crew is asking for.

The forward sprit projects this sail’s tack chiefly ahead of the boat. A conventional spinnaker pole can place its windward corner well to the side. That difference affects which part of the sail can reach clear air, particularly as the apparent wind moves aft. Both arrangements need tensioned lines, sound corner reinforcement and a structure able to receive the reactions. Neither geometry alone establishes a universal faster or easier sail.

The older bowsprit lesson now has a new application. A stemhead fitting can retain the principal forestay at the bow while a separate bowsprit end carries the flying tack beyond it. On Seldén’s deck-mounted sprit, the heel fitting locks to a deck eye and a lined ring supports the tube farther forward. Those separated contacts return the projecting sail load into the deck structure; the tack-control line runs through the tube and aft.

Compare those two contacts with the longer traditional bowsprit assembly. Knight’s heel and gammon iron retained a sliding spar; the bobstay and lateral stays restrained its outer end through the cranse iron. Nares’s added jibbooms needed further support through their overlaps and martingale gear. The short modern tube concentrates the flying tack’s load into its own section and separated deck supports. Removing the external restraining ropes makes the tube’s unsupported length and these receiving contacts more consequential. Seldén’s dimensioned sprit description shows this different allocation of structure.

The distinction extends to the cloth. Nares’s flying jib was carried on a flying-jib stay, farther out than the ordinary jib on its jibstay. Knight’s jib topsail used the topmast stay and sliding luff attachments. Their names identify positions in those rigs; neither name proves that the sail had the free edge of this asymmetric. Here the halyard holds the head while the tack line and sheet tension the remaining corners without attachments along the luff.

The movement also differs from Knight’s traveller. His inhaul and outhaul moved the tack on a ring along the fixed spar; this tack line draws the corner towards the sprit-end guide. Retracting the whole tube moves that guide itself. Before asking the crew to ease a line, identify which of these movements the arrangement permits.

Hold an ordinary headsail out instead

A larger flying sail is one choice. The existing jib or genoa can also be spread differently. In a goosewinged, or wing-and-wing, arrangement, the mainsail lies on one side of the boat and the forward sail is held out on the other as the yacht sails downwind. With airflow arriving from aft, the two surfaces can expose cloth on opposite sides of the hull.

A whisker pole holds the headsail’s clew out. In Forespar’s documented arrangement, the heel attaches to a mast fitting or car and the outer jaw guides the headsail sheet, which can run through it. An upper lift supports the pole’s weight; hauling the sheet brings the clew towards the outer end. These separated supports maintain the spar’s position while it keeps the corner away from the mast. Forespar’s description also distinguishes its telescoping length adjustment from the sheet controlling the sail.

The opposite-side spread can bring the headsail out from behind the mainsail’s disturbed wake and help it remain filled. Its luff still follows its existing support. The whisker pole changes the clew’s location, whereas the conventional spinnaker pole controls the full sail’s windward lower corner and the forward sprit locates an asymmetric’s tack. A spar suitable for one of those loads cannot be assumed suitable for another.

Choose the shape as well as the name

For an angle where the wind comes across the boat, a flatter surface may work better than the deep, broad shape wanted farther downwind. A flying sail with a relatively straight, tensioned luff and a sheet-controlled clew can supply area beyond a modest working jib without requiring the fullest spinnaker shape. Used principally for this job, it is a reacher. The word describes its intended work; its actual cut and supports still need stating.

Code sail names a changing family of such specialised flying sails. North Sails describes relatively flat surfaces intended for close reaching, while explaining that different sailors and rules use the name differently. Code Zero is a particular light-air reaching name with an asymmetric outline. In North’s stated Code Zero spinnaker convention, the design seeks a flat working shape while meeting the applicable minimum width at mid-height. That requirement can leave cloth in the shoulders that a purely geometric reaching design would not otherwise choose.

For a precise present measurement reference, World Sailing’s Equipment Rules of Sailing 2025–2028, version 2, classify a spinnaker by a half-width at least 75 per cent of its foot length, and a headsail below that boundary. Half-width here measures between the midpoints of the side edges, across the sail. The numerical boundary decides a governed category; the airflow does not change abruptly as a sail crosses it. North’s qualified Code descriptions and the actual equipment rules therefore answer different questions.

Seldén’s sheet dated 11 May 2010 uses gennaker for the fuller, curved-luff flying downwind sail and contrasts it with a straighter-luff Code Zero requiring higher luff tension. In that usage the gennaker has the asymmetric arrangement already followed: head on a halyard, tack restrained forward and clew sheeted aft. The name is common commercial language rather than one universal specification. Its fuller outline and corner supports are more informative than an assumed fixed boundary between gennaker and asymmetric spinnaker.

That higher luff tension is a structural consequence, not just a trim preference. A flatter flying sail may carry a cable sewn into its luff or a reinforced luff panel able to carry the required load. Head and tack attachments must react that tension, as must the mast hoist and the forward support. A sprit dimensioned for a full gennaker must not automatically be assumed suitable for a highly tensioned Code Zero. Seldén’s dated comparison makes the distinction explicit.

On Corsair’s trimaran, the corresponding specialised reaching sail is called a screecher, spelled screacher in the 2014 manual. Its wire or Kevlar luff permits a relatively straight tensioned leading edge, its tack uses the projecting bow pole, and its sheet leads to the movable after-beam attachment. The maker describes light-air closer sailing and reaching uses. That is a particular multihull cut and support, not a definition of every sail sold under the name. Its shallow shape and luff tension distinguish it from the same boat’s fuller asymmetric.

Keep these choices separate from the headsail measurements already learned. LP measures the clew’s perpendicular distance from the luff; overlap compares a headsail’s extent with the foretriangle reference. Neither specifies the depth or projected area of a filled flying sail. Clew height changes the sheet’s downward lead, whether the clew belongs to a high-cut yankee, an overlapping genoa or a specialised reacher. Those geometric descriptions remain useful, but none selects the whole arrangement.

Likewise, the No. 1, No. 2 and No. 3 jibs compare progressively smaller working units within the stated inventory. A drifter’s light-air job does not settle whether it has hanks, a retained furling luff or a flying edge. Passmore’s lightweight ghoster supplied another documented light-air choice, with material and gathering demands of its own. Day’s balloon jib could stand away from the ordinary jib stay while the working sail was prepared. These earlier names describe useful choices; they do not confer the pole, corner symmetry or fixed bow tack of a particular spinnaker system.

The history also resists a single sequence of shapes. Ratsey & Lapthorn sailmaker J. N. Howard Williams’s 1965 retrospective points to printed spinnaker uses in 1866 and describes early large sails boomed out by the tack that were not all symmetrical. Later changes in panel orientation and shoulder shape altered how the cloth stretched and filled. This is a bounded nineteenth-century use context, rather than proof that today’s asymmetric is merely the successor of today’s symmetric. The light cloth, panel cutting and reinforcement examined earlier made different working surfaces possible alongside the changing supports.

One specialised addition had its own period and purpose. The blooper was a loose, curved-luff sail carried beside a spinnaker in the arrangement described by Offshore in 1976. Its head used a spare spinnaker halyard, its tack attached low at the bow and its high clew had a sheet led above the main boom to the transom. Easing the halyard and adjusting the sheet together let the curved cloth stand to leeward of the spinnaker.

This added area beside the main downwind sail, with its own hoist and clew control. The account relates the shape and low tack to the contemporary racing measurement context, and describes reducing the mainsail to expose the additional surface. Its dated explanation, pages 8–9, shows why blooper is a specific historical inventory choice. It supplies no universal wind range or promise that another sail will make a boat stable.

Bring the cloth under control

Every flying surface eventually has to come down. A filled sail can still pull hard while its head descends, and loose cloth can reach the water or snag on fittings. Gathering therefore requires both reducing the aerodynamic load and receiving the surface as its supports are eased. The sail’s lower-corner lines and halyard remain part of that controlled transition.

A turtle is a sail bag arranged to store and deploy a spinnaker. The Navy 44 manual secures it at the side of the boat, with the sail’s head and corners accessible for their connections. As the halyard and lower-corner controls take up the sail, cloth leaves the bag. During lowering, the crew gathers the foot and receives the descending cloth before stowing it again. The bag contains the sail; it does not replace the lines that control it while drawing.

A snuffer, or spinnaker sock, takes the container aloft. This fabric sleeve surrounds the sail during the hoist. A control raises the sleeve’s lower mouth towards the head, exposing the cloth below so that it can fill. Pulling the mouth back down progressively contains the surface while the head remains hoisted.

The snuffer hoop holds that mouth open and guides the cloth into the sleeve. Its shape and smoothness affect whether fabric gathers readily or catches. In ATN’s arrangement, a separate narrow channel keeps the operating line alongside the sleeve and apart from the sail. The line passes through an upper block and forms a loop: pulling one side raises the mouth; pulling the other lowers it. The sail’s halyard continues to support the head while this separate line controls its container. Once contained, the assembly can be lowered on the halyard.

In a 2021 interview, ATN’s Etienne Giroire described developing his equipment from the mid-1980s after seeing earlier sleeves tangle. Putting the control line in its own channel separated it from the cloth; a smoother oval mouth improved how the fabric entered. These were refinements to an existing idea, making the gathering mechanism more manageable without removing the sail’s loads.

A small boat can pull the cloth into a fixed opening instead. A spinnaker chute is the tube or opening through which the sail is retrieved and stored. In the RS500, a retrieval line, also called a dousing line, is the returning end of the spinnaker halyard. It leads aft through a take-up block, forward through a drop block and up the chute, then passes through reinforced rings in the lower and middle parts of the sail before fastening to webbing at an upper patch.

Pulling this return draws the attached patch towards the chute. The intervening rings bring other parts of the cloth into the gathering path as the head is allowed to come down. Reinforcement spreads those local pulls into the sail; the mouth guides the bundle into its stowage space. The tack line and clew sheets remain separate connections and must allow the cloth to move. The RS500’s actual rigging guide, pages 30 and 39–41, shows this route.

The sock moves over the cloth; the chute receives cloth drawn towards it; the turtle receives a gathered sail. Each controls loose material in a different way. None of these containers establishes the reinforced corners and edges needed for a smaller sail to remain set under load.

Rolling a sail offers another means of gathering it, with a different transmission of movement through drum, support and cloth. That mechanism needs its own explanation. The next chapter separates bringing a sail under control, stowing it completely and creating a smaller working surface when conditions demand less canvas.