Use the Space Ahead of the Mast

The battened sail divided one surface into supported panels. Another division can leave the main working while a separate sail is lowered, exchanged or adjusted ahead of it. This adds useful cloth without requiring a longer main boom or a taller mainsail. It also creates another object to hoist and another clew to control.

Begin with the familiar boat carrying one mainsail. A forestay already runs down and forward from the mast towards the bow. That structural member can also provide a path along which another sail’s leading edge is retained. Its two jobs must remain visible: it supports the mast, and it can receive additional force from attached cloth.

Put a separate sail on the forward support

A sail set ahead of the mast, or ahead of the foremost mast on a vessel with several, is a headsail. The name locates the sail. To understand its machinery we still need its edge support, corner attachments and controls.

In our first example, a triangular headsail has its tack secured near the forestay’s bow attachment, its head raised towards the stay’s upper attachment, and its luff connected along the stay. Its clew extends aft, where sheets control its setting. This is the familiar jib arrangement. We will distinguish its outline from the larger overlapping genoa shortly; jib has also been used more broadly in particular inventories.

The attachments from the earlier chapter now work along a diagonal stay. Spaced hanks retain the luff while it rises or falls; the piston closures let the crew disconnect a lowered sail for exchange. A headfoil, or luff foil, instead receives a continuous beaded tape through its feeder. Changing sails then means withdrawing one retained edge and feeding another into the passage. The chosen connection changes the handling of the whole forward sail.

Compare the mainsail’s groove or track, with its slides, slugs or luff cars. Both arrangements permit travel along a support while restraining pull away from it. Here the stay and its attachments carry that transverse reaction. The feeder’s entry job remains distinct from a mast gate retaining slides across a loading opening. Above, the jib halyard turns over its sheave and supported box, then descends through the mast to its exit. That separate route carries the head’s hoisting load; the hanks or foil retain the long edge beside it.

A sail supported along a stay is a staysail. That functional name has wider reach than this one position: later examples will place staysails between masts. In common yacht conversation, however, staysail often identifies a separate inner forward sail, while jib identifies the outer one. The bare staysail stay is the supporting tension member; the staysail is the cloth carried on it.

To make that inner-and-outer arrangement, retain the forward stay from high on the mast to the bow and add another from a lower mast attachment to a deck attachment farther aft. The first is now the outer forestay, and the second the inner forestay. Both pull between their own mast and hull connections. The added inner member needs a supported deck attachment and adequate restraint for its pull on the mast; another sail cannot be obtained merely by clipping a line to convenient deck skin.

The cloth carried along that inner member is an inner staysail. In the working arrangement in which it is used together with an outer jib, it is commonly the cutter staysail, and its supporting member the cutter stay. Those names describe the inner unit here. The complete one-mast cutter arrangement will follow after we have examined its parts.

The crew can now lower the outer jib while leaving the inner staysail working, or lower both while retaining the main. Each forward sail has its own head, tack, luff and clew, making those separate operations possible. Dividing the area creates smaller individual operations and more possible combinations, alongside more connections, sheets and sail changes. Total work depends on the rig and conditions, not just on the size of one piece of cloth.

Foresail needs its context stated. In the one-mast main-and-headsail usage, it can mean the forward sail carried on this stay: Seldén uses it in its description of the genoa or jib sheet. In E. F. Knight’s English yacht account of 1889, foresail also identifies the inner forward sail beside an outer jib. On a schooner or square-rigged vessel the word can instead name a principal sail carried on the foremast itself. Those other arrangements will receive their own support descriptions. Here, foresail means the stated forward sail. Seldén’s rigging terminology.

Measure the sail that extends aft

The mast, principal forestay and a base along the deck define the foretriangle in the conventional side view. It is a reference space ahead of the mast; the headsail need not fit wholly inside it. Extend the clew aft past the mast’s region and the sail overlaps the area occupied by the main in that view. That extension is overlap.

A genoa commonly means an overlapping headsail. It obtains extra area by extending aft rather than by moving the forestay or raising its upper attachment. During a tack the extra cloth must travel past the mast and standing rigging. Its sheets need leads that can pull usefully on a clew farther aft. More overlap therefore changes both the surface and the handling geometry.

To put a number on it, first identify the boat’s reference length. J is the horizontal foretriangle base: in the ordinary deck-terminated arrangement used here, from the forward face of the mast to the intersection of the principal forestay’s extended centreline with the deck reference. World Sailing’s measurement rules state the exact reference points, including cases with a superstructure or bowsprit. J is measured horizontally, not along the sloping stay.

Now measure the sail. LP, the luff perpendicular, is the shortest distance from the clew to the luff. Imagine a straight measuring line from the clew meeting the luff at a right angle. Moving its meeting point up or down the luff would make that line longer. LP measures across the sail; J measures along the boat’s foretriangle base.

For an illustrative boat with J of 4 metres and a headsail with LP of 6 metres, LP divided by J is 6 ÷ 4 = 1.5. Multiplying by 100 gives 150 per cent. This is the sail’s LP/J percentage, a comparison between two lengths in the same units. It does not say that the sail has 150 per cent of the mainsail’s area, or that its foot is 6 metres long. An LP of 4 metres on that boat would give 100 per cent.

The proportion is more dependable than a product name. Genoa usually suggests substantial overlap and jib little or none, but makers and classes draw their boundaries differently. UK Sailmakers’ own description includes sails called genoas at 98, 135 and 150 per cent. A stated LP/J value tells us which geometrical comparison is intended even when the catalogue’s name is loose. World Sailing’s measurement definitions and UK Sailmakers’ headsail account supply these conventions.

Clew position has a vertical dimension too. Clew height is measured above a stated datum; use the deck beneath the clew for this comparison. Raising the clew while keeping the deck lead fixed makes the sheet descend more steeply from sail to lead. Moving the lead changes that direction again. The sheet’s pull therefore depends on the corner’s height as well as its fore-and-aft position.

A yankee is a relatively high-clewed headsail, commonly the outer sail paired with a cutter staysail. Its raised clew leaves an opening beneath the after part of the sail and requires an appropriate sheet lead. A smaller high-cut outer sail can also pass an inner stay more readily than a large low-clewed overlapping genoa in the same arrangement. High clew, overlap percentage and inner-versus-outer position describe different properties; none can substitute for the other two.

Give each unit its own controls

The jib halyard raises the jib’s head along its support and holds the selected hoist. Its jib sheets pull on the clew. In the familiar two-sheet arrangement, one runs towards a lead on each side of the deck and then aft to a control the crew can work. The sheet on the lee, or leeward, side normally controls the filled sail; the sheet on the weather, or windward, side remains eased enough to let it set. Windward and leeward here refer to the wind the sailing boat is experiencing. As the boat tacks and those sides exchange, the formerly working sheet is eased and the other takes over.

Replacing the jib with the overlapping sail gives us a genoa halyard at the genoa’s head and a genoa sheet at its clew. A boat can use the same suitable halyard for alternative sails on one support; the compound name describes the present job. The larger sail’s clew position can require a different deck lead, and the sheet must pass clear of the rigging it crosses.

Add the inner sail and another pair of controls comes with it: a staysail halyard from head to mast block or sheave and down to its control, and a staysail sheet from clew through its deck lead. Their independence lets the crew change one sail while the other remains set. Within each assembly, halyard tension, edge retention and sheet direction still make separate adjustments.

A handling alternative lets the forward sail change sides without exchanging two separately worked sheets. In Seldén’s documented self-tacking jib system, a car travels on a transverse track ahead of the mast. One sheet leads from the jib clew through a block on that car, forward through a block at the bow, then aft to the cockpit. The car supplies a movable sheet lead. When the boat tacks, it travels across towards the new leeward side while the same sheet continues controlling the sail.

Force from the sheet enters the car block, its attachment, the car’s bearings and the track, then passes through the track supports into the boat. The car changes the line’s lateral position; the crew can still haul or ease its working length. A self-tending sail is arranged to make this side change with little separate sheet work. The expression describes handling equipment. The crew still chooses the course, steers through the tack and judges the resulting setting. Seldén’s sheet-routing example shows the actual connections.

A short boom offers another way to control the lower part of a jib. A jib club, or club, supports its clew; club boom is a related name for that spar in the chosen jib arrangement. In Donald Launer’s documented example, the boom’s forward gooseneck pivots at the stay or on a deck pedestal behind the tack, and the clew attaches towards its after end. The sheet controls the boom’s movement, and the boom carries the clew with it.

Launer’s self-tending version uses a transverse traveller and a sheet passing from its purchase through a block at the boom’s after end, forward through another boom block, then aft to the cockpit. Leading the rope forward before bringing it aft allows the traveller to cross without the cockpit lead immediately opposing that movement. The club adds a swinging member on the foredeck and can complicate lowering: with the clew fixed aft, the lower luff cannot keep sliding down a fixed stay indefinitely. His arrangement addresses that geometry with a relieving line that allows the lower luff to move aft as the sail descends. The documented club-footed jib and the boomless track system solve related handling problems through different components.

Choose the forward inventory

A working jib is the inventory’s choice for ordinary useful sailing conditions, rather than the exceptional light-air or storm case. It needs the familiar head hoist, luff support, tack attachment and clew control. Its place in that boat’s inventory gives it the name; working does not prescribe an identical outline or wind range for every boat.

The inventory can include several sizes. A No. 1 jib is generally its largest working headsail, a No. 2 jib a step smaller, and a No. 3 jib a smaller unit again. The numbers compare sails carried for one boat or class. They do not specify three universal sizes.

The Stewart 34 class’s 2011 rules make the progression concrete. Its maximum foot/luff pairs are 22 ft 2 in / 43 ft 6 in for No. 1, 18 ft 7 in / 42 ft 8 in for No. 2, and 14 ft 1 in / 39 ft 6 in for No. 3. Across that sequence the foot shortens substantially while the luff shortens more modestly. The smaller sail gives up both width and height, rather than being the same shape made from heavier cloth. A separately listed working jib has a shorter luff again. These are permitted measurement envelopes for that class, not measurements of individual sails. Stewart 34 sailing regulations, section 5.

The intended progression is from a larger surface useful under modest loading towards smaller working surfaces as that loading becomes harder to manage. The actual crossover depends on the boat, course, sea, sail construction and crew. The class dimensions supply no numerical wind limits, so they cannot tell a skipper at what wind speed to change. Nor does No. 3 automatically mean a dedicated storm sail.

In stronger apparent wind, the same area and shape can receive much greater aerodynamic load. One useful measure of the incoming flow is dynamic pressure: half the air density multiplied by the square of its speed relative to the sail. At the same air density, doubling apparent wind speed makes that measure four times as large. In a steady comparison, aerodynamic force would also quadruple if sail area, shape, angle to the flow and the resulting flow response all remained the same. A working sail can stretch, be eased or partly lose attached flow, so this comparison explains the strong rise in loading without predicting an actual rig’s load or setting a sail-change limit.

Under increased load, a larger sail may stretch into an unsuitable shape or impose sheet forces and handling demands beyond the useful range of the arrangement. A smaller sail designed for that duty can remain controllable and hold a better working shape. Its fibre directions, seams and reinforcements matter along with its area. Merely selecting heavier cloth does not settle the design.

At the other end of the range, a drifter provides light material and ample spread for weak wind. UK Sailmakers’ documented version is a full-draft nylon sail with the outline of a large No. 1 genoa. It can be made for hanks, a furling luff or a flying luff without continuous stay attachment. The sailmaker therefore specifies both the light-air surface and the chosen support: drifter alone does not tell us which connection is aboard. UK Sailmakers’ drifter description.

Ghoster overlaps this light-air vocabulary. In his recollection of preparing for the 1987 Singlehanded Transatlantic Race, John Passmore describes ordering a very large, lightweight ghoster from Crusader Sails. It was made with Mylar and needed more careful gathering and stowage than he gave it. That example locates the name in a particular inventory and exposes a handling consequence of its material; it does not make every ghoster a Mylar sail or establish a sharp boundary from drifter. Passmore’s account.

An earlier light-weather name was balloon jib, for a large, full forward sail. Thomas Fleming Day’s 1904 yacht-handling book distinguishes his light balloon sails from working canvas and describes separate sheets attached to the balloon jib’s clew. His discussion also allows a ballooner to be carried away from the ordinary jib stay, leaving that stay available for a working headsail before the light sail comes down. Head hoist, forward tack and sheet-controlled clew still locate the sail, but its luff arrangement must be checked in the particular rig. The name does not supply a spinnaker’s pole and corner arrangement. Day’s light-sail account records a dated handling choice, not a universal modern shape.

These alternatives coexist because a support can carry different cloth and an inventory can favour different transitions. Adding another sail to the locker adds a choice; it does not make that sail suitable for every use of the rig.

Let the two sails share the air

Main and headsail can be handled separately, but their aerodynamic work is coupled. Sail interactions are the changes each makes to the flow and loading of the other. The jib meets air already affected by the main, and the main meets air already affected by the jib. Their useful angles of attack are therefore not obtained by treating each as an isolated sail in undisturbed apparent wind.

The slot is the space between the neighbouring sails. Slot effect names their aerodynamic interaction in this arrangement. A gap is visible; the complete flow and pressure field extend around both sails. Calling the gap a nozzle would miss that wider relationship.

Arvel Gentry’s 1971 analysis follows this interaction through calculated two-dimensional sections. The jib moderates the main’s strong suction, the particularly low pressure near its leading edge. Farther aft along the leeward surface, pressure rises again: this is pressure recovery. Moderating that rise makes it easier for the flow to remain attached instead of separating. The main, in turn, changes the flow arriving at the jib and the speed of the flow into which the jib’s leech discharges. The two sails can consequently sustain a different distribution of pressure and load from either alone.

In that example, adding the jib actually reduces the quantity of air flowing between the stay and mast compared with the main alone. The useful interaction therefore cannot be explained by assuming that a narrowing gap simply forces more air through faster. Gentry’s sections do not reproduce every height of a real twisted rig. Actual shape, overlap, separation and settings matter, so neither a fixed slot width nor a fixed percentage improvement follows from the paper. Gentry, “The Aerodynamics of Sail Interaction”.

Changing a headsail therefore changes more than the area forward of the mast. It changes the other sail’s flow as well as the number and size of the crew’s tasks. Divided cloth supplies separate controls within one interacting sailing system.

Read the work as well as the rig

Those choices mattered to working vessels with particular jobs. A pilot cutter carried a pilot out to another ship so that local knowledge could guide the ship through its approach. National Historic Ships records Alpha, built in 1904 for Newport pilot William Prosser, as a one-masted gaff cutter. Competition for the pilotage job required speed, while a crew sometimes as small as two needed manageable sails. Divided forward cloth gave selectable units, though it also demanded separate hoists and sheets. The record connects that working requirement to the complete vessel, without measuring a speed benefit from one feature. Her spars were shortened after the Second World War and later restored closer to their earlier form. The Alpha record therefore belongs to dated configurations, not one permanent silhouette.

A fishing smack is a working-vessel designation with regional variations in hull and rig. Pioneer, built in Essex in 1864 for oyster dredging, illustrates the distinction. Her decked fishing hull was lengthened in 1889 and fitted with a flooded well to carry the catch alive over longer journeys. The owner’s history records a change from cutter to ketch rig: two masts, with a smaller after mast, rather than one mast with more headsails. Separate sails divided the handling work, while the well answered the fishing trade’s demand. Dredge hauling was another substantial task, performed by a handspike capstan, turned by people pushing its bars, before steam power was added in 1925. The Pioneer Sailing Trust’s history preserves these changes; smack does not name one compulsory sail plan.

Cutter itself can describe a service vessel. The American revenue cutter Active, launched in 1791, protected customs revenue by checking vessels and intercepting smugglers. Her official history identifies a two-masted topsail schooner, a rig with fore-and-aft sails and additional square sail aloft whose full arrangement we will meet later. Cutter here names her service; her two masts already rule out the one-mast working cutter arrangement introduced above. US Coast Guard history of Active.

The sail’s job, its support and the vessel’s occupation can now be read separately. A forward sail may add area, provide a smaller working unit or ease a particular transition. It still needs room for its lower attachment. The next change moves that attachment beyond the bow, where a projecting spar and its restraints must bring the loads back to the hull.