The peak is the upper, aft corner of a four-sided sail – the corner where the head meets the leech on a gaff mainsail, gaff mizzen or lugsail. By extension it is also the outer end of the gaff spar itself, and the peak halyard is the line that hoists that end. On a modern Bermudan (Marconi) mainsail the sail has only three corners and the top one is called the head, so if you sail a sloop built after about 1930 you may never use the word. The detail the old hands add is that the peak is the corner that controls leech tension on a gaff rig: peak it up hard and the leech goes taut and the sail flattens; let the peak sag and the whole leech falls off in twist.
Anatomy of a four-sided sail
A gaff sail has four corners and four edges, and every one has its own name. Working round the sail from the bottom forward corner:
- Tack: the lower forward corner, at the gooseneck or boom jaws.
- Clew: the lower aft corner, at the end of the boom.
- Peak: the upper aft corner, at the outer end of the gaff.
- Throat: the upper forward corner, where the gaff jaws sit against the mast.
The edge between throat and peak is the head, laced or tracked to the gaff. The edge between peak and clew is the leech (also spelled leach). Because the head is a hard edge on a spar and the peak is a free corner pulled aloft by a halyard, the peak takes a heavy, concentrated load. A sailmaker builds it with a substantial patch, a stainless or bronze cringle and, on larger sails, a headboard-style plate or a webbed strop that spreads the load into the cloth along the leech and head.
Two halyards, one sail
Setting a gaff sail is a two-handed job because the gaff is lifted by two separate halyards. The throat halyard hoists the inner end of the gaff up the mast and puts tension on the luff. The peak halyard, usually rigged as a span along the gaff to a block or blocks aloft, lifts the outer end. Hoist the throat first until the luff is snug, then peak up until the gaff sits at the angle the sailmaker designed, typically somewhere between 30° and 45° from the mast. The tell-tale of a correctly peaked sail is a smooth leech with no diagonal wrinkle from throat to clew; a hard crease from peak to tack means the peak is over-tensioned, a sagging leech means it is under-tensioned.
On the water the peak halyard becomes a live trimming control. In a rising breeze, a little more peak flattens the sail and tightens the leech; in light air, easing the peak a touch lets the leech open and the sail breathe. Traditional skippers use the peak the way a Bermudan sailor uses the vang and mainsheet together.
Why the peak matters for sail shape
Gaff sails are cut differently from triangular sails. Many are still cross-cut, with the panels running perpendicular to the leech, so the fill threads carry the leech load from peak to clew and the peak load is fed straight into the strongest direction of the cloth. Others are vertically cut or mitre-cut to balance the loads between the head and the leech. In every case the peak is the corner where the two highest-loaded edges meet, and the cloth around it works hard. A sailmaker watching a gaffer sail will look first at the peak: if the sail is bagging in the upper leech or the peak patch is distorting, the cloth has stretched and the sail wants recutting.
Peak height also sets the twist of the sail. A gaff sail is inherently a twisty shape, because there is no fixed batten structure aloft to stop the head falling off to leeward. Peaking up harder reduces that twist and improves pointing; easing the peak increases twist for running and for very light air.
Frequently Asked Questions about Peak
Does a Bermudan mainsail have a peak?
No. A three-cornered sail has a head, tack and clew only. The word peak is reserved for the upper aft corner of four-sided sails such as gaff, lug and sprit sails.
Which halyard do I hoist first, throat or peak?
Hoist the throat first to get the luff tensioned, then peak up. Lowering is the reverse: ease the peak first so the gaff comes down parallel to the boom rather than hanging outer-end-high in the lazyjacks.
How do I know the peak is set correctly?
Sight up the leech. It should be smooth and gently twisted with no hard diagonal wrinkle. A crease running from peak towards tack means too much peak; a loose, fluttering upper leech means too little.
The peak is a small word with a big job. On a gaff rig it is the corner that turns a loose sheet of canvas into a driving foil, and the peak halyard is the control that keeps it that way as the wind changes. Learn to read your leech, peak up when the breeze fills in, ease it when it fades, and let it run when you need to stop – and your traditional rig will reward you with a sail that sets as well as anything with battens.