![]() Genoa jib, showing reinforcement and attachment points: The roach allows the foot of the sail to clear stays coming up the mast, as the sails are rotated from side to side. The greater the departure from the straight line, the greater the "hollow" in the roach. Roach is a term also applied to square sail design-it is the arc of a circle above a straight line from clew to clew at the foot of a square sail, from which sail material is omitted. Offshore cruising mainsails sometimes have a hollow leech (the inverse of a roach) to obviate the need for battens and their ensuing likelihood of chafing the sail. This added area would flutter in the wind and not contribute to the efficient airfoil shape of the sail without the presence of battens. ![]() Ī fore-and-aft triangular mainsail achieves a better approximation of a wing form by extending the leech aft, beyond the line between the head and clew in an arc called the roach, rather than having a triangular shape. On a fore-and-aft mainsail, the foot is often attached, at the tack and clew, to a boom on a square sail to a spar by clews on both ends if no boom or spar is present, the sail is said to be "loose-footed". Foot – The foot of a sail is its bottom edge.When on a reach, the windward leech of a spinnaker (symmetrical or not) is called the luff and, when on a reach or close-hauled, the windward leech of a square sail may be called the luff or the weather leech. Luff – The forward (leading) edge of a fore-and-aft sail is called the luff, and may be attached along a mast or a stay.However, once a symmetrical sail has wind blowing along its surface, whether on a reach or close-hauled, the windward leech may be called a luff (see below). The leech is either side edge of a symmetrical sail-triangular or square. Leech – The aft (back) edge of a fore-and-aft sail is called the leech (also spelled leach).For a triangular sail the head refers to the topmost corner. Head – The head is the upper edge of the sail, and is attached at the throat and peak to a gaff, yard, or sprit. ![]() The top of all sails is called the head, the leading edge is called the luff, the trailing edge is the leech, and the bottom edge is the foot. In use, the sail becomes a curved shape, adding the dimension of depth or draft. The edges may be curved, either to extend the sail's shape as an airfoil or to define its shape in use. The shape of a sail is defined by its edges and corners in the plane of the sail, laid out on a flat surface. Square sail edges and corners (top), running rigging (bottom)
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