Parts of a sail

Sail components include the features that define a sail's shape and function, plus its constituent parts from which it is manufactured. A sail may be classified in a variety of ways, including by its orientation to the vessel (e.g. fore-and-aft) and its shape, (e.g. (a)symmetrical, triangular, quadrilateral, etc.). Sails are typically constructed out of flexible material that is shaped by various means, while in use, to offer an appropriate airfoil, according to the strength and apparent direction of the wind. A variety of features and fittings allow the sail to be attached to lines and spars.

Whereas conventional sails form an airfoil with one layer of fabric, wingsails comprise a structure that has material on both sides to form an airfoil—much like a wing placed vertically on the vessel—and are beyond the scope of this article.

Sails may be classified as either triangular, which describes sails that either come to one point of suspension at the top or where the sail comes to a point at the forward end, or quadrilateral, which includes sails that are attached to a spar at the top and have three other sides, or as square. They also may be classified as symmetrical (square sails and symmetric spinnakers) or asymmetrical (most other sails). Typically, asymmetrical sails perform better on points of sail closer to the wind and are designed for fore-and-aft rigs than symmetrical sails, which perform best on points of sail that are further from the wind direction.

Triangular sails have names for each of three edges and three corners. Rigs with such sails include Bermuda, cutter, lateen and vessels with mixed sail plans that include jibs and other staysails. Most triangular sails are classified as asymmetrical and fore and aft; symmetric spinnakers are symmetrical triangular sails that are designed for off-the-wind use.

Gaff, gunter, lug, junk and some sprit sails have four sides and are set fore and aft so that one edge is leading into the wind. Naming conventions are consistent with triangular sails, except for the top edge and corners.

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