Sail

A Sail is any surface used to harness wind power in order to provide propulsion. The most common sails are made of cloth, though modern sails are made of various man-made materials, including some very high-tech composite solid "wing sails". In most modern boats, a sail works on similar principles to an airplane wing when the vessel is pointed towards the wind, and more like a parachute when the vessel is pointed away. The most common modern arrangement of sails for pleasure craft is called a sloop rig, in which a single large triangular mainsail is placed aft (behind of) the mast, and a smaller triangular foresail, usually called a jib or genoa, depending on its size, is mounted forward of the mast, attached to a cable called a forestay.