page_title: Sail
section_title: Running rigging
hierarchical_section_title: Sail / Running rigging
caption_attribution_description: English: Edges and corners of a square sail are shown on the uppermost sail: The sail is attached to a spar (or yard) at its head and tensioned outwards at the head cringles. The side edges are the leeches. The bottom edge is the foot and is attached to the yard below by sheets (not labelled) at the clews which are the corners. Running rigging is shown on the lower sail: The lifts are shown slack, because the spar (or yard) is raised, but would support the lowered spar, as shown on the topmost spar. The sheets pull the clews down to the yard below when setting sail. The clewlines raise the clews to the yard above when dousing (striking or furling) sail. The halyard raises a yard into place, seen as two line converging on a block, which is attached to a line that goes up to the crosstrees and through a sheave to raise the yard. The braces adjust the sail side-to-side by tension applied from below to a block on the spar, countered by tension at the other end on a mast behind the spar, pulling one end aft and allowing the other end to rotate forward. References: Biddlecombe, George (1990) The Art of Rigging: Containing an Explanation of Terms and Phrases and the Progressive Method of Rigging Expressly Adapted for Sailing Ships, Dover Maritime Series, Courier Corporation, pp.&#160;155 ISBN: 9780486263434. Underhill, Harold A. (1969) Masting and Rigging the Clipper Ship &amp; Ocean Carrier: With Authentic Plans, Working Drawings and Details of the Nineteenth and Twentieth Century Sailing Ship, Glasgow: Brown, Son and Ferguson, pp.&#160;304 ISBN: 0851741738.
context_page_description: A sail is a tensile structure—made from fabric or other membrane materials—that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails may be made from a combination of woven materials—including canvas or polyester cloth, laminated membranes or bonded filaments—usually in a three- or four-sided shape.
  A sail provides propulsive force via a combination of lift and drag, depending on its angle of attack—its angle with respect to the apparent wind. Apparent wind is the air velocity experienced on the moving craft and is the combined effect of the true wind velocity with the velocity of the sailing craft. Angle of attack is often constrained by the sailing craft's orientation to the wind or point of sail. On points of sail where it is possible to align the leading edge of the sail with the apparent wind, the sail may act as an airfoil, generating propulsive force as air passes along its surface—just as an airplane wing generates lift—which predominates over aerodynamic drag retarding forward motion.
context_section_description: The lines that attach to and control sails are part of the running rigging and differ between square and fore-and-aft rigs. Some rigs shift from one side of the mast to the other, e.g. the dipping lug sail and the lateen. The lines can be categorized as those that support the sail, those that shape it, and those that control its angle to the wind.
caption: Square sail edges and corners (top). Running rigging (bottom).
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