Gaff-rig

Gaff rig is a sailing rig (configuration of sails, mast and stays) in which the sail is four-cornered, fore-and-aft rigged, controlled at its peak and, usually, its entire head by a spar (pole) called the gaff. Because of the size and shape of the sail, a gaff rig will have running backstays rather than permanent backstays.

The gaff enables a fore and aft sail to be four sided, rather than triangular. A gaff rig typically carries 25 percent more sail than an equivalent bermudian rig for a given hull design.

A sail hoisted from a gaff is called a gaff-rigged (or, less commonly, gaff rigged or gaffrigged) sail.

Gaff rig remains the most popular fore-aft rig for schooner and barquentine mainsails and other course sails, and spanker sails on a square rigged vessel are always gaff rigged. On other rigs, particularly the sloop, ketch and yawl, gaff rigged sails were once common but have now been largely replaced by the Bermuda rig sail, which, in addition to being simpler than the gaff rig, usually allows vessels to sail closer to the direction from which the wind is blowing (i.e. "closer to the wind").

The gaff is hoisted by two halyards:

Additionally, a gaff vang may be fitted. It is a line attached to the end of the gaff which prevents the gaff from sagging downwind. Gaff vangs are difficult to rig on the aft-most sail, so are typically only found on schooners or ketches, and then only on the foresail or mainsail.

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Wikipedia