Lug sail

The lug sail, or lugsail, is a fore-and-aft, four-cornered sail that is suspended from a spar, called a yard. When raised the sail area overlaps the mast. For "standing lug" rigs, the sail remains on the same side of the mast on both the port and starboard tacks. For "dipping lug" rigs, the sail is lowered partially to be brought around to the leeward side of the mast in order to optimize the efficiency of the sail on both tacks.

The lug sail is evolved from the square sail to improve how close the vessel can sail into the wind. Square sails, on the other hand, are symmetrically mounted in front of the mast and are manually angled to catch the wind on opposite tacks. Since it is difficult to orient square sails fore and aft or to tension their leading edges (luffs), they are not as efficient upwind, compared with lug sails. The lug rig differs from the gaff rig, also fore-and-aft, whose sail is instead attached at the luff to the mast and is suspended form a spar (gaff), which spar is attached to and raised at an angle from the mast.

The lug sail was one of the earliest fore-and-aft rigs. Campbell cites the lug sail as an intermediate step between the square sail and the lateen sail, developed for use on the Indian Ocean. McGrail notes the presence of temple carvings of vessels with lug sails, dating from the eighth-ninth century in Borobudur, Indonesia. Block reports a sixth-century depiction of a vessel with lug sails in the Ajanta Caves of India. Salamon suggests that the lateen may have evolved back towards a balanced lug rig, as used in the Adriatic.

The origin of its name is uncertain. According to Skeat, the name of the sail may derive from the ease with which it may be raised or "lugged" or it may derive from the vessel type, " lugger", on which the sail is used, which name may come from Dutch, logger meaning "slow ship", and East Friesian, log meaning "slow".

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