Square rig refers to a type of sail and rigging where the sails are mounted on horizontal spars. The number of masts, the square sails and how the yards (spars) are set out distinguishes a square-rigged ship. The classic example of a square-rig is a three masted fully rigged ship. The square-rigger descends from the lateen-rig. Its angled sails became square sails. The full-rigged ship is a ship with square-rigged sails on all its masts. The square rig with all its sails and rigging is hard to handle when tacking or "coming about". In the trade winds, square-rigged ships have an advantage, especially in deep water.
- Gershom Bradford, 'Rigs of Vessels', The Rudder, Volume 23, ed. Thomas Fleming Day (1910), p. 505
- Otmar Schäuffelen, Chapman Great Sailing Ships of the World (New York: Hearst Books, 2005), p. xxi
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- Fred B. Jacobs, 'The Modern Sailor is Economical—II', Marine Review, Volume 50 (1920), p. 459
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