The single-masted, square-rigged Humber keel performed well to windward.[3]:54
Single sail square rigs were used by the ancient Egyptians, the Phoenicians, the Greeks, the Romans, and the Celts. Later the Scandinavians, the Germanic peoples, and the Slavs adopted the single square-rigged sail, with it becoming one of the defining characteristics of the classic "Viking" ships.[4]
↑Mannering, Julian, ed. (1997). The Chatham directory of inshore craft: traditional working vessels of the British Isles. London: Chatham Pub. ISBN1-86176-029-9.