Kick or hit a bail in such a way that it spins and its trajectory will curve. This effect on spinning spheres, or cylinders, is known as the Magnus force and has a novel use in the propulsion of ships. Named after the scientist Heinrich Magnus, who researched the force in the 19th century, the effect was later harnessed in the 1920s by aviation engineer Anton Flettner. Flettner had the schooner Buckau modified, with her traditional sails being replaced by two rotating cylinders, one forward and one aft. Each one, 15m (50ft) high, was topped with an overhanging plate, and power came from 50hp (37kW) motors.
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