What Leonardo da Vinci device used paddles on a wheel to propel a boat?

Leonardo da Vinci’s boat-propulsion device used a paddle wheel.

Leonardo studied paddle-wheel mechanisms as part of his efforts to improve water transport. In such a system, blades or paddles attached to a rotating wheel push against the water, producing forward motion. His sketches explored how human power could be transferred through gears and shafts to the wheel.

The concept was not a steam-powered paddle steamer. Steam engines and practical steamboats appeared much later. Leonardo’s proposals relied on mechanical power supplied by people, and some drawings show arrangements in which operators turn cranks or treadle-like mechanisms.

Leonardo did not invent the general idea of using paddles to move a boat; paddle propulsion had older precedents. His importance lies in the detailed mechanical studies he made and in his attempts to integrate gearing, rowing, and wheel propulsion. The design also differs from a screw propeller, which moves water with helical blades rotating underwater rather than with broad paddles on a wheel.