What Leonardo da Vinci device was designed to turn a paddle wheel for a boat?

Leonardo da Vinci designed a paddle-wheel boat intended to move through water using rotating paddles.

Leonardo’s notebooks contain sketches for boats propelled by paddle wheels rather than by oars or sails. In the concept, human effort turns a mechanical system connected to wheels at the sides or rear of the vessel. The paddles push against the water and produce forward motion.

The design belongs to Leonardo’s wider interest in mechanical transmission. Gears, cranks, and shafts allowed motion made by people to be redirected into useful work. The boat was not a steam-powered ship, because steam engines were not available in Renaissance Italy and Leonardo’s drawings show no such engine.

Leonardo’s paddle-wheel concept also should not be treated as proof that he built a working vessel. His notebooks preserve proposals and studies, many of which remained unconstructed. The historical importance is the clear mechanical idea: rotating paddles could replace direct rowing as a method of propulsion.