What Leonardo da Vinci machine used a large wheel to propel a paddle-powered boat?

Leonardo da Vinci designed paddle-wheel boats that used rotating wheels to push a vessel through water.

His notebooks include sketches of boats propelled by paddle wheels rather than oars. In these designs, human operators would turn mechanisms that transferred motion to wheels fitted with paddles. As the paddles pressed against the water, they produced forward thrust.

Paddle propulsion offered a possible alternative to banks of rowers, especially for military or transport vessels. Leonardo’s drawings explore gears, cranks, and the placement of the wheels, but they do not prove that a working boat was built during his lifetime.

Paddle wheels predate steam power and were used in several ancient and medieval experiments. Steam-powered paddle steamers became practical much later, particularly during the 18th and 19th centuries. Leonardo’s proposed boat should therefore be understood as a human-powered mechanical vessel, not a steamship. Its significance lies in applying rotating machinery to marine propulsion.