What type of protective hull did Leonardo da Vinci propose for ships?

Leonardo da Vinci proposed a double hull as protection for ships.

His ship designs included an inner and outer layer intended to reduce the danger of flooding if the outer skin were damaged. The idea belongs to Leonardo’s extensive studies of water engineering, shipbuilding, and military technology. A separated hull can provide a barrier between the sea and the vessel’s interior, although the practical value depends on construction, compartmentalization, and maintenance.

The concept was centuries ahead of the double-hulled vessels that later became important in naval architecture. It should not be confused with a modern catamaran, whose two separate hulls support the vessel side by side. Leonardo’s proposal concerned protective layers around a ship rather than two independent hulls used primarily for stability.

Leonardo left many inventions as drawings and notes rather than finished machines. His notebooks often combine observations, alternative sketches, and brief statements, so historians must reconstruct the intended arrangement from context. The double-hull idea is therefore best understood as a conceptual safety feature, not as proof that Leonardo built a successful watertight ship.