Leonardo da Vinci designed a double hull to help keep a ship afloat after damage to its outer hull.
The concept placed a second layer inside the ship’s outer shell, creating a protected space between the two hulls. If the external hull was pierced, the inner hull could limit the spread of water and preserve buoyancy. Leonardo included the idea among his naval and military engineering studies.
A double hull is not the same as a watertight bulkhead. A bulkhead divides the interior into compartments, while a double hull creates an additional shell around the vessel. Modern ships use both kinds of protection in different forms, but Leonardo’s proposal should be identified specifically as a double-hull arrangement.
The design was a proposal rather than a documented shipbuilding project completed by Leonardo. Its underlying principle later became important in naval architecture, especially for reducing flooding and, in some vessels, containing spills. Leonardo’s drawing shows how he applied structural design to problems of safety and survival at sea.