French submarine Z
The French submarine Z was an experimental submarine built for the French Navy () in the first decade of the 20th century. Designed by Gabriel Maugas, it was the first French submarine to be completed with a diesel engine and the only one with four sets of diving planes. It was commissioned for its sea trials in 1904, although its propulsion machinery was unreliable and it was never fit for service with the fleet. It may have been completed in 1905. An extensive refit for Z was planned in 1907, but this was cancelled as too expensive. Disposal of the submarine was first proposed the following year, although it was not stricken from the navy list until 1910. Z was sold for scrap in 1911. Background and description Z was a single-hull design by Gabriel Maugas based on the hull of the all-electric that was modified to use a diesel engine on the surface and to recharge its batteries. He estimated a maximum speed on the surface of and submerged, but the boat was considerably slower on the surface than he anticipated. The submarine had a surfaced displacement of and a submerged displacement of . It had an overall length