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 of , with a beam of and a draught of . Like the Farfadets, most of its ballast tanks were inside the hull and it was fitted with a pair of side-thrusting propellers () on the stern to help steering that were geared to the propeller shaft. Z had two rudders, one each above and below the stern and was the only French submarine to be fitted with four sets of diving planes. Unlike the Farfadets, the boat was fitted with a free-flooding forward ballast tank above the hull and had a lengthy walking deck above the hull that extended from forward of its conning tower to the telescoping funnel. A lower walking deck was installed aft of the funnel after 1905. Its crew consisted of 2 officers and 14 ratings. Its armament comprised two torpedo tubes side-by-side in the bow. Z was equipped with a single variable-pitch propeller that was driven on the surface by a diesel engine built by ; ordered on 8 May 1901, it was one of the earliest diesels built in France. Based on the experimental engine installed on the canal barge Petit Pierre, it had two vertical cylinder with the flywheel located between them. Although rated at , it only produced during its initial testing, because of "excessive torsional vibration in the shaft connecting the two separate cylinder assemblies". It was later replaced by a more powerful model. An electric motor was used underwater. During the boat's comparative trials against the submarine in early 1905, Z reached a speed of from on the surface and from while submerged. The submarine had a designed surfaced range of at and a submerged range of at . Construction and career Z was ordered with the budget number Q36 from the on 10 June 1901 and was laid