The Pluviôse class were built as part of the French Navy's 1905 building program to a double-hull design by Maxime Laubeuf.[1] The submarines displaced 404 metric tons (398 long tons) surfaced and 553 metric tons (544 long tons) submerged. They had an overall length of 51.12 meters (167 ft 9 in), a beam of 4.96 meters (16 ft 3 in), and a draft of 3.15 meters (10 ft 4 in). Their crew numbered 2 officers and 23 enlisted men.[2]
For surface running, the boats were powered by two 350-metric-horsepower (345 bhp; 257 kW) triple-expansion steam engines, each driving one propeller shaft using steam provided by two Du Temple boilers. When submerged each propeller was driven by a 230-metric-horsepower (227 bhp; 169 kW) electric motor.[3] On the surface they were designed to reach a maximum speed of 12 knots (22 km/h; 14 mph) and 8 knots (15 km/h; 9.2 mph) underwater.[1] The submarines had a surface endurance of 865 nautical miles (1,602 km; 995 mi) at 11.6 knots (21.5 km/h; 13.3 mph) and a submerged endurance of 70 nmi (130 km; 81 mi) at 2.8 knots (5.2 km/h; 3.2 mph).[4]
The first six boats completed were armed with a single 450-millimeter (17.7 in) internal bow torpedo tube; Vendémiare had one fitted in early 1910 while she was still under construction. All of the boats were fitted with six 450 mm external torpedo launchers; the pair firing forward were fixed outwards at an angle of seven degrees and the rear pair had an angle of five degrees. Following a ministerial order on 22 February 1910, the aft tubes were reversed so they too fired forward, but at an angle of eight degrees. The other launchers were a rotating pair of Drzewiecki drop collars in a single mount positioned on top of the hull at the stern. They could traverse 150 degrees to each side of the boat. The Pluviôse-class submarines carried eight torpedoes.[5]
d'Ausson, Enseigne de Vaisseau de la Loge (1978). "French Battleship St. Louis". F. P. D. S. Newsletter. VI (1). Akron, Ohio: F. P. D. S.: 6–7. OCLC41554533.
Couhat, Jean Labayle (1974). French Warships of World War I. London: Ian Allan. ISBN0-7110-0445-5.
Gardiner, Robert & Gray, Randal (1985). Conway's All The World's Fighting Ships 1906–1921. London: Conway Maritime Press. ISBN0-85177-245-5.
Garier, Gérard (2002). A l'épreuve de la Grande Guerre. L'odyssée technique et humaine du sous-marin en France (in French). Vol. 3–2. Bourg-en-Bresse, France: Marines édition. ISBN2-909675-81-5.
Garier, Gérard (1998). Des Émeraude (1905-1906) au Charles Brun (1908–1933). L'odyssée technique et humaine du sous-marin en France (in French). Vol. 2. Bourg-en-Bresse, France: Marines édition. ISBN2-909675-34-3.