French submarine Cugnot

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, but this was deleted from the rest of the submarines after an accident with their sister Fresnel in 1909. 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]

Cugnot, named after the 18th-century inventor Nicolas-Joseph Cugnot, was ordered on 19 October 1906 from the Arsenal de Rochefort.[6] The submarine was laid down in 1906,[7] launched on 14 October 1909, and commissioned on 10 September 1910.[8][9]

At the outbreak of the First World War Cugnot was part of the French Mediterranean Fleet, and sailed with that force to the Adriatic tasked with bringing the Austro-Hungarian Fleet to battle or blockading it in its home ports.

On 29 November 1914, under the command of Lt. Henri Fournier, Cugnot attacked the naval base at Cattaro, one of a series of raids by French submarines on Austro-Hungarian ports. She was successful in penetrating the net defences at the entrance of Cattaro bay; however, once in she was unable to find a target before being detected and driven off by three Austrian torpedo boats. For this exploit Fournier was honoured by having a submarine named after him.

Cugnot remained in service throughout the war, and was stricken in December 1919.[9][10]

• Couhat, Jean Labayle (1974). French Warships of World War I. London: Ian Allan. ISBN 0-7110-0445-5.
• Gardiner, Robert & Gray, Randal (1985). Conway's All The World's Fighting Ships 1906–1921. London: Conway Maritime Press. ISBN 0-85177-245-5.
• 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. ISBN 2-909675-81-5.
• 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. ISBN 2-909675-34-3.

• Castel, Marc: Fresnel at Sous-marins Français 1863 -, pagesperso-orange.fr (French)
• Sieche, Erwin: French naval operations in the Adriatic at gwpda.org