French submarine Amiral Bourgois

Amiral Bourgois was one of four experimental submarines ordered for the French Navy in 1906. Each boat was built to a different design and Amiral Bourgois was intended to test a novel powerplant. The experimental diesel engines took over six years to build and greatly delayed the boat's completion until 1913. Although engine problems plagued the submarine throughout her service, she was commissioned shortly after the start of the First World War in 1914, but never made an operational patrol. Amiral Bourgois was under repair when the war ended in 1918, but the work was cancelled shortly afterwards. The boat was struck the following year and offered for sale in 1920. There were no offers and she was used for torpedo testing in 1924–1926. The submarine was sold for scrap in 1927.

Background and description
The Board of Construction (Conseil des travaux) intended to order 20 submarines for the 1906 naval program, including two large long-range experimental boats, one of which was a design by naval constructor Pierre Marc Bourdelle using an unproven Sabathé-cycle diesel engine. The board was preempted by Navy Minister (Ministre de la Marine) Gaston Thomson who opened a competition for submarines that were faster on the surface and with longer range than the preceding Pluviôse-class submarine on 6 February 1906. Surfaced requirements were for a maximum speed of 15 kn, a range of 1250 nmi without using an auxiliary fuel tank, and a range of 2500 nmi with the extra fuel. Submerged, the boats had to have a maximum speed of 10 kn and a range of 100 nmi at 5 kn. Four designs were submitted, including Bourdelle's Amiral Bourgois, all of which were authorized by the board, along with 16 Brumaire-class submarines.

The submarine was an enlarged version of the twin-hulled Brumaire design with a surfaced displacement of 580 t and a submerged displacement of 746 t. The boat had an overall length of 56.2 m, a beam of 5.52 m and a draft of 3.7 m. She had a metacentric height of 0.852 m when surfaced. Her crew numbered three officers and 26 sailors.

The submarine's inner hull was divided into seven watertight compartments. The boat had two rudders, one at the stern and the other below the forward torpedo room. She had three sets of diving planes, fore, aft, and amidships, to control her depth below the water. The boat was fitted with 16 ballast tanks in the space between the inner and outer hulls, plus a single interior tank. Amiral Bourgois carried 15420 L of kerosene.

On the surface, the boat was powered by a pair of four-cylinder Sabathé-cycle diesel engines built by Schneider et Cie, each driving one three-bladed, 1.7 m propeller. The engines were designed to develop a total of 1400 PS and a speed of 13.5 kn. When submerged the propellers were driven by two 500 PS electric motors using electricity from two 120-cell batteries. During her sea trials Amiral Bourgois reached 13.85 kn from 1354 PS on the surface and 8.65 kn underwater. The boat demonstrated a range of 1500 nmi at 10 kn, submerged, she had a range of 89 nmi at 4.2 kn.

Internally, Amiral Bourgois was armed with two superimposed 45 cm torpedo tubes in the bow. Externally, the boat had one tube at the stern and two pairs of rotating Drzewiecki drop collars, one pair each fore and aft of the sail. The submarine was equipped with Modèle 1911V torpedoes. These had a 110 kg warhead and a range of 2000 m at a speed of 36 kn.

Construction and career
Amiral Bourgois, named for the naval architect and admiral, Siméon Bourgois, who had designed the first FRENCH SUBMARINE Plongeur, was ordered on 31 December 1906 from the Rochefort Naval Base (Arsenal de Rochefort). She was laid down on 19 May 1908 and was launched on 25 November 1912. Her diesels had been ordered on 15 January 1906, but did not arrive until 4 May 1912 and proved very unreliable in service, seriously delaying completion. Sea trials of her electric motors on the surface began on 21 July 1913 and testing of her diesels began on 19 August and lasted through 4 March 1914. The submarine had made a test dive down to a depth of 25 m on 27 February. Underwater testing of her electric motors was conducted on 7–10 July. At some point during her trials a "walking deck" was installed over her outer hull to improve surface operations.

The boat was commissioned on 7 August, shortly after the beginning of the First World War, and was assigned to the 2nd Light Squadron (2e Escadre légère) defending the English Channel. By the time Amiral Bourgois was transferred from Rochefort to Cherbourg a month later, her diesel engines had only run for nine hours. The boat made no operational patrols and did not conduct the endurance trials of her diesels until 17 December 1916. The vice admiral commanding the squadron commented on 11 April 1917 that the submarine was never available for operations and recommended that she be disposed of. Amiral Bourgois struck a rock on the approaches to Brest on 15 May 1917 and a 65 mm deck gun was installed on 10 August. The submarine was transferred to the Normandy submarine squadron in January 1918, but was reassigned to the School of Underwater Navigation at Toulon on 13 May to get her engines repaired. The work was ordered to be stopped on 25 November and she was struck from the navy list on 12 November 1919. Although she was subsequently listed for sale, Amiral Bourgois was taken off the list and reserved for torpedo testing on 21 March 1924. The submarine was sold for scrap at a price of 176,135 francs on 25 June 1927.