Daphné was one of two s built for the French Navy during World War I. Completed in 1917, she survived the war and was refitted in 1924–1925. The boat was sold for scrap on 25 November 1936.
Design and description The Diane class was built as part of the French Navy's 1912 building program,Smigielski, p. 211 as scaled down versions of adapted to use diesel engines. The boats displaced surfaced and submerged. They had an overall length of , a beam of , and a draft of . Their crew numbered 34 officers and crewmen.Roberts, p. 453
For surface running, the Diane-class boats were powered by two diesel engines, each driving one propeller shaft. The Sulzer two-cycle engines in Daphné were designed to produce a total of , but proved to be unreliable at that rating and output was restricted to . This reduced the boat's speed from the designed to . When submerged each shaft was driven by a electric motor. The designed speed underwater was , but Daphné only reached during her sea trials on 11 November 1915. The Dianes carried enough fuel oil to give them a surface endurance of at . Their designed submerged endurance was at , but sea trials showed that it fell short of that figure at .
The Diane class was armed with a total of 10 torpedoes. Four of these were positioned in the bow; two in internal torpedo tubes in the bow angled outwards three and a half degrees and two in external tubes above them angled outwards nine degrees. Four more were located in four external rotating launchers amidships, two on each broadside; one pair each fore and aft of the conning tower that could traverse 130 degrees to the side of the boats. The last pair were in external tubes in the stern aimed directly aft. While the boats were under construction in 1915 a Mle 1897 gun with high-angle capacity was ordered to be installed aft of the conning tower.Garier 2000, p. 118
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