The Amphitrite-class boats were built as improved versions of the Clorinde class. They displaced 418 metric tons (411 long tons) surfaced and 614 t (604 long tons) submerged. They had a length between perpendiculars of 54 meters (177 ft 2 in), a beam of 5.41 meters (17 ft 9 in), and a draft of 3.46 meters (11 ft 4 in). The crew numbered 27 officers and crewmen.[1]
For surface running, the Amphitrite class was powered by a pair of two-cycle diesel engines provided by three different manufacturers, each driving one propeller shaft. Amphitrite was equipped with six-cylinder Chaléassière engines that were intended to produce a total of 1,300 metric horsepower (1,282 bhp; 956 kW), but only produced 615 PS (607 bhp; 452 kW) during her sea trials on 16 November 1915, enough for a speed of 12.7 knots (23.5 km/h; 14.6 mph) rather than the designed 15 knots (28 km/h; 17 mph). The engines were generally capable of 800 PS (789 bhp; 588 kW), enough for a speed of 12–13 knots (22–24 km/h; 14–15 mph) in service. After a lengthy rebuild, the engines produced 1,170 PS (1,154 bhp; 861 kW) at 90% power during another set of trials on 15 June 1917 and gave Amphitrite a speed of 14.56 knots (26.97 km/h; 16.76 mph).[1] When submerged each shaft was driven by a 700-metric-horsepower (690 bhp; 515 kW) electric motor.[2] The designed speed underwater was 9.5 knots (17.6 km/h; 10.9 mph). The Amphitrites had a maximum fuel capacity of 12 t (12 long tons) of kerosene which gave them a surface endurance of 785 nautical miles (1,454 km; 903 mi) at 13 knots (24 km/h; 15 mph). Their designed submerged endurance was 100 nmi (190 km; 120 mi) at 5 knots (9.3 km/h; 5.8 mph).[1]
The Amphitrite-class boats were armed with a total of eight 450-millimeter (17.7 in) torpedoes. Two of these were positioned in the bow in external tubes angled outwards 4° 25'. The other six were located in external rotating Drzewiecki drop collars, three on each broadside that could traverse 100 degrees to the side of the boats. The boats were also equipped with a 47 mm (1.9 in) Mle 1885-1915 gun aft of the conning tower.[2][1][3]
France