SM UC 90

Design

A German Type UC III submarine, UC-90 had a displacement of 491 tonnes (483 long tons) when at the surface and 571 tonnes (562 long tons) while submerged. She had a length overall of 56.51 m (185 ft 5 in), a beam of 5.54 m (18 ft 2 in), and a draught of 3.77 m (12 ft 4 in). The submarine was powered by two six-cylinder four-stroke diesel engines each producing 300 metric horsepower (220 kW; 300 shp) (a total of 600 metric horsepower (440 kW; 590 shp)), two electric motors producing 770 metric horsepower (570 kW; 760 shp), and two propeller shafts. She had a dive time of 15 seconds and was capable of operating at a depth of 75 metres (246 ft).

The submarine was designed for a maximum surface speed of 11.5 knots (21.3 km/h; 13.2 mph) and a submerged speed of 6.6 knots (12.2 km/h; 7.6 mph). When submerged, she could operate for 40 nautical miles (74 km; 46 mi) at 4.5 knots (8.3 km/h; 5.2 mph); when surfaced, she could travel 9,850 nautical miles (18,240 km; 11,340 mi) at 7 knots (13 km/h; 8.1 mph). UC-90 was fitted with six 100 centimetres (39 in) mine tubes, fourteen UC 200 mines, three 50 centimetres (20 in) torpedo tubes (one on the stern and two on the bow), seven torpedoes, and one 8.8 centimetres (3.5 in) Uk L/30 deck gun. Her complement was twenty-six crew members.

Construction and career

The U-boat was ordered on 12 January 1916 and was launched on 19 January 1918. She was commissioned into the German Imperial Navy on 15 July 1918 as SM UC-90. As with the rest of the completed UC III boats, UC-90 conducted no war patrols and sank no ships. She was surrendered to Japan on 1 December 1918. The U-boat was renamed O-4 for Japanese service from 1920 to 1921. In 1921 O-4 was partially dismantled at the Kure Navy Yard. Between 1924 and 1926, the hulk of O-4 was used as an antisubmarine warfare target before being sold for scrap.