R-class submarine
History
United Kingdom
Name	HMS R12
Builder	Cammell Laird, Birkenhead
Laid down	1 December 1917
Launched	9 April 1918
Commissioned	29 October 1919
Decommissioned	December 1919
Fate	Sold, 21 February 1923
General characteristics
Class and type	R-class submarine
Displacement	410 long tons (417 t) surfaced 503 long tons (511 t) submerged
Length	163 ft 9 in (49.91 m)
Beam	15 ft 3 in (4.65 m)
Draught	11 ft 6 in (3.51 m)
Installed power	240 bhp (180 kW) (diesel) 1,200 hp (890 kW) (electric)
Propulsion	1 × diesel engine 1 × electric motor
Speed	9.5 knots (17.6 km/h; 10.9 mph) surfaced 15 knots (28 km/h; 17 mph) submerged
Range	2,400 nmi (4,400 km; 2,800 mi) at 9 knots (17 km/h; 10 mph) surfaced; 60 nmi (110 km; 69 mi) at 5 knots (9.3 km/h; 5.8 mph) submerged
Test depth	150 feet (45.7 m)
Complement	2 officers and 20 ratings
Sensors and processing systems	Bow hydrophone array
Armament	6 × bow 18-inch (45 cm) torpedo tubes

HMS R12 was one of 10 R-class submarines built for the Royal Navy during the First World War. The boat was not completed before the end of the war and was sold for scrap in 1923.

The R-class submarine was designed to meet an Admiralty requirement for a specialised hunter-killer submarine with an emphasis on submerged performance. The boats had a length of 163 feet 9 inches (49.9 m) overall, a beam of 15 feet 3 inches (4.6 m) and a mean draft of 11 feet 6 inches (3.5 m). They displaced 410 long tons (420 t) on the surface and 503 long tons (511 t) submerged. The R-class submarines had a crew of 2 officers and 20 ratings.^[1] They had a diving depth of 150 feet (45.7 m).^[2]

For surface running, the boats were powered by a single eight-cylinder ^[3] 240-brake-horsepower (179 kW) diesel engine that drove the single propeller shaft. When submerged it was driven by a 1,200-horsepower (895 kW) electric motor. They could reach 9.5 knots (17.6 km/h; 10.9 mph) on the surface and 15 knots (28 km/h; 17 mph) underwater. On the surface, the R class had a range of 2,400 nautical miles (4,400 km; 2,800 mi) at 9 knots (17 km/h; 10 mph) and 60 nmi (110 km; 69 mi) at 5 knots (9.3 km/h; 5.8 mph) submerged.^[4]

The boats were armed with six 18-inch (45 cm) torpedo tubes in the bow. They carried six reload torpedoes for a grand total of a dozen torpedoes. They were equipped with an array of five hydrophones in the bow to allow them to locate and engage targets while submerged.^[4]

HMS R12 was laid down on 1 December 1917 by Cammell Laird at Birkenhead, launched on 9 April 1918 and commissioned on 29 October 1919. She came too late to see any combat in World War I, like most of the other R class submarines. R12 was paid off in December 1919, and sold on 21 February 1923 to J. Smith.

• Akermann, Paul (2002). Encyclopaedia of British Submarines 1901–1955 (reprint of the 1989 ed.). Penzance, Cornwall: Periscope Publishing. ISBN 1-904381-05-7.
• Colledge, J. J.; Warlow, Ben (2006) [1969]. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). London: Chatham Publishing. ISBN 978-1-86176-281-8.
• Gardiner, Robert & Gray, Randal, eds. (1985). Conway's All the World's Fighting Ships 1906–1921. Annapolis, Maryland: Naval Institute Press. ISBN 0-85177-245-5.
• Harrison, A. N. (January 1979). "The Development of HM Submarines From Holland No. 1 (1901) to Porpoise (1930) (BR3043)". RN Subs. Retrieved 27 September 2022.