HMS H21

HMS H4, another submarine of the same class
History
United Kingdom
Name	H21
Builder	Vickers Limited, Barrow-in-Furness
Launched	20 October 1917
Commissioned	28 January 1918
Fate	Sold, 13 July 1926
General characteristics
Class and type	H class submarine
Displacement	423 long tons (430 t) surfaced 510 long tons (518 t) submerged
Length	171 ft 0 in (52.12 m)
Beam	15 ft 4 in (4.67 m)
Propulsion	1 × 480 hp (358 kW) diesel engine 2 × 620 hp (462 kW) electric motors
Speed	11.5 knots (21.3 km/h; 13.2 mph) surfaced 9 knots (17 km/h; 10 mph) submerged
Range	2,985 nmi (5,528 km) at 7.5 kn (13.9 km/h; 8.6 mph) surfaced 130 nmi (240 km) at 2 kn (3.7 km/h; 2.3 mph) submerged
Complement	22
Armament	4 × 21 in (533 mm) bow torpedo tubes 8 × 21 inch torpedoes

HMS H21 was a British H class submarine built by Vickers Limited, Barrow-in-Furness, as the first of the Batch 3 H class submarines. She was launched on 20 October 1917 and was commissioned on 28 January 1918. H21 was an improved design of the H class which produced a larger displacement and the latest 21 inch torpedo tubes replacing the old 18 inch torpedo tubes. This would be incorporated into all batch 3 H class submarines. HMS H21 was sold to John Cashmore Ltd on 13 July 1926 for scrapping at Newport.