HMS K7

HMS K7 was a K class submarine built by HM Dockyard, Devonport. She was laid down on 8 November 1915 and commissioned in July 1917.

History
United Kingdom
Name	HMS K7
Builder	HM Dockyard Devonport
Laid down	8 November 1915
Launched	31 May 1916
Commissioned	July 1917
Fate	Sold, 9 September 1921
General characteristics
Class and type	K-class submarine
Displacement	1,980 long tons (2,010 t) surfaced 2,566 long tons (2,607 t) submerged
Length	339 ft (103 m)
Beam	26 ft 6 in (8.08 m)
Draught	20 ft 11 in (6.38 m)
Propulsion	2 × 10,500 shp (7.8 MW) Brown-Curtis or Parsons geared steam turbines 2 × Yarrow boilers 4 × 1,440 hp (1,070 kW) electric motors 1 × 800 hp (600 kW) Vickers diesel generator for charging batteries on the surface 2 × 3-blade 7 ft 6 in (2.29 m) diameter screws
Speed	24 knots (44 km/h; 28 mph) surfaced 8 knots (15 km/h; 9.2 mph) submerged
Range	Surfaced : 800 nmi (1,500 km; 920 mi) at 24 kn (44 km/h; 28 mph) 12,500 nmi (23,200 km; 14,400 mi) at 10 kn (19 km/h; 12 mph) Submerged : 8 nmi (15 km; 9.2 mi) at 8 kn (15 km/h; 9.2 mph) 40 nmi (46 mi; 74 km) at 4 kn (4.6 mph; 7.4 km/h)
Complement	59 (6 officers and 53 ratings)
Armament	8 × 18 in (460 mm) torpedo tubes, (4 beam, 4 bow) 8 × spare torpedoes 2 × 18 in torpedo tubes fitted on deck (later removed) 2 × BL 4 in (100 mm) Mk.XI guns 1 × 3 in (76 mm) gun

K7 was the only one of the disastrous K class to engage with an enemy; on 16 June 1917 she fired a salvo of torpedoes at the U-boat U-95 and scored a direct hit. However, the torpedo failed to explode with what has been described as typical "K" luck; K-7 escaped retaliation by steaming away at speed.^[1]

K7 was involved in an accident with the 4th Light Cruiser Squadron. She was also involved in the catastrophic series of accidents during a night exercise that came to be known sarcastically as the Battle of May Island; K7 was damaged by running over the sinking K4. K7 was sold on 9 September 1921 at Sunderland.

Design

K7 displaced 1,800 long tons (1,800 t) when at the surface and 2,600 long tons (2,600 t) while submerged.^[2] It had a total length of 338 feet (103 m), a beam of 26 feet 6 inches (8.08 m), and a draught of 20 ft 11 in (6.38 m).^[3] The submarine was powered by two oil-fired Yarrow Shipbuilders boilers supplying one geared Brown-Curtis or Parsons steam turbine that developed 10,500 ship horsepower (7,800 kW) to drive two 7 ft 6 in (2.29 m) screws. Submerged power came from four electric motors each producing 350 to 360 horsepower (260 to 270 kW).^[3] It also had an 800 hp (600 kW) diesel engine to be used when steam was being raised, or instead of raising steam.^[4]

The submarine had a maximum surface speed of 24 kn (44 km/h) and a submerged speed of 9 to 9.5 kn (16.7 to 17.6 km/h).^[3][5] It could operate at depths of 150 ft (46 m) at 2 kn (3.7 km/h) for 80 nmi (150 km).^[2] K7 was armed with ten 18-inch (460 mm) torpedo tubes, two 4-inch (100 mm) deck guns, and a 3-inch (76 mm) anti-aircraft gun.^[3] Its torpedo tubes were fitted to the bows, the midship section, and two were mounted on the deck.^[2] Its complement was fifty-nine crew members.^[5]