Military Wiki
British K-class submarine
Class overview
Name: K

HM Dockyard Portsmouth K1, K2, K5 HM Dockyard Devonport K6, K7 Vickers K3, K4, K8, K9, K10, K17, K26 Armstrong/Whitworth K11, K12 Fairfield K13, K14 Scotts K15

Beardmore K16[1]
Operators:  Royal Navy
In commission: 1917—1931
Completed: 17
General characteristics
Type: Submarine
Displacement: 1,980 tons surfaced
2,566 tons dived
Length: 339 ft (103 m)
Beam: 26 ft 6 in (8.08 m)
Draught: 20 ft 11 in (6.38 m)

Twin 10,500 shp (7.8 MW) oil-fired Yarrow boilers each powering a Brown-Curtis or Parsons geared steam turbines, Twin 3 blade 7 ft 6 in (2.29 m) screws
Four 1,440 hp (1.074 MW) electric motors.

One 800 hp (0.6 MW) Vickers diesel generator for charging batteries on the surface.
Speed: 24 knots (44 km/h) surfaced/8 knots (14.8 km/h) dived

Surface: 800 nautical miles (1,500 km) at maximum speed, 12,500 nautical miles at 10 knots (20,000 km at 19 km/h)

Dived: 8 nautical miles at 8 knots (10 km at 10 km/h), 40 nautical miles at 4 knots (64 km at 7 km/h)
Complement: 59 (6 officers and 53 ratings)

Four 18-inch (450-mm) torpedo tubes (beam), four 18-inch (450-mm) bow tubes, plus 8 spare torpedoes
two BL 4-inch (101.6 mm) Mk XI guns
one 3-inch (76.2-mm) gun

Twin 18 inch (460 mm) deck tubes originally fitted but later removed.

HMS K4 aground on Walney Island

The K class submarines were a class of steam-propelled submarines of the Royal Navy designed in 1913. Intended as large, fast vessels which had the endurance and speed to operate with the battle fleet, they gained notoriety, and the nickname of Kalamity class, for being involved in many accidents. Of the 18 built, none was lost through enemy action but six sank in accidents. Only one ever engaged an enemy vessel, hitting a U-boat amidships though the torpedo failed to explode.

Design and development

In 1913 an outline design was prepared for a new submarine class which could operate with the fleet, sweeping ahead of it in a fleet action. At that time the only way which they could have sufficient surface speed, of 24 knots (44 km/h), to keep up with fleet was to be steam powered. In a fleet action, the submarines would get around the back of the enemy fleet and ambush it as it retreated.

The boats were to be 338 ft (103 m) long and displace 1,700 tons on the surface. The design was not to proceed until results from trials of HMS Nautilus and Swordfish had taken place. After the trials, the slightly smaller three-screw submarine, the J class, was designed. By the middle of 1915 it was clear that the J class would not meet expectations, in particular they would only reach 19 knots (35 km/h) — less than the 21 knots (39 km/h) needed to accompany the fleet.

The K class design was resurrected and 21 boats ordered in August at a cost of £340,000 each. Only 17 were constructed, the orders for the last four being cancelled and replaced by orders for the M class.

Six improved versions, K22 to K28 were ordered in October 1917 but the end of the First World War meant that only K26 was completed.

The double hull design had a reserve buoyancy of 32.5 percent.[2] Although powered on the surface by oil-fired steam turbines, they were also equipped with an 800 hp (0.6 MW) diesel generator to charge the batteries and provide limited propulsive power in the event of problems with the boilers.

This pushed the displacement up to 1,980 tons on the surface, 2,566 tons submerged. They were equipped with four 18 inch (460 mm) torpedo tubes at the bow, two on either beam and another pair in a swivel mounting on the superstructure for night use. The swivel pair were later removed because they were prone to damage in rough seas.

They were fitted with a proper deckhouse built over and around the conning tower which gave the crew much better protection than the canvas screens which had been fitted in previous Royal Navy submarines.

The great size of the boats compared to their predecessors led to control and depth keeping problems particularly as efficient telemotor controls had not yet been developed. This was made worse by the estimated maximum diving depth of 200 ft (60 m) being much less than their length. Even a 10 degree angle on the 339 ft (103 m) long hull would cause a 59 ft (18 m) difference in depth of the bow and stern, and 30 degrees would produce 170 ft (50 m) which meant that while the stern would almost be on the surface, the bow would almost be at its maximum safe depth. The problems were made even more dangerous because the eight internal bulkheads were designed and tested during development to stand a pressure equivalent to only 70 ft (20 m).


K3 was the first of the class to be completed, in May 1916 and trials showed numerous problems. The most serious was the high temperatures in the boiler room which was to some extent alleviated by installing bigger fans.

Steaming at speed tended to push the bow into the water making the already poor sea-keeping worse. To fix this a bulbous swan bow was added. Nevertheless there were still problems, the most embarrassing being that in a heavy sea water could enter the boat through the twin funnels and put the boiler fires out.

They suffered numerous accidents, largely caused by their poor manoeuvrability coupled with operating with the surface fleet, and which caused the loss of the following:

  • K13 sank on 19 January 1917 during sea trials when an intake failed to close whilst diving and her engine room flooded. She was eventually salvaged and recommissioned as K22 in March 1917.
  • K1 collided with K4 off the Danish coast on 18 November 1917 and was scuttled to avoid capture.

    A Bridge window from a K class submarine

  • Two boats were lost in an incident known as the Battle of May Island on 31 January 1918. The cruiser HMS Fearless collided with the head of a line of submarines, K17, which sank in about 8 minutes, whilst other submarines behind her all turned to avoid her. K4 was struck by K6 which almost cut her in half, and was then struck by K7 before she finally sank with all her crew. At the same time K22 (the recommissioned K13) and K14 collided although both survived. In just 75 minutes, two submarines had been sunk, three badly damaged and 105 crew killed.
  • K5 was lost due to unknown reasons during a mock battle in the Bay of Biscay on 20 January 1921. Nothing further was heard of her following a signal that she was diving, but wreckage was recovered later that day. It was concluded that she exceeded her safe maximum depth.
  • K15 sank at her mooring in Portsmouth on 25 June 1921. This was caused by hydraulic oil expanding in the hot weather and contracting overnight as the temperature dropped and the consequent loss of pressure causing diving vents to open. The boat flooded through open hatches as it submerged.

HMS K4 ran aground on Walney Island in January 1917 and remained stranded there for some time.

Dive time was around 5 minutes, with the record being 3 minutes 25 seconds which was claimed by K8. The leisurely time allowed the captain the luxury of being able to walk around the superstructure to ensure that the funnels were securely folded.

The last, improved, boat, K26 was completed slowly, being commissioned in 1923. She had six 21 inch (530 mm) bow torpedo tubes but retained the 18 inch (460 mm) beam tubes. Her higher casing almost cured the problems of seawater entering the boiler room and improved ballast tank arrangements cut the diving time to 3 minutes 12 seconds to get to 80 ft (24 m). She also had an increased maximum diving depth of 250 ft (75 m).

Depth charge thrower originally fitted to the K class

Most were scrapped between 1921 and 1926 but K26 survived until 1931, being broken up because her displacement exceeded the limits for submarine displacement in the London Naval Treaty of 1930.

K18, K19 and K20 became the new M class submarines. K21, K23, K24, K25, K27 and K28 were cancelled.

Although the concept of a submarine fast enough to operate with a battle fleet eventually fell out of favour, it was still an important consideration in the design of the Thames class in the late 1920s.

A model of a K class submarine

External links


  • Everitt, Don (1963). The K Boats. London: George Harrap. 


  1. Building information Observer's Directory of Royal Naval Submarines 1901-1982 by M. P. Cocker, Frederick Warne, London 1982, ISBN0723229643 page 42.
  2. A modern nuclear submarine has a reserve of around 13 percent

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