Sjöormen-class submarine

The Sjöormen class (Sea serpent) was a class of submarines built for the Swedish Navy in the late 1960s. They had a teardrop hull shape and were capable of diving to 150 metres (490 ft). At the time of their deployment they were regarded as one of the most advanced non-nuclear submarine-classes in the world, incorporating many new features including x-rudder and anechoic tiles.[1] Both speed and underwater endurance was at this time very high for a conventional submarine. The submarines were retired by Sweden in the early 1990s. In the late 1990s, four submarines were acquired by the Republic of Singapore Navy (RSN) and relaunched as the Challenger class following modernisation and tropicalisation.

HSwMS Sjöormen in August 1967
Class overview
NameSjöormen class
Builders
Operators
Preceded byDraken class
Succeeded byNäcken class
Planned5
Completed5
Active2
Retired3
General characteristics
TypeSubmarine
Displacement
  • Surfaced: 1,075 t (1,058 long tons; 1,185 short tons)
  • Submerged: 1,400 t (1,400 long tons; 1,500 short tons)
Length51 m (167 ft 3.9 in)
Beam6.1 m (20 ft 0.2 in)
Draught5.8 m (19 ft 0.3 in)
Propulsion
Speed
  • Surfaced: 15 knots (28 km/h; 17 mph)
  • Submerged: 20 knots (37 km/h; 23 mph)
Endurance21 days
Test depth150 m (490 ft)
Complement23
Sensors and
processing systems		FAS
Armament
  • Bow:
  • 4 × 533 mm (21 in) torpedo tubes
  • 2 × 400 mm (16 in) torpedo tubes
  • Mines

Description

As built, the Sjöormen class were designed with a teardrop hull shape, based on the United States' Barbel class. They had bow planes on the sail and their stern diving planes were configured in a x-shape.[2] They had a standard displacement of 1,075 tonnes (1,058 long tons; 1,185 short tons) and 1,400 tonnes (1,400 long tons; 1,500 short tons) when dived.[3][lower-alpha 1] The submarines had a waterline length of 50 metres (164.0 ft) and a length overall of 51 metres (167.3 ft). They had a beam of 6.1 metres (20.0 ft) and a draught of 5.8 metres (19.0 ft). The Sjöormen class was powered by a diesel-electric propulsion system composed of two Pielstick diesel engines providing power to an ASEA electric motor driving one shaft with a five-bladed propeller. The entire system was rated at 2,200 brake horsepower (1,600 kW). This gave the submarines a surfaced speed of 15 knots (28 km/h; 17 mph) and 20 knots (37 km/h; 23 mph) submerged. Designed for the confined waters of the Baltic sea, the vessels had an endurance of 21 days and a test depth of 150 metres (490 ft).[2][3]

As built the Sjöormen class were equipped with surface search radar and sonar.[3] The submarines were armed with four 533 mm (21 in) torpedo tubes located in the bow for surface attack and two 408 mm (16 in) torpedo tubes in the stern for either anti-submarine warfare or for naval mines. The Sjöormen class had a complement of 23 officers and enlisted.[2][3]

Swedish upgrades

In 1984–85, the Sjöormen class received upgraded Ericsson IBS-A17 fire control system and CSU-83 sonar suite. In 1992, refits began on Sjölejonet and Sjöhunden that improved their electronics and their towed sonar array.[2]

Ships
Ship name Builder Launched Commissioned Status
Sjöormen Kockums 25 January 1967 31 July 1968 sold to Singapore as RSS Centurion
Sjölejonet Kockums 29 June 1967 16 December 1968 sold to Singapore as RSS Conqueror
Sjöbjörnen Karlskrona Navy yard 9 January 1968 28 February 1969 sold to Singapore as RSS Challenger
Sjöhunden Kockums 21 March 1968 25 June 1969 sold to Singapore as RSS Chieftain
Sjöhästen Karlskrona Navy yard 6 August 1968 15 September 1969 sold to Singapore as spare parts

Service history

The Sjöormen class were ordered by the Swedish Navy in 1961. The first boat in the class, Sjöormen, entered service in 1968. In 1992, two vessels in the class, Sjölejonet and Sjöhunden, underwent modernisation. The remaining three were supposed to remain in service until the Gotland class became operational, but due to lack of funding, all were laid up in 1993.[2]

Four submarines were sold to the Republic of Singapore Navy (RSN) in the 1990s and entered service as the Challenger class following modernisation and tropicalisation.[4][5]

References

Notes

  1. Gardiner & Chumbley have the standard displacement as 1,125 tonnes (1,107 long tons; 1,240 short tons).[2]

Citations

  1. "From a submarine point of view" (PDF). Kockums. Archived from the original (PDF) on 26 July 2011. Retrieved 18 April 2011.
  2. Gardiner & Chumbley, 1995, p. 446.
  3. Chant 1984, p. 77.
  4. "Dr Tan Launches First Submarine in Sweden". Ministry of Defence Singapore. Retrieved 6 December 2012.
  5. "Submarine Tropicalisation Programme". MINDEF. Retrieved 6 December 2012.

Bibliography

  • Chant, Christopher (1984). Naval Forces of the World. Seacaucus, New Jersey: Chartwell Books. ISBN 0-89009-626-0.
  • Gardiner, Robert; Chumbley, Stephen; Budzbon, Przemysław, eds. (1995). Conway's All the World's Fighting Ships 1947–1995. Annapolis, Maryland: Naval Institute Press. ISBN 1-55750-132-7.
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