The ''Sjöormen'' class (''Sea serpent'') was a class of

submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...

s built for the

Swedish Navy The Swedish Navy ( sv, Svenska marinen) is the naval branch of the Swedish Armed Forces. It is composed of surface and submarine naval units – the Fleet () – as well as marine units, the Amphibious Corps (). In Swedish, vessels o ...

in the late 1960s. They had a

teardrop hull A teardrop hull is a submarine hull design which emphasizes submerged performance over surfaced performance. It was somewhat commonly used in the early stages of submarine development, but was gradually abandoned in the early 20th century in fav ...

shape and were capable of diving to . 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 __NOTOC__ Anechoic tiles are rubber or synthetic polymer tiles containing thousands of tiny voids, applied to the outer hulls of military ships and submarines, as well as anechoic chambers. Their function is twofold: *To absorb the sound waves ...

. 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 following modernisation and tropicalisation.

Description

As built, the ''Sjöormen'' class were designed with a

shape, based on the United States' . They had

bow plane Bow often refers to: * Bow and arrow, a weapon * Bowing, bending the upper body as a social gesture * An ornamental knot made of ribbon Bow may also refer to: * Bow (watercraft), the foremost part of a ship or boat * Bow (position), the rowe ...

s on the

sail A sail is a tensile structure—which is made from fabric or other membrane materials—that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails may ...

and their stern diving planes were configured in a x-shape. They had a

standard displacement The displacement or displacement tonnage of a ship is its weight. As the term indicates, it is measured indirectly, using Archimedes' principle, by first calculating the volume of water displaced by the ship, then converting that value into wei ...

of and when dived. The submarines had a

waterline length A vessel's length at the waterline (abbreviated to L.W.L)Note: originally Load Waterline Length is the length of a ship or boat at the level where it sits in the water (the ''waterline''). The LWL will be shorter than the length of the boat over ...

of and a

length overall __NOTOC__ Length overall (LOA, o/a, o.a. or oa) is the maximum length of a vessel's hull measured parallel to the waterline. This length is important while docking the ship. It is the most commonly used way of expressing the size of a ship, an ...

of . They had a

beam Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized grou ...

of and a draught of . The ''Sjöormen'' class was powered by a diesel-electric propulsion system composed of two

Pielstick SEMT Pielstick was a French company that designed and built large diesel engines. Its full name was (Company of Thermal Machines Studies). Founded in 1948, SEMT was bought by MAN Diesel in 2006 During its existence as an independent compa ...

diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-call ...

s providing power to an

ASEA ''Allmänna Svenska Elektriska Aktiebolaget'' (English translation: General Swedish Electrical Limited Company; Swedish abbreviation: ASEA) was a Swedish industrial company. History ASEA was founded in 1883 by Ludvig Fredholm in Västerås a ...

electric motor driving one shaft with a five-bladed

propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...

. The entire system was rated at . This gave the submarines a surfaced speed of and submerged. Designed for the confined waters of the

Baltic sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and from ...

, the vessels had an endurance of 21 days and a test depth of . As built the ''Sjöormen'' class were equipped with surface search

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

and

sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect o ...

. The submarines were armed with four

torpedo tube A torpedo tube is a cylindrical device for launching torpedoes. There are two main types of torpedo tube: underwater tubes fitted to submarines and some surface ships, and deck-mounted units (also referred to as torpedo launchers) installed aboa ...

s located in the bow for surface attack and two torpedo tubes in the stern for either

anti-submarine warfare Anti-submarine warfare (ASW, or in older form A/S) is a branch of underwater warfare that uses surface warships, aircraft, submarines, or other platforms, to find, track, and deter, damage, or destroy enemy submarines. Such operations are t ...

or for

naval mine A naval mine is a self-contained explosive device placed in water to damage or destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, any ...

s. The ''Sjöormen'' class had a

complement A complement is something that completes something else. Complement may refer specifically to: The arts * Complement (music), an interval that, when added to another, spans an octave ** Aggregate complementation, the separation of pitch-clas ...

of 23 officers and enlisted.

Swedish upgrades

In 1984–85, the ''Sjöormen'' class received upgraded Ericsson IBS-A17

fire control system A fire-control system (FCS) is a number of components working together, usually a gun data computer, a director, and radar, which is designed to assist a ranged weapon system to target, track, and hit a target. It performs the same task as a h ...

and CSU-83 sonar suite. In 1992, refits began on ''Sjölejonet'' and ''Sjöhunden'' that improved their electronics and their towed sonar array.

Ships

Service history

The ''Sjöormen'' class were ordered by the

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 became operational, but due to lack of funding, all were laid up in 1993. Four submarines were sold to the Republic of Singapore Navy (RSN) in the 1990s and entered service as the following modernisation and tropicalisation.

References

Notes Citations Bibliography * *

External links

Official Kockums website on the Challenger class submarines
{{DEFAULTSORT:Sjoormen class submarine Submarine classes Nuclear weapons programme of Sweden