Sjöormen-class submarine


The Sjöormen class 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. 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. 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 and relaunched as the following modernisation and tropicalisation.

Description

As built, the Sjöormen class were designed with a teardrop hull shape, based on the United States'. They had bow planes on the sail and their stern diving planes were configured in a x-shape. They had a standard displacement of and when dived. The submarines had a waterline length of and a length overall of. They had a beam of and a draught of. 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. This gave the submarines a surfaced speed of and submerged. The vessels had an endurance of 21 days and could reach a depth when dived of. Their diving depth is limited by the shallow waters of the Baltic Sea compared to the ocean depths.
As built the Sjöormen class were equipped with surface search radar and sonar. The submarines were armed with four torpedo tubes located in the bow for surface attack and two 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.

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.

Ships

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 became operational, but due to lack of funding, were all laid up in 1993.

Singapore service

Four submarines were sold to the Republic of Singapore Navy in the 1990s and entered service as the following modernisation and tropicalisation.