Coastal corvettes that evade radar

    The Visby corvettes developed and manufactured at the Kockums shipyard in Karlskrona are among the most notable achievements in the history of modern Swedish technology. Not only do the vessels have a characteristic appearance, but they are also particularly difficult to detect on radar, which was their whole point.

    The development of the Visby corvettes began in the early 1990s. In 1991 the Karlskrona shipyard built the experimental ship Smyge. The Swedish Navy intended to create a platform for testing new weapons technology, sensors and communications for what is known as stealth technology.

    The irregular shape of the hull made the ship difficult to detect on radar. This design formed the basis for the final configuration of the Visby-class corvette. The ship has as many flat and angled surfaces as possible, making it difficult to detect by radar, infrared sensors and hydroacoustics. The sandwich structure of the hull, consisting of carbon fibre reinforced plastic laminate, provides yet another advantage – it is non-magnetic, which also makes detection more difficult.

    All the weapons systems are contained in the hull, and the weapons are not exposed until just before firing. Even the general purpose gun on the foredeck can be folded into the hull. Heat and exhaust gases from firing the missiles is drawn into channels and out to the other side of the ship. The exhaust gases from the ship’s waterjet propulsion system are also drawn off through hidden outlets close to the waterline to leave as few traces as possible.

    HMS Helsingborg (K32) is the second corvette of the Visby class and was launched in Karlskrona on 27 June 2003. In 2006, there was a trial run in the Mediterranean. The ship was handed over to the Swedish Armed Forces, 2009. Photo: Terje Fredh. The Maritime Museum.

    The Visby corvettes were built at Kockums shipyard in Karlskrona and the first ship, Visby, was launched in June 2000. The remaining ships were launched in the period up to 2006 and were named Helsingborg, Härnösand, Nyköping and Karlstad.

    The corvettes are capable of undertaking a variety of tasks including mine clearance, anti-submarine warfare, surface warfare, maritime surveillance and maritime security and providing support for civil society, for example in the event of accidents at sea.