Flyvefisken-class patrol vessel

The Flyvefisken class, also known as the Standard Flex 300 or SF300 class, is a group of patrol vessels of the Royal Danish Navy; the name means flying fish in Danish. Its defining idea is StanFlex, a modular design in which a standard hull carries containerised weapons or systems in four container positions measuring 3.5 by 3 by 2.5 metres, so a ship can change role in about 48 hours between surveillance, combat, minelaying, pollution control, anti-submarine warfare and mine countermeasures. The hulls are built as a sandwich of fibreglass either side of a PVC foam core, a method that reduces maintenance costs. Fourteen ships were built in three series, differing mainly in their propulsion arrangements, and the class replaced Søløven torpedo boats, Sund-class minesweepers and Daphne-class seaward defence craft. Four vessels were acquired by the Portuguese Navy in 2010 and renamed Mondego, Douro, Guadiana and Tejo, with a fifth bought as a spare-parts hull; Portugal knows them as the Tejo class. The LM500 gas turbine is among the engines that power them.