Castle-class trawler
The Castle-class minesweeper was a highly seaworthy naval trawler adapted for patrol, anti-submarine warfare and minesweeping duties and built to Admiralty specifications. Altogether 197 were built in the United Kingdom between 1916 and 1919, with others built in Canada, India and later New Zealand. Many saw service in the Second World War.
First World War
The Castle class originated with the commercial trawler Raglan Castle of 1915, taken up for Royal Navy service. The design was adapted by Smith's Dock Company Ltd to Admiralty requirements for building in quantity.During World War I, 145 were built in the United Kingdom for the Admiralty. The names of the vessels were derived from the official crew rosters of ships at the Battle of Trafalgar. Non-standard ships included in the class varied between and, with dimensions varying between length and beam. The first standard vessel, Nathaniel Cole, was delivered in May 1917. After the war 52 further ships on order were completed as fishing vessels and many of the minesweepers were converted for commercial use. 20 ships were also cancelled, but many were completed by the shipbuilders for commercial owners.
The Admiralty also ordered 60 Castle-class trawlers from Canadian shipyards, the minesweeping trawler|TR series], which were loaned to the Royal Canadian Navy for seaward defence of the east coast of Canada. Some entered service with the United States Navy. Nine ships were also built in India with teak planking on steel frames.