Castle-class trawler

The Castle-class minesweeper was a highly sea worthy naval trawler adapted for minesweeping and built to Admiralty specifications. Altogether about 200 were built between 1916 and 1919.

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 for the Admiralty. After the war about 55 further ships were built as trawlers and many of the minesweepers were converted to trawlers

New Zealand additions
In 1940 the New Zealand Marine Department opted for this class in preference to the more modern Blomvlei design, also by Smith's Dock, 1935, and another 13 vessels of the class were built and put into service.