There were four types of coastal defence craft during the Second World War. These were: Motor Torpedo Boats (MTBs), Motor Gun Boats (MGBs), Motor Launches (MLs) and Harbour Defence Motor Launches (HDMLs), with the main ones being the MTBs and the MGBs.
In 1939, there were three flotillas of coastal craft, comprising of MTB “short boats” being between 60’ – 71’ 6” long. These were built mainly by south coast shipbuilders: British Power Boat Co (Hythe), Vosper (Portsmouth) and Thornycroft (Southampton). They were armed with 2 torpedo tubes for either 18” or 21” torpedoes. In 1940, it was thought that a similar craft could be built to complement the MTBs, and the MGBs were created. These were armed with a variety of weapons including 0.5” Browning machine gun, 2 pdr pom pom, and a single or twin 20mm Oerlikon and, ultimately, a 6pdr Hotchkiss.
It was also realised that a large craft would be useful as the operation of the short boats was limited by the prevailing weather conditions. Fairmile designed a series of coastal craft, Types A and B were MLs, Type C was an MGB and Type D was the MTB – nicknamed Dog Boat. It first appeared in 1943 and could be fitted up as either a gun or torpedo boat, being 115’ long. It was, however, heavier than the short boats and averaged a speed of 30kts at full load as compared to the short boat’s 40kts. Since the Fairmile D could be either gun or torpedo boat, the designation MGB disappeared and all the craft were MTBs. The last of the D craft built had 4 18” torpedo tubes plus guns.
Coastal craft operated mainly in Channel and North Sea waters, especially in the build up to the Normandy invasion of 1944. They were also used in the Mediterranean and Norwegian campaigns. They were used to disrupt German convoys, carry out clandestine raids and landings and also to pick up secret agents in Norway and Brittany.
The coastal craft were manned by various Allied nationalities including Dutch, Norwegian, Canadian , Australian and New Zealanders. The officers were drawn mainly from the RNVR – hostilities only service.
©Royal Naval Museum Library, 2001
The information contained in this fact sheet is correct as far as we are able to ascertain from our sources. It is not intended to be an exhaustive or complete history of the subject. Please contact the library for a bibliography of further reading materials, if available.