“Admiralty design in 1938 for destroyer *76 boats built to the original design. Re-designed at admiralty in 1940 and 1120 boats built to re-design. Carried on board destroyers (as seaboats), small cruisers, corvettes, etc.
The boats built during the 1939-45 war showed a marked tendency to sag between chock supports when hanging in davits. The keel structure is being generally stiffened to overcome this defect in boats ordered after 1943.”