Fact Sheet 2
The Escort Sloop
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| HMS Penzance - A Bridgewater class sloop. Launched in April 1930, Plymouth. |
During the nineteen thirties the British Admiralty recognised that the tasks of minesweeping and escorting needed to be separated. The BRIDGWATER class first introduced in 1929 was the origin of the true escort vessel, with a decent turn of speed (16/17 knots), anti-surface and anti-aircraft guns, although early versions retained minesweeping gear and were fitted to receive mining rails and depth charge throwers in times of war. The first ASDIC sets were installed in later ships of the class.
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| HMS Wellington |
Many of the earlier classes of sloop which had been stationed overseas in September 1939 were recalled to UK to escort Atlantic convoys. HMS WELLINGTON a GRIMSBY class sloop, built in 1934 as a minesweeper and now preserved on the Thames embankment, was one of these.
Through later years of the decade more powerful escort sloops were developed by Assistant Naval Constructor Roland Baker working for Constructor Victor Shepheard (both later knighted) culminating in the BITTERN and BLACK SWAN classes. The first of the BLACK SWANs appeared in the 1937 building programme. With the outbreak of the war in 1939 the need for additional sloops with good A/A and A/S armament quickly became apparent and orders for further BLACK SWAN Class vessels were included in the 1940, 1941, and 1942 building programmes. These well appointed sloops were generally reckoned to be one of the most potent and successful of all the Second World War escort designs.
A total of twenty-seven improved BLACK SWAN sloops were completed for the Royal Navy between 1942 and 1946 and two of the same design for India. The title of “sloop” was replaced by “frigate” in 1947.
The design included 3 twin 4 inch HA/LA (High Angle/ Low Angle) guns to provide effective AA defence and a large number of depth charges for attacks against submarines. 110 depth charges with 4 throwers and 2 sets of rails were fitted aft.
The 4 inch Mk. XVI twin mountings were generally appreciated to be superior to all other British light calibre weapons of the period with a maximum elevation of 800 and a firing cycle of 5 seconds. In the first years of the war, the lack of a suitable fire-control system for the main armament was a significant deficiency, but as soon as RADAR became available it was fitted for fire control and surface warning and provided accurate ranging data.
Earlier vessels were all-riveted using Admiralty derived scantlings that produced a heavy hull. As the war progressed the demand for faster building increased and the Admiralty allowed the lighter construction standards of the Ship Classification Societies laid down for merchant ships to be used for smaller warships. More welding was introduced until in the last few of the BLACK SWANs as much as 30% of the structure was welded. All vessels were built of mild steel.
Some ships were fitted with lattice masts on build - most of those built with tripod masts soon received a replacement lattice mast to carry more effective RADAR.
On trials with a displacement of 1,790 tons a speed of 19.5 knots was typically achieved.
