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Isles-class trawler
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Isles class
HMT Ailsa Craig in 1944
Class overview
Operators
Subclasses German Navy: Type 139 patrol trawler
Built1939–1945
Completed
Lost23
General characteristics
TypeNaval trawler
Displacement545 long tons (554 t)
Length164 ft (50 m)
Beam27 ft 8 in (8.43 m)
Draught11 ft 1 in (3.38 m) (mean)
Propulsion1 triple expansion reciprocating engine, 1 shaft, 850 ihp (634 kW)
Speed12 knots (22 km/h; 14 mph)
Complement40
ArmamentSee text

The Isles-class trawlers were a class of naval trawler used by the Royal Navy, Royal Canadian Navy and Royal New Zealand Navy during World War II.

The type comprised 197 vessels built between 1939 and 1945 in the nearly identical Isles, Dance, Tree and Shakespearian classes. Similar to the Castle-class trawlers of 1916–1918, though somewhat larger, they were mainly used on minesweeping and harbour defence duties. Most were armed with one 12-pounder gun (76 mm) and three or four 20 mm Oerlikon AA guns with 30 depth charges. In the Dance class a 4-inch AA gun (102 mm) was fitted in place of the 12 pdr, and there were six 20 mm Oerlikons in Annet, Bressay, Damsay, Fiaray, Foulness and Lindisfarne. Four of the trawlers were given "bird" names when converted to controlled minelayers in 1943–44: Blackbird (M15), Dabchick (M22), Stonechat (M25) and Whitethroat (M03). A total of 23 of these trawlers were lost during the war.[1] Six trawlers were loaned to Canada in 1942–1945 and five to Norway in 1943–1945.

Postwar, 17 of the trawlers were disarmed as wreck disposal vessels: Bardsey (DV13), Bern (DV4), Caldy (DV5) Coll (DV6), Earraid (DV7), Fetlar (DV8), Flatholm (DV9), Graemsay (DV10), Lindisfarne (DV11), Lundy (DV12), Neave (DV14), Scalpay (DV15), Skomer (DV16), Steepholm (DV17), Switha (DV18), Tiree (DV19), and Trondra (DV20). At least five were employed as danlayers (laying and retrieving dan buoys during minesweeping operations): Imersay (J422), Sandray (J424), Shillay (J426), Sursay (J427) and Tocogay (J451). After decommissioning, Switha and Coll were converted to oil tank cleaning vessels for dockyard service in 1949–1950.

By 1949, there were 31 trawlers and four controlled minelayers in Royal Navy service, one controlled minelayer in the Royal Canadian Navy and four trawlers in the Royal New Zealand Navy. Sixteen were in service in the Italian Navy and six in the Portuguese Navy.[2] Most of the surviving Royal Navy examples were discarded in the 1950s but a few remained until the 1960s. Two acquired post-war by the Federal German Navy remained in service as training vessels well into the 1970s, with one, Trave (ex-Dochet), resold to Turkey for further service in 1977.

Builders

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Ships in class

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Royal Navy

[edit]
Construction data for Isles-class trawlers of the Royal Navy
Ship Builder Laid down Launched Commissioned/Completed Fate
Ailsa Craig Cook, Welton & Gemmell 16 October 1943[3] 24 December 1943[4] Sold 1946 and renamed Veslemoy. Renamed Toran in 1952. Lost 19 February 1955.[3]
Annet[5] Cook, Welton & Gemmell 25 March 1943[3] 19 June 1943[4] Became a Wreck disposal vessel in 1946.[3] Still in use as diving Vessel for clearance diving in 1953.[6] Sold 1957.[7] Became fishery protection vessel FPV Ulva for Fishery Board for Scotland in 1958. Withdrawn from use 1971 and scrapped 1972.[3][8]
Arran Cook, Welton & Gemmell 16 November 1940[3] 1 May 1941[9] Sold 1946 and renamed Assan Reis. Renamed Professor Henking 1952.[3]
Balta Cook, Welton & Gemmell 2 December 1940[3] 19 May 1941[10] Sold 1946
Bardsey Fleming & Ferguson 17 July 1943[3] 15 September 1943[4] Still in service 1949 as wreck disposal vessel (DV13)
Benbecula Cook, Welton & Gemmell 28 October 1943[3] 13 January 1944[4] Sold 1946, bought by HM Customs and Excise and served as HMRC Vigilant
Bern Cook, Welton & Gemmell 2 May 1942[3] 9 October 1942[10] Still in service 1949 as wreck disposal vessel (DV4)
Biggal Ferguson Bros. 4 December 1944[3] Sold 1946
Blackbird (ex-Sheppey) Cook, Welton & Gemmell 20 February 1943[11] Converted to controlled minelayer (M15) 1943: still in service 1949
Bressay Cook, Welton & Gemmell 20 January 1942[3] 10 May 1942[10] Sold 1946
Brora Cook, Welton & Gemmell 18 December 1940[3] 11 June 1941[10] Grounded off Hebrides 6 September 1941
Bruray Cook, Welton & Gemmell 16 May 1942[3] 1 December 1942[10] Transferred to Portugal 1943 as Sam Miguel (P1)
Bryher Cook, Welton & Gemmell 8 April 1943[3] 20 July 1943[4] Still in service 1949
Burra Goole S.B. & R. Co. 29 March 1941[3] 18 July 1941[10] Transferred to Italy 1946 as DR 301
Bute Goole S.B. & R. Co. 12 May 1941[3] 15 September 1941[10] Sold 1946
Caldy John Lewis & Sons 31 August 1943[3] 14 December 1943[4] Still in service 1949 as wreck disposal vessel (DV5)
Campobello Collingwood Shipbuilding 19 June 1942[12] War loss 16 Mar 1943.
Copinsay Cochrane & Sons 12 April 1940[13] 25 April 1941[10] Sold 1946
Crowlin Cook, Welton & Gemmell 15 November 1943[13] 28 January 1944[14] Sold 1946
Cumbrae Cochrane & Sons 20 December 1940[13] 17 May 1941[10] To Italy 1946 as DR 302
Damsay George Brown & Co. 27 June 1942[13] 3 September 1942[10] Still in service 1949
Dochet G.T. Davie & Sons 26 June 1942[12] 13 November 1942[15] Acquired by Federal German Navy postwar and renamed Trave (A51) as a Type 139 patrol trawler; sold to Turkey in 1977
Earraid (ex-Gruna) John Crown & Sons 18 December 1941[16] 11 May 1942[10] Later wreck disposal vessel (DV7); sold 1948
Eday Cochrane & Sons 26 June 1941[13] 22 November 1941[10] Loaned to Norway as Tromöy (i) 1943–44; sold into mercantile use 1946
Egilsay Cook, Welton & Gemmell 7 February 1942[13] 28 May 1943[10] To Italy 1946 as DR 306
Ensay Cook, Welton & Gemmell 5 March 1942[13] 15 June 1942[10] To Italy 1946 as DR 314
Eriskay Fleming & Ferguson 28 August 1942[13] 28 October 1942[10] To Portugal 1943 as P8
Fara Cochrane & Sons 27 January 1941[13] 28 June 1941[10] Sold 1946
Farne Cook, Welton & Gemmell 22 April 1943[13] 31 August 1943[14] Sold 1946
Fetlar Cochrane & Sons 10 July 1941[13] 13 December 1941[10] Still in service 1949 as wreck disposal vessel (DV8)
Fiaray Goole S.B. & R. Co. 13 June 1942[13] 27 September 1942[10] Sold 1946
Filla John Crown & Sons 2 April 1942[13] 28 August 1942[10] To Italy 1946 as DR 305
Flatholm Cook, Welton & Gemmell 8 May 1943[13] 20 August 1943[14] Later wreck disposal vessel (DV9); sold 1948
Flint G.T. Davie & Sons 14 July 1942[12] 13 November 1942[15] Acquired by Federal German Navy postwar and renamed Eider (A50) as a Type 139 patrol trawler
Flotta Cochrane & Sons 13 February 1941[13] 7 June 1941[10] Grounded off East Scotland 6 Nov 1941.
Foula Cochrane & Sons 28 July 1941[13] 3 January 1942[10] To Italy 1946 as DR 313
Foulness John Lewis & Sons 23 March 1942[13] 30 June 1943[14] Still in service 1949
Fuday Cook, Welton & Gemmell 1 January 1944[13] 24 March 1944[14] Sold 1946
Gairsay Ardrossan Dockyard Co. 28 May 1942[13] 2 September 1943[14] War loss 4 Aug 1944.
Ganilly Cook, Welton & Gemmell 22 May 1943[13] War loss 5 July 1944
Gateshead G.T. Davie & Sons 1 August 1942[12] 11 May 1943[15] Sold 1947
Gillstone Cochrane & Sons 19 July 1943[16] 13 November 1943[14] Sold 1946
Gorregan Ardrossan Dockyard Co. 30 December 1943[16] 16 June 1944[14] Still in service 1949
Graemsay Ardrossan Dockyard Co. 3 August 1942[16] 16 June 1943[10] Still in service 1949 as wreck disposal vessel (DV10)
Grain Cochrane & Sons 17 August 1943[16] 16 November 1943[14] To Italy 1946 as DR 309
Grassholm John Lewis & Sons 20 April 1943[16] 17 August 1943[14] Sold 1946
Gruinard John Crown & Sons 20 November 1943[16] 1 March 1943[10] To Portugal 1943 as P7
Gulland Cook, Welton & Gemmell 30 April 1943 5 August 1943[16] 30 October 1943[14] Sold to mercantile use 1946; renamed Henken 1947 and Arab Trader 1949; wrecked north of Mombasa 13 April 1951. Boiler and wreckage still on reef.[17]
Gweal (ex-Boreray) Cook, Welton & Gemmell 17 June 1943[3] 3 November 1942[4] Sold 1946
Hannaray Cook, Welton & Gemmell 12 February 1944[16] 3 May 1944[14] Sold 1946
Harris Cook, Welton & Gemmell 29 January 1944[16] 12 April 1944[14] Sold 1946
Hascosay Cook, Welton & Gemmell 28 March 1944[16] 26 May 1944[14] Sold 1946
Hayling Cook, Welton & Gemmell 17 August 1942[16] To Portugal 1943 as Terceira (P3)
Hellisay Cochrane & Sons 27 March 1944[16] 17 July 1944[14] Sold 1946
Hermetray Cochrane & Sons 11 April 1944[16] 22 August 1944[14] Sold 1947
Herschell G.T. Davie & Sons 5 November 1942[12] 29 May 1943[15] Sold 1946
Hildasay Cook, Welton & Gemmell 29 April 1941[16] 30 September 1941[10] Grounded on Diani reef south of Mombasa, Kenya on 21 Jun 1945. Broke up during the next three months. Boiler visible at low tide.

[17]

Hoxa Cook, Welton & Gemmell 15 January 1941[16] 18 July 1941[10] Sold 1946
Hoy Cook, Welton & Gemmell 1 February 1941[16] 10 July 1941[10] Sold 1946
Hunda Ferguson Bros. 4 February 1942[16] 31 March 1942[10] Sold 1946
Imersay Cochrane & Sons 21 August 1944[16] 8 December 1944[14] Still in service 1949 as danlayer (J422)
Inchcolm Cook, Welton & Gemmell 3 March 1941[16] 25 July 1941[10] Sold 1946
Inchmarnock John Lewis & Sons 25 August 1941[18] 28 November 1941[10] Loaned to Norway as Karmöy 1944–45; sold mercantile 1946
Islay Smith's Dock Co. 10 April 1941[18] 17 June 1941[10] Sold 1946
Jura Ardrossan Dockyard Co. 22 November 1941[18] War loss 7 Jan 1943
Kerrera Ferguson Bros. 22 September 1941[18] 31 October 1941[10] Loaned to Norway as Oksöy 1944–45; sold mercantile 1946
Kintyre Ardrossan Dockyard Co. 21 October 1941[18] 24 April 1942[10] Sold 1946
Kittern Cook, Welton & Gemmell 28 August 1943[18] 13 November 1943[14] Sold 1946
Lindisfarne Cook, Welton & Gemmell 17 June 1943[18] 17 August 1943[14] Still in service as wreck disposal vessel (DV11)
Lingay Cochrane & Sons 6 September 1944[18] 6 January 1945[14] Sold 1946
Longa Cochrane & Sons 15 October 1943[18] 13 February 1944[14] Sold 1946
Lundy Cook, Welton & Gemmell 29 August 1942[18] 15 January 1943[4] Still in service in 1949 as wreck disposal vessel (DV12)
Mewstone Cook, Welton & Gemmell 16 September 1943[18] 26 November 1943[14] Sold 1946
Minalto Cook, Welton & Gemmell 3 July 1943[18] 30 September 1943[14] Sold 1946
Mincarlo Ardrossan Dockyard Co. 28 March 1944[18] 24 October 1944[14] Loaned to Norway as Tromöy (ii) 1944–45, sold mercantile 1946
Mousa Goole S.B. & R. Co. 1 June 1942[18] 30 August 1942[10] To Italy 1946 as DR 311
Mull Cook, Welton & Gemmell 27 March 1941[18] 19 August 1941[10] Sold 1946
Neave Cook, Welton & Gemmell 16 July 1942[18] 25 November 1942[4] Still in service in 1949 as wreck disposal vessel (DV14)
Orfasy A. Hall & Co. 17 March 1942[18] War loss 22 October 1943
Oronsay Cochrane & Sons 30 October 1943[18] 16 February 1944[14] Still in service 1949
Oxna A. & J. Inglis 26 January 1943[11] 18 July 1943[4] Sold 1946
Pladda Cook, Welton & Gemmell 16 April 1941[11] 19 August 1941[4] Sold 1946
Porcher Midland Shipyards 26 May 1942[19] 27 October 1942[15] Sold 1946
Prospect Midland Shipyards 16 June 1942[19] 4 November 1942[15] Sold 1946
Ronaldsay Cochrane & Sons 14 February 1941[11] 17 July 1941[4] Sold 1946
Rosevean Cook, Welton & Gemmell 17 July 1943[11] 16 October 1943[14] Sold 1946
Rousay Goole S.B. & R. Co. 20 December 1941[11] 17 April 1942[4] Sold 1946
Ruskholm Goole S.B. & R. Co. 4 February 1942[11] 10 May 1942[4] To Portugal 1945 as Baldaque da Silva
Rysa Cochrane & Sons 15 March 1941[11] 9 August 1941[4] War loss 8 Dec 1943
Scalpay Cook, Welton & Gemmell 2 June 1942[11] 20 October 1941[4] Later wreck disposal vessel (DV15); sold 1948
Shapinsay Cochrane & Sons 29 March 1941[11] 5 September 1941[4] Sold 1946
Shiant Goole S.B. & R. Co. 9 August 1941[20] 24 November 1941[4] Loaned to Norway as Jelöy 1944–45; sold mercantile 1946
Skokholm Cook, Welton & Gemmell 29 September 1943[20] 10 December 1943[14] Sold 1946
Skomer John Lewis & Sons 17 June 1943[20] 4 November 1943[14] Still in service 1949
Skye Henry Robb 17 March 1942[20] 22 July 1942[10] Still in service 1949
Sluna Cochrane & Sons 14 April 1941[20] 10 October 1941[4] Sold 1946
St. Agnes John Lewis & Sons 19 May 1943[11] 21 September 1943[14] Sold 1946
St. Kilda A. Hall & Co. 29 May 1942[11] 30 September 1942[4] Sold 1946
Staffa Henry Robb 15 June 1942[20] 31 August 1942[4] Sold 1946
Steepholm John Lewis & Sons 15 July 1943[20] 1 December 1943[14] Converted to wreck disposal vessel December 1945. Still in use as the last of 18 wreck disposal vessels in 1958.[21]
Stroma Hall, Russell & Co. 19 November 1941[20] 22 January 1942[4] To Italy 1946 as DR 315
Stronsay A. & J. Inglis 4 March 1942[20] War loss 5 Feb 1943
Switha A. & J. Inglis 3 April 1942[20] 15 June 1942[4] Later wreck disposal vessel (DV18); converted to oil fuel tank cleaning vessel 1949–50
Texada Midland Shipyards 27 July 1942[12] 17 November 1942[15] Sold 1946
Tiree Goole S.B. & R. Co. 6 September 1941[20] 12 January 1942[4] Still in service 1949 as wreck disposal vessel (DV19)
Trondra John Lewis & Sons 4 October 1941[20] 16 January 1942[4] Still in service 1949 as wreck disposal vessel (DV20)
Ulva Cook, Welton & Gemmell 30 July 1942[20] 15 December 1942[4] Sold 1946
Unst Ferguson Bros. 28 May 1942[20] 31 July 1942[4] To Italy 1946 as DR 303
Vatersay Cochrane 13 November 1943[12] 9 March 1944[14] Sold 1946
Wallasea Henry Robb 22 April 1943[20] 26 July 1943[15] War loss 6 Jan 1944.
Westray John Lewis & Sons 4 November 1941[12] 2 March 1942[4] Sold 1946
Whalsay Cook, Welton & Gemmell 4 April 1942[12] 28 August 1942[4] To Portugal 1943 as Santa Maria (P4)

The following 21 trawlers may be[citation needed] described as comprising the Repeat Isles class:

Construction data for Repeat Isles–class trawlers of the Royal Navy
Ship Builder Laid down Launched Commissioned/Completed Fate
Calvay Cook, Welton & Gemmell 29 November 1943[3] 16 February 1944[14] Sold 1946
Canna Cochrane & Sons 18 November 1940[3] 3 March 1941[10] War loss 5 December 1942[3]
Cava Fleming & Ferguson 3 March 1941[3] 3 March 1941[10] Sold 1946
Coll Ardrossan Dockyard Co. 7 April 1942[13] 21 September 1942[10] Later wreck disposal vessel (DV6); converted to oil fuel tank cleaning vessel 1949–50
Colsay Cook, Welton & Gemmell 15 December 1943[13] war loss 1944
Dabchick (ex-Thorney) Cook, Welton & Gemmell 9 March 1943[20] converted 1943 to controlled minelayer (M22); still in service 1949
Orsay Cochrane & Sons 1 January 1945[18] still in service 1949
Rona Cochrane & Sons February 1945 still in service 1949
Sandray Cook, Welton & Gemmell 5 October 1944[11] 27 December 1944[15] Still in service 1949 as danlayer (J424)
Scaravay Cook, Welton & Gemmell 22 October 1944[11] 14 January 1945[15] Sold 1946
Sheppey (ex-Raasay) Cook, Welton & Gemmell 1 April 1942[11] 18 September 1942[10] Sold 1946
Shillay Cook, Welton & Gemmell 18 November 1944[20] 30 January 1945[15] Still in service 1949 as danlayer (J426)
Stonechat Cook, Welton & Gemmell 22 August 1944[12] 1944 as controlled minelayer (M25); still in service 1949
Sursay Cook, Welton & Gemmell 16 December 1944 26 February 1945[15] Still in service 1949 as danlayer (J427)
Tahay Cook, Welton & Gemmell 31 December 1944[20] 23 March 1945[15] Still in service 1949
Tocogay Cook, Welton & Gemmell 7 February 1945[20] still in service 1949 as danlayer (J451)
Trodday Cook, Welton & Gemmell 3 March 1945[20] still in service 1949
Vaceasay Cook, Welton & Gemmell 17 March 1945[12] still in service 1949
Vallay Cook, Welton & Gemmell 10 April 1945[12] still in service 1949
Whitethroat Welton & Gemmell 6 September 1944[12] 1944 1944 as controlled minelayer (M03); still in service 1949
Wiay Cook, Welton & Gemmell 26 April 1944[12] still in service 1949

Royal Canadian Navy

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Construction data for Isles–class trawlers of the Royal Canadian Navy
Ship Builder Laid down Launched Commissioned Paid off Fate
Anticosti Collingwood Shipbuilding 1 April 1942[3] 8 August 1942[22] Sold 1946 to Norway as Guloy, to Sweden as Barbro and to Ethiopia as Giuseppina in 1968. Wrecked in Massawa in 1996.[23]
Baffin Collingwood Shipbuilding 14 October 1941 13 April 1942[12] 20 August 1942[22] 20 Aug 1945 Sold mercantile 1947; renamed Niedermehnen 1952, Broken up 1983.
Cailiff Collingwood Shipbuilding 30 April 1942[12] 19 September 1942[22] 10 June 1945 Formerly HMS Cailiff (T276). Sold mercantile 1946; converted to Norwegian commercial trawler Borgenes. Laid up in 1990s, but proposals to restore her as a steam trawler [24] were unfulfilled. Sold for demolition in Oct 2012 [25][26]
Ironbound Kingston Shipyards 14 January 1942[12] 5 October 1942[22] Sold 1946
Liscomb Kingston Shipyards 23 March 1942[12] 3 September 1942[22] Sold 1946
Magdalen Midland Shipyards 7 March 1942[12] 19 August 1942[22] Sold 1946
Manitoulin Midland Shipyards 23 April 1942[19] 8 September 1942[22] Sold 1946
Miscou Collingwood Shipbuilding 1 June 1942[12] 20 October 1942[22] Later HMS Campenia and HMS Bowell. Lent to RCN by RN. Sold to Bergen as Cleveland, 1946; to Nordlandslinjen and renamed Sigurd Hund, 1950; to Ålesund and renamed Vestfar, 1963; to Hans Hansen in 1971 to Faroe Islands. Broken up in 1974.

Royal New Zealand Navy

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Construction data for Isles–class trawlers of the Royal New Zealand Navy
Ship Builder Laid down Launched Comm. Fate
Inchkeith John Lewis & Sons 16 November 1940[27] 10 July 1941[18] 24 October 1941[10] Still in service 1949
Killegray Cook, Welton & Gemmell 24 January 1941[27] 27 May 1941[18] 14 October 1941[10] Still in service 1949
Sanda Goole S.B. & R. Co. 23 December 1940[27] 12 July 1941[11] 3 November 1941[4] Still in service 1949
Scarba Cook, Welton & Gemmell 6 March 1941[27] 25 November 1941[4] 25 June 1941[11] Still in service 1949

See also

[edit]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Isles-class trawler

View on Grokipedia
from Grokipedia
The Isles-class trawler was a class of purpose-built naval trawlers developed for the Royal Navy during World War II, characterized by their sturdy fishing-vessel hulls adapted for minesweeping, anti-submarine warfare, and convoy escort duties. These vessels measured 164 feet (50 m) in length, with a beam of 27 feet 8 inches (8.4 m) and a draft of 11 feet (3.4 m), displacing 545 tons standard and up to 740 tons at full load. Powered by a single triple-expansion reciprocating engine delivering 850 indicated horsepower on one shaft, they achieved a top speed of 12 knots and carried a crew of approximately 40 officers and ratings. A total of 145 Isles-class trawlers were constructed between 1939 and 1945 by various British shipyards, including Cook, Welton & Gemmell in Beverley, Ardrossan Dockyard, and John Lewis & Sons, often in parallel with nearly identical sister classes such as the Dance, Tree, and Shakespearian designs, which together numbered around 197 vessels. The class drew design inspiration from earlier Admiralty trawlers like the 1935 HMS Basset, featuring a silhouette reminiscent of the Flower-class corvettes but optimized for coastal and harbor operations. Armament typically included one 12-pounder (76 mm) anti-aircraft gun forward, three single 20 mm Oerlikon anti-aircraft guns, and up to 30 depth charges for anti-submarine roles, reflecting their versatility in defending against U-boats and aerial threats. Primarily serving with the Royal Navy, the Isles-class also saw limited allocations to allied forces, including nine to the Royal Canadian Navy, four to the Royal New Zealand Navy, and five transferred to the Royal Norwegian Navy in 1944 for operations in Scandinavian waters. Throughout the war, they performed critical tasks such as clearing minefields in the North Sea and Atlantic approaches, patrolling harbors, and supporting convoys, with notable losses including 23 vessels sunk—three by German U-boats, such as HMS Ganilly by U-390 in July 1944. Postwar, most were decommissioned by 1946, with many sold for civilian use or repurposed for wreck clearance and disposal, marking the end of their military service by 1948.

Development

Design origins

The Isles-class trawler originated from the Admiralty's 1935 design for the 460-ton HMS Basset, a purpose-built vessel intended for anti-submarine and minesweeping roles, which served as the foundational prototype for subsequent wartime adaptations into armed naval trawlers. This pre-war concept emphasized robust, versatile hull forms derived from commercial fishing trawlers, enabling rapid navalization to bolster fleet auxiliaries. Developed amid escalating tensions in the late 1930s, the Isles-class responded directly to the Royal Navy's need for cost-effective, easily mass-produced ships to counter the mounting threat of German U-boats, which endangered Atlantic convoys and coastal waters through unrestricted submarine warfare. By 1939, as war loomed, the Admiralty initiated an emergency expansion program, conceptualizing these vessels to repurpose familiar trawler silhouettes for essential tasks like anti-submarine patrols, convoy escorts, and minesweeping, thereby addressing the acute shortage of dedicated escort forces without diverting resources from larger warships. While sharing conceptual similarities with the World War I-era Castle-class trawlers—such as their overall trawler-like profile—the Isles-class incorporated larger dimensions for superior seaworthiness in North Atlantic conditions, displacing approximately 545 tons standard. It stood apart from the contemporaneous smaller Tree-class (20 vessels), Dance-class (20 vessels), and Shakespearian-class (12 vessels), which together formed a related family of compact designs totaling 52 units built between 1939 and 1945, prioritizing quicker production over enhanced endurance. Key engineering choices included all-steel construction to withstand combat damage and harsh environments, paired with single-screw propulsion using a triple-expansion reciprocating engine for straightforward manufacturing and maintenance in wartime shipyards.

Technical specifications

The Isles-class trawlers had a standard displacement of 545 long tons, increasing to approximately 770 long tons at full load. Their dimensions measured 164 feet (50 meters) in length overall, with a beam of 27 feet 8 inches (8.43 meters) and a draught of 11 feet 1 inch (3.38 meters). These proportions provided a stable platform suited for North Atlantic conditions, featuring a riveted steel hull construction typical of wartime naval trawlers built for durability in harsh seas. Propulsion was provided by a single triple-expansion steam engine driving one shaft, developing 850 indicated horsepower (ihp). This arrangement enabled a maximum speed of 12 knots and a range of about 1,200 nautical miles at that speed, sufficient for convoy escort and patrol duties. The vessels carried a complement of 40 personnel, including officers and ratings, to operate the ship and its equipment. The superstructure included a forecastle design extending forward to improve seaworthiness in rough weather, with the bridge positioned amidships for better visibility during operations. Basic fittings for detection comprised ASDIC (sonar) for anti-submarine warfare and rudimentary radar sets, such as Type 286, to enhance situational awareness in low-visibility conditions. Power was generated by coal-fired boilers, allowing for sustained endurance on patrols with fuel capacities supporting several days of operation at economical speeds without frequent replenishment. This coal-burning system, while less efficient than later oil-fired designs, aligned with the use of readily available commercial trawler components for rapid wartime production.

Construction

Shipyards and builders

The construction of the Isles-class trawlers relied on a network of established shipyards in the United Kingdom, with a heavy concentration in northeast England to capitalize on regional expertise in commercial fishing vessel production. These yards, many of which were specialist trawler builders, were rapidly mobilized under Admiralty contracts to support wartime needs for minesweepers and anti-submarine vessels. Primary contributors included Cook, Welton & Gemmell in Beverley, Yorkshire, a firm renowned for its pre-war trawler output, which delivered multiple Isles-class ships such as HMS Annet (T341) in 1943. Cochrane & Sons in Selby, Yorkshire, also played a key role, constructing vessels like HMS Fetlar (T202) in 1941 from its facilities on the River Ouse, adapting its capabilities for naval specifications. Smith's Dock Company in Middlesbrough (South Bank-on-Tees), another trawler-building specialist, produced units including HMS Islay (T172), launched in 1941, as part of its expanded wartime efforts. Additional yards contributed to the program, such as Goole Shipbuilding & Repairing Co. in Goole, Yorkshire, which built HMS Rousay (T210) in 1941, further exemplifying the regional focus on Humber and Tees-area facilities. Overall, more than 20 shipyards across the UK produced approximately 145 Isles-class vessels between 1939 and 1945, enabling swift wartime output through the repurposing of commercial infrastructure. This distributed approach highlighted the Admiralty's strategy to harness peacetime fishing industry know-how for naval expansion.

Production and variants

The production of the Isles-class trawlers spanned from 1939 to 1945, with the peak output occurring between 1941 and 1943 to address urgent wartime demands for minesweeping and anti-submarine vessels. A total of 145 standard Isles-class vessels were constructed, alongside 52 closely related designs in the Tree (20 ships), Dance (20 ships), and Shakespearian (12 ships) classes, which shared nearly identical hull forms and capabilities but differed slightly in early fittings. Construction proceeded at an average rate of 2-3 vessels per month at major shipyards such as Smith's Dock, Henry Robb, and Cook, Welton & Gemmell, facilitated by simplified Admiralty designs that prioritized rapid assembly over commercial refinements. Wartime material shortages, particularly in steel and specialized fittings, prompted the standardization of components across classes to streamline production and replacements for losses. In total, 23 vessels from these groups were lost during the war, necessitating accelerated builds to maintain fleet strength. Variants within the Isles class included minor adaptations for specific roles, such as conversions to controlled minelayers on vessels like HMS Blackbird (M15) and HMS Dabchick (M22), which received additional mine rails for laying defensive fields. Differences in equipment also arose from availability, with some ships fitted with Type 271 surface-search radar and others with the earlier Type 286 set. Postwar, 17 Isles-class trawlers were disarmed and repurposed as wreck disposal vessels, while some were converted to danlayers for laying marker buoys in clearance operations by 1946.

Armament and equipment

Weapons systems

The primary offensive and defensive armament of the Isles-class trawler consisted of a single 12-pounder (76 mm) QF gun mounted forward, capable of engaging surface targets and providing limited anti-aircraft fire. This gun was the main battery for the class, reflecting the vessels' role in coastal escort and patrol duties where heavier ordnance was impractical due to their fishing trawler-derived hulls. For anti-aircraft protection, the trawlers were equipped with three to four 20 mm Oerlikon cannons in single mounts, typically one aft and two on the bridge wings, offering rapid fire against low-flying aircraft threats common in convoy operations. Early production vessels from 1939 initially carried .303-inch Lewis machine guns in lieu of the Oerlikons for anti-aircraft and close-range defense, but these were progressively replaced by the more effective Oerlikon mounts by 1942 as wartime priorities shifted toward enhanced air defense. No torpedo tubes were fitted, as the class's limited displacement and stability precluded such heavy anti-submarine weaponry. Anti-submarine capabilities centered on 30 depth charges, deployed from throwers and stern rails to create patterns around submerged threats detected by onboard ASDIC. These armaments underscored the Isles-class's defensive orientation, prioritizing survival in contested waters over aggressive engagement.

Minesweeping gear

The Isles-class trawlers were fitted with standard Royal Navy minesweeping equipment designed for clearing contact, magnetic, and acoustic mines encountered during World War II operations. Primary gear included paravane sweeps, which were torpedo-shaped devices towed from the bow to sever the mooring wires of contact mines, preventing them from drifting into shipping lanes. These paravanes were deployed via bow booms that pivoted from the ship's side, a configuration adapted from commercial fishing trawler designs to suit auxiliary naval roles. Complementing the paravanes were Oropesa sweeps for systematic clearance of moored contact mines, consisting of a serrated wire towed at a predetermined depth by streamlined floats, otters, and kites to ensure coverage of potential minefields. For magnetic mines, the class employed the LL (low-frequency loop) sweep, utilizing long cables carrying an electric current to simulate a ship's magnetic signature and trigger detonation. Acoustic threats were addressed through SA (sweep acoustic) gear, featuring towed hammers such as the Kango vibrating type or Fessenden oscillator, which generated propeller-like noises to activate German acoustic fuzes. Deployment of these sweeps relied on adapted fishing winches, typically steam-powered capstans, enabling operations at speeds up to 10 knots while maintaining tension on the wires. Sensors to minesweeping included the system for detecting submerged mines and obstacles, providing ranging up to several thousand yards in shallow waters typical of trawler operations. Early surface search was also fitted for surface and spotting floating hazards, enhancing during night or poor sweeps. The LL sweep specifically targeted induction-based magnetic mines by inducing a changing along the cable path. Operation of this gear required dedicated minesweeping teams within the vessel's complement of approximately 40 personnel, including officers and ratings trained in sweep deployment and recovery. Training emphasized precise coordination to avoid fouling or premature detonation, with crews often drawn from the Royal Naval Reserve and practicing in controlled areas like the Thames Estuary. The equipment could be managed by this reduced crew, allowing flexibility for anti-submarine duties alongside minesweeping. By 1943, some Isles-class vessels received adaptations such as enhanced magnetic coil systems integrated into the LL sweep configuration, improving effectiveness against evolved German threats including combined magnetic-acoustic mines. These upgrades involved additional cabling and power generation to broaden the sweep's electromagnetic influence, reflecting ongoing refinements in response to Axis mine technology.

Operational history

World War II

The Isles-class trawlers played a vital role in Allied naval operations during World War II, primarily serving the Royal Navy in minesweeping and anti-submarine duties across multiple theaters. With over 100 vessels allocated to the Royal Navy, the class formed the backbone of local escort forces and harbor defense groups, particularly in the Atlantic and Channel areas. A smaller number were transferred to allied navies, including seven to the Royal Canadian Navy for operations in Canadian waters and the North Atlantic, four to the Royal New Zealand Navy for Pacific patrols, and five to the Royal Norwegian Navy for coastal defense. These trawlers were instrumental in the Battle of the Atlantic, providing convoy escorts despite limited direct kills. Their modest speed and armament made them essential for close protection rather than offensive actions, helping sustain vital shipping lanes against U-boat threats. In the European theater, Isles-class trawlers were heavily engaged in Channel minesweeping operations to counter German minelaying campaigns. They participated in clearing British coastal waters and approaches to key ports. By 1944, several were converted for minelaying support, including as danlayers to mark swept channels during major operations. Their most critical contribution came in the lead-up to D-Day, where trawlers participated in minesweeping operations ahead of the Normandy invasion in June 1944. In the Mediterranean, vessels like HMT Islay operated in support roles, rescuing survivors from sunk ships in 1942 and aiding convoy protection in North African waters. These efforts ensured safe passage for amphibious forces and supply lines, though the class's wooden hulls and limited defenses exposed them to high risks from mines, aircraft, and submarines. The Isles-class suffered significant attrition, with 13 vessels lost to enemy action between 1939 and 1945. Notable sinkings included three by U-boats: HMS Jura torpedoed by U-371 off Algiers on January 7, 1943; HMS Orfasy by U-68 in the central Atlantic on October 22, 1943; and HMS Ganilly by U-390 off Utah Beach during post-D-Day operations on July 5, 1944. Other losses occurred to mines and air attacks, such as HMS Gairsay sunk by a German human torpedo while minesweeping off Normandy on August 4, 1944. Despite few confirmed U-boat kills, the class's persistent patrols and sweeps were crucial for Allied logistics, preventing far greater shipping losses and enabling operations like the Normandy invasion. Their wartime service underscored the importance of auxiliary vessels in sustaining the Allied war effort against Axis naval threats.

Postwar use

Following World War II, numerous Isles-class trawlers were repurposed for non-combat roles within the Royal Navy, particularly in clearing wartime wrecks to ensure safe navigation. Seventeen vessels were disarmed and converted into wreck disposal ships, tasked with using surplus depth charges to dismantle sunken hulls in hazardous areas such as the Thames Estuary. For instance, HMS Bern (DV4) served in this capacity until her scrapping in 1960. These operations addressed the environmental hazards posed by unexploded ordnance and submerged debris, preventing threats to postwar shipping. By 1949, the Royal Navy maintained 31 Isles-class trawlers in active service, alongside four converted controlled minelayers, while the Royal Canadian Navy operated one and the Royal New Zealand Navy four. Due to their obsolescence in frontline duties, no major modernizations were undertaken, and many were placed in reserve during the early 1950s. The last Royal Navy wreck disposal vessel of the class was scrapped in 1960. Several vessels were transferred to allied navies as part of postwar aid and disposal efforts. In January–March 1946, the Royal Navy transferred 11 Isles-class trawlers to Italy, where they served as coastal minesweepers; these received minor updates in 1956, including three 20 mm anti-aircraft guns, before being decommissioned in 1962 and repurposed as auxiliaries. Portugal acquired four Isles-class trawlers in 1946 after wartime loans, renaming them São Miguel, Faial, Terceira, and Santa Maria for patrol duties; they were decommissioned between 1956 and 1968, with one additional unit (Baldaque da Silva, later Salvador Correia) serving into the early 1970s. Two others went to the Federal German Navy as training ships, remaining in use until the 1970s, and one Portuguese unit was resold to Turkey in 1977. Most surviving Isles-class trawlers were scrapped between 1946 and 1955, with the remainder following in the 1950s and early 1960s as naval priorities shifted to newer designs.

Ships of the class

Royal Navy

The Royal Navy commissioned approximately 130 Isles-class trawlers, with many remaining in service with it after transfers to allied navies, out of a total class build of 145 vessels constructed between 1939 and 1945; several others were allocated directly or transferred to allied navies such as the Royal Canadian Navy and Royal Norwegian Navy. These ships were named after islands, isles, and coastal features of the British Isles, with examples including HMS Ulva (T248) and HMS Arran (T06). Of the Royal Navy's Isles-class vessels, 13 were lost during wartime operations, primarily to mines, submarines, or aircraft attacks in various theaters including the Atlantic, Mediterranean, and North Sea. The losses included:
Ship NamePennant NumberDate of LossCause and Location
HMS BroraT996 September 1941Mined off Scapa Flow, Orkney Islands
HMS FlottaT1716 November 1941Sunk by German aircraft off East Coast of Scotland
HMS CannaT1615 December 1942Torpedoed by U-515 off Trinidad
HMS JuraT1697 January 1943Torpedoed by U-371 east of Algiers, Mediterranean
HMS StronsayT1785 February 1943Mined off Philippeville, Algeria
HMS CampobelloT27816 March 1943Scuttled after iceberg damage off Newfoundland
HMS OrfasyT20422 October 1943Torpedoed by U-68 southeast of Freetown, Sierra Leone
HMS RysaT1648 December 1943Sunk by German aircraft in the Adriatic Sea
HMS WallaseaT3456 January 1944Torpedoed by U-343 off Anzio, Italy
HMS GairsayT2904 August 1944Sunk by German explosive motor boat off Normandy
HMS GanillyT3675 July 1944Torpedoed by U-390 off Utah Beach, English Channel
HMS ColsayT3842 November 1944Sunk by human torpedo (Neger) off Ostend, Belgium
HMS HildasayT17321 June 1945Grounded on reef near Kilindini, East Africa
The surviving vessels were largely decommissioned and disposed of postwar, with many sold for scrap or mercantile use between 1946 and 1950; for instance, HMS Annet (T341) was sold in 1946. By 1949, only 31 remained in Royal Navy service or reserve, alongside four converted controlled minelayers, and none saw active military duty beyond 1950. Notable conversions included four trawlers refitted as controlled minelayers in 1943–1944, redesignated with "bird" names such as HMS Blackbird (M15). Records for the fates of 5 to 10 vessels remain incomplete in available wartime logs and postwar inventories.

Royal Canadian Navy

The Royal Canadian Navy operated seven Isles-class trawlers transferred or built for it during World War II, manned by Canadian crews with minimal unique modifications such as adapted signaling equipment for local operations. These vessels, primarily employed for anti-submarine patrols, convoy escort duties, and minesweeping along the East Coast and in the Great Lakes, included HMCS Anticosti (T 274, ex-HMS Anticosti), HMCS Baffin (T 275, ex-HMS Baffin), HMCS Cailiff (T 276), HMCS Ironbound (T 284, ex-HMS Ironbound), HMCS Liscomb (T 285, ex-HMS Liscomb), HMCS Magdalen (T 279, ex-HMS Magdalen), and HMCS Miscou (T 277). Additionally, the RCN received two Isles-class variants completed as controlled minelayers: HMCS Stonechat (M 25) and HMCS Whitethroat (M 03). HMCS Whitethroat served in a similar role during the war and was retained postwar, modified for hydrographic survey duties until 1960. None of these vessels were lost during RCN service, and all were decommissioned between 1945 and 1946, with most returned to the Royal Navy or sold for civilian use or scrap by 1950.

Royal New Zealand Navy

The Royal New Zealand Navy acquired four Isles-class trawlers in 1941 for minesweeping and anti-submarine duties, primarily to bolster local defenses and support operations in the Pacific theater. These vessels—HMNZS Inchkeith (T155), HMNZS Killegray (T174), HMNZS Sanda (T160), and HMNZS Scarba (T175)—were commissioned between October and November 1941 and sailed from Scotland to New Zealand, arriving in Auckland in August 1942. Following their arrival, the ships conducted minesweeping operations in New Zealand harbors, such as the Bay of Islands, and participated in anti-submarine exercises off Auckland as late as July 1945. From late 1943, they supported Pacific theater efforts, including escorting motor launches to Nouméa and the Solomon Islands in February 1944, contributing to Allied advances without sustaining any wartime losses. Armed with a single 12-pounder gun and depth charges consistent with the class's standard fit, the trawlers adapted effectively to regional requirements, including local convoy protection and patrol tasks. All four vessels were decommissioned in 1946 and placed in reserve, where they remained available for potential training and survey roles through the early postwar period before final disposal in 1958. They were sold for scrap that year, with HMNZS Scarba broken up in Auckland in 1959; none were scuttled or repurposed otherwise. This service marked an early expansion of RNZN capabilities, with the ships providing essential support in home waters and the southwest Pacific.
Ship NamePennantCommissionedDecommissionedFate
HMNZS InchkeithT15524 October 19411946Sold for scrap, September 1958
HMNZS KillegrayT1747 November 19411946Sold for scrap, September 1958
HMNZS SandaT16030 October 19411946Sold for scrap, 1958
HMNZS ScarbaT17525 November 19411946Sold for scrap August 1958; broken up 1959

Royal Norwegian Navy

The Royal Norwegian Navy received five Isles-class trawlers transferred from the Royal Navy in 1943–1944 for minesweeping and patrol duties in Scandinavian and North Sea waters. These vessels—HNoMS Jeløy (ii) (T 170, ex-HMS Shiant), HNoMS Karmøy (ii) (T 166, ex-HMS Inchmarnock), HNoMS Oksøy (ii) (T 200, ex-HMS Kerrera), HNoMS Tromøy (ii) (T 201, ex-HMS Eday), and HNoMS Tromøy (iii) (T 388, ex-HMS Mincarlo)—operated primarily in northern European theaters, supporting Allied operations against German forces without recorded losses during service. Postwar, the ships were returned to the Royal Navy or disposed of by the late 1940s, contributing to the rebuilding of Norwegian naval capabilities in coastal defense and mine clearance.

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