Flower-class corvette
The Flower-class corvette was a class of small, inexpensive warships developed by the Royal Navy in 1939 specifically for anti-submarine warfare during the Second World War, adapted from a commercial whale-catcher design to enable rapid mass production in civilian shipyards.[1][2] Measuring approximately 205 feet (62.5 meters) in length with a beam of 33 feet (10 meters) and displacing around 925 tons standard (up to 1,170 tons fully loaded), these vessels featured a single-screw steam propulsion system delivering 2,750 horsepower for a top speed of 16 knots and a range of about 3,500 nautical miles at 12 knots.[3][4] Their armament typically included a single 4-inch (102 mm) naval gun for surface engagements, anti-aircraft weapons such as a 2-pounder "pom-pom" gun and 20 mm Oerlikon cannons, and up to 40–70 depth charges for submarine hunting, with later modifications adding the Hedgehog mortar projector to improve effectiveness against U-boats.[1][2] Designed by William Reed of Smith's Dock Company in response to the growing threat of German submarines following the 1938 Munich Crisis, the Flower-class prioritized simplicity, durability, and quick construction over speed or comfort, allowing them to be crewed largely by naval reserves and operated in the harsh conditions of the North Atlantic.[4][1] A total of 294 vessels were built across British and Canadian yards during the war, with 123 serving in the Royal Canadian Navy, making them a cornerstone of Allied convoy protection efforts.[1][3][5] These corvettes played a pivotal role in the Battle of the Atlantic from 1940 to 1944, escorting merchant convoys and contributing to the sinking of at least 47 German and 4 Italian U-boats while protecting vital supply lines to Britain, though 36 were lost to enemy action, mines, or accidents.[2][3] Their rugged "flower-like" hulls, often named after plants (e.g., HMS Snowberry or HMCS Hepatica), allowed them to withstand heavy seas despite poor habitability, and modified versions extended the forecastle for better seaworthiness and increased endurance to 7,400 nautical miles.[4][3] By 1943, as U-boat threats waned, many were phased out in favor of more advanced frigates and Castle-class corvettes, but their contributions were essential to Allied victory, with only one surviving example, HMCS Sackville, preserved as a memorial in Halifax, Canada.[1][4]Development and Design
Origins and Designation
The Flower-class corvettes originated in the British Admiralty's urgent response to the escalating threat of German U-boat warfare in the Atlantic, as World War II began in September 1939. Anticipating a repeat of the unrestricted submarine campaign that had nearly starved Britain during World War I, the Admiralty initiated a rapid naval rearmament program under the 1939-1940 Naval Estimates to produce inexpensive, mass-producible convoy escorts. On 25 July 1939, an initial order for 26 such vessels was placed, drawing from a design brief that prioritized simplicity and quick construction using civilian shipyards to counter the vulnerability of merchant shipping to submarine attacks.[6][7] This effort was part of a broader Anglo-French naval cooperation program, with France placing orders for 18 corvettes in early 1940 to bolster joint anti-submarine defenses, though only a few were completed before the fall of France, some later serving with the Free French Naval Forces. The class designation "Flower" derived from the Royal Navy's tradition of naming small warships after garden flowers, such as HMS Gladiolus (the lead ship, launched in January 1940) and HMS Snowberry, with names assigned in alphabetical order starting from A (e.g., Aconite, Anemone) to facilitate organization. This naming convention was extended to Allied navies, including the Royal Canadian Navy and the United States Navy upon transfer, ensuring a unified thematic identity across operators.[2][7] The initial 1939 design brief specified a modest displacement of approximately 925 tons standard, a length of 205 feet (62.5 meters), and a top speed of 16 knots, features that emphasized economical reciprocating steam engines and a hull adapted from commercial whale catchers to enable rapid production without straining military resources. The design was developed by William Reed of Smith’s Dock Company in Middlesbrough, United Kingdom, who adapted the hull form of the pre-war whale catcher Southern Pride for naval use, focusing on anti-submarine capabilities over advanced engineering. While this approach allowed for swift deployment, it resulted in inherent trade-offs, such as limited seaworthiness in heavy seas.[6][5][7]Design Features
The Flower-class corvettes featured a single-screw hull constructed from riveted steel plates, drawing from commercial whale-catcher designs to enable rapid production in civilian yards.[7] The hull incorporated a straight stem for ramming capability against submarines and an initial transom stern, which was later modified to a cruiser stern on many vessels to enhance seaworthiness in heavy seas by reducing pitching and improving stability.[2] Stability was achieved through a metacentric height of approximately 1.5 feet, calculated to provide sufficient righting moment in rough North Atlantic conditions despite the ship's short length and shallow draft.[7] Propulsion relied on a single vertical triple-expansion reciprocating steam engine delivering 2,750 indicated horsepower to one shaft, powered by two coal-fired Scotch boilers that were often converted to oil fuel during wartime for improved efficiency and reduced smoke signature.[5] This arrangement yielded a top speed of 16.5 knots and an operational range of 3,500 nautical miles at 12 knots, adequate for convoy escort duties but limiting pursuit of faster threats.[7] Crew accommodations were severely cramped, designed for 70 to 90 personnel in forward mess decks and cabins that quickly became stuffy and inadequate for extended patrols, with limited berths often doubling up and poor ventilation exacerbating discomfort.[7] Habitability suffered from insufficient heating, exposure to constant spray, and damp conditions, contributing to high rates of crew attrition due to illness, fatigue, and seasickness in the harsh Atlantic environment.[8] Early sea trials in 1939 revealed excessive slamming from North Atlantic waves on the short forecastle, prompting modifications to extend its length from one-quarter to one-third of the overall hull, which improved wave-handling and provided better protection for the forward gun and crew areas.[7]Construction and Production
The Royal Navy placed its initial order for 26 Flower-class corvettes on 25 July 1939 under the 1939-40 Naval Estimates, with subsequent batches expanding this to 145 ships by the end of 1939 as part of the urgent wartime expansion program.[6][2] Orders continued through the early war years, including 31 additional vessels under the 1940 War Programme (of which six were later cancelled), culminating in a total of 294 corvettes constructed by 1944—comprising 225 of the original design and 69 modified variants.[2][9] The production program emphasized speed, with the first ship, HMS Gladiolus, launched in January 1940 and the initial batch of around 20 vessels entering service by mid-1940.[2] Peak output occurred amid the intensifying Battle of the Atlantic.[2] Construction relied heavily on civilian shipyards repurposed for naval work, leveraging the design's simplicity—adapted from commercial whaler hulls—to achieve short build times of about nine to twelve months per vessel.[2] In the United Kingdom, over 30 yards participated, with major contributors including Smith's Dock Company in Middlesbrough and Harland & Wolff in Belfast, which together accounted for a significant portion of the 145 British-built originals.[2] Canadian shipyards, energized by the Allied war effort, produced 123 corvettes, including at facilities like Collingwood Shipyards Ltd. in Ontario, which handled multiple hulls as part of the broader transatlantic production push.[10] Wartime constraints, including material shortages and supply chain disruptions, occasionally delayed completions, though the program's decentralized approach across numerous yards mitigated broader bottlenecks.[2] To support Allied navies, transfer agreements were integral to the program, ensuring efficient distribution without inflating overall counts. Under reverse Lend-Lease, the United States Navy received 32 vessels—ten original UK-built transferred directly from the Royal Navy, eight original Canadian-built ships diverted upon completion, and 14 modified Canadian-built.[11] Canada received direct allocations of 123 corvettes for the Royal Canadian Navy, forming the backbone of its escort fleet.[10] Additionally, seven ships were allocated to the Free French Naval Forces, enhancing their anti-submarine capabilities in joint operations.[2] These arrangements underscored the class's role in multinational convoy protection.[2]Armament and Modifications
Original Configuration
The original Flower-class corvettes were equipped with a primary armament centered on a single 4-inch (102 mm) BL Mk IX naval gun mounted forward on the forecastle, designed primarily for engaging surfaced submarines at ranges up to approximately 10,000 yards.[2] This gun, with a rate of fire of 10-12 rounds per minute for a trained crew, provided the main surface firepower but was limited in elevation for effective anti-aircraft use.[2] For anti-aircraft defense, the unmodified ships typically carried two twin Lewis .303-inch machine gun mounts positioned amidships in a bandstand structure over the engine room, reflecting initial shortages of more advanced pom-pom guns that were sometimes substituted later.[12] These light machine guns offered minimal protection against low-flying aircraft, contributing to vulnerabilities observed in early wartime engagements.[13] Anti-submarine warfare equipment formed the core of the corvettes' role, with unmodified vessels fitted with Asdic Type 123A sonar for detecting submerged submarines at ranges up to 1,000-2,000 yards under ideal conditions, supplemented by hydrophone arrays for passive listening.[14] The primary offensive tools were depth charge racks and throwers, carrying up to 40 Mark VII depth charges (each weighing 420 pounds with 290 pounds of TNT, settable to depths of 300 feet), deployed via two stern racks and two side throwers capable of projecting charges approximately 200 yards astern or abeam to create attack patterns around a detected target.[2] While the Hedgehog forward-firing mortar was introduced on some ships from 1942 to extend engagement ranges to 250-300 yards without revealing the ship's position through wake, it was not standard on early 1939 commissions.) Crews required specialized training for Asdic operation, often conducted during workups to interpret echoes and coordinate depth charge attacks effectively, as the system's rudimentary nature demanded skilled ratings to distinguish submarine signals from sea clutter.[15] Sensors and communications were basic but essential for convoy duties, with Type 286 short-wave surface-search radar installed from 1940 onward on many unmodified ships to provide air and surface warning up to 8-10 miles, mounted on the foremast without rotation for simplicity.[2] Wireless telegraphy (W/T) sets enabled coordination with convoys via Morse code signals, requiring operators trained in naval codes and procedures to maintain escort formations.[13] The inadequate anti-aircraft suite, limited to Lewis guns, proved a significant weakness, resulting in several early losses to Luftwaffe aircraft during operations in 1940-1941 before enhancements were prioritized.[7] Fuel capacity consisted of 230 tons of oil in bunkers, yielding an endurance of 3,500 nautical miles at 12 knots economic speed, sufficient for transatlantic convoy legs but constraining independent operations.[13]Modified Variants
As wartime experience highlighted the limitations of the original Flower-class design in rough seas, modifications were introduced starting in 1942 to enhance seaworthiness and habitability. The most notable change was the adoption of a "long forecastle" configuration, where the forecastle deck was extended approximately 10 feet aft past the bridge to the base of the funnel, increasing the overall length to 208 feet from the original 205 feet. This alteration provided additional sheltered crew space and improved seakeeping by reducing spray over the bow, while also contributing to better stability through redistributed weight.[2][16] These modifications resulted in an increased standard displacement of 1,000 long tons, up from 925 tons in the baseline design, with full load reaching around 1,370 tons due to added equipment and stores. Armament was upgraded for improved anti-aircraft and anti-submarine capabilities; twin 20 mm Oerlikon guns replaced earlier Lewis machine guns on the bridge wings, and a single 2-pounder QF "pom-pom" or 40 mm Bofors gun was added amidships for enhanced defense against low-flying aircraft. Anti-submarine weaponry evolved to include the Hedgehog forward-firing mortar in place of some depth charge throwers, supplementing the standard 70 to 100 depth charges.[6][2][16] Approximately 61 modified Flower-class corvettes were constructed from 1942 onward, primarily influenced by the emerging Castle-class but retaining the Flower designation for simplicity in production and logistics; of these, the Royal Navy commissioned 27 while the Royal Canadian Navy received 34, with a few allocated to other Allied operators. Radar systems were standardized with the Type 271 or 272 surface search sets, mounted on the mast aft of the bridge, enabling better detection of surfaced U-boats and surface threats at ranges up to 20 miles. The first such vessel, HMCS Halifax (K237), was laid down in 1941 under the revised program and commissioned in December 1942, exemplifying the updated layout with its extended forecastle and initial Hedgehog installation.[2] Performance saw marginal gains from the modifications, with top speed reaching 16.5 to 17 knots under forced draft—slightly higher than the original's 16 knots—thanks to refined hull form and propeller adjustments, though the added topweight from armament occasionally required ballast tweaks to maintain stability in heavy weather. These changes made the modified variants more effective convoy escorts, balancing the trade-offs of increased complexity against the urgent need for rapid production in civilian yards.[2][6][16]Wartime Service
Role and Operations
The Flower-class corvettes served primarily as convoy escorts during the Battle of the Atlantic, protecting vital supply lines of merchant shipping from German U-boat attacks.[17] They formed the backbone of escort forces for slow convoys (SC series) departing from Sydney, Nova Scotia, and fast convoys (HX series) from Halifax or New York, screening thousands of vessels across hundreds of transatlantic crossings.[17] In these roles, the corvettes contributed to defensive efforts during critical engagements, such as the wolfpack assaults on Convoy SC 7 in October 1940, where limited escort strength highlighted early vulnerabilities, and Convoy ON 92 in May 1942, where sustained anti-submarine actions helped mitigate heavier losses despite intense U-boat pressure.[7] Their maneuverability and sonar-equipped depth charge attacks proved essential in disrupting U-boat tactics, though initial configurations limited offensive impact until modifications enhanced hedgehog mortar capabilities.[2] Beyond the North Atlantic, Flower-class corvettes participated in several high-risk operations. In the Murmansk runs from 1941 to 1943, they escorted PQ-series Arctic convoys through treacherous icy waters to deliver aid to the Soviet Union, facing combined U-boat and Luftwaffe threats amid extreme cold that froze equipment and exposed crews to hypothermia.[2] During Operation Torch in November 1942, Royal Canadian Navy examples provided anti-submarine screens for invasion convoys off North Africa, sinking two Italian submarines (Tritone and Avorio) and one German U-boat (U-224) through depth charge barrages and ramming, while damaging several others amid encounters with approximately 37 Axis submarines.[18] Later, in 1944, select Royal Canadian Navy corvettes transferred to the Pacific theater for escort duties against Japanese submarine threats, though their involvement remained limited compared to Atlantic service, focusing on convoy protection in the Indian Ocean approaches.[2] Tactical doctrines evolved significantly by 1943, with Flower-class corvettes integrated into "hunter-killer" groups designed for offensive anti-submarine patrols rather than purely defensive escort.[7] These formations, often comprising four to six corvettes supported by very long range (VLR) aircraft for detection, roamed independently to pursue surfaced U-boats, leveraging improved radar and the hedgehog weapon for forward-throwing attacks that overcame depth charge blind spots.[2] Such groups, like Escort Group B7 with its mix of Flower-class vessels, accounted for multiple U-boat sinkings through coordinated depth charge patterns and air-surface coordination, marking a shift that contributed to the Allies gaining the upper hand in the Atlantic.[19] Collectively, Flower-class corvettes were credited with sinking 47 German U-boats and four Italian submarines, though post-war assessments debate the exact attributions due to shared kills among escorts and aircraft.[2] These successes, often achieved in grueling wolfpack engagements, underscored their impact despite modest individual firepower. Service aboard Flower-class corvettes incurred high casualty rates, with 36 vessels lost to enemy action—22 to U-boat torpedoes—amid relentless wolfpack tactics that overwhelmed outnumbered escorts.[6] Crews of around 85-90 endured notoriously harsh conditions, earning the moniker "corvette navy" for the cramped, perpetually wet quarters, constant rolling in heavy seas, and exposure to freezing Atlantic gales that soaked bridges and fouled mess decks.[1] These factors, compounded by limited sleeping space and the psychological strain of prolonged submarine hunts, tested the resilience of personnel across Allied navies.[17]Service by Operator
The Royal Navy operated 145 Flower-class corvettes, which formed the backbone of Western Approaches Command's escort forces during the Battle of the Atlantic and other convoy operations. These vessels provided critical anti-submarine protection while suffering 22 losses to enemy action. Notable examples include HMS Bluebell, which escorted Arctic convoys such as JW 64 before being sunk by U-711 on 17 February 1945 off the Norwegian coast.[7][2][20] The Royal Canadian Navy manned 111 Flower-class corvettes, the majority built in Canadian shipyards, transforming the RCN into a dedicated "corvette navy" focused on North Atlantic escorts. These ships played a pivotal role in Operation Neptune, screening invasion convoys during the D-Day landings on 6 June 1944, and later supported operations in the English Channel. Later Canadian-built examples incorporated oil-fired boilers for enhanced range and reliability in harsh conditions, an adaptation suited to the RCN's extended patrol demands. Of the 111 vessels, 10 were lost to enemy action, representing a significant portion of RCN wartime casualties.[13][21][2] Under the Lend-Lease program, the United States Navy received 18 Flower-class corvettes—10 transferred directly from the Royal Navy as the Temptress class and 8 Canadian-built modified versions as the Action class—for anti-submarine warfare and convoy duties in the Atlantic. Ships like USS Intensity (PG-93, formerly HMS Milfoil) exemplified their use in patrol operations, often crewed by U.S. Coast Guard personnel. None were lost during American service.[11] The Free French Naval Forces operated 9 Flower-class corvettes loaned from the Royal Navy, integrating them into Allied escort groups for North Atlantic operations. FS Aconit achieved a notable success on 11 March 1943, sinking U-432 with depth charges and gunfire in the North Atlantic (position 51°35'N, 28°20'W) after coordinating with the damaged HMS Harvester, which had rammed the U-boat. Two Free French Flowers were lost during the war.[22][2] Smaller Allied and neutral navies received limited allocations of Flower-class corvettes, adapting them to regional needs such as minelaying and local patrols. The Royal Norwegian Navy operated 6, modifying several for offensive minelaying in northern European waters to disrupt Axis shipping, with 2 losses recorded. The Royal Australian Navy received 4 for Pacific theater duties, focusing on anti-submarine sweeps and convoy protection amid Japanese threats. The Royal New Zealand Navy manned 2, the Royal Indian Navy 4 (transferred in 1945 for Indian Ocean operations), and the South African Naval Forces 1 (SAS Protea, used for Atlantic convoy escorts), all with no wartime losses. These assignments highlighted the class's versatility across diverse operational environments.[7][2]Captured Ships and Axis Use
During the German occupation of France in 1940, the Kriegsmarine seized four incomplete Flower-class corvettes that had been laid down for the French Navy at the Penhöet shipyard in Saint-Nazaire. These vessels, originally named Arquebuse, Hallebarde, Sabre, and Poignard, were completed to a modified design under German supervision and designated as the PA (Patrouillenboot Ausland, or "foreign patrol boat") class.[23] The ships were intended to bolster coastal defense and escort operations in the English Channel, addressing shortages in suitable escort vessels for protecting merchant shipping against Allied submarines and motor torpedo boats.[24] However, construction delays due to wartime priorities meant that only three entered service, with the fourth remaining unfinished.[7] The completed vessels—PA-1 (ex-Arquebuse), PA-2 (ex-Hallebarde), and PA-3 (ex-Sabre)—were commissioned between 1943 and 1944 and assigned to the 15th Vorpostenflottille for patrol duties along the French coast. Their operational roles were limited by chronic fuel shortages in the Kriegsmarine during the later war years, restricting them primarily to training exercises and short-range coastal patrols rather than extended combat deployments. Crew shortages further hampered effectiveness, leading to reduced combat readiness and minimal engagement in offensive actions. PA-4 (ex-Poignard) was never commissioned and instead served as a blockship.[23][24] Modifications to the original Flower-class design included replacement of the 102 mm main gun with a single 105 mm SK C/32 naval gun forward, supplemented by enhanced anti-aircraft armament consisting of two twin 37 mm SK C/30 guns and ten single 20 mm C/30 guns in various mountings. Depth charge throwers (two per side) and minesweeping equipment, including the "Toni" paravane device and MES cable, were retained and adapted for German use, while the hulls were painted in standard Kriegsmarine grey. Although specific radar installations are not documented for these ships, the late-war commissioning period aligns with the widespread adoption of search radars like the FuMO 21 on similar-sized vessels for improved detection capabilities.[24][2] The service lives of the PA-class were brief and ended in 1944 amid the Allied invasion of Normandy. PA-1, PA-2, and PA-3 were all sunk by RAF bombing raids at Le Havre on 15 June 1944 while undergoing maintenance. PA-4 was scuttled as a blockship in the Loire River at Nantes in August 1944 to obstruct the port; it was later raised by Allied forces and scrapped in 1946. None of the vessels were returned to Allied service post-war, marking the limited Axis utilization of captured Flower-class designs.[25][26][27][28]| Ship | Original Name | Commissioned | Fate |
|---|---|---|---|
| PA-1 | Arquebuse | 15 April 1944 | Sunk by RAF, 15 June 1944, Le Havre |
| PA-2 | Hallebarde | 10 November 1943 | Sunk by RAF, 15 June 1944, Le Havre |
| PA-3 | Sabre | 10 November 1943 | Sunk by RAF, 15 June 1944, Le Havre |
| PA-4 | Poignard | Never commissioned | Scuttled August 1944, Nantes; scrapped 1946 |
Ships and Losses
Commissioned Vessels
A total of 269 Flower-class corvettes were commissioned during World War II, comprising 217 original-class vessels and 52 modified-class ships; this excludes three vessels completed only for Kriegsmarine service that never entered Allied use.[1][2] These small, mass-produced anti-submarine escorts were distributed primarily among Allied navies, with the Royal Navy (RN) and Royal Canadian Navy (RCN) receiving the bulk, alongside transfers to other operators such as the Free French, United States Navy (USN), Royal Norwegian Navy, and Royal Hellenic Navy.[7] The RCN received approximately 123 in total service. Commissioning occurred rapidly from 1940 onward, often within months of launch, to meet urgent convoy protection needs; production drew from multiple shipyards in Britain and Canada, with batches overlapping wartime demands.[29]Original Class
The original Flower-class vessels, standardized at around 925 tons displacement with a single 4-inch gun and depth charge armament, formed the core of the program with 217 ships entering service.[2] The RN commissioned approximately 112, named after flowers in alphabetical order from HMS Abelia (K184, launched 28 November 1940 by Harland & Wolff, commissioned 6 February 1941) to HMS Zinnia (K99, launched 28 June 1940 by Charles Hill & Sons, commissioned 25 September 1940).[30] The RCN received 70 purpose-built originals plus 10 transfers from RN stocks, spanning HMCS Agassiz (K126, launched 15 August 1940 by Kingston Shipbuilding, commissioned 1 November 1940) to HMCS Zackville (K144, launched 3 March 1944 by Davie Shipbuilding, commissioned 20 June 1944).[7] Smaller operators included the Free French Navy (9 transfers, such as FFL Aconit, ex-HMS Aconite (K58, launched 31 March 1941 by St. Nazaire yards under British contract, commissioned 15 July 1941)), the USN (initially 10 via Lend-Lease as the Temptress-class patrol gunboats), the Royal Norwegian Navy (6, e.g., HNoMS Acantus, ex-HMS Acanthus (K39, launched 1 June 1941, commissioned 23 June 1941)), and the Royal Hellenic Navy (4, including RHS Apostolis, ex-HMS Lotus (K130, launched 17 July 1941, commissioned 30 October 1941)).[31] Other minor allocations comprised one each to the South African Naval Service (HMSAS Protea, ex-HMS Southern Protea (K107, launched 30 June 1941, commissioned 23 September 1941)) and Royal Netherlands Navy, plus four to the Royal Indian Navy.[2] Records for these lesser operators remain incomplete, particularly for the Hellenic Navy's single documented vessel, RHS Apostolis.[7] The following table provides representative examples of original-class commissions by primary operator, highlighting pennant numbers, build yards, and key dates:| Navy | Ship Name | Pennant | Builder | Launch Date | Commission Date |
|---|---|---|---|---|---|
| RN | HMS Gladiolus | K34 | Joseph T. Eltringham | 24 January 1940 | 6 April 1940 |
| RN | HMS Sunflower | K41 | Smiths Dock | 14 December 1939 | 28 April 1940 |
| RCN | HMCS Chambly | K116 | Canadian Vickers | 29 July 1940 | 18 December 1940 |
| RCN | HMCS Sackville | K181 | Saint John Shipbuilding | 25 January 1941 | 29 December 1941 |
| Free French | FFL Mimosa | K22 | Harland & Wolff | 11 January 1940 | 20 May 1940 |
| USN (ex-RN) | USS Ready (ex-HMS Calendula) | PG-68 | Harland & Wolff | 21 March 1940 | 15 January 1942 (US service) |
Modified Class
The modified Flower-class, introduced in 1941 with improved stability, twin engines, and enhanced anti-aircraft fittings (displacement around 1,020 tons), saw 52 vessels commissioned, primarily for the RCN (42 built in Canadian yards) and RN (10 completed from orders placed in 1941-1942).[2] RN examples included HMS Loosestrife (K127, launched 14 September 1941 by Hall Russell, commissioned 11 November 1941).[30] RCN modified ships ranged from HMCS Drumheller (K167, launched 25 August 1941 by Collingwood Shipyards, commissioned 15 November 1941, with Hedgehog mortar added) to HMCS New Liskeard (K374, launched 6 May 1944, commissioned 1 November 1944), contributing to the total of approximately 123 in RCN service.[7] Key specs across the class emphasized twin-shaft propulsion for better maneuverability, with most built post-1941 to address original design seaworthiness issues.[2] Representative modified-class examples:| Navy | Ship Name | Pennant | Builder | Launch Date | Commission Date | Key Specs |
|---|---|---|---|---|---|---|
| RN | HMS Loosestrife | K127 | Hall Russell | 14 September 1941 | 11 November 1941 | Hedgehog fitted |
| RCN | HMCS Drumheller | K167 | Collingwood | 25 August 1941 | 15 November 1941 | 16.5 knots |
| RCN | HMCS Calgary | K231 | Canadian Vickers | 26 September 1941 | 10 December 1941 | Enhanced AA |