Since one of our members has a completed model, and two more are in progress, this seems a suitable subject for this month.

The ‘Flower’ Class corvettes, hurriedly-built, armed with obsolescent weapons and slower than a surfaced U-boat, will always be linked inextricably with the Battle of the Atlantic. Yet, despite their limitations, they were to become formidable opponents and claimed a significant number of U-boat kills.
Origins
In 1938 the British Admiralty, which expected Great Britain to be at war in 1940, began to consider the construction of a new class of coastal escorts. Following discussions between the Admiralty and the Smith's Dock Co Ltd in January 1939, it was agreed that Smith Dock’s recently-built whalecatcher Southern Pride could be adapted. Subsequently, the design was approved on 27th February 1939 and specified a ship of 700 tons with an endurance of 4,000 miles and a speed of 16 knots with an estimated construction time of seven months costing £90,000.
Design
By October 1939, the new escort’s design had grown to nearly 1,200 tons and, fortunately, coal-burning boilers had been rejected. The final legend of particulars was for a ship of 1,170 tons (full load) measuring 205 feet overall with a beam of 33 feet and a draft of 7 feet 9 inches forward, 14 feet 10 inches aft. Propulsion was by means of a four-cylinder vertical triple expansion engine which developed 2,750 ihp to give a top speed of just 16 knots and a range of 4,000 miles at 12 knots. A total of 200 tons of fuel oil would be carried. The planned armament at this stage was to include a single 4in gun with 100 rounds of ammunition, a twin Lewis 0.303in machine gun aft for anti-aircraft (AA) defence and two depth-charge throwers plus twenty-five charges. The depth charge armament was increased progressively during the war and rose eventually to 72 charges which could be launched from two depth charge rails and four throwers. The intended complement of just 29 officers and men was shown to be inadequate especially when ships were moved to the physically more demanding Western Approaches area. By the end of the war, the standard ‘Flower’ complement had risen to 85, an increase which led to serious overcrowding.
Construction
A total of around 260 ‘Flower’ Class corvettes were constructed with 150 of these being built in eighteen British shipyards and a further 110 being constructed in sixteen Canadian yards. There were considerable variations in construction times between and within shipyards. Construction in Canadian yards was generally quicker than in the UK. This difference is accounted for by a combination of the effects of bombing, shortages of labour and materials, war weariness and inadequate pre-war investment, coupled to out of date shipbuilding and trade union practices in the UK. When the first Flower completed her sea trials in March 1940 there was little intention to use these ships as long range escorts in the North Atlantic and therefore the consequences of the ships’ short forecastle and lack of overall length had not become apparent.
Modifications
The Flowers were nicknamed "the pekingese of the ocean". They had a reputation of having poor sea-handling characteristics, most often rolling in heavy seas, with rolls 40 degrees each side of upright, being fairly common; it was said they "would roll on wet grass". Many crewmen suffered severe motion sickness for a few weeks until they became acclimatised to shipboard life. Although poor in their sea-handling characteristics, the Flowers were extremely seaworthy; no Allied sailor was ever lost overboard from a Flower during World War II, outside combat.
Service on “Flowers” in the North Atlantic was typically cold, wet, monotonous and uncomfortable. Every dip of the forecastle into an oncoming wave was followed by a cascade of water into the well deck amidships. Men at action stations were drenched with spray, and water entered living spaces through hatches opened to access ammunition magazines. The galley was aft and food had to be brought forward along the same open deck with the result that it was always cold on arrival (if it hadn't been spilt on the way). Interior decks were constantly wet and condensation dripped from the overheads. The head (or sanitary toilet) was drained by a straight pipe to the ocean; and a reverse flow of the icy North Atlantic would cleanse the backside of those using it during rough weather. By 1941 corvettes carried twice as many crewmen as anticipated in the original design. Men slept on lockers or tabletops or in any dark place that offered a little warmth. The inability to store perishable food meant a reliance on preserved food such as corned-beef and powdered potato for all meals. The combination of damp, poorly-ventilated mess decks and overcrowding led to a very high incidence of tuberculosis among corvette crews during the war.
Conditions were improved in most ‘Flowers’ by extending the forecastle aft to increase the amount of enclosed space while, in some ships, the hull section was altered forward above the waterline to give more sheer and flare. Apart from providing a very useful space where the whole crew could gather out of the weather, the added weight improved the ships' stability and speed and was retroactively applied to a number of the original Flower-class vessels during the mid and latter years of the war. In addition, widened bilge keels were fitted in an attempt to reduce rolling. Bridges were enlarged and improved, splinter protection was increased while enhanced electric power, steam heating and artificial ventilation was provided in living spaces.
These small warships could be supported by any small dockyard or naval station, so many ships came to have a variety of different weapons systems and design modifications depending upon when and where they were refitted; there is really no such thing as a 'standard Flower-class corvette'. Numerous changes were made as the war progressed.
A major difference between the RN vessels and the RCN, USN, and other navies' vessels was the provision of upgraded ASDIC and radar. The RN was a world leader in developing these technologies, and thus RN Flowers were somewhat better-equipped for remote detection of enemy submarines. A good example of this is the difficulty that RCN Flowers had in intercepting U-boats with their Canadian-designed SW1C metric radar, while the RN vessels were equipped with the technologically advanced Type 271 centimetric sets. In addition, RCN vessels were incapable of operating gyrocompasses, making ASDIC attacks more difficult.
Anti-submarine Warfare
The Mark VII depth charge of 1939 contained 290Ibs of amatol and was not very effective. sinking at an initial rate of 7 feet/second and having a lethal radius of about 20 feet. A submerged U-boat could move a distance equal to three times the lethal radius in just 10 seconds. In late 1940, the Mark VII ‘heavy’ depth charge was introduced and featured a sinking rate of 16.5 feet/second and a minol charge with a lethal radius of 26 feet. The effectiveness of attacks was improved by the introduction of a ten-charge pattern attack instead of the earlier five charge pattern. In the ten-charge pattern, five charges were set to explode above and five below the target.
The solution to the problem of the lag between target detection and depth charge arrival around the submarine lay with the introduction of an ahead-throwing weapon. The first to be adopted was ‘Hedgehog’ which fired a circular pattern, forty yards in diameter, of twenty-four, 65lb, contact fused bombs 200 yards ahead of the ship. Initially, because of installation and maintenance problems, ‘Hedgehog’ was not very successful and there was also concern that, as the bombs exploded only on
contact, the morale shattering effects of a near miss was lost. Conversely, an explosion signified a lethal hit on the target. The introduction of this ahead throwing weapon meant that it became far more difficult for submarine commanders to avoid attack by correct timing of evasive manoeuvres. The majority of ‘Flower’ Class corvettes were fitted with ‘Hedgehog’ on the port side upper deck abaft the 4in gun mounting immediately forward of the bridge. This installation increased greatly the anti-submarine warfare effectiveness of the ‘Flowers’.
Post-war data suggests that ‘Flower’ Class corvettes were involved in the destruction of forty-seven U-boats as well as four Italian submarines.
Losses and Vulnerability
A total of thirty-two ‘Flower’ and one ‘Modified Flower’ Class ships were lost during the war with twenty-three being sunk by torpedoes, four by mines, two by aircraft bombs and four by collision. The RCN sank or helped sink more than 30 U-boats, but at a steep price. The RCN lost 14 warships to enemy attack and another eight ships to accidents at sea during the Second World War, with approximately 2,000 crewmen losing their lives.

Information from wikipedia and from “The Corvettes” by Richard Osborne in “Ships Monthly” June 1993.

Nautical lore - the 'Flower' class corvettes