FLOWER CLASS CORVETTES OF WORLD WAR II

The Flower class corvette will always be associated with the Battle of the Atlantic, soldiering on manfully in the war against the German U-boats from 1940 to the last years of the war. Albeit not designed primarily for deep ocean work, they gave sterling service initially armed only with depth charges before the introduction of the Castle class and the later ultimate submarine killers such as the Loch class fitted with the deadly Squid and Hedgehog firing projectiles.

ABOVE: JAMES POTTINGER’S PAINTING OF THE FLOWER-CLASS CORVETTE HMS SPIRAEA.

In the year before the beginning of WWII, it was realised that there would be a shortage of escort vessels, being required for ocean and east coast duties, but with rearmament starting, the shipbuilding and engineering capacity was already being stretched, thus consideration was given to the requisition of whale catchers, even accepting their lack of subdivision and the cost of altering them to suit naval requirements. The basic naval requirements were that they had to be in great numbers, faster than a trawler and less costly than the usual escort types. It was accepted that yards capable of building warships were going to be fully occupied and after review of a number of so called “cheap” anti-submarine vessels the only recourse would be to use those familiar and capable of building vessels somewhat similar to that common to their normal production.

Whilst consideration was given to a number of builders, Smith’s Dock shipyard at the South Bank of Middlesbrough, a shipyard well known for building trawlers and whale catchers, and also having built numerous of the “Zed” and “Kil” class A/S vessels of WWI, appeared to offer the most promising proposals.

Their initial proposal in 1938, by Mr W Reed, the Managing Director, was for a design, but extended by 30 feet, loosely based on the Salvesen whale catcher Southern Pride, and at a subsequent meeting in Jan 1939 with Director of Naval Construction (DNC) and some consideration as to the requirements for increased speed etc outlined by the DNC, Mr Reed agreed to forward more specific design proposals.

Indicative of the urgency associated with this requirement is that the sketch design was approved on the 27 February. These, briefly tabulated were:

Displacement tons – 940, 1,170 deep LPP 190ft. LOA 205ft 6 and beam 33ft Speed -16 knots, 2750 IHP Engine – one four cylinder triple expansion, HP cyl 18.5 ins dia; IP cyl 31ins dia; two LP cyls each of 38.5ins dia and stroke of 30 ins. Boilers- two cylindrical Scotch type, oil fired. (Some later vessels, and mostly Canadian built, had water tube boilers).

This above machinery more or less as fitted in the Southern Pride, was well proven and reliable and well within the manufacturing capabilities of many trawler and coaster builders, and with drawings and patterns provided by Smith’s Dock to other builders, no less than 1,150 engines were manufactured for the corvettes, frigates and later transport ferries. Initial armament included one 4ins gun forward, 2-twin Lewis 303 machine guns and 2 depth charge throwers and 25 charges carried, later much increased to 40 with two more throwers. The hulls were built to scantlings according to the usual merchant ship practice thus were of heavier construction than similar naval vessels, their robustness being borne out by the fact that no structural defects were reported in service. It was accepted that the shipbuilders could use whatever fabrication method they were currently employing as regards welding and riveting.

The stern deadwood aft was cut away substantially and a large rudder fitted to ensure they could turn quickly. The initial bilge keels were later deepened significantly in an effort to counter rolling. However, any relatively small ship such as these will have a violent motion when exposed to long high seas in the open ocean such as the Atlantic. Having experienced these in a November gale on a ship over 500 ft long, I can readily imagine what it must have been like in a Flower.

The ship’s complement was initially planned for 47, but inevitably this rose with the addition of gunnery and radar specialists such that it was almost doubled often reaching 85 persons, adding to the cramped and inhospitable accommodation, initially without any internal thermal insulation. Seven PO’s shared one toilet and three washbasins, the rest of the ratings had a single urinal, two toilets and four washbasins. The seamen’s mess and accommodation was right forward under the forecastle and the galley at the extreme after end of the deckhouse at the stern, a combination of which it would be difficult to plan anything less acceptable.

WEATHER REPORTER

Between 1941-2 a significant improvement was made when the forecastle was extended aft to amidships, thereby providing more space for accommodation, as the war progressed many additions and changes were made to the bridge and deckhouse to accommodate extra Oerlikons on the bridge wings, asdic, radar, Hedgehog, and heightened bridge to allow for the bow gun being raised to allow sufficient depression for close range firing and water tube boilers with forced draught stokehold, identified by the elimination of the four large cowl ventilators.

The hull was also modified with more sheer and increased flare at the more raking stem, some having a vertical funnel without rake designed to make it more difficult to confirm the course.

In July 1939, an order for 26 ships was placed initially with 11 of the smaller shipyards, followed by 30 on 31 August, then a further 10 on 21 September, just after an order for 20 from Harland & Wolff of Belfast, the largest single order to any one British yard and being unusual that it was the only order given to a large shipbuilder. This order was deemed a priority over others by Winston Churchill in a phone call to the yard. The first, HMS Arabis was completed less than seven months after receiving the contract and five months after the keel was laid, an average which was maintained over the length of the programme, the first batch were laid down in batches of four, the remainder in pairs, the last being handed over on 9 Jan 1941, with an average of one being handed over every fortnight.

The grand total of Flowers built has been difficult to establish as the records do not coincide, but the general accepted number is as follows:

UK built 136 for RN with 7 cancelled, 16 for France. Canadian built 130, 6 cancelled, 15 lend lease. French built 6, 2 cancelled, 4 completed for German navy. Total 288, being the largest number of any members of same class ever ordered for the RN.

The first to be completed on 6 April 1940, HMS Gladiolus by Smith’s Dock and reached 16.6 knots on trials and did not waste any time as in fact was the first Flower to sink a U-boat.

This was U-26 on 1 July 1940 and U-65 on 28 April 1941, but her short life ended when she was torpedoed and sunk on 17 Oct 1941 by U-558 in the North Atlantic when escorting the eastbound convoy SC48.

The Flowers sank over 50 U-boats, either singly or participating in a group role. When the US entered the war in December 1941, it was immediately recognised that they were short of escorts, thus the RN transferred 10 ships and 15 building in Canada were allocated although only 8 were transferred.

WEATHER OBSERVER

The Flowers have been a very popular subject for model makers, with a number of plastic kits being marketed and has resulted in numerous outstanding examples of the model makers craft. Whilst the Flowers gave sterling service, it was accepted that something bigger was required to cope with the conditions in the North Atlantic and also more space was needed for the latest weapon and sensor systems and increased crewing. Smith’s dock forwarded a proposal to the Admiralty, which was developed by the Admiralty design team. This vessel came to be known as the Castle class, both classes of which some were converted to Ocean Weather Reporting ships.

Interestingly, despite being 420 tons heavier than the Flowers and having the same engine, the Castles were slightly faster due to the additional 37ft in length.

Somewhat ironically some Flowers and Castles were converted to ocean weather ships, and dodged around in the Atlantic for a month, in conditions similar to that experienced in WWII.

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