Editing Flower-class corvette (section)

==Armament==
[[File:HMS Vervain 4 inch Mk IX gun 1942 IWM A 10666.jpg|thumb|{{center|Typical [[BL 4-inch Mk IX naval gun|BL 4-inch Mk IX gun]] mounting, here seen on {{HMS|Vervain|K190|6}}}}]]
The original Flower class were fitted with a 4-inch (102&nbsp;mm) gun on the bow, depth charge racks carrying 40 charges on the stern, a minesweeping winch and a 2-pounder (40&nbsp;mm) [[QF 2-pounder naval gun|pom-pom gun]] on a "bandstand" over the engine room. Due to shortages, a pair of [[Lewis gun]]s or quadruple Vickers HMG was sometimes substituted for the pom-pom, which would have left the ship very vulnerable to aircraft attack in its envisaged role of coastal convoy escort and patrol in the [[North Sea]]. The long-range endurance of the vessels, coupled with early war-time shortages of larger escort warships, saw Flowers assigned to trans-Atlantic convoy escort where ''[[Luftwaffe]]'' aircraft were rarely encountered. Vessels assigned to the [[Mediterranean Sea]] usually had more anti-aircraft guns fitted. Underwater detection capability was provided by a fixed [[Sonar|ASDIC]] dome; this was later modified to be retractable. Subsequent inventions such as the High Frequency Radio Direction Finder ([[High frequency direction finding|Huff-Duff]]) were later added, along with various [[radar]] systems (such as the [[Type 271 radar|Type 271]]), which proved particularly effective in low-visibility conditions in the North Atlantic.

[[File:Mk VII depth charge.jpg|thumb|{{center|Loading a depth charge thrower on HMS ''Dianthus''}}]]
The Flower class had been designed for inshore patrol and harbour anti-submarine defence and many required minor modifications when the Allied navies began to use them as trans-Atlantic convoy escorts. These small warships could be supported by any small dockyard or naval station, so many ships came to have a variety of 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'

Several of the major changes that vessels in the class underwent are indicated below, in a typical chronological order:
* Original twin mast configuration changed to single mast in front of the bridge, then moved behind the bridge for improved visibility.
* Heavy minesweeping gear removed for deep-sea escort work and to improve range.
* Galley relocated from the stern to midships.
* Extra depth charge storage racks were fitted at the stern. Later, more depth charges stowed along walkways.
* [[Hedgehog (weapon)|Hedgehog]] fitted to enable remote attacks while keeping ASDIC contact.
* Surface radar fitted in a "lantern" housing on the bridge.
* Forecastle lengthened to midships to provide more accommodation and better seaworthiness. Several vessels were given a "three-quarters length" extension.
* Increased flare at the bow. This and the above modification created the modified Flower design for subsequent orders.
* Various changes to the bridge, typically lowering and lengthening it. Enclosed compass house removed.
* Extra twin Lewis guns mounted on the bridge or engine room roof.
* Oerlikon 20&nbsp;mm cannons fitted, usually two on the bridge wings but sometimes as many as six spread out along the engine-room roof, depending on the theatre of operations.

A ship could have any mix of these, or other specialist one-off modifications. Ships allocated to other navies such as the RCN or USN usually had different armament and deck layouts. 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 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 [[gyrocompass]]es, making ASDIC attacks more difficult.