Loch-class frigate

HMS Loch Fyne
Class overview
Name:	Loch class
Operators:	Royal Navy South African Navy Royal Canadian Navy  Royal New Zealand Navy  Royal Malaysian Navy
Preceded by:	River class
Succeeded by:	Bay class
Completed:	30
Cancelled:	54
General characteristics
Type:	Frigate
Displacement:	1,435 long tons (1,458 t)
Length:	307 ft 9 in (93.8 m)
Beam:	38 ft 9 in (11.8 m)
Draught:	8 ft 9 in (2.7 m)
Installed power:	2 Admiralty 3-drum boilers 5,500 ihp (4,100 kW) (steam engines) or 6,500 shp (4,800 kW) (steam turbines)
Propulsion:	2 shafts 2 × vertical triple-expansion steam engines or 2 × Parsons steam turbines
Speed:	20 knots (37 km/h; 23 mph)
Range:	9,500 nmi (17,600 km; 10,900 mi) at 12 knots (22 km/h; 14 mph)
Complement:	114
Sensors and processing systems:	Types 144 and 147B ASDIC Type 277 surface-search radar
Armament:	1 × single QF 4-inch Mark V 1 × quadruple QF 2-pounder 2 × twin Oerlikon 20 millimetres (0.79 in) AA guns or 2 × single Bofors AA guns 2–8 × single 20 mm Oerlikon AA guns 2 × Squid triple-barrelled anti-submarine mortars 1 rail and 2 throwers for 15 depth charges

The Loch class was a class of anti-submarine (A/S) frigate built for the Royal Navy and her Allies during World War II. They were an innovative design based on the experience of three years of fighting in the Battle of the Atlantic and attendant technological advances.

The Lochs were based upon the hull of the preceding River class with increased sheer and flare to improve seakeeping and modified to suit it to mass pre-fabrication, with sections riveted or welded together at the shipyard. Accordingly, as many curves as possible were eliminated, producing a noticeable kink in the main deck where the increased sheer forwards met the level abreast the bridge.

The fighting capability of the Loch class was a great jump forward, being based around the new Squid ahead-throwing A/S mortar. Previously, escorts had attacked with depth charges, requiring the attacking vessel to pass over the submerged submarine and drop warheads over the stern. Consequently, the ahead-looking ASDIC (sonar) set lost contact at the vital moment before the weapons were launched, allowing a skilled submarine commander to take successful evasive action. Squid, however, lobbed three 12-inch (300 mm), 390 pound warheads up to 600 yards (550 m) ahead of the launching vessel falling in a triangular pattern with sides of 40 yards (37 m). As the clockwork fuses detonated the warheads at a depth determined by the ships' ASDIC set, the Squid therefore attacked in full ASDIC contact for greater accuracy and lethality. Two mortars were carried, with the bombs set to explode at different depths in order to create a convergent pressure wave to crush the hull of a submarine. The first successful "kill" was by Loch Killin on 31 July 1944, sinking the German submarine U-333. Such was the utility of Squid that depth charge carriage was reduced to only 15, with a single rack and a pair of throwers being carried at the stern, resulting in a clear quarterdeck compared to the eight throwers, two racks and stowage for 100 plus charges in the Rivers.

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Wikipedia