Hunt Class Destroyer - Design

Design

The Hunts were modelled on the 1938 escort sloop Bittern, a 262-foot (80 m) ship of 1,190 tons with 3,300 shp (2,500 kW) on geared turbines for 18¾ knots and an armament of three twin Mark XIX mounts for the QF 4-inch (102 mm) gun Mark XVI. The guns were controlled by a Fuze Keeping Clock AA fire control computer when engaging aircraft. The Hunt class was to ship the same armament, plus a quadruple QF 2 pounder mount Mark VII on a hull of the same length but with 8 feet (2 m) less beam and installed power raised to 19,000 shp (14,000 kW) to give 27 knots (50 km/h). The first twenty were ordered in March and April 1939. They were constructed to Admiralty standards, as were contemporary destroyers, unlike the frigates which conformed much more to mercantile practice.

Clearly the Hunts posed a major design challenge. They would be too short and narrow and of insufficient range for open ocean work, being restricted to the North Sea and Mediterranean Sea. This sacrifice was accepted to give any chance of meeting the requirements. The demanding specifications in an overworked Admiralty design department resulted in a major design miscalculation. When the detailed calculations were done the centre of gravity was lower than expected and the beam was increased. As the first ships were being completed it was found that the design was as much as 70 tons overweight, top heavy, leaving them dangerously deficient in stability. The first twenty ships were so far advanced in construction that it was necessary to remove the 'X' 4 inch mount and add 50 tons of permanent ballast. These ships became the Type I group, and had the multiple 2 pounder gun relocated from behind the funnel to the more advantageous 'X' position.

The design deficiency of the Type I was rectified by splitting the hulls lengthwise and adding a 2½ foot section, increasing the beam to 31 ft 6 in and the margin of stability sufficiently for the designed armament to be shipped. These ships became the Type II group, and also had a revised design of bridge with the compass platform extending forwards to the wheelhouse face. Under the 1939 Emergency War Programme 36 more Hunts had been ordered: three of these were completed to the original (Type I) design. Depth charge stowage could also be increased from 40 in the Type I to 110.

For the 1940 building programme, torpedoes were deemed necessary. The next 27 ships were completed to a revised design, the Type III group, and were intended specifically for Mediterranean work. They sacrificed 'Y' gun for a pair of 21 inch torpedo tubes amidships, the searchlight being displaced to the aft shelter deck as a result. The Type III Hunts could be easily identified as they had a straight funnel with a sloping top and the foremast had no rake. Fourteen of them had their stabilizer fins removed (or not fitted in the first place) and the space used for extra fuel oil.

The last two Hunts came from an independent lineage and were built to a private design that had been prepared pre-war by John I. Thornycroft & Company. Submitted to the Admiralty and rejected in 1938, a modified design had been accepted in 1940. They were known as the Type IV. They had a novel hull design, with a U-shaped forward section with a distinctive double knuckle and a full centre section with a square turn at the bilge. This form was intended to increase low-speed efficiency and reduce rolling without the need for ballast or stabilisers to improve the ships as gun platforms; testing showed an 8% increase in steaming efficiency at 20 knots (37 km/h) for a 2% loss full ahead. Other features included a long fo'c'sle stretching for most of the length of the ship, which increased internal accommodation space (the lack of which was a perennial problem in wartime ships with enlarged crews) and allowed the crew to fight the ship almost completely under cover. As a result, 'X' gun was now at the fo'c'sle deck level rather than on a raised shelter deck. The design was large enough to carry a triple set of torpedoes, but as they too were at fo'c'sle deck level the training apparatus had to be remotely mounted a deck below. Armament was completed by a pair of single 20 mm Oerlikon guns in the bridge wings and a pair of power operated twin 0.5 inch Vickers machine guns amidships, quickly discovered to be ineffective and replaced by the Mark V twin mounting for the Oerlikon gun. The level of protection afforded to the crews in these two ships was found to be beneficial in wartime, where crews were often closed up at action stations for extended periods of time in appalling weather conditions, and the design - although it was something of a dead end - heavily influenced post-war escort designs.

All Hunt class except three Type II and the Type IV Brissenden had fin stabilisers forward to reduce rolling to make for a steadier gun platform. These were subsequently removed from the majority of the Type III ships to allow for an increase in bunkerage of 63 tons.