Editing G and H-class destroyer (section)

==Design and description (G and H classes) ==
The G class were ordered as part of the 1933 Naval Construction Programme, the H class following in 1934. These ships were based on the preceding [[E and F-class destroyer|F class]], but the elimination of cruising turbines and the development of more compact machinery allowed their dimensions and [[displacement (ship)|displacement]] to be slightly reduced. The H class were repeats of the G's with some minor differences. All of the destroyers were fitted with [[Sonar#History|ASDIC]] (sonar) and the ability to use the Two-Speed Destroyer Sweep (TSDS) [[minesweeper (ship)|minesweeping gear]].<ref>English, pp. 75, 88, 102</ref>

The G- and H-class destroyers displaced {{convert|1340|-|1350|LT|t|lk=on}} at [[Displacement (ship)|standard]] load and {{convert|1854|-|1860|LT|t}} at [[deep load]]. The ships had an [[length overall|overall length]] of {{convert|323|ft|m|1}}, a [[beam (nautical)|beam]] of {{convert|33|ft|m|1}} and a [[draft (hull)|draught]] of {{convert|12|ft|6|in|m|1}}.<ref name="l59">Lenton, pp. 159–160</ref> Their peacetime complement was 137 officers and [[naval rating|ratings]], which was intended to increase to 146 in wartime. The ships were at their [[ship stability|stability]] limit as built and the [[Director of Naval Construction]] believed that no additions in top weight should be made without an equal amount of weight being removed.<ref>English, pp. 89–90</ref>

They were powered by two [[Parsons Marine Steam Turbine Company|Parsons]] geared [[steam turbine]]s, each driving one [[propeller shaft]], using steam provided by three [[Admiralty 3-drum boiler]]s that operated at a pressure of {{convert|300|psi|kPa kg/cm2|0|abbr=on|lk=on}} and a temperature of {{convert|620|°F}}. {{HMS|Hyperion|H97|2}} was fitted with one [[Johnson boiler]] in her aft boiler room. The turbines developed a total of {{convert|34000|shp|lk=on}} and gave a maximum speed of {{convert|35.5|kn|lk=in}}. The destroyers carried a maximum of {{convert|450|-|475|LT|t}} of [[fuel oil]] that gave them a range of {{convert|5500|nmi|lk=in}} at {{convert|15|kn}}.<ref name="l59"/>

All of the ships had the same main armament, four [[List of British ordnance terms#QF|quick-firing (QF)]] [[4.7 inch QF Mark IX & XII|{{convert|4.7|in|mm|adj=on}} Mark IX]] guns in single mounts, designated 'A', 'B', 'X', and 'Y' from front to rear. The guns had a maximum elevation of 40°; the G class achieved this with a lowered section of the deck around the mount, the "well", that allowed the [[breech-loading weapon|breech]] of the gun to be lowered below deck height, but the new gun mount used in the H class was designed to reach that elevation without the necessity for the clumsy "wells".<ref name="Whitley, pp. 109–10">Whitley, pp. 109–110</ref> They fired a {{convert|50|lb|kg|adj=on}} shell at a [[muzzle velocity]] of {{convert|2650|ft/s|m/s|abbr=on}} to a range of {{convert|16970|yd|m}}.<ref>Campbell 1985, p. 48</ref> {{HMS|Hereward|H93|2}} served as the [[testbed]] for the twin 4.7-inch gun mount used for the {{sclass2|Tribal|destroyer (1936)|5}} and the [[J-, K- and N-class destroyer|J, K and N]] classes that temporarily replaced 'B' gun. For [[Anti-aircraft warfare|anti-aircraft]] (AA) defence, they had two quadruple mounts for the [[Vickers .50 machine gun|QF 0.5-inch Vickers Mk III]] machine gun on platforms between the [[funnel (ship)|funnel]]s. The G- and H-class ships were fitted with two quadruple mounts for [[British 21-inch torpedo|21-inch (533&nbsp;mm)]] [[torpedo tube]]s, although {{HMS|Glowworm|H92|2}} trialled the new quintuple mount. The ships were also equipped with two throwers and one rack for 20 [[depth charge]]s.<ref name=l1>Lenton, pp. 159–161</ref>

The main guns were controlled by an [[Admiralty Fire Control Clock]] Mk I that used data derived from the manually-operated [[List of British ordnance terms#DCT|director-control tower]] and the separate [[Rangefinding telemeter|rangefinder]] situated above the [[bridge (nautical)|bridge]]. They had no capability for anti-aircraft fire and the anti-aircraft guns were aimed solely by eye.<ref>Campbell 1985, pp. 14–15; Hodges & Friedman, pp. 12, 17</ref> {{HMS|Hero|H99|2}} and ''Hereward'' saw the introduction of a new style of bridge that would become standard on all Royal Navy fleet destroyers from the {{sclass2|I|destroyer|4}} through to the {{sclass2|Battle|destroyer|4}} of 1944. This was necessary as ''Hereward'' was fitted with a prototype twin-gun mounting that had a [[trunnion]] height {{convert|13|in|cm|1}} higher than the previous weapons, therefore it was necessary to raise the [[Pilothouse|wheelhouse]] to allow the [[helmsman]] to see over the top. Raising the wheelhouse meant it had to be placed in front of, rather than underneath, the bridge, and it was given angled sides, resulting in a characteristic wedge shape with a sloping roof.<ref>Friedman, p. 224</ref>

===Wartime modifications===
Beginning in May 1940, the after bank of torpedo tubes was removed and replaced with a [[QF 12 pounder 12 cwt naval gun|QF 12-pounder Mk V anti-aircraft gun]], the after mast and funnel being cut down to improve the gun's field of fire. Four to eight [[Oerlikon 20 mm cannon|QF 20&nbsp;mm Oerlikon]] [[Autocannon|cannon]]s were added to the surviving ships, usually replacing the .50-calibre machine gun mounts between the funnels. One pair of these was added to the bridge wings and the other pair was mounted [[wikt:abreast|abreast]] the [[searchlight]] platform.<ref name=l1/> Early in the war, depth charge stowage increased to 44.<ref>Friedman, pp. 236–237</ref> By 1943, only four ships were still afloat and all had the 'Y' gun on the [[Deck (ship)|quarterdeck]] removed to allow for additional depth charge stowage and two additional depth charge throwers. The 12-pounder was removed to allow for the installation of a [[Huff-Duff]] [[radio direction finder]] on a short [[mainmast]] and for more depth charges. All of the survivors, except {{HMS|Garland|H37|2}}, had 'A' or 'B' gun replaced by a [[Hedgehog (weapon)|Hedgehog]] anti-submarine [[spigot mortar]], and their director-control tower and rangefinder above the bridge removed in exchange for a [[Type 271 radar|Type 271]] target-indication [[radar]]. 'A' gun was later replaced in {{HMS|Hotspur|H01|2}} while ''Hero'' had exchanged 'B' gun for a Hedgehog and a twin-gun mount for [[QF 6 pounder Hotchkiss|QF six-pounder]] [[Hotchkiss gun]]s for use against U-boats at very close range. A [[Type 286 radar|Type 286]] short-range, surface-search radar, adapted from the [[Royal Air Force]]'s ASV radar, was also added. The early models, however, could only scan directly forward and had to be aimed by turning the entire ship.<ref name=l1/>

===Flotilla leaders===
[[File:HMS Hardy 1936.jpg|thumb|''Hardy'', 1936]]
As per the E and F class, the [[flotilla leader]]s were built to an enlarged design, incorporating a fifth 4.7-inch gun in 'Q' position, between the funnels and were based on the F-class leader, {{HMS|Faulknor|H62|2}}.<ref name=w7>Whitley, p. 107</ref> ''Grenville'' was shorter and heavier than ''Hardy'' as she used compact [[Yarrow boiler|Yarrow-type side fired boilers]] while ''Hardy'' was slightly beamier. They displaced {{convert|1445|-|1465|LT|t}} at standard load and {{convert|1953|-|2033|LT|t}} at deep load.<ref name="l59"/> The ships had an overall length of {{convert|330|-|337|ft|m|1}},<ref name=w7/> a beam of {{convert|33.75|-|34|ft|m|1}}<ref>Friedman, pp. 224, 299</ref> and a draught of {{convert|12|ft|6|in|m|1}}. The ships carried a total of 175 personnel which included the staff of the [[Captain (D)]], commanding officer of the flotilla.<ref>Whitley, pp. 97, 107</ref> Their turbines were {{convert|2000|shp|abbr=on}} more powerful than the [[private ship]]s, which made them {{convert|0.5|kn}} faster; their propulsion machinery was otherwise identical. Both ships were early wartime losses and consequently received no modifications.<ref name=l1/>