L and M class destroyer

From Wikipedia, the free encyclopedia

You have new messages (last change).
HMS Laforey

L and M class

RN Ensign
General Characteristics
Displacement: 1,935 tons (standard), 2,840 tons (full)
Length: 362 ft o/a (110.5 m)
Beam: 36 ft 9 in (11.2 m)
Draught: 10 ft (3.05 m) mean
Propulsion: 3 x Admiralty 3-drum boilers, steam turbines, 2 shafts, 48,000 shp
Speed: 36 kt
Range: 467 tons oil, 5,500 nm at 15 kt
Complement: 221
Armament (designed):
3 x twin 4.7 in L/50 QF Mark XI, mounting LA/HA Mk.XX

1 x quad 2 pdr "pom-pom" mount Mk.VII
2 x quad Vickers 0.5 in MG AA
2 x quad tubes for 21 in torpedoes Mk.IX
Armament (war modifications):
3 x twin 4.7 in L/50 QF Mark XI, mounting LA/HA Mk.XX

1 x single 4 in gun QF Mk.V on mounting HA Mk.III
1 x quad 2 pdr "pom-pom" mount Mk.VII
Up to 5 x single and/or twin 20 mm Oerlikon guns
1 x quad tubes for 21 in torpedoes Mk.IX
Armament (4 in armed L class):
4 x twin 4 in L/45 QF Mark XVI, mount HA Mk.XIX

1 x quad 2 pdr "pom-pom" mount Mk.VII
2 x quad Vickers 0.5 in MG AA, later;
Up to 5 x single and/or twin 20 mm Oerlikon guns
2 x quad tubes for 21 in torpedoes Mk.IX

The L and M class was a class of sixteen destroyers of the Royal Navy, launched in 1939–1942.

Contents

[edit] Design Details

Their design and armament was the subject of major debate as the proponents of heavier anti-aircraft armaments for such vessels were at last beginning to be listened to at the Admiralty, mainly as a result of the lessons of the Spanish Civil War.

They had single funnels as per the J class, a tripod foremast and a short mainmast just aft of amidships. One feature of note was the bridge design. From the I class to the Weapon class, all Royal Navy destroyers shared a distinctive wedge-shaped face to the bridge, incorporating an armoured wheelhouse, raised in order that the helmsman could see over the guns. The increased height of the new gunhouses of the L class meant that the wheelhouse was raised further, and the sloped roof of the wheelhouse (to direct the airflow over the compass platform) was almost flat. This feature was unique to the Ls and Ms.

As ordered the class comprised a leader and 7 destroyers. Each ship was to mount 6 x 4.7 inch guns and 8 torpedo tubes. Close range armament had still to be decided, with the expected time to delivery being a crucial factor.

They were the first British destroyers to have their guns in fully enclosed mountings. They also continued the practice introduced in the Js of the leader Laforey being almost indistinguishable from the rest of the class, having only a more extensive cabin accommodation and better W/T (wireless telegraph a.k.a. radio) equipment.

[edit] Main Armament

As ordered the ships were to have six QF Mark XI 4.7 inch guns in Mark XX twin mountings. They were to be in 'A', 'B', and 'X' positions. The 'X' mount was especially interesting in that it gave an arc of fire of around 320 degrees at low elevations and 360 degrees at elevations above around 20 degrees (estimated figures). The Mark XI gun itself was a major improvement on the previous version in that it threw a 62 lb shell (as opposed to the 50 lb (23 kg) in the preceding 'J's). The Mark XX mount was fully enclosed and supposedly weatherproof; however crews found that they were not. It also allowed the guns to be elevated independently. The Mark XX is not technically a turret, as the ammunition feed system was distinct from the weapon mounting, and did not train with the revolving mass. This meant that ammunition supply when the guns were at the limit of training was somewhat difficult. This also meant that the ammunition hoists had to be located between the guns. As a result, the axes of the guns were very widely spaced, a feature instantly obvious with the mounting Mark XX.

The Mark XX mounting permitted an increased elevation to 50 degrees (compared to 40 for previous marks). However, even this was to prove totally inadequate for dealing with the threats posed by enemy aircraft, particularly dive bombers. The Imperial Japanese Navy had already introduced a 5 inch gun with 70 degree elevation into service, while the United States Navy's 5"/38 cal Mark 32 mount count elevate to 85 degrees, why British designers had so much trouble has never been made clear. The 4.5 inch guns fitted to Ark Royal were already in service and capable of elevations of 70 degrees plus, although the mountings were not suitable for a ships of destroyer size. Coupled with the lack of powered elevation, the Mark XX mounting was compromised in its chosen anti-aircraft use.

Another development regarding the main armament was the adoption of a combined High Angle / Low Angle director tower, the HA/LA Mk.IV (TP). Unfortunately this was never entirely satisfactory in the HA mode, and was at least a ton overweight. It was later reworked, somewhat unsuccessfully again, as the Mk.I "K tower" of the Z class.

As originally ordered they had no close-range armament at all as the various departments could not agree on what to fit ! Arguments as to one or two 4-barrelled 2 pdr "pom poms", one pom-pom and one of the 0.661 inch multiple machine guns then in development, one pom-pom and the traditional 0.5 inch machine gun raged, stoked by the manufacturing schedules (a second pom-pom per ship would not be available until 1942), the poor performance of the development models of the 0.661 and the campaign by a number of younger officers (led by Lord Louis Mountbatten) as to the effectiveness of all three weapons. Eventually development of the 0.661 was dropped as it clearly would not be available and effective in a sensible timescale, this simplified the arguments somewhat.

The outbreak of war focussed minds somewhat. Apart from the AA armament issue concerns started to be raised about progress generally. By February 1940 the two factors led to a proposal to change the design of four of the 'L's and fit a main armament of 4 inch Mark XVI* guns in Mark XIX High Angle/Low Angle (HA/LA) twin mounts as used as secondary armament in the Southampton-class cruisers already in service and main armament in the Black Swan class of sloops then under construction. Associated changes were dropping of the pom-poms altogether and provision of two quad 0.5 inch machine guns.

The lessons of the Norwegian campaign and Dunkirk drove home the need for this change and it was agreed in July 1940, there were also to be four of the twin mounts instead of the originally proposed three. The fourth was to be at the forward end of the after superstructure which cut down on the fire arcs of both mounts but ensured the fourth would still be available for use in heavy weather.

Not all senior officers were in favour, and some openly expressed opinions that it would mean the ships could not successfully fight their foreign equivalents. Experience in the Mediterranean, especially that of Force K which contained two of the 4 inch 'L's, made a mockery of the idea, with the reduced weight of each shell being compensated for by the much higher rate of fire.

Review of AA armament continued, and in October a decision was taken to remove the after bank of four torpedo tubes and fit a single 4 inch HA gun instead, and that is how the 4.7 inch gunned ships eventually got to sea.

[edit] L class

The L class (also known as the Laforeys) were approved under the 1937 Naval Estimates. Lance, Lively, Legion and Larne were built with 4 inch armament

[edit] M class

HMS Matchless
HMS Matchless
Retrieved from "http://en.wikipedia.org../../../l/_/a/L_and_M_class_destroyer_7fbd.html"
In other languages