Acasta class destroyers

The Acasta class destroyers were a development of the previous Acheron class, but with a big increase in power and armed entirely with 4in guns. They served with the 4th Flotilla of the Grand Fleet from 1914-16, suffering heavy losses at Jutland, then moved to the Humber and the south coast to take part in the struggle against the U-boats.

The Acasta class were the fourth in a series of similar destroyers that had been produced after Admiral Fisher’s experiment with a mix of high speed (Tribal class) and coastal destroyers (Cricket class) had been abandoned. The coastal class ships were too small to operate at any great range from their base and the Tribal class destroyers too expensive, so the next class, the Beagle class, was a development of the successful River class. The key change was a focus on seaworthiness and endurance instead of theoretical top speed.

HMS Ambuscade from the left HMS Ambuscade from the left

The Beagle class was followed by the Acorn class, which saw coal power replaced with oil, and the Acheron class, a slightly modified version of the Acorn class. However the Acheron class also included a number of ‘specials’, where the constructors were given more freedom to try and achieve high speed. The last of these, the Firedrake group, were designed late in 1910 in response to rumours of faster German destroyers, and were ten feet longer than the standard type (255ft compared to 246ft), but with a similar displacement and basic layout (780 tons). She had three boilers that produced 20,000shp, well up on the 13,500hp of the standard type. The Firedrake reached 33.17 knots at 19,174shp at a displacement of 774 tons on her trials, and would become the basis of the Acasta class, which was sometimes known as the ‘new Firedrake’ class.

In December 1910, while the Firedrake was still being developed, Wilmot Nicholson, the Captain Superintending Torpedo Boat Destroyers, wrote up his thoughts on future destroyers for the Controller. He wanted quick firing guns, an increase in speed, good endurance and seaworthiness and low cost (to allow for larger numbers). He was opposed to paying for the increase in speed by reducing the structural strength of the ship or by increasing length much above 255ft, but believed that an increase in engine power to around 18,000shp would produce trials speeds of 29 knots and loaded speeds of 27 knots. This would be above the expected realistic loaded speed of the new German destroyers.

The DNC submitted the first sketch design for the 1911-12 destroyers on 6 February 1911. It was based on the Firedrake (although that ship was still over a year away from being launched!). The new design was expected to reach 32knots on trial, although this dropped to 29.5 knots (see below for more on this). It would carry more fuel than the Acherons – rising from 170 to 200 and finally 250 tons, which gave her a range of 2,750nm at 15 knots and 36,50nm at thirteen knots. The original design was stretched by 5ft to allow her to carry the extra fuel and another 12-pounder gun. The extra engine power was in part provided by increasing the maximum rate at which the boilers were allowed to use oil and in part by adding an extra boiler – four compared to the three of the Acherons.

In the same month the DNO suggested replacing the 12-pounders with a breach loading 4in gun, on the grounds that one 4in shell was as powerful as four 12-pounder shells. This would make up for the greater speed of fire of the 12-pounder. He suggested changing the planned armament from two 4in and three 12-pounders to three 4in guns. This would provide just as much firepower and save fifteen men from the crew. The change was approved before the design had been finalised. The last seven ships in the class would be given a new quick firing 4in gun, improving their firepower even further.

The addition of an extra 4in gun meant that the layout of the weaponry had to be altered. The 4in gun needed sturdy gun supports under the deck, and there were a limited number of places where these could be installed (with so much space take up by the boilers and turbines). On the Acorns and Acherons one 4in gun was near the stern, with the two torpedo tubes between the gun and the rear funnel. The two 12-pounders were on the sides between the first and second funnels, where their supports could be placed outside the boilers, not possible for a 4in gun on the centreline. The solution was to move the torpedo tubes forward, so one was between the second and third funnels and one just behind the third funnel. The new gun was placed where the rear torpedo tubes had been, and the rear gun was moved further back.

The 4un guns were given sights calibrated for ranges of up to 8,500 yards (elevated at 15 degrees), while the mount could reach 20 degrees, which allowed for ranges of up to 10,200 yards.

HMS Achates, 1914 HMS Achates, 1914

At first glance an increasing in speed of only two knots from an increase in power from 13,500shp to 24,500shp appears somewhat disappointing, even taking into account the increase in dimensions and displacement. However a key reason for this was a change in the way trials were carried out. When they were first designed destroyers trials were carried out with a realistic but not full load. At first the Acastas were expected to undergo trials with a load of 130 tons (compared to 122 tons on an Acorn class ship), taking into account their much greater fuel storage. The rules then changed so that trials were carried out fully loaded, so the Acasta class ships carried out their trials at a load of 310 tons, including 258 tons of oil. The initial target of 29.5 knots with a full load was calculated to be the equivalent of 32 knots at the original load.                   

The completed design was presented to the Board on 13 March 1911, approved by the First Sea Lord on 7 April and given the Board Stamp on 12 June 1911. By then it had already been decided to order twelve ships to the Admiralty design and eight as specials, including one using internal combustion engines.

The twelve admiralty ships were split between four builders – John Brown, Hawthorn Leslie, Swan Hunter and London & Glasgow, each of which built three. Most used Parsons turbines apart from the John Brown ships which used their Brown-Curtis turbines.

Thornycroft built four turbine powered specials and one diesel powered specials.

The turbine powered specials (Paragon, Porpoise, Unity and Victor) had originally been designed with a space for either diesel engines or mines, but these were rejected and replaced with anti-roll tanks. They were shorter than the standard ships (257 feet), produced 21,300shp and made 31 knots. The third gun was located over the engine room, despite objections from the DNC.

The diesel powered special, HMS Hardy, was ordered as part of a long term interest in diesel power, dating back to 1904. Yarrow and Thornycroft had both already put forward suggestions for mixed power ships, and were asked to submit designs for a mixed power ship for the 1911-12 programme. The Thornycroft design used Sulzer diesels giving 1,800shp and normal steam boilers giving the same 21,000shp as the other Thornycroft specials. The boilers would drive turbines attached to the wing shafts while the diesels would drive two central shafts, which would only be used at cruising speeds. The diesels would be much more efficient than the normal cruising turbines, massively increasing her range. However the diesels weren’t ready in time, so the Hardy was delivered without them.

Denny built one special, the Ardent. She used longitudinal framing, which improved the strength of the hull without increasing weight. She had three boilers and two funnels, and her middle 4in gun was mounted above the bulkhead between the two boiler rooms.

Fairfield built one special, the Fortune. She had a clipper bow, and carried her second 4in gun on a platform between No.2 and No.3 funnels. This layout was chosen for the next group of destroyers, the Laforey or L Class.

Parsons built one special, the Garland. She had the standard Admiralty hull, but with semi-geared turbines.

Service Record

At the outbreak of the First World War the twenty K class destroyers formed the 4th Destroyer Flotilla, which joined the Grand Fleet. The first loss was the Lynx, sunk by a mine on 9 August 1915. The heaviest toll came at Jutland, where four of the class were lost (Ardent, Fortune, Lynx and Sparrowhawk). The flotilla wasn’t rebuilt after Jutland, and instead was replaced with a new flotilla with newer destroyers. The remaining fifteen Acasta class ships moved with the Fourth Flotilla to the Humber Force, where they spent most of the rest of 1916.

The class was temporarily split up in December 1917, when five were transferred to the Sixth Destroyer Flotilla at Dover (Ambuscade, Paragon, Porpoise, Unity and Victor) while the remaining ten moved to Portsmouth with the Fourth Flotilla. One of the Dover boats, HMS Paragon, was sunk by German destroyers on 17-18 March 1917.

HMS Acasta from the right HMS Acasta from the right

In March 1917 the ten ships at Portsmouth moved to Devonport. However the Paragon was sunk in March 1917.

In April 1917 the five ships at Dover moved to Devonport and rejoined the 4th Flotilla. Most of the remaining ships remained at Devonport to the end of the war.

HMS Contest was sunk by U-106 on 18 September 1917, while based at Devonport.

In May 1918 the Acasta moved to the Torpedo School at Portsmouth, leaving twelve with the Fourth Flotilla.

At some point between August and November 1918 three, Ambuscade, Christopher and Cockatrice moved to join the Northern Patrol at Dundee, although the exact date of the move isn’t clear.

Ships in Class

HMS Acasta – Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916, Portsmouth, 1917, Devonport, 1917-1918; Torpedo School, Portsmouth, 1918
HMS Achates – Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916, Portsmouth, 1917, Devonport, 1917-1918
HMS Ambuscade – Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916, Portsmouth, 1917, Devonport, 1917-1918; Northern Patrol, Dundee, 1918
HMS Christopher Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916, Portsmouth, 1917, Devonport, 1917-1918; Northern Patrol, Dundee, 1918
HMS Cockatrice – Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916, Portsmouth, 1917, Devonport, 1917-1918; Northern Patrol, Dundee, 1918
HMS Contest – Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916, Portsmouth, 1917, sunk by U-106 18 September 1917
HMS Shark - Fourth Destroyer Flotilla, Grand Fleet, 1914 until sunk at Jutland in 1916
HMS Sparrowhawk  - Fourth Destroyer Flotilla, Grand Fleet, 1914 until sunk at Jutland in 1916
HMS Spitfire – Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916, Portsmouth, 1917, Devonport, 1917-1918
HMS Lynx - Fourth Destroyer Flotilla, Grand Fleet, 1914 until sunk by mine, 9 August 1915
HMS Midge – Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916, Portsmouth, 1917, Devonport, 1917-1918
HMS Owl - Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916, Portsmouth, 1917, Devonport, 1917-1918

Thornycroft Specials

HMS Hardy - Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916, Portsmouth, 1917, Devonport, 1917-1918
HMS Paragon - Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916; Sixth Destroyer Flotilla, Dover, to 17-18 March 1917 when sunk by German destroyers
HMS Porpoise - Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916, Portsmouth, 1917, Devonport, 1917-1918
HMS Unity  – Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916; Sixth Destroyer Flotilla, Dover, early 1917; Fourth Flotilla, Devonport, 1917-1918
HMS Victor – Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916; Sixth Destroyer Flotilla, Dover, early 1917; Fourth Flotilla, Devonport, 1917-1918

Denny Special

HMS Ardent - Fourth Destroyer Flotilla, Grand Fleet, 1914 until sunk at Jutland in 1916

Fairfield Special

HMS Fortune - Fourth Destroyer Flotilla, Grand Fleet, 1914 until sunk at Jutland in 1916

Parsons Special

HMS Garland - Fourth Destroyer Flotilla, Grand Fleet, 1914-1916, Humber Force, 1916, Portsmouth, 1917, Devonport, 1917-1918

Displacement (standard)

1,072t

Displacement (loaded)

1,300t

Top Speed

29 knots

Engine

2-shaft Parsons turbines (most)
2-shaft semi-geared Parsons turbines (Garland)
2-shaft Brown-Curtis turbines (Acasta, Achates, Ambuscade)
4 Yarrow boilers
24,500shp

Range

 

Length

267ft 6in

Width

27ft

Armaments

Three 4in/ 45cal BL Mk VIII
Two 21in torpedo tubes with four torpedoes

Crew complement

73

Ships in class

HMS Acasta
HMS Achates
HMS Ambuscade
HMS Christopher
HMS Cockatrice
HMS Contest
HMS Shark
HMS Sparrowhawk
HMS Spitfire
HMS Lynx
HMS Midge
HMS Owl

Thornycroft Specials
HMS Hardy
HMS Paragon
HMS Porpoise
HMS Unity
HMS Victor

Denny Special
HMS Ardent

Fairfield Special
HMS Fortune

Parsons Special
HMS Garland

 

British Destroyers From Earliest Days to the Second World War, Norman Friedman. A very detailed look at the design of British destroyers from their earliest roots as torpedo boat destroyers, though the First World War and up to the start of the Second World War, supported by vast numbers of plans and well chosen photographs [read full review]
cover cover cover

Books on the First World War | Subject Index: First World War

How to cite this article: Rickard, J (30 December 2021), Acasta class destroyers , http://www.historyofwar.org/articles/weapons_acasta_class_destroyer.html

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