Arethusa Class Cruiser (1913)

The eight light cruisers of the Arethusa Class were completed in 1914 and 1915. Oil-fired and capable of thirty knots, they were designed primarily to act as destroyer leaders in the North Sea. Two were in service at outset of war, followed soon by the remaining six.

Overview of 8 vessels
Citations for this data available on individual ship pages
Name	Builder	Laid Down	Launched	Completed	Fate
Arethusa	Chatham Royal Dockyard	28 Oct, 1912	25 Oct, 1913	Aug, 1914	Mined 11 Feb, 1916
Aurora	Devonport Royal Dockyard	24 Oct, 1912	30 Sep, 1913	5 Sep, 1914	Sold Aug, 1927
Galatea	William Beardmore & Company	9 Jan, 1913	14 May, 1914	Dec, 1914	Sold 25 Oct, 1921
Inconstant	William Beardmore & Company	3 Apr, 1914	6 Jul, 1914	Jan, 1915	Sold 9 Jun, 1922
Penelope	Vickers	1 Feb, 1913	25 Aug, 1914	Dec, 1914	Sold Oct, 1924
Phaeton	Vickers	12 Mar, 1913	21 Oct, 1914	Feb, 1915	Sold 16 Jan, 1923
Royalist	William Beardmore & Company	3 Jun, 1913	14 Jan, 1915	Mar, 1915	Sold 24 Aug, 1922
Undaunted	Fairfield Shipbuilding and Engineering Company	21 Dec, 1912	28 Apr, 1914	29 Aug, 1914	Sold 9 Apr, 1923

Purpose

A minute jotted by the Chief of the War Staff from 19 November 1914 opined that "The Arethusas are meant to act in squadrons: & shd not be frittered away among the flotillas."

Binoculars

In September 1914, the ships were allowed six additional pairs of Pattern 343 Service Binoculars.

Armament

The ships had their torpedo and gun outfits augmented during the course of the war.

After Jutland, it was desired to double their torpedo armament, and each broadside got a second double revolving torpedo mount aft, just forward of the aft 6-in gun. These would have the torpedoes formerly available, but not conveniently so, loaded and ready within. A 3-in H.A. gun was replaced by a 4-in H.A. gun at the same time.

In 1918, a third 6-in gun was desired, and its placement aft replaced the aft-most pair of 4-in mounts and required the 4-in H.A. gun and the new torpedo mounts to be moved forward. Some of the ships had their single 4-in H.A. gun replaced by two 3-in H.A. guns as part of this change.

The last alteration approved was to remove the four remaining 4-in guns that were not H.A. mounts and reduced conning tower armour from four inches to just one inch in order to add a fourth 6-in mount well forward, but this not carried out.

Guns

The ships were originally equipped with:

• Two 6-in 45cal B.L. Mark XII guns, fore and aft, on P. VII mountings (one source indicated P. VII* for units other than Penelope), able to elevate 15 degrees.
• Six semi-automatic 4-in 45cal Q.F. Mark IV guns on P. X mountings, three on each broadside
• one 3-pdr on H.A. mounting

Although the forward 6-in mount seemed problematic enough to inspire a move in the Caroline class to place it aft, the charm of 6-in hitting power was such that it was decided that the Arethusas should receive a third 6-in aft (on the flip-side, the Carolines were receiving third guns forward as part of the same initiative).

The 6-in mountings were modified to a 20 degree elevation limit, increased from the original limit of 15 degrees, as the ships were refitted for director firing in late 1917-1918. It is not clear whether their elevation receivers were updated from a 15 degree standard recorded in late 1917.

The arrangements to permit mixed calibres to be commanded by the same director proved less than desireable, and this prompted a decision in mid-1918 to remove the 4-in guns in favour of an all 6-in scheme. It is not clear when and if this occurred.

By the end of 1918, Inconstant, Penelope, Phaeton, Galatea and Royalist had three 6-in P. VII 20 degree mountings; Aurora and Undaunted still had two 6-in guns, but on 20 degree mountings; Arethusa was lost before rearmament of any kind. Calliope had merely had her three 6-in mountings modified for 20 degree elevation, but was brought up to spec after the Armistice and prior to 1921.

Torpedoes

21-in D.R. Torpedo Mounting Mark II
Note the guard rails to safeguard trainers, as these were sited on the broadside in this class

Originally, these ships had two 21-in D.R. Mark II torpedo tubes, arranged port and starboard. While this gave them two torpedos in a single mounting on each broadside – the first British cruiser to enjoy this new disposition, the spare torpedoes were stored below which was not expedient for quick reloading in action.

In 1916-1917, the ships received two additional mountings port and starboard — first near the aft 6-in, and later afore the foremost centreline tubes when the third 6-in gun was added aft. These new tubes now carried the spare torpedoes and ensured they would be ready for use in action.

In 1918, the Arethusa class was one of several light cruiser classes ordered to receive refits so that their A.W. torpedo tubes would use two impulse charges firing in a cascade to increase the torpedo discharge velocity and thus reduce the angle at which the torpedoes entered the water.

In mid-1920, it was ordered that Galatea, Phaeton and Royalist should replace their 21-in Mark IV S.L. torpedoes with the Mark II***** version. All other units would also receive this torpedo, except Inconstant, which would retain her 21-in Mark IV S.L. torpedoes.

Fire Control

Mechanical Aid-to-Spotter

By 1920, the seven surviving ships were equipped with Mechanical Aid-to-Spotter Mark II*s with Evershed Bearing Transmitters. The installations generally consisted of placing one on each side of the foretop, driven by flexible shafting from a gearbox on the director tower's Evershed rack.

Supplies of these devices began in June 1918.

Range Dials

In 1918, it was ordered that these and ten other classes of light cruisers should receive "range instruments for concentration of fire". Presumably, this meant range dials.

As of 1920, Galatea and Aurora were each equipped with a Range Dial Type B and a Type C. The other five surviving ships had two Type C dials.

Rangefinders

Sometime during or after 1917, an additional 9-foot rangefinder being handed down from a battleship or battlecruiser (likely an F.T. 24) was to be added specifically to augment torpedo control.

By June 1918, it was determined that the ships would probably eventually carry two 12-foot and one 9-foot rangefinders.

A confusing decree from 1918 indicates that a traversing 9-foot R.F. on the manœuvring platform on this and three other classes is to be replaced by a fixed 12-foot R.F., "but no addition to the manœuvring platform can be accepted." Also, the roof of the after control is to be lowered and a 12-foot R.F. mounted on it, "but this alteration is not to be carried out pending the trials which are being carried out in Calliope.

By 1921, the ships were equipped as follows:

• Fore bridge: 9ft F.Q. 2 on M.Q. 1 mounting
• After control: 9ft F.Q. 2 on M.P. 2
• High Angle: 1m F.T. 28 on M.T. 9

Evershed Bearing Indicators

The Centaur class were the first light cruisers fitted with Evershed gear for gun control, but it is not clear whether older light cruisers were ever fitted.

Orders for Evershed installations for searchlight control from February 1917 first applied to the Danae class, but seem unlikely to have applied to earlier ships.

Gunnery Control

Control Groups

It seems the guns were in 4 groups, with the 4-in broadsides being separate and the 2 6-in guns being separate or jointly worked: The port and starboard 4-in batteries had separate transmitters in the TS. The 6-in guns had two sets of transmitters in the TS with a C.O.S. to permit control from:

• fore control (presuming this means one set of transmitters in the TS)
• after control (presuming this means the other set of transmitters in the TS)
• separate control

Directors

In 1916, it was approved that the ships of this class should be retrofitted with directors as time, resources and opportunity permitted. This intention was reiterated in 1917.

All eight ships were fitted with directors in 1917 and 1918.

Elevation and Training Circuits
Director Firing Handbook, 1917, Plate 81.

The director was on a pedestal mounting without a tower. Likely, there was no directing gun. The mixed armament required the director to have separate sets of elevation and training transmitting gear, though a single slewing transmitter sufficed for all guns. The director had elevation and training receivers for the 6-in guns, but not for the 4-in guns.

The elevation limits of their weapons may have increased in late 1917 or early 1918, resulting in orders for adapting their director systems issued 13 November, 1917. It is not clear whether these alterations were for the entire class or just Arethusa herself, or when they were effected.

In late 1917, at least, the remaining ships had 6-in P. XIII Type Elevation Receivers with electrical tilt correction capable of indicating 15 degrees elevation, Pattern V.E. 3 (except Penelope with 6-in P. VII Type and similar features). The 4-in guns had 4-in P. X models with electrical tilt correction and 20 degree elevation, Pattern F. C. 5 (except Penelope's gear relied on "hand tilt correction"). Their Small Type Training Receivers were pattern number 22 on the forward 6-in gun, pattern number 23 on the aft 6-in gun, pattern number 20 on P1, P2, S1, and S2 and pattern number 21 on P3 and S3.

Dreyer Table

These ships had no fire control tables.

Fire Control Instruments

Vickers Mark III F.T.P. to the gunsights. Fire gongs fitted at each gun worked from pushes for each group (4?) in the T.S..

By mid-1918, it had been approved to issue these ships, along with several other classes of light cruisers range repeat receivers for their fore bridge and control positions so that their captains and control officers could know the gun range.

Torpedo Control

Torpedo Control Circuits
Pertinent to all except Penelope

Torpedo Control Circuits
Pertinent to Penelope

Torpedo Control Circuits

In 1916, it was decided that all light cruisers of Bristol class and later should have torpedo firing keys (Pattern 2333) fitted on the fore bridge, in parallel with those in the CT, and that a flexible voice pipe be fitted between these positions.

In 1916, torpedo control lessons pertinent to the equipment of light cruisers and destroyers that had been taken from experience the Battle of Jutland were to be apply to light cruisers "of Penelope class and later". The baseline capabilities required that primary control be exercised from the fore bridge, where Fore Bridge Firing Gear and a sight or director would be fitted, and that this position should enjoy efficient communication to a similar secondary position located some distance away. Additionally, the ships would need:

• Fore Bridge Firing Gear
• order instruments from control positions to A.W. tubes
• deflection instruments
• fire gongs and alarm gongs

The A.W. tubes were to have local sights fitted, and the tubes should enjoy order and sightsetting instruments from the control positions as well as firing gongs in case fore bridge firing should fail.

This work was still underway in the various light cruisers as of early 1918.

Penelope differed from the others in that she never had her torpedo outfit doubled. Inconstant had a complete Wise Pressure Telegraphy System Type C for orders and deflection; the others had Chadburn's Torpedo Telegraph to pass orders from control positions to the tubes, with deflections coming by Wise Pressure Telegraphy System Type Bs whose dials had been adapted to the purpose.

In mid-1920, it was decided that the seven surviving ships in this class should each receive a Renouf Torpedo Tactical Instrument Type A.

Alterations

By November 1918 the seven surviving ships, were fitted with rails for 70 mines (66 in Royalist, for some reason). The torpedo tubes and guns removed when the mines were shipped could be placed back aboard with enough notice.

See Also

• Wikipedia

Bibliography

• Admiralty, Technical History Section (1920). The Technical History and Index: Alteration in Armaments of H.M. Ships during the War. Vol. 4, Part 34. C.B. 1515 (34) now O.U. 6171/20. At The National Archives, Kew, United Kingdom.
• Admiralty, Gunnery Branch (1917). The Director Firing Handbook. O.U. 6125 (late C.B. 1259). Copy No. 322 at The National Archives. ADM 186/227.
• Admiralty, Gunnery Branch (1910). Handbook for Fire Control Instruments, 1909. Copy No. 173 is Ja 345a at Admiralty Library, Portsmouth, United Kingdom.
• Admiralty, Gunnery Branch (1914). Handbook for Fire Control Instruments, 1914. G. 01627/14. C.B. 1030. Copy 1235 at The National Archives. ADM 186/191.
• Admiralty, Gunnery Branch (1918). Handbook of Captain F. C. Dreyer's Fire Control Tables, 1918. C.B. 1456. Copy No. 10 at Admiralty Library, Portsmouth, United Kingdom.
• Admiralty, Technical History Section (1919). The Technical History and Index: Fire Control in H.M. Ships. Vol. 3, Part 23. C.B. 1515 (23) now O.U. 6171/14. At The National Archives. ADM 275/19.
• Admiralty, Technical History Section (1919). The Technical History and Index: Fire Control in H.M. Ships. Vol. 3, Part 23. C.B. 1515 (23) now O.U. 6171/14. At The National Archives. ADM 275/19.
• Brown, D.K. (1983). "The Design of HMS Arethusa 1912". Warship International 1983 (1): pp. 35-42.
• Pearsall, Alan. "Arethusa Class Cruisers." Warship VIII (31).
• Pearsall, Alan. "Arethusa Class Cruisers." Warship VIII (32).