Chatham Class Cruiser (1911)

The six light cruisers of the Chatham Class were completed between 1912 and 1916.

They were sometimes treated as the second sub-type of an encompassing "Town Class" which included the five earlier Bristol and four Weymouth class and the following four Birmingham and two Birkenhead class cruisers.

Overview of 6 vessels
Citations for this data available on individual ship pages
Name	Builder	Laid Down	Launched	Completed	Fate
Chatham	Chatham Royal Dockyard	3 Jan, 1911	19 Nov, 1911	Dec, 1912	Sold 13 Jul, 1926
Dublin	William Beardmore & Company	3 Jan, 1911	30 Apr, 1912	11 Mar, 1913	Sold Jul, 1926
Southampton	John Brown & Company	6 Apr, 1911	16 May, 1912	Nov, 1912	Sold
Brisbane	Cockatoo Dockyard	25 Jan, 1913	30 Sep, 1915	Nov, 1916	Sold
Melbourne	Cammell Laird	14 Apr, 1911	30 May, 1912	Jan, 1913	Sold 8 Dec, 1928
Sydney	London & Glasgow	11 Feb, 1911	29 Aug, 1912	Jun, 1913	Broken up Apr, 1929

Binoculars

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

Fore Top

In late 1913, there was some doubt as to whether the sides of the fore top in these ships needed to be raised, and indeed there was some confusion as to how high the sides were in various units. It was mentioned that altering them to a height of 4 feet would allow a seated observer to do his work.

Boats

The ships were ordered in July 1914 to surrender one of their two 30-foot drop-keel gigs. As Chatham had only one, and one 30-foot gig of ordinary type, she was asked to return either one.

Armament

Guns

• eight 6-in B.L. guns on P. VI mountings at the outset of war.

Torpedoes

• Two 21-in submerged broadside tubes forward depressed 2 degrees with the axis of the tube 1 foot 5.25 inches above the deck.

At the Battle of Jutland, Southampton fired a 21-in Mark II** torpedo from her starboard tube; various persons aboard thought a hit was achieved.

In 1917, at least some of these tubes were firing 21-in Mark II***** torpedoes.

Fire Control

Mechanical Aid-to-Spotter

By 1920, these 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, Brisbane had two Range Dial Type Cs, Melbourne had one Range Dial Type B and a Range Dial Type BR. The remaining ships each a Range Dial Type B and a Type C.

Rangefinders

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

Evershed Bearing Indicators

As of 1919, this equipment was unlikely to have been fitted for gun or searchlight control, but it may have been present by 1920 to support the Aids-to-Spotters.

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 ships except Brisbane (owing to her service in the Pacific) were fitted with directors in 1917 and 1918.

In order to speed the delivery if the systems in the Chatham class with their 6-in Mark XI guns, their director cams were identical to those of the 6-in Mark XII guns of the Birmingham class (average dip 53 feet 8 inches), with the difference in muzzle velocity and the actual variation in dip from gun to gun being allowed for in the Dip Strips. Furthermore, the range dials on the director for this class also used newer range data than those on the local gun sights, creating small differences to consider when testing the director for elevation.

The Elevation Receivers on the guns were 6-in P. VIII Type with electrical tilt correctors, Pattern F.C. 6, capable of 15 degrees elevation. The Small Type Training Receivers on all were pattern number 20 on #1, P2, P3, S2 and S3, whereas P4, S4 and #5 had pattern number 21.

Dreyer Table

These ships had no fire control tables.

Fire Control Instruments

For some reason, this class is not listed in Appendix I of Handbook for Fire Control Instruments, 1914, but I would suppose that the next paragraph applies to Chatham as it did to the Weymouth class that preceded it, but that the Mark III supposition is more plausible.

The four ships in this class were likely completed with the latest Vickers F.T.P. Fire Control Instruments Mark III in the manner of the Weymouth as follows:

• Range Transmitters: 2 (P & S)
• Deflection Transmitters: 2 (P & S)
• Range Receivers: 8
• Deflection Receivers: 8
• C.O.S.: none
• Vickers Fire Gongs: 8 with 2 keys

By 1915, a 4-way C.O.S. had been added to permit some freedom in assigning the CL guns to either broadside group:

1. both on port
2. both on starboard
3. fore on port, aft on starboard
4. aft on port, fore on starboard

In addition, navyphones addressing telaupads at the guns supported a finer control by breaking each broadside down into 2 groups, fore and aft. 3-way change-over (fore, after, separate) switches dictated which navyphones addressed which guns. The aft navyphones were in the aft control platform. The fore navyphones could be either in the fore control platform or plugged in in the TS.

The CL guns can be joined to either broadside battery by 2-way switches located in the T.S. and the control platforms (when the control platform switches are used, the T.S. switches are left "off". In the other case, plugs were removed at the control platform switches).

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. Additionally, the "Town" class cruisers were to receive two "Graham type" bearing transmitters in their spotting tops.

Torpedo Control

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 C.T., and that a flexible voice pipe be fitted between these positions. Additionally, those with submerged tubes were to be equipped with gyro angle and order instruments from fore bridge (and after control position, if present) to the tubes. Chatham class already has (or will have) Barr and Stroud for this purpose.

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 (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.