Indefatigable Class Battlecruiser (1909)

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Overview of 3 vessels
Citations for this data available on individual ship pages
Name Builder Laid Down Launched Completed Fate
Indefatigable Devonport Royal Dockyard 23 Feb, 1909 28 Oct, 1909 1911 Sunk 31 May, 1916
New Zealand Fairfield, Govan 20 Jun, 1910 1 Jul, 1911 1912 Sold 19 Dec, 1922
Australia John Brown, Clydebank
(Ship no. 402) 		23 Jun, 1910 25 Oct, 1911 Jun, 1913 Scuttled 12 Apr, 1924

Radio

According to the ambitions of 1909, these ships had Service Gear Mark II wireless upon completion.[1]

Armament

Main Battery

This section is sourced in The Sight Manual, 1916.[2]

The eight 12-in guns were Mark X mounted in B. VIII* turrets. The mountings could elevate 13.5 degrees and depress 5 degrees.[3]

The gun sights were cam-worked sights limited to 15 degrees elevation.

The deflection gearing constant was 67.75, with 1 knot equalling 2.42 arc minutes, calculated as 2700 fps with 4 CRH shells at 5000 yards. Range drums were provided for 2 CRH projectiles at full charge at 2625 fps, reduced charge at 2250 fps, as well as 6-pdr sub-calibre gun and .303-in aiming rifles. By some time in 1916, dials and drums were on hand for 4 CRH heads.

Muzzle velocity was corrected by adjustable scale plate. An adjustable temperature scale plate could vary between 60 to 100 degrees Fahrenheit,[Fact Check] and a "C" corrector could alter the ballistic coefficient by at least +/- 15% and possibly 20% as in other sights.[Fact Check]

Drift was corrected by inclining the sight bracket by 3 degrees with a permanent correction of 2.07 knots left.

The side position sighting lines were 37.25 inches above and 38.25 inches abreast the bore, and the central scopes were 49.25 inches above and 42 inches abreast.

The mountings had free trainers sights, though perhaps only in the centre position.

Secondary Battery

This section is sourced in The Sight Manual, 1916.[4]

Sixteen 4-in B.L. Mark VII guns on P II* mountings were arranged for broadside fire. They were similar to the P. II and P. II* equipment fitted in the Bellerophon class, H.M.S. Neptune and other ships.

The mounting could elevate 15 degrees and depress 7 degrees, but though its sight could match the 15 degree elevation, the range dial was only graduated to 11.5 degrees (10,000 yards).

These cam-worked sights had range dials for 2750 fps, and 1-in and .303-in aiming rifles. MV could be corrected by adjustable pointer through +/- 150 fps.

The range dial may have been 14 inches in diameter with markings that came closer together at higher ranges, as in the P II. If so, the marks were 3⁄4 inch apart for 50 yards difference at 500 yards and was 1⁄8 inch for 50 yards difference at 9,000 yards.

Unlike some P. II* sights such as those on Neptune, these sights were F.T.P. sights.

The deflection gearing constant was 64.277 with 1 knot equal to 2.41 arc minutes, corresponding to 2800 fps at 2000 yards. Drift was corrected by inclining the sight 2 degrees.

The layer's sight line was 14 inches above the bore, and 15.25 inches left. The trainer's sight line was 15.25 inches above and 12.5 inches right.

The sight had a temperature corrector, but not a "C" corrector.

The layer had an open sight. The trainer's sight could be used as a free sight with a counterweight.

Torpedoes

Two 18-in submerged broadside tubes forward, depressed 3 degrees.[5]

In 1913, it was approved, as part of a general reallocation of 18-in torpedoes, to replace the torpedoes on these ships with Mark VII* or Mark VII** torpedoes.[6]

Fire Control

Range Dials

As of 1920, New Zealand had two Range Dial Type Bs and a single Type C. Australia had a single Type B and a single Type C.[7]

Rangefinders

Indefatigable was completed in the same form as the Invincibles with two 9-ft rangefinders, one in each control top. The delay in bringing Australia and New Zealand along permitted them to incorporate a new wrinkle: a third 9-ft rangefinder added atop "A" turret. Indefatigable received her "A" turret rangefinder during a refit between 1911 and 1914.[8]

Rangefinders were added to the echelon turrets by at least 1917 when photos depict them on Australia.[9] Australia had a small one on her after super structure, but Indefatigable did not.[10]

Sometime during or after 1917, an additional 9-foot rangefinder on an open mounting was to be added specifically to augment torpedo control.[11]

Evershed Bearing Indicators

Only Indefatigable is explicitly mentioned in Handbook for Fire Control Instruments, 1914,[12] but the other ships were approved to receive equipment in 1916 (see Alterations, below).

The transmitting positions for Indefatigable were

  • Fore control platform (transmitters to port and starboard with a local switch to select one in use)
  • "A" turret
  • "X" turret
  • Upper aft conning tower

The protocols for how her crew should handle wooding of the turrets was outlined in the Handbook for Fire Control Instruments, 1914.[13]

Mechanical Aid-to-Spotter

At some point, Australia and New Zealand were equipped with a pair of Mechanical Aid-to-Spotter Mark Is, one on each side of the foretop, keyed off the Evershed rack on the director. As the need for such gear was apparently first identified in early 1916, it seems likely that these installations were effected well after Jutland.[14]

Gunnery Control

The control arrangements were likely as follows.[15]

Control Positions

  • Fore top
  • Main top (Australia lacked one)[Inference]
  • "A" turret[Inference]
  • "Y" turret[Inference]

Some ships had C.O.S.s within the control positions so they could be connected to either T.S..[16]

Control Groups

The four 12-in turrets were separate groups, each with a local C.O.S.[Inference] so that it could be connected to

  • Forward T.S.
  • After T.S.
  • Local control from officer's position within turret

Directors

Main Battery

The ships were fitted with a tripod-type director in a light aloft tower on the foremast below their forward control top along with a directing gun in the Y turret.[17][18] The battery was not divisible into for split director firing.[19]

Secondary Battery

The 4-in broadside guns are not listed as ever having had directors installed.[20]

Torpedo Control

Transmitting Stations

Like all large British ships of the era prior to King George V and Queen Mary, these ships had 2 T.S.es.[21]

Dreyer Table

As of 1918, the New Zealand and Australia carried Mark I Dreyer tables[22]. As to time of installation, one secondary source asserts that Indefatigable and New Zealand had Mark I tables at the Battle of Jutland,[23] but no primary source confirms this. Moreover, a first-hand account seems to suggest a manual plotting board was being used in the T.S. of New Zealand.[24]

The ships were never given Dreyer Turret Control Tables.[25]

Fire Control Instruments

The ships used Vickers F.T.P. Mark III range and deflection instruments to send data to gun sights (likely with cross-connected Mark III* range transmitters[26]), retaining Barr and Stroud (probably Mark II*[Inference]) instruments for other destinations.[27]

Target Visible and Gun Ready signals mounted in the TSes and control positions indicated which turrets could see the target and which guns were ready.[28]

Alterations

In 1916, the surviving units New Zealand and Australia were approved to receive Evershed Bearing Indicators for their main battery.[29]

See Also

Footnotes

  1. ↑ Annual Report of the Torpedo School, 1908. Wireless Appendix, p. 13.
  2. ↑ The Sight Manual. 1916. pp. 4, 34, 106, 108-109, Plate 10.
  3. ↑ I assume the B. VIII* elevation is as in the B VIII
  4. ↑ The Sight Manual. 1916. pp. 7, 89-90, 108, Plate 39.
  5. ↑ Addenda (1911) to Torpedo Manual, Vol. III, 1909. p. 155.
  6. ↑ Annual Report of the Torpedo School, 1913. p. 8.
  7. ↑ Manual of Gunnery (Volume III) for His Majesty's Fleet, 1920. p. 44.
  8. ↑ Roberts. Battlecruisers. pp. 90-91.
  9. ↑ Roberts. Battlecruisers. Photo page 30.
  10. ↑ Burt. British Battleships of World War One. p. 98.
  11. ↑ Annual Report of the Torpedo School, 1917. p. 198. (C.I.O. 481/17).
  12. ↑ Handbook for Fire Control Instruments, 1914. pp. 33-9.
  13. ↑ Handbook for Fire Control Instruments, 1914. p. 36.
  14. ↑ The Technical History and Index, Vol. 3, Part 23. pp. 25-6.
  15. ↑ Handbook for Fire Control Instruments, 1914. pp. 7-8. (some inferences drawn due to fundamental differences between this design and that of Orion to which it is likened).
  16. ↑ Handbook for Fire Control Instruments, 1914. p. 7.
  17. ↑ The Director Firing Handbook. pp. 88, 142.
  18. ↑ Burt. British Battleships of World War One. p. 98.
  19. ↑ The Director Firing Handbook. p. 88.
  20. ↑ The Director Firing Handbook. pp. 143.
  21. ↑ Handbook for Fire Control Instruments, 1914. pp. 6-7.
  22. ↑ Handbook of Captain F. C. Dreyer's Fire Control Tables, 1918. p. 3.
  23. ↑ Sumida, Jon. In Defence of Naval Supremacy p. 300.
  24. ↑ Midshipman Gordon Eady quoted in Steel & Hart. Jutland 1916, p. 75.
  25. ↑ Handbook of Captain F. C. Dreyer's Fire Control Tables, 1918. p. 3.
  26. ↑ Annual Report of the Torpedo School, 1910. p. 148.
  27. ↑ Handbook for Fire Control Instruments, 1914. pp. 72.
  28. ↑ Handbook for Fire Control Instruments, 1914. p. 11.
  29. ↑ Annual Report of the Torpedo School, 1916. p. 145.

Bibliography

  • 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, 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 (1918). Handbook of Captain F. C. Dreyer's Fire Control Tables, 1918. C.B. 1456. Copy No. 10 at Admiralty Library, Portsmouth, United Kingdom.
  • Sumida, Jon Tetsuro (1989). In Defence of Naval Supremacy: Finance, Technology and British Naval Policy, 1889-1914. Winchester, Mass.: Unwin Hyman, Inc.. ISBN 0044451040. (on Amazon.com and Amazon.co.uk).
  • Brooks, John (2005). Dreadnought Gunnery and the Battle of Jutland: The Question of Fire Control. Oxon: Routledge. ISBN 0714657026. (on Amazon.com and Amazon.co.uk).
  • Roberts, John (1997). Battlecruisers. London: Chatham Publishing. ISBN 186176006X. Annapolis: Naval Institute Press. ISBN 1557500681. (on Amazon.com and Amazon.co.uk).
  • Steel, Nigel; Hart, Peter (2003). Jutland 1916: Death in the Grey Wastes. London: Cassell. ISBN 0304358924. (on Amazon.com and Amazon.co.uk).


Indefatigable Class Battlecruiser
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