Invincible Class Battlecruiser (1907)

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The three Invincible class battlecruisers were the first ships of their type.

Name Builder Laid Down Launched Commissioned Pendant Numbers Fate
1914 January, 1918 April, 1918
Indomitable Fairfield's 16 March, 1907 77 74 05 Sold, 1 Dec., 1921
Inflexible John Brown 26 June, 1907 83 75 47 Sold, 1 Dec., 1921
Invincible Armstrong's 13 April, 1907 85 Sunk, 31 May, 1916

Construction

The outline design based on Design "E" was approved by the Board of Admiralty on 16 March, 1905. The sheer, midship section, armour and rig drawings were approved on 22 June.[1] Uniquely, the vessels of the Invincible class were not put out for competitive tender and in late 1905 Armstrong's, Fairfield and John Brown were invited to construct the class. The Admiralty's reasoning was to prevent the closure of large private yards and thus lose Britain her competitive edge in shipbuilding.[2]

Armament

Main Battery

This section is sourced in The Sight Manual, 1916.[3]

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

The gun sights were gear-worked sights with telescopes (not periscopes) with a range gearing constant of 48 and limited to 15 degrees elevation, but 6 degree super-elevation prisms would have been provided by 1916.

The deflection gearing constant was 70, with 1 knot equalling 2.53 arc minutes, calculated as 2700 fps 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 pointer between +/- 75 fps. The 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]

Deflection was corrected by inclining the sight bracket by 2 degrees.

The side position sighting lines were 36 inches above and 41.25 inches abreast the bore, and the central scopes were 37.5 inches above and 42 inches abreast.

Secondary Battery

Torpedoes

In 1913, it was approved, as part of a general reallocation of 18-in torpedoes, to replace the torpedoes on Invincible class and Warrior class except Cochrane with Mark VI** H. or Mark VI** H. torpedoes.[4]

Fire Control

Rangefinders

The ships were completed with two 9-ft rangefinders, one in each control top. Between 1911 and 1914, a third 9-ft rangefinder was added to "A" turret, based upon their successful incorporation in later units of the Indefatigable class.[5]

Additional turret-top rangefinders were added as time went on. Inflexible had them at least from 1917 atop "P" and "Q" turrets.[6]

Sometime during or after 1917, an additional 9-foot rangefinder on an open mounting was to be added specifically to augment torpedo control.[7]

Evershed Bearing Indicators

All units were likely fitted with this equipment by late 1914.[8]

The transmitting positions 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.[9]

Mechanical Aid-to-Spotter

At some point, Indomitable and Inflexible 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.[10]

Gunnery Control

The control arrangements were likely as follows.[11]

Control Positions

The ships featured control positions in:[12]

  • Fore top, this being the preferred one
  • Main top
  • "A" turret
  • "X" turret[Inference]

Some ships had changeover switches within the control positions so they could be connected to either T.S.[13]

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 TS
  • After TS
  • 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 along with a directing gun (in Y turret?).[14] The battery was not divisible into groups for split director firing.[15]

Secondary Battery

The 4-in broadside guns are not listed as ever having had directors installed.[16]

Torpedo Control

Torpedo Control Systems
As shown in Annual Report of the Torpedo School, 1913.

A description of the torpedo control system for this class is found in the Annual Report of the Torpedo School, 1913. It features descriptions of adapted forms of existing Barr and Stroud instruments for torpedo order and the setting of gyro angles.

Transmitting Stations

Like all large British ships of the era prior to King George V and Queen Mary, these ships had two T.S.es.[17]

Dreyer Table

As of 1918, Inflexible still carried the Mark I Dreyer Table she'd been outfitted with.[18] Invincible was lost with her Mark I table at the Battle of Jutland. It appears likely that Indomitable never was fitted with a Dreyer table.[19]

The ships were never given Dreyer Turret Control Tables.[20]

Fire Control Instruments

By 1909, these ships were equipped with Barr and Stroud Mark II equipment for range, orders and deflection.[21]

The Handbook for Fire Control Instruments, 1909 lists the Barr and Stroud Mark II equipment on this class as:[22]

  • Combined Range, Order, Deflection: 8 transmitters, 30 receivers
  • Group Switches: 4
  • Rate: 4 transmitters, 16 receivers
  • Bearing: none
  • Range: none

Additionally, in 1909 this class had the following Graham fire control equipment:[23]

  • Turret fire gongs: 8 with 8 keys
  • Fire Gongs: none
  • Captain's Cease Fire Bells: 10 with 1 key

But by the Battle of the Falklands, Inflexible's gunnery officer reported that she had Siemens fire gongs in place and "an electrical [time-of-flight instrument] which operate[d] a rattler in the control position."[24]

The ships had Target Visible and Gun Ready signals, indicating which turrets could see the target and which guns were ready in the TSes and control positions.[25]

In 1911, it was decided that the three ships should be fitted with "range, buzzer and bearing instruments for communication between control positions, control turrets and transmitting and plotting stations."[26]

In 1916, it was approved that the Inflexible and Indomitable, should have fire control instruments fitted for their 4-in armament. Apparently they had not had range and deflection before, but it is not clear what else might be entailed.[27]

See Also

Footnotes

  1. Roberts. Battlecruisers. p. 25.
  2. Lambert. Sir John Fisher's Naval Revolution. pp. 147-148.
  3. The Sight Manual, 1916, pp. 4, 40, 106, 108-109, Plates 14-15.
  4. Annual Report of the Torpedo School, 1913, p. 8.
  5. Roberts. Battlecruisers, pp. 90-91.
  6. Roberts. Photo page 82.
  7. Annual Report of the Torpedo School, 1917, p. 198. (C.I.O. 481/17)
  8. Handbook for Fire Control Instruments, 1914. p. 34.
  9. Handbook for Fire Control Instruments, 1914. p. 34.
  10. The Technical History and Index: Fire Control in HM Ships, 1919. pp. 25-26.
  11. 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).
  12. Roberts. Battlecruisers, pp. 90-91.
  13. Handbook for Fire Control Instruments, 1914. p. 7.
  14. The Director Firing Handbook, 1917. pp. 88, 142.
  15. The Director Firing Handbook, 1917. p. 88.
  16. The Director Firing Handbook, 1917. pp. 143.
  17. Handbook for Fire Control Instruments, 1914. pp. 6-7.
  18. Handbook of Capt. F.C. Dreyer's Fire Control Tables. p. 3.
  19. absent from list in Handbook of Capt. F.C. Dreyer's Fire Control Tables. p. 3.
  20. Handbook of Capt. F.C. Dreyer's Fire Control Tables. p. 3.
  21. Handbook for Fire Control Instruments, 1909. p. 56.
  22. Handbook for Fire Control Instruments, 1909. p. 58.
  23. Handbook for Fire Control Instruments, 1909. p. 58.
  24. Verner. The Battle Cruisers at the Action of the Falkland Islands. pp. 20-23.
  25. Handbook for Fire Control Instruments, 1914. p. 11.
  26. Annual Report of the Torpedo School, 1911. p. 95.
  27. Annual Report of the Torpedo School, 1916, p. 145. Invincible was lost by the time of this mandate.

Bibliography

Primary Sources

Template:Invincible Class (1907)

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