Difference between revisions of "Laforey Class Destroyer (1913)"

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[[File:ARTS1913Plate16.jpg|thumb|512px|'''Firing Mechanism'''{{ARTS1913|Plate16}}<br>Training Brake ball on right, Firing Ball on left with safety pin "D"<br>Safe arc interlock illustrated on right side<br>Modified design fitted to aft mounting in {{UK-Laurel}}]]
 
[[File:ARTS1913Plate16.jpg|thumb|512px|'''Firing Mechanism'''{{ARTS1913|Plate16}}<br>Training Brake ball on right, Firing Ball on left with safety pin "D"<br>Safe arc interlock illustrated on right side<br>Modified design fitted to aft mounting in {{UK-Laurel}}]]
  
* two 21-in D.R. Mark I Tubes on the centreline (2x2) w/ 50&deg; (later reduced to 20&deg;) arcs centered on the beam.{{March|Plate 17/A}}{{ARTS1913|p. 36}}
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* two [[21-in D.R. Torpedo Tube (UK)|21-in D.R. Mark I torpedo tubes]] on the centreline (2x2) w/ 50&deg; (perhaps later reduced to 20&deg;) arcs centered on the beam.{{March|Plate 17/A}}{{ARTS1913|p. 36}}
  
 
These ships were the first British destroyers to have D.R. (Double Revolving) tubes, a doubling of previous torpedo armament standards.  The [["W" Class Destroyer (1917)|"W" class]] was to debut the triple mounting in 1917.{{March|p. 513}}
 
These ships were the first British destroyers to have D.R. (Double Revolving) tubes, a doubling of previous torpedo armament standards.  The [["W" Class Destroyer (1917)|"W" class]] was to debut the triple mounting in 1917.{{March|p. 513}}
  
The Mark I D.R. mounting was designed to be trained by two men standing on the platforms marked "H" in the first image, each working a large cross-crank to effect the worm-screw engaging the circular training rackThe Mark I mounting had just a single trigger for both tubes.  This deficiency was worked around by keeping the safety pin for one tube in place when firing a single torpedo.
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In 1914 firing trials in {{UK-Liberty}}, it was found that the torpedoes from the aft torpedo mount struck the ship's deck when fired on extreme bearings. While investigations were undertaken, the expedient precaution was taken of restricting fire to 10 degrees to either side of the beamAfter fitting plugs of some kind it was eventually determined that the full 50 degree arc could be used and the torpedo would always clear the gunwale by 19 inches.{{ARTS1914|pp. 39-40.  (T.O. No. 61 of July 1914.  G. 16299/14)}}
  
The two tubes, being offset to either side of the axis of training, required the mounting to be fixed in train before firing to avoid stress and yaw errors upon firing.  Despite this, it was also desireable for destroyers to be able to fire their torpedoes at any moment.  The solution to these offsetting needs was accomplished in the Mark I by a cleverly designed firing system:  the hand trigger would cause two braking balls (actually weighted cylinders, it appears) to drop; their fall would lock the mount in train and precipitate the release of firing balls whose fall would fire the unsafed tube.  Safety gear prevented the firing balls from falling when the tube was on an unsafe bearing, the safe angles being indicated by a cutaway in a ring at the base of the central spindle.  While this solved the larger problem, it resulted in slow firing action which aroused complaint.  As a proper fix for the slow firing was sought, {{UK-Laurel}}'s aft mount had a trial modification applied which caused the braking and firing balls to fall simultaneously, as illustrated in Plate 16 above.  This variant also gave two triggers, either of which dropped both braking balls but only one firing ball.
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The new double tubes were found satisfactory in the end, though they were slow to train and the slow response to the firing lever would make firing under helm worrisome.  {{UK-Laurel}}'s tubes were initially found to require four men working the training wheel and four more pushing the ends of the tubes around.  {{UK-Lysander}} reported better, if still abysmal results: two men could barely train the tubes when the tubes were loaded.{{March|pp. 138-9}}  Testing revealed that the design was sensitive to alignment during erection, and alterations improved things to a point that a training speed of 8&deg; per second was achievable with two men.  The firing timing in ''Laurel'' was measured as:{{ARTS1913|p. 37.  This source described the D.R. mountings as being based on the Mark II, which I feel is a likely error}}
 
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The earliest-built Mark I tubes had their firing cartridge pocket on their back door, and this was found to make them prone to damage while training the tubes.  Later articles had these placed on the side of the tubes at the back, a change that also produced a better ejection pressure of 49 rather than 29 psi on average using the standard 10oz service cartridge, though no one could account for the difference in performance.  The central spindle also contained concentric steam pipes to feed warming coils to keep the mount ready in freezing weather.  The weight of the trainable tubes was borne by eight rollers on the roller path.{{ARTS1913|pp. 36, 37, 38}}
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In 1914 firing trials in {{UK-Liberty}}, it was found that the torpedoes from the aft torpedo mount struck the ship's deck when fired on extreme bearings. While investigations were undertaken, the expedient precaution was taken of restricting fire to 10 degrees to either side of the beam.  By fitting plugs of some kind, it was eventually determined that the full 50 degree arc could be used and the torpedo would always clear the gunwale by 19 inches.{{ARTS1914|pp. 39-40.  (T.O. No. 61 of July 1914.  G. 16299/14)}}
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The new double tubes were found satisfactory in the end, though were slow to train and the slow action of the firing lever would make firing when under helm worrisome.  {{UK-Laurel}}'s tubes were found to require four men working the training wheel and four more pushing the ends of the tubes around.  {{UK-Lysander}} reported better, if still abysmal results: two men could barely train the tubes when the tubes were loaded.{{March|pp. 138-9}}  Testing revealed that the design was sensitive to alignment during erection, and alterations improved things to a point that a training speed of 8&deg; per second was achievable with two men.  The firing timing in ''Laurel'' was measured as:{{ARTS1913|p. 37.  This source described the D.R. mountings as being based on the Mark II, which I feel is a likely error}}
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Revision as of 15:09, 12 July 2019

Twenty-two destroyers of the Laforey Class were completed, twenty as part of the 1912-1913 Programme, and two as part of the 1914 War Emergency Programme.

They were the first Royal Navy destroyers to ship twin torpedo tubes, effectively doubling their outfit.

Electric Logs

In March, 1914, it was ordered that these ships were to receive two Trident Electric Logs and one Charthouse Receiver during the 1914-15 financial year.[1]

Performance

The ships averaged a little over 30 knots on their 8 hour trials, with a few units making only a little over 29.5 knots.[2]

Anti-rolling tanks were tried in at least some of the ships. Turning circles had the same perplexing variety as seen in other classes. At 35 degrees helm, Laurel averaged 535 yards, whereas Liberty reported 953 yards. and Landrail 1127 yards. Leonidas required a full 1405 yards! Yarrow-built specimens and Lydiard were most fuel economical, using 17.5 tons less fuel on 8 hour full power trials. Landrail burnt 33.01 tons and Laurel 51.33 tons in a 24 hour test.[3]

The ships had recurrent problems with their dynamos. By October 1914, the issue was proving so serious that a reversion to reciprocating engines from the turbo generators was requested. The generators ran so hot that the hatches to the compartment were often left open, admitting spray which caused stoppages.[4]

In May 1915, Lark's commander said the ship was very unreliable in steering at speeds over 20 knots, that helm less than 15 degrees did little, and that 20-25 degrees did more than 35 degrees did. At the Battle of Dogger Bank, the ship proved utterly unresponsive five times to full helm despite the gentle sea conditions, prompting him to state, "I consider H.M.S. Lark to be dangerous at high speed..." He recommended that the ship either lead its division or be tail-end charlie to reduce the peril. Lark was moved to the last position in her division and a comparative turning trial with Miranda confirmed the dismal turning performance. Sister ships with the same rudder, propellors and design did not seem to experience the same issues.[5]

Armament

4-in Guns

  • Three 4-in Q.F. Mark IV guns on P. IX mountings on the centre line.

These quick-firing guns had also been fitted to the last seven of the previous Acasta class, but their use here reflected their standardisation over the earlier B.L. models.[6] There were 120 rounds per gun.

The mounting could elevate 20 degrees and depress 10 degrees, but its sight could only elevate 15 degrees and the range dial was actually only graduated to 12.5 degrees (7,900 yards). "This was soon remedied by the supply of additional sight strips graduated to the extreme range of 10,200 yards."[7]

These gear-worked sights had gearing constants of 26.66 and range dials for 2200 fps, and 1-in aiming rifle. M.V. could be corrected by a cam pointer allowing for a decrease to 2000 fps.

Unlike some P. IX sights, these were not F.T.P. sights.

The midship gun was supplied with ammunition from the forward stores.[8]

The deflection gearing constant was 52.6 with 1 knot equal to 3.18 arc minutes, corresponding to 2200 fps at 2000 yards. Drift was corrected by inclining the sight about pivot pins 2 degrees.

The layer's telescope sight line was 12.5 inches above the bore, and 21.45 inches left. The trainer's telescope sight line was 12.5 inches above and 17.4 inches right. Open sights were 13.3 inches above the bore and 24.35 inches left for layer and 20.3 inches right for trainer.

The sight had a temperature correcting scale plate and a "C" corrector.

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

During the war, some of the ships were required to land their aft gun to accommodate depth charges.[9]

As the midship 4-in mounting could train in a full circle and thus might break the electrical firing circuit wires, in June 1914 it was ordered that the pedestal to these guns have a warning plate fitted to them reading, "See circuits clear when training across limit stops."[10]

In late September, 1914, the Admiralty ordered that the guns on the Tribals and later classes were to be given loading lights, initially on temporary circuits.[11]

Other Guns

Originally, the ships may have been provided a single .303-in Maxim machine gun on a portable mounting.[12]

By 1920, some or all had one 2-pdr pom-pom for air defence.[13]

Torpedoes

21-in D.R. [Double Revolving] Torpedo Mounting Mark II[14]
The "L" Class's Mark I mounting had just a single trigger
The guard rails on the training platforms were not installed in destroyers
Firing Mechanism[15]
Training Brake ball on right, Firing Ball on left with safety pin "D"
Safe arc interlock illustrated on right side
Modified design fitted to aft mounting in Laurel

These ships were the first British destroyers to have D.R. (Double Revolving) tubes, a doubling of previous torpedo armament standards. The "W" class was to debut the triple mounting in 1917.[18]

In 1914 firing trials in Liberty, it was found that the torpedoes from the aft torpedo mount struck the ship's deck when fired on extreme bearings. While investigations were undertaken, the expedient precaution was taken of restricting fire to 10 degrees to either side of the beam. After fitting plugs of some kind it was eventually determined that the full 50 degree arc could be used and the torpedo would always clear the gunwale by 19 inches.[19]

The new double tubes were found satisfactory in the end, though they were slow to train and the slow response to the firing lever would make firing under helm worrisome. Laurel's tubes were initially found to require four men working the training wheel and four more pushing the ends of the tubes around. Lysander reported better, if still abysmal results: two men could barely train the tubes when the tubes were loaded.[20] Testing revealed that the design was sensitive to alignment during erection, and alterations improved things to a point that a training speed of 8° per second was achievable with two men. The firing timing in Laurel was measured as:[21]

Mounting Timing in Seconds (after trigger press)
Striker fell Torpedo Moves Air Lever hit
by Tripper
Gyro released
stock Mark I mounting 0.497 0.62 0.747 1.077
modified Mark I mounting 0.283 0.35 0.431 0.761
earlier, single tubes N/A 0.144 0.474

Other Weapons

The ships were able to accomodate four Vickers Elia Mark IV mines and had a hatch and derrick to support their laying and handling. The mines had 220 pounds TNT and weighed about one half ton.[22]

The "H" type mine replaced the Mark IV in 1917, but only Lawford and Legion may have been switched over to the new munition, presumably removing minelaying from the job description for the other ships.[23]

Depth charges were added to most of these destroyers during the war, requiring some of this class to surrender their aft gun.[24]

Fire Control

By 1915, at least, these ships also had fixed voice pipes installed between decks with the last lengths being flexible (one voice pipe for gunnery, one for torpedoes) fitted between bridge and guns, torpedo tubes, and searchlights. A third voicepipe, entirely flexible, ran from bridge to the forward gun.[25]

Range and Order Instruments[26]
Applicable to Lassoo and Lochinvar only.

Being completed later than their sisters, Lassoo and Lochinvar had or were to be provided the same range and order data system being given the "M" class.[27] The scheme placed the combined transmitter on the forebridge, and a combined receiver near the sightsetter position of each gun. Ranges from 0 to 9900 yards in increments of 100 yards, and orders were "Independent", "Control" and "Fire" with illuminated indicators and a red indicator on the receivers to signal loss of power from the battery pack located below decks.

By 1920, the ships in Acorn to Laforey classes had Wise Pressure Telegraphy Systems in place to support fire control.[28]

Rangefinders

A 1-m base rangefinder was supplied to all destroyers of the "Tribal" class through "L" class around 1916, but this was later withdrawn.[29]

Directors

The first installations of the British Destroyer Director Firing System were being effected in this class in May 1918.[30]

Torpedo Control

Fire Gong and Lamp Reply Circuits, 1917[31]

A single sighting position was located high up in the centre of the bridge, thus requiring only a single set of firing pushes or keys as well as keys for operating a buzzer at the forward torpedo mount and a rattler at the aft mount.[32]

The "L" class differed from most of their contemporaries by using primarily non-electrical instruments for orders and deflection: Wise Type C for both purposes except in Loyal, Lance and Laertes which had Chadburn's Torpedo Order Telegraph and Wise Pressure Telegraphy System Type B for deflection. Electrical lamps worked off a battery provided the reply function the mechanical and pressure systems lacked. [33]

Alterations

By November 1918, Legion was fitted to carry 38 mines, as she was operating with the Twentieth Destroyer Flotilla which was uniformly capable in this regard. The torpedo tubes and guns removed when the mines were shipped could be placed back aboard with enough notice.[34]

See Also

Footnotes

  1. Admiralty Weekly Order No. 967 of 27 Mar, 1914.
  2. March. British Destroyers. p. 134.
  3. March. British Destroyers. pp. 139-140.
  4. March. British Destroyers. p. 141.
  5. March. British Destroyers. p. 142.
  6. The Technical History and Index, Vol. 4, Part 34. p. 11.
  7. The Technical History and Index, Vol. 4, Part 34. p. 13.
  8. March. British Destroyers. Plate 17/A.
  9. The Technical History and Index, Vol. 4, Part 34. p. 14.
  10. Admiralty Weekly Order No. 76 of 3 July 1914.
  11. Admiralty Weekly Order No. 416 of 29 Sep, 1914.
  12. March. British Destroyers. p. 133.
  13. The Technical History and Index, Vol. 4, Part 34. p. 16.
  14. Annual Report of the Torpedo School, 1913. Plate15.
  15. Annual Report of the Torpedo School, 1913. Plate16.
  16. March. British Destroyers. Plate 17/A.
  17. Annual Report of the Torpedo School, 1913. p. 36.
  18. March. British Destroyers. p. 513.
  19. Annual Report of the Torpedo School, 1914. pp. 39-40. (T.O. No. 61 of July 1914. G. 16299/14).
  20. March. British Destroyers. pp. 138-9.
  21. Annual Report of the Torpedo School, 1913. p. 37. This source described the D.R. mountings as being based on the Mark II, which I feel is a likely error.
  22. March. British Destroyers. p. 142.
  23. Conway's All the World's Fighting Ships 1906–1921. p. 76.
  24. The Technical History and Index, Vol. 4, Part 34. p. 14.
  25. Manual of Gunnery, Vol. III., 1915., p. 150.
  26. Admiralty.  Handbook of Fire Control in Torpedo Boat Destroyers of "M" Class and Later and Flotilla Leaders, 1915, Plate XVI.
  27. Admiralty. Handbook of Fire Control in Torpedo Boat Destroyers of "M" Class and Later, and Flotilla Leaders, 1915, Plate XVI.
  28. Technical History and Index Vol. 4, Part 34, pp. 15-16.
  29. The Technical History and Index, Vol. 3, Part 23. pp. 31, 32.
  30. The Technical History and Index, Vol. 3, Part 23. p. 12.
  31. Annual Report of the Torpedo School, 1917. Plate 85.
  32. Annual Report of the Torpedo School, 1917. p. 211.
  33. Annual Report of the Torpedo School, 1917. p. 211.
  34. Admiralty. Annual Report of the Torpedo School Mining Appendix, 1917-1918, p. 11. Plate 7.

Bibliography


Laforey Class Destroyer
Admiralty Design
Llewellyn Lennox Loyal Legion Laforey
Lawford Louis Lydiard Laertes Lysander
  Lance Lookout  
White 2-Funnelled Type
  Laurel Liberty  
Yarrow 2-Funnelled Type
  Lark Landrail Laverock Linnet  
War Emergency Repeat "L" Class
  Lochinvar Lassoo Leonidas Lucifer  
<– Acasta Class Destroyers (UK) "M" Class –>