21-in Weymouth Mark II Torpedo

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The 21-in Weymouth Mark II Torpedo was a heater torpedo built by Whitehead. The company loaned a single experimental torpedo to the Royal Navy in 1913.[1]

Development and History

At the start of the war, all 21-in Weymouth torpedoes in England were purchased. Among these were twenty-four 21-in Weymouth Mark IIs intended for Japan. These were given to foreign-ordered vessels whose tubes could accommodate them.

Mark II

These originally had settings for:[2]

  • 40 knots to 2,000m
  • 38 knots to 3,500m
  • 30 knots to 7,000m
  • 25 knots to 10,000m

They had 4 cylinder standard Weymouth design engines. Counter gear was Fiume type, graduated in metres. Gyros were air driven, and non-angled, but could be interchanged with Service type. Ulan type depth gear. Tail similar to Service type.

The Royal Navy found that only the 25 knot setting provided stable depth-keeping in top bracket torpedoes, and that S.L. torpedoes could retain the 38 knot and 25 knot setting.

Mark II*

Six of the 24 torpedoes bought up at the outbreak of war were given to Broke with slight modifications, differing from Mark II as follows.[3]

Extreme range of 12,000 metres (at unstated speed) and settings for:

  • 38 knots to 3,500 metres
  • 25 knots to 10,000 metres

The warhead was 330 pounds of T.N.T.. The gyros were replaced with Service (standard Weymouth) type.

A.V. pressure of 2,200 psi in 21.7 cubic inches, holding 249 pounds when fully charged.

These had an overall length of 262.71 inches without a pistol (which would add 4.5 or 5 more inches), a total weight of 2,908 +/- 10 pounds, all on, and double valve Mark I* type depth gear.[4]

The passing tests for Broke included three runs to 3,000 yards at 37.5-38.5 knots, retaining 800 psi of air, and others. These torpedoes required side lugs to work with Broke's Service single revolving tubes.[5]

Mark II 6.5m

Eighteen of 24 torpedoes were given to Erin (10), and Agincourt (8), but their Elswick type submerged tubes required the torpedoes to be shortened to 6.5m from 6.8m by removing a section at the rear of the head. These were like the Mark II except as follows.

They had more settings to an extreme range of 12,000m:[6]

  • 41 knots to 1,000 metres
  • 41 knots to 2,000 metres [sic]
  • 38 knots to 3,500 metres
  • 29 knots to 7,000 metres
  • 25 knots to 10,000 metres

It appears, however, that their depth-keeping was absolutely unreliable on anything but the 25 knot setting when using Ulan gear.[7]

The warhead was lighter than the unmodified Mark II's: 245 pounds of T.N.T..

These had an overall length of 255.72 inches with 5 inch Weymouth pistol, a total weight of 2,794 +/- 8 pounds, all on, and Ulan type depth gear.

Footnotes

  1. ↑ Annual Report of the Torpedo School, 1913. p. 8.
  2. ↑ Annual Report of the Torpedo School, 1914. p. 12.
  3. ↑ Annual Report of the Torpedo School, 1914. pp. 11-12.
  4. ↑ Annual Report of the Torpedo School, 1914. p. 11.
  5. ↑ Annual Report of the Torpedo School, 1914. p. 11.
  6. ↑ Annual Report of the Torpedo School, 1914. pp. 10-12.
  7. ↑ Annual Report of the Torpedo School, 1914. p. 14.

Bibliography

See Also

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