18-in Mark VIII Torpedo (UK)

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The 18-in R.N.T.F. Mark VIII Torpedo was a British torpedo developed at the Royal Navy Torpedo Factory in 1912, specifically designed for use in submarines.[1]

Development and History

To make a torpedo for submarines, the design called for a "very heavy explosive charge", obtained at the expense of range. Two were built for trial in 1913.[2]

The test torpedoes' warheads were 320 pounds of T.N.T., allowing operation at stamped speeds of 41 knots to 1,500 yards and 29 knots to 3,500 yards when charged to 1,600 psi. They had Service depth gear with double hydrostatic valves and an engine like the Mark VII's, but with lightened pistons and connecting rods.[3]

In 1917, t was decided that the VIII and VIII* torpedoes were to re-ranged to deliver 2,500 yards at 35 knots and 4,000 yards at 29 knots.[4]


Mark VIII G.S.

Described in 1914.[5]

Mark VIII*

Introduced in 1915, and rolled out in two small increments of modest improvements beyond the Mark VIII's core design.[6]

Commencing with those torpedoes R.N.T.F. No. 312 and W. & Co. No. 501, four small improvements were provided while maintaining warhead compatiblity with the Mark VIII torpedoes. Then, from R.N.T.F. No. 323 and W. & Co. No. 623, three additional features were provided, most notably improved Guide Strips able to take greater stress.


  1. Annual Report of the Torpedo School, 1912. p. 11.
  2. Annual Report of the Torpedo School, 1913. p. iv.
  3. Annual Report of the Torpedo School, 1913. p. 11.
  4. Annual Report of the Torpedo School, 1917. p. 25.
  5. Annual Report of the Torpedo School, 1914. pp. 9-10.
  6. Annual Report of the Torpedo School, 1915. p. 37.


See Also