21-in Mark II Torpedo (UK)

R.G.F. Torpedoes Mark I and II, 1909

The 21-in R.G.F. Mark II Torpedo was a British torpedo developed at the Royal Gun Factory and first ordered for service in 1909-1910.^{[Citation needed]}

Development and History

It was developed in parallel with the Mark I torpedo, which was shorter at 18.5 feet.

Mark II

In 1909-1910, 4 hook bracket torpedoes were ordered.^{[Citation needed]}

In May, 1918, the torpedo and its Mark II* variant were noted as having the following settings at a charge of 2350 pounds per square inch, though each torpedo would have either the 35 or 44.5 knot setting, but not both:

• 44.5 knots to 4200 yards (High Speed)
• 35 knots to 6000 yards (High Speed)
• 23 knots to 14,000 yards (Medium Speed)
• 18 knots to 17,000 yards (E.R.)

The 2350 psi pressure was the "action" pressure; normal was 2200. Ranges were 300 yards less at 44.5 knots and 1,000 yards less at lower speeds at the normal pressure.

Mark II*

Introduced in 1914, these featured rectified threads throughout, air vessel pressures of 2,350 psi for 10,750 yard range and two other improvements.

Mark II**

Introduced in 1914, these included the improvements of the II** and added three other small features.

Mark II***

In 1915, Commander-in-Chief Home Fleet wanted a proportion of torpedoes able to reach the greatest possible range. By year's end, trials of a torpedo with a projected range of 18,000 yards at 19-20 knots were anticipated.