View source for 21-in Mark II Torpedo (UK)

[[File:ARTS1909Plate1.jpg|thumb|600px|'''R.G.F. Torpedoes Mark I and II, 1909'''{{ARTS1909|Plate 1}}]]
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.{{CN}}

==Development and History==
It was developed in parallel with the [[21-in Mark I Torpedo (UK)|Mark I torpedo]], which was shorter at 18.5 feet.

===Mark II===
In 1909-1910, 4 hook bracket torpedoes were ordered.{{CN}}

By the end of 1917, these torpedoes had all been converted to E.R. 3 design.{{ARTS1917|p. 27}}

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:{{GFGTO|p. 16}}
* 44.5 knots to 4,200 yards (High Speed)
* 35 knots to 6,000 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.

In December, 1918, the performance and settings were unchanged.{{GFGTO|p. 16}}

In mid-1920, it was ordered that Mark II and II* H.B. and S.L. torpedoes should be withdrawn from all ships and used as reserves and for special practices.{{ARTS1920|p. 6. (G. 10141/20-6.8.1920)}}

Early in 1923, all Mark II-II**** torpedoes had their low speed performance downgraded to 23 knots to 13,000 yards &ndash; 1,000 yards less than previously.  This required issuance of a new deflection disc for [[Torpedo Control Disc Mark III*]] numbered T. 226A to all ships carrying these weapons, meaning ships of the [[Iron Duke Class Battleship (1912)|''Iron Duke'']] and [[King George V Class Battleship (1911)|''King George V'']] classes, as well as {{UK-Thunderer|f=p}}.{{ARTS1913|p. 126}}

===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.{{ARTS1914|p. 9}}

By the end of 1917, these torpedoes had all been converted to E.R. 3 design.{{ARTS1917|p. 27}}

In May, 1918, the torpedo and its Mark II ancestor 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:{{GFGTO|p. 16}}
* 44.5 knots to 4,200 yards (High Speed)
* 35 knots to 6,000 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.

In December, 1918, the performance and settings were unchanged.{{GFGTO|p. 16}}

In mid-1920, it was ordered that Mark II and II* H.B. and S.L. torpedoes should be withdrawn from all ships and used as reserves and for special practices.{{ARTS1920|p. 6. (G. 10141/20-6.8.1920)}}

Early in 1923, all Mark II-II**** torpedoes had their low speed performance downgraded to 23 knots to 13,000 yards &ndash; 1,000 yards less than previously.  This required issuance of a new deflection disc for [[Torpedo Control Disc Mark III*]] numbered T. 226A to all ships carrying these weapons, meaning ships of the [[Iron Duke Class Battleship (1912)|''Iron Duke'']] and [[King George V Class Battleship (1911)|''King George V'']] classes, as well as {{UK-Thunderer|f=p}}.{{ARTS1913|p. 126}}

===Mark II**===
Introduced in 1914, these included the improvements of the II** and added three other small features.{{ARTS1914|p. 9}}

By the end of 1917, these torpedoes had all been converted to E.R. 3 design.{{ARTS1917|p. 27}}

In May, 1918, the Mark II**-II*** torpedoes were noted as having the following settings at a charge of 2500 pounds per square inch, though each torpedo would have either the 35 or 44.5 knot setting, but not both:{{GFGTO|p. 16}}
* 44.5 knots to 4,500 yards (High Speed)
* 35 knots to 6,000 yards (High Speed)
* 23 knots to 15,000 yards (Medium Speed)
* 18 knots to 18,000 yards (E.R.)

The 2500 psi pressure was the "action" pressure; normal was 2350.  Ranges were 300 yards less at 44.5 knots and 1,000 yards less at lower speeds at the normal pressure.

In December, 1918, the performance and settings were unchanged.{{GFGTO|p. 16}}

In mid-1920, it was ordered that Mark II** to Mark II***** H.B. torpedoes should be allocated to capital ships and light cruisers presently armed with Mark II to Mark II***** torpedoes, enriching the full commission ships with the latest Marks.  The Mark II** to Mark II*** S.L. torpedoes would go to leaders and destroyers of local defence flotillas and in reserve except "S", "V" and "W" class destroyers, which would all get [[21-in Mark IV* Torpedo (UK)|Mark IV* torpedoes]].{{ARTS1920|p. 6. (G. 10141/20-6.8.1920)}}

===Mark II***===
By the end of 1917, these torpedoes had all been converted to E.R. 3 design.{{ARTS1917|p. 27}}

In submarine use (at least), in 1917 it was decided that they were to deliver:{{ARTS1917|pp 25-26}}
* 45 knots to 4,200 yards 
* 29 knots to 10,750 yards 

In May, 1918, the Mark II**-II*** torpedoes were noted as having the following settings at a charge of 2500 pounds per square inch, though each torpedo would have either the 35 or 44.5 knot setting, but not both:{{GFGTO|p. 16}}
* 44.5 knots to 4,500 yards (High Speed)
* 35 knots to 6,000 yards (High Speed)
* 23 knots to 15,000 yards (Medium Speed)
* 18 knots to 18,000 yards (E.R.)

The 2500 psi pressure was the "action" pressure; normal was 2350.  Ranges were 300 yards less at 44.5 knots and 1,000 yards less at lower speeds at the normal pressure.

In December, 1918, the performance and settings were unchanged.{{GFGTO|p. 16}}

In mid-1920, it was ordered that Mark II** to Mark II***** H.B. torpedoes should be allocated to capital ships and light cruisers presently armed with Mark II to Mark II***** torpedoes, enriching the full commission ships with the latest Marks.{{ARTS1920|p. 6. (G. 10141/20-6.8.1920)}}

Early in 1923, all Mark II-II**** torpedoes had their low speed performance downgraded to 23 knots to 13,000 yards &ndash; 1,000 yards less than previously.  This required issuance of a new deflection disc for [[Torpedo Control Disc Mark III*]] numbered T. 226A to all ships carrying these weapons, meaning ships of the [[Iron Duke Class Battleship (1912)|''Iron Duke'']] and [[King George V Class Battleship (1911)|''King George V'']] classes, as well as {{UK-Thunderer|f=p}}.{{ARTS1913|p. 126}}

===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.  This initiative was to result in the creation of the Extreme Range (E.R.) torpedoes by the end of 1916, and they were intended to be used against the enemy battle line, two torpedoes of the latest type from each battleship and battle cruiser to be fitted for this new setting.{{ARTS1915|p. 37}}{{ARTS1916|pp. 43-46}}

The torpedoes were described in further detail in 1916, differing in seven details from the II***, including a tappet engine, wider gyroscope rudders and a "bye-pass valve on group" in torpedoes after No. 1168 R.N.T.F. and No. 1925 Whitehead & Co..  They could share warheads with earlier Mark IIs.{{ARTS1916|p. 40}}

By the end of 1917, these torpedoes had all been converted to E.R. 3 design.{{ARTS1917|p. 27}}

In submarine use (at least), in 1917 it was decided that they were to deliver:{{ARTS1917|pp 25-26}}
* 45 knots to 4,200 yards 
* 29 knots to 10,750 yards 

In May, 1918, the Mark II**-II*** torpedoes were noted as having the following settings at a charge of 2500 pounds per square inch, though each torpedo would have either the 35 or 44.5 knot setting, but not both:{{GFGTO|p. 16}}
* 44.5 knots to 4,500 yards (High Speed)
* 35 knots to 6,000 yards (High Speed)
* 23 knots to 15,000 yards (Medium Speed)
* 18 knots to 18,000 yards (E.R.)

The 2500 psi pressure was the "action" pressure; normal was 2350.  Ranges were 300 yards less at 44.5 knots and 1,000 yards less at lower speeds at the normal pressure.

In December, 1918, the performance and settings were unchanged.{{GFGTO|p. 16}}

In mid-1920, it was ordered that Mark II** to Mark II***** H.B. torpedoes should be allocated to capital ships and light cruisers presently armed with Mark II to Mark II***** torpedoes, enriching the full commission ships with the latest Marks.{{ARTS1920|p. 6. (G. 10141/20-6.8.1920)}}

Early in 1923, all Mark II-II**** torpedoes had their low speed performance downgraded to 23 knots to 13,000 yards &ndash; 1,000 yards less than previously.  This required issuance of a new deflection disc for [[Torpedo Control Disc Mark III*]] numbered T. 226A to all ships carrying these weapons, meaning ships of the [[Iron Duke Class Battleship (1912)|''Iron Duke'']] and [[King George V Class Battleship (1911)|''King George V'']] classes, as well as {{UK-Thunderer|f=p}}.{{ARTS1913|p. 126}}

===Mark II*****===
The torpedoes were first described in 1916, differing in six details from their near-contemporary II****, including that the ranges were not marked on the shell and that they had a new three-speed generator that allowed the E.R. setting to be selected rather than hard-plumbed into a given torpedo.{{ARTS1916|pp. 40-41, 44}}

In May, 1918, these torpedoes were noted as having the following settings at a charge of 2500 pounds per square inch, though each torpedo would have either the 35 or 44.5 knot setting, but not both:{{GFGTO|p. 16}}
* 44.5 knots to 4,500 yards (High Speed)
* 35 knots to 6,000 yards (High Speed)
* 24 knots to 15,000 yards (Medium Speed)
* 19 knots to 18,000 yards (E.R.)

The 2500 psi pressure was the "action" pressure; normal was 2350.  Ranges were 300 yards less at 44.5 knots and 1,000 yards less at lower speeds at the normal pressure.

In December, 1918, the performance and settings were unchanged.{{GFGTO|p. 16}}

In mid-1920, it was ordered that Mark II** to Mark II***** H.B. torpedoes should be allocated to capital ships and light cruisers presently armed with Mark II to Mark II***** torpedoes, enriching the full commission ships with the latest Marks.  The Mark II***** S.L. torpedoes would go to {{UK-Canterbury}}, the ''Caroline'' class and the ''Aurora'' class (except {{UK-1Inconstant}}, which would retain her existing {{Torp|21-in Mark IV|UK}}).{{ARTS1920|p. 6. (G. 10141/20-6.8.1920)}}

==Footnotes==
{{reflist}}

==Bibliography==
{{refbegin}}
{{refend}}

==See Also==

{{CatTorpedo|21-in|UK}}