Anti-Torpedo Net

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An Anti-Torpedo Net (sometimes "Torpedo Net") is a heavy metal mesh intended to block and stop torpedoes.

They came in two basic forms: ship's nets which could be deployed from a ship on metal booms that swung out from the beam, and harbour defence nets which were generally suspended from floats to guard ships at anchor within a port.

Nets and torpedoes (with or without cutters affixed) were a game of Rock, Paper, Scissors with probabilistic outcomes.

British Experience

Trials

In 1915 and 1916, the British conducted extensive tests of their own torpedo nets,[1] firing their own torpedoes at them fitted with a variety of net cutters. This augmented their battle experience where they could see how their nets fared when German torpedoes and cutters were fired against them.

In 1916, the latest British ship's net was the "Type Pa". It was noted that it was about as effective as the earlier "Type G", and was presently vulnerable to "[our] own torpedoes and pioneers." Their harbour net model at the same time was "Type R", and was currently proving 75% effective by the Fiume net cutter (a type the Germans were known to have at least evaluated) on 3 out of 12 tests in 1916. Whether or not the Germans were using the Fiume net cutter, the British knew that the Germans regarded their cutter as being able to defeat any known net if it struck it at a speed over 5 knots.

Lacking further insights into the cutters the Germans were actually using, the British set out to develop a net that could reliably thwart the Fiume net cutter, and declared success in this regard by developing the "Type T" harbour net during 1916.

Type of Net Torpedo Speed
knots
Cutter No.
Trials
No.
Penetrated
Penetration
Rate
R 18-in Mark VII 41 ? Fiume 1 1 100%
RU 18-in R.G.F. Mark VII 41 Fiume 5 1 20%
RU 21-in Mark II*** 45 E 1 2 0
T 18-in Mark VII 41 Fiume 5 0
T 21-in Mark II*** 45 Fiume 1 0
S 18-in Mark VII 41 Fiume 2 0
S 21-in Mark II*** 33 Fiume 1 0
TL 18-in Mark VIII* 41 Fiume 3 0
TL 18-in Mark VII 41 Fiume 3 0
TL 21-in Mark II*** 45 Fiume 2 0
TE 18-in Mark VIII* 41 Fiume 5 0
TE 18-in Mark VII 41 Fiume 1 0
TE 21-in Mark II 45 E 2 8 3 38%
Pa 18-in Mark VIII-VIII* 41 E 2
fixed blades "B"
1 0
Pa 18-in Mark VIII-VIII* 29 E 1
sliding blades
3 0
Pa 18-in Mark VIII-VIII* 41 E 1
sliding blades
3 1 20%[2]
Pa 18-in Mark VIII-VIII* 41 E 1
existing pattern
sliding blades
6 3 50%
Pa 18-in Mark VIII-VIII* 41 18-in pattern
w/ strengthening shoes
4 2 50%
Pa 21-in Mark II*** 45 Hardy 1 0
Pa 18-in Mark VIII-VIII* 41 Hardy 15 3 20%
S 21-in Mark II*** 29 Spearhead
4 bladed
1 0
Pa 21-in Mark II*** 29 Spearhead
4 bladed
1 0
Pa 21-in Mark II*** 45 Spearhead
2 bladed
1 1 100%
TL 21-in Mark II*** 45 Spearhead
2 bladed
1 0

[TO BE CONTINUED - TONE] more trials from ARTS 1916, p66

Conclusions

The British had come, by 1916, to regard their "Type T" net as generally effective in harbours, but problematic for use as a ship's net unless it was to defend a bombarding ship, as the nets were found to slow and render un-handy the ships while under way. Their hope was in passive defence in hull design, and they expressed optimism that void spaces able to vent to the atmosphere when struck by a torpedo may prove promising.

[TO BE CONTINUED - TONE]

See Also

Footnotes

  1. Annual Report of the Torpedo School, 1915. pp. 62-65, Annual Report of the Torpedo School, 1916, pp. 60-66.
  2. May have exploited previous net damage.

Bibliography

  • H.M.S. Vernon. (Jan 1916) Annual Report of the Torpedo School, 1915. C.B. 1166. Copy 1025 at The National Archives. ADM 189/35.
  • H.M.S. Vernon. Annual Report of the Torpedo School, 1916. Originally C.B. 1329. Copy 4 at The National Archives. ADM 189/36.
  • H.M.S. Vernon. Annual Report of the Torpedo School, 1917. Originally C.B. 1474. Copy 7 at The National Archives. ADM 189/37.
  • H.M.S. Vernon. Annual Report of the Torpedo School, 1918. C.B. 1527. Copy 20 at The National Archives. ADM 189/38.