Rotating central torpedo tubes in French Submarines

[Dili]

I am trying to understand the propose of rotating (i also have read "revolving" but it appears to be more of rotating) torpedos tubes in french submarines usually placed mid submarine. Was it to fire broadsides? Seems a very few quantity for that. Did they had any success with it?

[David Reasoner]

Dili, although I do not know enough to address the issue of specific successes with them in combat, the purpose of the 'revolving' or trainable torpedo tubes was indeed to enable the submarine to fire at targets on either beam or broadside. The Dutch used similar torpedo tube installations on many of their pre-WW2 submarines:

http://www.dutchsubmarines.com/

The fact that K.XIV and K.XV appear to have had their trainable torpedo tubes removed during their 1942-43 refits in the U.S. could perhaps be taken as an indication the concept was not particularly successful in use.

David

[David Reasoner]

I forgot to mention that one of the problems with the trainable or rotating torpedo tube installations was that since the tubes were mounted outside the submarine's pressure hull, there was no practical way to reload them at sea and thus no reload torpedoes were carried for them. Once the torpedoes in those tubes had been fired, the rotating tubes were essentially useless until the submarine could return to base to have them reloaded.

David

[Dili]

Thanks David. In another place i was told the system was unreliable.

[kgvm]

According to Henry Le Masson, Les Sous-marins Francais (p. 164), there was another reason for the French to adopt the trainable torpedo tubes, which could be trained electrically from inside. The French torpedos had only a bad "gyrodéviation" (don't know how to translate it, but it's intended to steer a torpedo at an angle of it's original course to the right or to the left), so to achieve the spreading of a torpedo salvo which in subs of other nations was achieved by different gyrodevations they had the trainable torpedo tubes to cover a broader arc of fire with a salvo.

[Dili]

Thanks kgvm

[Takao]

Given that the Surcouf probably had very poor maneuverability the rotating torpedo mounts probably would have helped when engaging multiple targets while she was submerged.

I was just thinking that the trainable tubes would be somewhat useful as a self-defense mechanism if the submarine was caught on the surface while firing those monster guns of hers.

Can anyone explain the use of two different types of torpedoes used? She had 550mm and 400mm torpedoes. Depending on the source one of the rotating torpedo turrets was a battery of 550s and a second mount was the 400s or both batteries were a mix of 550s and 400s.

[Ironmachine]

There is certainly some confusion about the torpedo armament of the Surcouf. This may clarify the matter somewhat:

Some controversy surrounds her torpedo armament. She carried four bow tubes armed with 21.7" torpedoes for use while submerged, that much is agreed upon. Most secondary and Internet sources have her armed with six tubes, mounted on a platform at the stern for use when surfaced. Four of these were the fast but short-ranged 15.7" torpedoes. Other sources (Submarines by Anthony Preston, for example) and most importantly the two-volume history of the French Navy by Henri Le Messon, state that two quad mounted platforms were carried astern, one for both 15.7" and 21.7" torpedoes. Henri Le Messon was a member of the French Marine Academy and editor of the authoritative magazine, Les Flottes de Combat, so I think we can trust him as a most reliable source. Regardless of exact configuration, a total of fourteen 21.7" and eight 15.7" torpedoes were carried.

http://www.avalanchepress.com/Surcouf.php

[kgvm]

It's not fully correct to speak of the 400 mm torpedos as the fast ones. Of course they run at 44 knots (and had a range of 1800 m), but the 550 mm torpedos could run either at 44 knots, too (with a range of 3000 m) or at 35 knots with a range of 7000 m). Le Masson gives the following reason for the two different sizes:
the 550 mm torpedos could run only at a depth of at least 3 m. Furthermore their "payload" of 315 kg was deemed an overkill in using against smaller vessels, so the French resorted to the two different sizes of torpedos.
Unfortunately Le Masson doesn't say anything about the minimum depth of the 400 mm torpedos - may be anybody can help here?

[John T]

I forgot to mention that one of the problems with the trainable or rotating torpedo tube installations was that since the tubes were mounted outside the submarine's pressure hull, there was no practical way to reload them at sea and thus no reload torpedoes were carried for them. Once the torpedoes in those tubes had been fired, the rotating tubes were essentially useless until the submarine could return to base to have them reloaded.

David

OTOH as they where outside they did not take any space within the pressure hull.
And I understood it as a less successful but still not to bad Idea to add a couple of Torpedo tubes "Piggy backed" more or less for free. But the British use of fixed external Torpedo tubes (T and U Class) gave similar advantage at a much simpler technology.


Cheers
/John T,

[Mimbrogno]

The British and the French weren't the only ones to mount torpedos in external mounts. The US made a habit of it as well in their early fleetboats, the most notible of which were USS Narwhal (SS-167) and USS Nautilus (SS-168) which carried a total of 14 torpedo tubes. (4 internal forward, 2 internal aft, 4 external forward and 4 external aft.) The external torpedo tubes were in fixed mounts tucked away inside the large raised platforms for the two 6" gunmounts, making them hard to spot and giving them a moderate degree of protection from depth charge blasts. The tubes fired over the decking of the sub, making them accessible for maintance and much easier to reload than other subs who's tube muzzels hung out over the water.

Later prewar fleetboats that were armed with only 4 internal tubes forward would be suplimented with an additional two torpedo tubes sliced into the top of the bow casing. These mounts were rather exposed, and torpedo's inside them were prone to being activated or even detonated by the blasts of depth charges. As such, many skippers preffered to leave these tubes empty, or at least make sure they fired them first before being depth charged by an enemy destroyer.



And, like the Dutch and French, the US also experimented with rotating or "trainable" torpedo tubes on their very first class of fleet/cruiser submarines: the AA class of 1920. The first of these subs was laid down in 1916 as the US entry into the newly developed cruiser submarine class. They had (or were at least intended to have) two 3" guns on disappearing mounts and six 21" torpedo tubes on 2 trainable mounts built into the upper hull casing. Unlike most external torpedo mounts, the mounts on the AA class were able to fire while on the surface as well as when submerged.

[Takao]

The USS Narwhal and USS Nautilus only had two external tubes aft and angle outward at about 10 degrees to either side. They were located underneath the gun deck on either side of the aft 6 inch mount. Also, there were only two forward external tubes and these were in the bow above the forward dive planes. I think you have mistaken the containers for carrying extra torpedoes externally as being actual tubes, this the were not. They carried torpedoes, but could not fire them. Similarly, the German Type IXs carried their external spares in the deck, unlike the Narwhal and Nautilus which carried theirs underneath the raised decking surrounding the sail and 6 inch guns.

[Hautpoul]

Exemples of rotating central torpedo tubes on french 1 500 tons submarines :

[SVaaka]

According to my knowledge these rotating tubes were build for two purpouses - for training and sinking merchantships - that´s why these 400mm torpedo had quite short usingdistance.

[Dili]

Thanks for the photos Hautpoul