SURCOUF Submarine

sgeorges4

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http://3dhistory.de/wordpress/warship-drawings-warship-blue-prints-warship-plans/french-submarine-drawingsplan-sets/french-submarine-surcouf-as-build-1929/
It's the sous marin de croisière type Q5 concept for the Surcouf.
 

lastdingo

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Does anyone have an idea what these main guns were meant for?

Navies were well aware decades before the Surcouf that a salvo of at least six rounds is required for decent splash spotting and thus decent correction of fires.
Ships with four main guns were known to be very optimistic designs (Courageous and Glorious, for example - and they were soon rebuilt in part because they lacked a decent salvo).
A two-gun submarine would have been effective at relatively short distances only, maybe 4...10 km. The minimum distance would be required for the lengthy (likely 1 minute) diving procedure and an underwater sprint to safety followed by more silent slow escape undersea.
This ship would have been very poor at engaging convoy escorts.

Maybe the guns were meant for surprise coastal city or port bombardment?
 

Avimimus

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lastdingo said:
Does anyone have an idea what these main guns were meant for?

Navies were well aware decades before the Surcouf that a salvo of at least six rounds is required for decent splash spotting and thus decent correction of fires.
Ships with four main guns were known to be very optimistic designs (Courageous and Glorious, for example - and they were soon rebuilt in part because they lacked a decent salvo).
A two-gun submarine would have been effective at relatively short distances only, maybe 4...10 km. The minimum distance would be required for the lengthy (likely 1 minute) diving procedure and an underwater sprint to safety followed by more silent slow escape undersea.
This ship would have been very poor at engaging convoy escorts.

Maybe the guns were meant for surprise coastal city or port bombardment?
Covert shores's article linked above has the answers.

Engaging merchants outside of convoys at a great distance from port. A floatplane was carried to assist in ranging the guns and extending the gun ranges to 26km from 16km. The 203mm guns were favoured due to greater magazine capacity compared to torpedoes.

Your shore bombardment guess is reasonable though - the British M class was designed with such an attempt before ambushing merchant vessels from close range (1.2km) became its goal.
 

lastdingo

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Avimimus - aerial observer or not - two guns was no good for long range shooting at moving ships. So that article doesn't seem to offer a believable answer.
 

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Well it's beyond debate that Surcouf had two cruiser guns and was intended for engaging merchant shipping in the manner of a cruiser. How effective she would be was never put to the test. The US, Japan, UK, Italy and Germany all built cruiser subs although only Japan and UK came close to Surcouf in impressiveness.

And the tactics used in the war were adapted to the circumstances, so the fundemental concept was never really tested. You could argue that that is an indicator that it would never have worked. Or maybe it's just that defensive tactics and strategic circumstances never suited cruiser subs.

As for my article being believable, no worries, wasn't written to convince you. Surcouf is an interesting boat.
 

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I assume your article was based on source material though? ;)

As for the concept being tested... a number of merchants were sunk using deck guns on submarines during both wars... so the idea of engaging lone merchants using deck guns is well established.

It is really a matter of catching a ship outside of a convoy and silencing any defending guns on that ship. A merchant with one or two guns isn't going to be that good at getting the range on the low profile of a submarine... especially if the submarine is attacking at night. The gunners also won't have the advanced ranging and fire direction equipment of a warship.

Compared to a British DEMS from the period with a single BL 4-inch Mk VII Surcouf would have achieved a similar rate of fire. However, it would be able to open fire at a much longer range and would have twice the calibre of shells, a lower profile, and probably both better sighting equipment and better sea keeping. Surcouf would also be two or three times faster than most merchants and thus a considerably harder target.

Anyway, an engagement at 10-15 km between ships doing about 10-15 knots should be much easier to range than an engagement at 30-35 km at approximately 30 knots. One would have to check ballistics tables and also assess the ability to get a fix on the heading and speed of the opponent, but a very crude calculation assuming similar ballistics suggest that Surcouf would find it about five times easier to fix a merchant (as compared to the problem faced during the initial clash at Jutland).
 

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Yes I think it's difficult to really assess how well she would have done, or even whether her captain would have attempted such long distance engagements. I have questions about using the floatplane for spotting because that inhibits the submarine from submerging if countered, basically sacrificing the plane.

Fwiw, I read that she wasn't intended for night engagements. Presumably only at short ranges like other subs.

Remember she's a very ambitious 1927 boat. A work of art but maybe as flawed as she was elegant.
 

Silencer1

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Surcouf reminds me another France's attempts to design military items, that appears too late, too expensive and fulfilling the requirements, that WW2' circumstances presented as unuseful: giant military and civil flying boats.

There were a number of them: Potez-CAMS 161, Latecoere 611&631, SNCASE SE-200 - and remains as prototypes.
IMHO, any vehicle or vessel, which has been completed, tested and used for even short time could an example for contemporary or recent designers, how to build (or not to build) complex technical objects

P.S. Thanks for Surcouf article and drawing - quite entreating!
 

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Subs sank merchant ships with guns by going close and shooting at the waterline with 88...127 mm guns.
Cruiser subs were meant for great range and overwhelming q-ships.
There was a tendency to give bigger boats bigger calibres, but 88 mm was ok and I have never seen any infication that anything above 105 mm ever proved itself to be better than 195 in this rile. 195 did the job with a reasonable use ifmunition.

The only sub cruiser that came close to plausible gun fighter was typ xi, snd ut wasn't built. It was meant to engage escirts at 10+ km in dustant seas (south atlantic), mostly for navak diversion (drawing quality escorts from north atlantic). It would have been the nemesis of flower corvettes.
 

Dilandu

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lastdingo said:
Does anyone have an idea what these main guns were meant for?
As far as I knew, the general idea was to be able to engage transports and convoys from outside the reach of escorts artillery. In the interwar era, the accuracy of aerial spotting was... overestimated quite a bit, so it was assumed that she would be able to fight efficiently at max ranges. Of course, considering that the targets would be the merchant ships - which aren't very good in evading shells - it may be not too far-fetched.

Also, the idea was to be able to engage escort ships & q-ships, if needed, having the firepower advantage. Two 8-inch guns, firing from the splinter-protected mount with actually pretty good fire control system would be more than a overmatch for any escort ship of that era (and even WW2-era escort destroyers and corvettes would definitely NOT like the idea of fighting surface action vs "Surcouf").
 

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That seems quite plausible as a reason for the 203mm guns. Using 100mm/45s would've given it about 2-3 times the rate of fire and allowed more ammunition to be stored in the turret for a given attack - significantly increasing the likelihood of scoring hits early in the engagement, however range would decrease to less than 15 km and put the submarine within range of countering fire.

covert_shores said:
Fwiw, I read that she wasn't intended for night engagements. Presumably only at short ranges like other subs.

Remember she's a very ambitious 1927 boat. A work of art but maybe as flawed as she was elegant.
Indeed - your analysis represents everything I've ever heard about this ship!

That said, it'd be interesting to see a study that actually confirmed this computationally (i.e. just how close would she have needed to get to be successful - using data on the sighting system, data on ballistics and dispersion based on the guns, and information regarding the success of U-Boat deck guns at various ranges) - could be a nice thesis project for someone.
 

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covert_shores said:
New cutaway and Covert Shores article at http://www.hisutton.com/Surcouf.html
Wow...I didn't realize the 8" guns and torpedo tubes swiveled. That's pretty fascinating.
 

Dilandu

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GWrecks said:
covert_shores said:
New cutaway and Covert Shores article at http://www.hisutton.com/Surcouf.html
Wow...I didn't realize the 8" guns and torpedo tubes swiveled. That's pretty fascinating.
Well, trainable deck torpedo tubes were used on many of French pre-war submarines (and in some other navies, like Danish & Polish). The idea was to aim the torpedoes without turning the whole submarine & setting the gyro-angle; instead, you just rotated the external mount by rather simple mechanical gear. It was also pretty handy in self-defense - destroyer, charging to drop depth bombs on French submarine would clearly be worried about the possibility of being greeted with torpedo salvo. Most of French submarines have trainable tubes that could only be reloaded in base, but "Surcouf" actually have reloadable torpedo mounts.
 

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It also helps compensate for the lack of manoeuvrability in a large submarine like this. Some British submarines also had trainable mounts.

It is off-topic - but you might want to look up the pre-WWI Drzewiecki 'drop collars' which would actually hinge outward to fire the (essentially externally mounted) torpedoes at a chosen angle. In many cases the majority of the torpedo armament was carried in this way.
 

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Avimimus said:
It is off-topic - but you might want to look up the pre-WWI Drzewiecki 'drop collars' which would actually hinge outward to fire the (essentially externally mounted) torpedoes at a chosen angle. In many cases the majority of the torpedo armament was carried in this way.
Yep, I knew about them.




Were rather popular in Russian & French navies before and during WW1, but eventually fell out of use, since they were less accurate than internal tubes, and externally-mounted torpedoes tended to be less reliable due to deterioration. Also, there were a lot of worries about externally-mounted torpedo exploding under enemy fire on surface (or from depth charge shockwave).
 

covert_shores

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Yes that torpedo firing system was super interesting.

The Surcouf's were a generation much more modern though, with the torpedoes in sealed tubes on a turntable. That was popular with the French and also used by Britisj and Italians (/Swedes) and probably others. The French still used it post war although often fixed external tibes in the casing (per British WW2).
 
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