French Suffren Class SSN

[Akula54]

Here's some pics of new french SSN, the Suffren.











Sea trials at Cherbourg



Arrived at Toulon's Naval base on 07/13/2020

[trout]

X-tail and interesting, small planes - designed for speed? Or does the design of the rudder as a whole make it more efficient? Excellent photos, thank you for posting!

[coryhenry]

Also a cool sail retractable cover, would like to see that replicated in a model :)

[RCSubGuy]

Those rudders are crazy! In practice, x-tails are about 40% more efficient than standard cruciform, so perhaps they can get away with the control surfaces 40% smaller?

[a1965l]

Its interesting that there's a slot in front of the control surface.. You generally only see those in high lift devices, they prevent airflow separation at high angles of attack. I would think they get noisy, though.

[Akula54]

Its interesting that there's a slot in front of the control surface.. You generally only see those in high lift devices, they prevent airflow separation at high angles of attack. I would think they get noisy, though.

Don't know if it's noisy, but you can see same device on Le Redoutable class SSBN (here in the Cherbourg Museum).

[Albacore 569]

Semi-balanced control surfaces with forward fixed surfaces in front with their own hydrodynamic characteristics to smooth the flow for the moving surfaces aft of it - seems a distinctive common French design characteristic. Some may argue for the unbalanced or all moving surfaces too - common on other navies for control effectiveness and silencing.

Perhaps the French method helps create the control forces needed with less over all movement? Avoiding larger movements that induce more flow noise?

Semi-balanced surfaces also I imagine puts less loads on the boats hydraulic systems too - less work for the same purpose. Like in all designs, everything is a trade off - compromise which has the most appealing features to the designer for the mission.

It is remarkable the French even extend this characteristic to Suffren's X-stern too, which seems to reflect just how much they believe in this arrangement's effectiveness.

Note also in the top photo the twisted rudder surface which matches the water flow from propeller to reduce cavitation. (Arethuse class Museum boat Argonaute -early 1950's design) . It shows a great deal of sophistication & understanding of hydrodynamics I'm sure other navies are well aware of too, but the French seem to wish to take it to next degree.

As modelers, we are all looking for somethings on a model subject that's different.

Steve

[Akula54]

Suffren arrived in Faslane, Sotland












Francois

[Akula54]

Hi,

Some nice details of the towed array system:

Vidéo | Facebook



Cheers

[rwtdiver]

Hi Francois,

Looking at that Facebook video it sure does give you some idea of the massiveness of that boat.

Thank you for sharing that video!

Rob
"Firemen can stand the heat."

[Albacore 569]

Hi,

Some nice details of the towed array system:

Vidéo | Facebook



Cheers

Merci Francois! The STL files for the 1/64 Suffren were completed in March. Since late March 2025 still trying to make my 3d printer work. without success. Nothing wrong with it best I can tell, they ust suck as far as a operating manual! **** this. I will take a 3-d printing class and hope I can meet someone there that can help me turn my machine on and make it work as advertised. Watched all the you tube videos and videos on this actual same machine, and they all say how oh it's so easy and thy type in the numbers so fast and say of its so easy! **** NO! Its a a new AnyCubic Photon M 3 Max.

in mean time here are images enlarged from the Face book video.

The tarp covering th pump jet is very illuminating. It doesn't show the interior, BUT it shows tape holding the tarp t what are probably the pre swirl stators! I estimate using a stator count of 1/3 of the inlet diameter the Suffren may have 15 front stators. Plump jets almost always have an odd number of stators.

The Towed array I spotted early on but this s the first image that shows a fully assembled one? It almost matches the STL file already. The only question now besides getting the damn printer to work for me is will the array need an extension to clear the pump et inlet or is it hydrodynamically sufficient already not requiring one?

The STL file has a longer towed array intentionally so if there is any doubt it is easier to remove than to add.

[Akula54]

Hi Steven,

You're welcome !

The tarp covering th pump et is very illuminating. It doesn't show the interior, BUT it shows tape holding the tarp t what are probably the pre swirl stators! I estimate using a stator count of 1/3 of the inlet dk, the Suffren may have 15 front stators. Plump jets almost always have an odd number of stators.

I think you're right about the pre stator, like her big sister Perle, we can see an equivalent number of blades.



I agree with keeping the towed array longer and cut it .
Perhaps we'll have more photos at launch to confirm its size.
I still admire your work

Cheers !

[Albacore 569]

Hi Steven,

You're welcome !



I think you're right about the pre stator, like her big sister Perle, we can see an equivalent number of blades.



I agree with keeping the towed array longer and cut it .
Perhaps we'll have more photos at launch to confirm its size.
I still admire your work

Cheers !

The pre swirl stators on the Rubis class SSN (In French Navy SSN for Nuclear attack submarine is SNA) is to assist in propulsive efficiency. My question is I can see these common addons in merchant ships. These are quite common and give over long distances some fuel cost savings and profit by the ship company. But on a nuclear submarine?

On submarines the nuclear fuel is already prepaid for, and very different power densities. More important on submarines - silence is life. It is possible these stators also make a different noise signature to the propellor a 7-blade scimitar shaped blade in smoothing out the flow between the prop and the cruciform stern planes. So it must have some degree of acoustic benefit too. It's also possible these were added as a test on Perle only?

A pump jet is similar in some ways but visually is radically different. In the Suffren class and the French SSBNs or on all pump jets so far in general the fixed stators in front of the propulsor in the literature says it not only adds to quieting doing the same function in the pump jet, it adds structural strength in resisting battle damage and also ease of maintenance. Pump jets on nuclear submarines everywhere I imagine are now quite similar. At least as far in extent as our small models are concerned.

Mathematics is the same everywhere on the universe. If the specifications of expected performance are similar (yes) the working fluid the same (yes) . Convergent evolution. Streamline shapes similar for sharks and dolphins. The Concorde SST and the piece of **** TU-144. Similar requirements same mathematics. Where the soviets came up short was, they couldn't quite duplicate the French British Concorde's ogival wing shape. The French UK Wing design was far more efficient and economical once the airlines learned their customers were more than happy paying double the price the Concorde was making a nice profit. What killed Concorde was 9-11. Most of the business costumers of Concorde were killed in the twin towers. But I digress.

Pump jets are designed and built to such fine tolerances too. One of the few firsthand accounts from someone who actually seen and worked on one once told me (the only thing he said) was the separation between the propulsor tips and the interior of the shroud is less than a pencil width.

I almost chose a Rubis model project over the Suffren. But it looked to similar to all the skipjacks out there as important as the Rubis class is in French submarine evolution. The Suffrens were the present / future and a good match contrast to the Astute Virginias at the pond I thought.

What I find ballsy is the French took the bigger technical gamble building a SSBN first, usually a Country's Navy's first nuclear sub is an attack boat. That reflected Frances urgent need for an independent nuclear deterrent and very painful memories of France occupied 1940-44. Invade France again, no more! Then the entire world will die too.

[Akula54]

You're right about the Rubis class... but six boats, six differents specifications as far as I know.
No, some of them have 5 blades prop... with stator ;)

And when I was in well-informed circles, the 6 units of Rubis class each had 2 differents props.
5 or 7 blades, with or without stator... It depends the patrol area, mission, etc.
Mods were made during maintenance stops in dry docks.



The guy who took the picture during a visit must have thought... oops






If you want a model with a perfectly correct hull shape, look on cults3d.
Minialand designed a model of the Améthyste class, and I can guarantee the accuracy of the hull, sail, and appendages (the details, no, but I'm not the designer of the complete model ;)
The Rubis class represents for me the smallest SNA in the world, and just for that reason I find it interesting to make it into a sailing model (in addition to the different models of propellers, stators, etc.)
Not as good or as sexy as the LA Class... but cute

The French did with their SSBN what you Americans did with the George Washington/Skipjack class... but without first finishing the SSN that was supposed to be launched, until 1983.

[Albacore 569]

You're right about the Rubis class... but six boats, six differents specifications as far as I know.
No, some of them have 5 blades prop... with stator ;)

And when I was in well-informed circles, the 6 units of Rubis class each had 2 differents props.
5 or 7 blades, with or without stator... It depends the patrol area, mission, etc.
Mods were made during maintenance stops in dry docks.



The guy who took the picture during a visit must have thought... oops






If you want a model with a perfectly correct hull shape, look on cults3d.
Minialand designed a model of the Améthyste class, and I can guarantee the accuracy of the hull, sail, and appendages (the details, no, but I'm not the designer of the complete model ;)
The Rubis class represents for me the smallest SNA in the world, and just for that reason I find it interesting to make it into a sailing model (in addition to the different models of propellers, stators, etc.)
Not as good or as sexy as the LA Class... but cute
The French did with their SSBN what you Americans did with the George Washington/Skipjack class... but without first finishing the SSN that was supposed to be launched, until 1983.

Thank you for the added information on th Rubis class SSN SNA switching from 5 to 7 and back to 5 blade propellors is very interesting.

I looked at the cults 3d and was interesting, but some things are wrong. The sail and general hull form looks good from what I can see.

Here is a official drawing below I stumbled on years ago. The drawing was originally printed in red ink strangely. I changed to B&W. The drawing shows the stern planes much more accurately. The horizontal stem planes are off set forward from the vertical rudders offset longitudinally farther aft.

I wonder if the well-known dry dock photo of Perle is as she is about to have her front half removed after her fire in dry dock and replaced with the front half of the decommissioned Saphir sister boat?

Perle's repair was completed n 2021 and the back operational again in 2023. Essentially a San Francisco / Honolulu job. Perle is reportedly 1 meter longer and an extra 86 tons displacement now. The extra 86 tons may be reasoning the Perle is 1-meter longer - compensating for the weight with added hull volume needed for buoyancy and trim? Knowing the beam and is same dimension as the pressure hull, 7.6 meters diameter (24 ft 11 inches) 7.6 meters x 1 meter = 45.34 cubic meters extra volume.