French Suffren Class SSN

[Akula54]

Suffren arrived in Faslane, Sotland












Francois

[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]

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).

[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.

[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?

[coryhenry]

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

[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!

[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