Specifications:
Displacement: 3,300 tons surfaced, 4,373 tons submerged
Length: 110 meters (361 ft)
Beam: 9 meters (29 ft 6")
Draft: 7.25 meters (23 ft 9")
Speed: 18.5 knots surfaced, 10 knots submerged
Depth: 80-110 meters operating depth, 491 meters crush depth.
Range: ~7,000-10,000 nautical miles. ~70 nautical miles submerged on battery power @ 4.5 knots.
Complement: 118 (8 officers, 110 men)
Armament: 2 x 203mm (8") guns in turret, 4 x 550mm (22") heavyweight torpedo tubes in bow with 6 reloads, two triple trainable external torpedo mounts each with 1 x 550mm (22") tube and 2 x 400mm (16")tubes. 2 x 37mm anti-aircraft guns. After 1942 refit, 2 x twin 13.2mm anti-aircraft machine guns were fitted.
Aircraft: 1 × Besson MB.411 floatplane
Firepower
Surcouf was designed around the heavy cruiser armament of 203mm (8") guns, which was the largest calibre allowed under the Washington Treaty. It was considered more economical to engage merchant ships with guns rather than torpedoes as many more rounds could be carried. The guns also had a longer range and could be directed by the aircraft. Surcouf was also equipped with a range finder which rotated with the turret and was positioned sideways for underwater streamlining.
The guns could fire 26 km (28,000 yards) with aircraft direction, or 16 km (17,000 yards) using the periscope and fire director. The ammunition and charges were stored separately below the gun and hoisted into the turret via a single ammunition lift. The rounds and charges were mated in the turret.
The guns were in a fully enclosed turret which was integral to the pressure hull. To prevent flooding through the gun barrels, there were muzzle doors which could be opened and closed from within the turret, similar to on torpedo tubes. The gun could be trained and fired within 3.5 minutes of surfacing. One of the limitations of the gun turret was that it was only stable in light seas.
Airpower
Surcouf was the first submarine in the world to be built with a designed-in aircraft capability. A single hangar under the sail could accommodate a collapsible floatplane for reconnaissance and fire direction. The aircraft could only be launched and recovered while the submarine was surfaced
Fate
In 1930 the Treaty for the Limitation and Reduction of Naval Armament (aka London Naval Treaty) placed restrictions on submarines. France (and other signatories) was not allowed to possess more than three large submarines, with a surface displacement limit of 2,800 tons. Submarine gun armament was not to exceed 6.1" (150 mm). Surcouf, which was larger and more heavily armed than allowed by the terms, was specifically excepted. But it meant that no more submarines of the same design could be built.
arly in World War Two Surcouf served in the Caribbean and off the West Coast of Africa. She was being refitted in Brest when Germany invaded France. She was able to escape to England, running on the surface a single engine. Initially she remained under French control, but British forces seized her on 3rd July 1940 to prevent her falling into German hands with the French Armistice. Three British submariners and one French officer died during a scuffle as the boat was seized. In August Surcouf's refit was completed and she entered service with the Free French.
On 2nd February 1942 she departed Halifax, Canada, heading south towards the Panama Canal. The plan was to sail through the canal and on to Sydney, Australia, via Tahiti. She was last reported on the night of 18/19th February 1942, about 70 nautical miles north of Cristóbal, Colón. The cause of the disappearance has never been satisfactorially established although reports at the time pointed towards the American freighter Thompson Lykes which reported hitting a semi-submerged object. The entire crew perished and the wreck remains uncharted.
It was sunk because it was sinking the convoy ships .My dad got that from a man on the convoy.