The Lagrange-class submarines were constructed as part of the French fleet's expansion programmes from 1913 to 1914.[1] [2] The ships were designed by Julien Hutter, slightly modifying his previous project, using two Parsons steam turbines with a power of 2000hp.[3] During construction, though, the idea was abandoned and the ships were instead equipped with diesel engines.
Lagrange-class submarines were 75.2m (246.7feet) long, with a beam of 6.3m (20.7feet) and a draught of 3.6m (11.8feet), and could dive up to 50m (160feet). The submarine had a surfaced displacement of 9200NaN0 and a submerged displacement of 13180NaN0.[4] Propulsion while surfaced was provided by two 2600hp diesel motors built by the Swiss manufacturer Sulzer and two 1640hp electric motors.[5] The submarines' electrical propulsion allowed it to attain speeds of while submerged and on the surface.[6] Their surfaced range was 7700nmi at 9kn, and 4000nmi at 12kn, with a submerged range of 70nmi at 5kn.
The ships were equipped with eight 450 mm torpedo tubes (four in the bow, two stern and two external), with a total of 10 torpedoes and two on-board guns. The class was also armed with a 75 mm gun with an ammo supply of 440 shells. The crew of one ship consisted of four officers and 43 of officers and seamen.[7]
Regnault was built in the Arsenal de Toulon.[8] It was laid down in 1913, launched on 25 June 1924, and completed in 1924. It was named in honor of the distinguished French nineteenth-century chemist Henri Victor Regnault and was assigned the pennant number Q113. Regnault served in the Mediterranean Sea until 1935.