Lagrange-class submarine

The Lagrange-class submarines were a class of foursubmarines built for the French Navy during World War I and the interwar period. Threeships of this type were built in the Arsenal de Toulon from 1913 to 1924, and onewas built at the Arsenal de Rochefort shipyard. Entering the French Marine Nationale from 1918 to 1924, the submarines served until the mid-1930s.

Design
The Lagrange-class submarines were constructed as part of the French fleet's expansion programmes from 1913 to 1914. The ships were designed by Julien Hutter, who slightly modified his previous project, the Dupuy de Lôme-class submarines, using two Parsons steam turbines with a power of 2000 hp. During construction, though, the idea was abandoned and the ships were instead equipped with diesel engines.

75.2 m long, with a beam of 6.3 m and a draught of 3.6 m, Lagrange-class submarines could dive up to 50 m. The submarines had a surfaced displacement of 920 LT and a submerged displacement of 1318 LT. Propulsion while surfaced was provided by two2600 hp diesel motors built by Swiss manufacturer, Sulzer, and two1640 hp electric motors. The submarines' electrical propulsion allowed them to attain speeds of 11 kn while submerged and 16.5 kn on the surface. They had surfaced range of 4300 nmi at 10 kn and a submerged range of 125 nmi at 5 kn.

The ships were equipped with eight450 mm torpedo tubes (fourin the bow; twostern and twoexternal), with a total of tentorpedoes and two75 mm guns. The crew of a ship comprised forty-sevenmen.

Ships
Of the fourLagrange-class submarines, threewere built in the Arsenal de Toulon and one in the Arsenal de Rochefort. The ships were laid down between 1913 and 1914 and launched between 1917 and 1924. The ships were named after French scholars: Joseph-Louis Lagrange, Pierre-Simon Laplace, Henri Victor Regnault and the constructor of submarines Gaston Romazzotti.

Service
Of the foursubmarines, only twowere commissioned before the end of World War I: Lagrange and Romazzotti, which operated in the Mediterranean Sea.

From 1922 to 1923, the ships underwent a major refit in which they received new major conning towers, bridges and periscopes. All ships served in the Mediterranean Sea until 1935 for Lagrange and 1937 for the other threeships.