French submarine Opale

Opale was one of six Émeraude-class submarines built for the French Navy (Marine Nationale) in the first decade of the 20th century.

Design and description
The Émeraude class were built as part of the French Navy's 1903 building program to a Maugas single-hull design. The submarines displaced 395 t surfaced and 427 t submerged. They had an overall length of 44.9 m, a beam of 3.9 m, and a draft of 3.8 m. They had an operational diving depth of 40 m. Their crew numbered 2 officers and 23 enlisted men.

For surface running, the boats were powered by two Sautter-Harlé 300 PS diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 300-metric-horsepower electric motor. They could reach a maximum speed of 11.26 kn on the surface and 8.5 kn underwater. The Émeraude class had a surface endurance of 2000 nmi at 7.3 kn and a submerged endurance of 100 nmi at 5 kn.

The boats were armed with four internal 450 mm torpedo tubes, two in the bow and two in the stern, for which they carried six torpedoes.

Construction and career
Opale was laid down in October 1903 at the Arsenal de Cherbourg, launched on 27 November 1906 and commissioned on 19 December 1908.