Two boats (length 13 metres, beam 2.38 metres, draught 1.62 metres, displacement 7.05 tons; trial speed 13 knots) built by the Société des Ateliers et Chantiers de la Loire and fitted with a 150 millimetre by 230 millimetre by 340 millimetre by 240 millimetre stroke inverted-vertical triple-expansion condensing marine engine, operating at 400 revolutions per minute, with steam supplied by a marine locomotive boiler. Three standards were cast on the side of the condenser to support the cylinders at the rear to form the crosshead guides, as well as the four Plummer-blocks of the crankshaft. Hollow steel columns in the front supported the cylinders.