The motive power, of 720 h.p. is furnished by two independent electro-motors of 360 h.p. each of the Thury type, constructed by M. Sautter-Harlé and fed by accumulators of the Laurent-Cély type. The screw revolves at the rate of 250 revolutions a minute.
In order to endow the boat with a wide radius of action a battery was provided composed of 720 cells, each containing 29 plates and having an output of 400 amperes and a capacity of 1,800 amperes an hour. The Gustave Zédé had scarcely been placed in the water before the motive power gave out owing to the short-circuiting of most of the cells.
To remedy this, two plates were removed from each cell in order that each plate might be wrapped in a “chemise en toile d’amiante.” The result was no better for the covers, and the ebonite joints burst into flames and the boat was in danger of being consumed by fire. It was then decided to reduce it to 360 cells; this gave a speed of eight knots, though originally it was hoped that sixteen would be obtained.
The successive crews of the Gustave Zédé have suffered much from the poisonous fumes of the accumulators, and during the earlier trials all the men on board were ill.
In the bows is a torpedo tube and an arrangement is used whereby the water that enters the tube after the discharge of the torpedo is forced out by compressed air. Three 17½ Whitehead torpedoes are carried. In spite of the fact that a horizontal rudder placed at the stern had not proved serviceable on the Gymnote, such a rudder was fitted in the Gustave Zédé. With this rudder she usually plunged at an angle of about 5°, but on several occasions she behaved in a very erratic fashion, seesawing up and down, and once when the Committee and Experts were on board, she proved so capricious, going down at an angle of 30°–35°, often throwing the poor gentlemen on to the floor, that it was decided to fix a system of six rudders, three on each side.
Four water tanks are carried, one at each end and two in the middle, and the water is expelled by four Thirion pumps worked by a little electro-motor; these pumps also furnish the air necessary for the crew and for the discharge of the torpedoes.
For steering on the surface there was placed on the Gustave Zédé at first a movable shell with folded canvas similar to that of the Gymnote. It was found even more dangerous there than on the smaller boat; it was, therefore, taken away and replaced by a fixed kiosk, immovably attached to the hull, and of a shape tapering away fore and aft. The Gustave Zédé possesses, for under-water vision, an optical tube and a periscope.
The crew consists of an officer and eight men.
The first journey of any length undertaken by the Gustave Zédé was from Salins d’Hyères to Toulon. The sea was choppy, and a fresh breeze was blowing, and yet no mishap of any kind occurred. She navigated for the greater distance at the surface, with her cupola above the water, but when the water became too rough she plunged under the waves, occasionally emerging to take bearings. The distance between Toulon and Salins is short, and so the next journey was from Toulon to Marseilles, a distance of forty-one miles, and this the Gustave Zédé covered also in a rough sea without accident of any kind at the rate of six knots. Although accompanied by a tug, the Utile, it had no occasion for its services. She navigated on the surface all the way, but by reason of the swell everything was hermetically closed, and for more than seven hours the crew were kept in conditions exactly the same as if the vessel had been really under water.
On reaching Marseilles the accumulators had sufficient power left to perform the return journey.