Le Gymnôte, 30 tons, electric motor, launched in 1888.
Two have just been sent to sea for trials, Le Francais and L’Algerian, built with the funds organized by “Le Matin” Newspaper in 1898. These are two boats of 145 tons with electric motors of the same type as the Morse. Six similar boats are still in the dockyards, and it is in contemplation to build several submersible craft of the Narval type. The existing material is sufficient, therefore, to indicate what the next will be, and we propose here to give the principal features.
(1) LE GYMNÔTE.
The behavior on the sea of the boat when subjected to the influence of this rudder is somewhat unsatisfactory. For rather prolonged dives, such as would be necessary, for example, is forcing a blockade, the instability of the boat becomes very great, and the one man at the helm is unduly fatigued without succeeding in retaining the mastery of his craft. On account of this instability, no greater speed on submersions than six knots was attained. For this speed the inclination of the axis of the boat was from three to five degrees forward. The difference in the draft of water between the bow and the stern was 0.88 meters (about 34 inches) for an inclination of 3 degrees; for 5 degrees it reached 1.50 meters (nearly 5 feet.)
Another system of “dip” rudder proposed in 1891, executed in 1893, and tested towards the end of 1894, consists in the employment of two horizontal flat boards placed on each side of the boat at the height of the midship frame. Their use, combined with that of the stern rudder has given better results. The boat is inclined less for the “dive,” dips more regularly, and lurches or “yaws” less and more seldom. The apparatus for exterior vision – optical tube and periscope – gave, especially the second, unsatisfactory results. The Gymnôte still carries (to sea the horizon when her hull is immersed to the waterline) a movable shell, with the side lights or scuttles (uncasque mobile a hublots). The apparatus is composed essentially of a metal shell with side lights all round its circumference. A cylinder of strong, tarred canvas fixed on steel springs which ensure rigidity, bind the shell itself to the upper part of the hull. Horizontal folds in front permit this canvas to double up regularly upon itself after the style of a Venetian lantern, and in such a way that when the doubling up is complete, the height of the shell (of ‘Casque”) comes exactly on a level with the upper platform of the boat. During navigation at the surface of on the waterline, the whole structure can be raised or lowered by means of a vertical screw moved by a horizontal hand wheel of which the movable nut constitutes the lower part of a vertical frame formed of metallic uprights which go to rejoin the hull. When the system is at the end of an upward course the canvas is completely stretched, and the observatory is at its maximum height; when on the contrary it is at the end of a downward run, the canvas is completely contracted and the “kiosk” has externally disappeared.
Such a system is very faulty and dangerous, as may be easily conceived. In the first place, considering the feeble resistance which the canvas can oppose when mounted on steel rings, it was indispensable to protect it against the pressure of the water during the “dive”. This was believed to have been accomplished by providing the shell with an India Rubber crown, formerly a soft of a beak, which when the system was completely folded up and closed, came to rest on another washer of India rubber placed at the bottom of the groove, where it formed a water-tight joint. This would have been very good if there had been certitude that the beak or cap fixed on the shell rested exactly at the bottom of the groove. To make sure of that there had been arranged a small opening which ought to give water when the closure was not sufficient, but this only gave an almost illusory means of control, the opening being almost always constructed by some detritus, debris of seaweed, and other foreign bodies encountered by this vessel. It will be seen what permanent danger was created by this apparatus – danger which on two occasions just missed causing the loss of the craft and unlocked for chance alone preventing it from foundering.
It would further be easy to show that in spite of its danger, the movable shell, with canvas folded in accordion pleats, was almost unusable – that it could not serve when there was a slight sea on; that it caused even during progress on the water-line infiltrations capable of sinking the boat; and finally that, even in a calm sea, and under the best conditions the length of this maneuver of raising and lowering made the operations of the “dive” slow and wanting in precision – operations which demand so much rapidity and delicacy, and to which it is allowable to sacrifice something on a submarine boat. This movable shell was about 0.35 metre (about 12-1/2 to 14 inches) in diameter; it was abandoned after all the commandants had successfully condemned it and to-day it is never used.
The motor of the Gymnôte is electric; it was invented by Captain Krebs. It is a motor with 16 poles and with excitation in a series, fitted directly to the screw-shaft at the stern of the boat. The induction circuit, of which the coil is composed of copper plates soldered one to the other, and separated by thin sheets of cardboard coated with bitumen, for a crown round the armature, which is an ordinary gamme ring. The motor was calculated to develop 55 horse power under the constants on 200 volts and 200 amperes. It weighs 2,000 kilos (about 4,400 pounds) and carries two pairs of brushes, one for motion ahead and the other for backward.
This motor has a number of serious drawbacks. Trimmed to the stern of the boat, its stern bearing is inaccessible and it cannot be repaired in place; the mode of rolling up the armature does not easily allow of inspection, nor the removal of defects of insulation when they are produced; finally – and what is the most serious – the mode of excitation does not permit the immediate stoppage of the armature. The consequence is that even in case of risk of collision all that one can do is to cut the induction current and wait until the armature stops of itself before being able to discharge the current for motion astern. Now, this armature is rather heavy and turns rapidly – that is to say, its momentum is great and its stoppage slow.
The Krebs motor gave so much trouble on the Gymnôte, that at the finish it was taken away and put on a boat in the service of the part of Toulon. The electrical machine of the Gymnôte is now an ordinary dynamo. The electric energy is furnished to the motor by an accumulator battery placed towards the bows. The first battery employed was composed of 540 “Comelin Desmazures” elements of alkaline zincate of potash, grouped in six elementary batteries of 90 couples each associated in twos and in quantity and 45 in tension. To vary the speed a variation was made in the difference of potential to the extreme limits by coupling in different ways the elementary batteries among themselves. The following results were thus given.
The hull of the ship is of steel, 6 millimeters (about ¼ inch) thick in the middle, and 4 millimeters (about 1/6 inch) at the extremities. The form is that of a torpedo, and the section is circular. This hull has stood the sea water well, and has not suffered internally from the new accumulators which are of sulphuric acid. It is true, care was taken to cover the inside with a thick coating of coal tar. The armament of the Gymnôte consists of two apparatus, each capable of discharging a torpedo of 355 mm. (about 14 inches) caliber,. The Gymnôte is attached to the movable defenses of Toulon.
II – THE GUSTAVE ZÉDÉ