Propulsion of the Surface.
While the “Holland” boats for the British and United States navies are driven on the surface by a gasoline engine, this type of motor has not yet been used on the French boats, a steam engine fed with liquid fuel being employed in the Narval and vessels of this class, while in the Gustave Zédé, Morse, &c., electricity is the sole motive power both above and below the waves. Le Yacht states that France has always avoided the use of gasoline owing to the danger which arises from its presence on board submarine craft.
THE GASOLINE ENGINES OF THE FIRST BRITISH SUBMARINES.
(a) The Steam Engine.—In the Nordenfelt boat steam was raised, when running on the surface, by the burning of coal, but of late the advances that have been made by the employment of liquid fuel have led to the employment of this combustible for submarine boat propulsion in preference to coal.
The great drawback at present to the use of the steam engine is the length of time necessary for the unshipping of the chimney, the cooling of the engines, &c.
(b) The Oil Engine.—At the present time there is no oil motor in existence of sufficient power to give even moderate speed to a large boat, but the ingenuity of the engineer will probably overcome this drawback.
Those who make the dogmatic assertion that the submarine boat cannot be very fast because she cannot be endowed with much power, remind one of the wiseacres who were so convinced that steamboats would never replace sailing-vessels, nor steam locomotives the horse-drawn coach.
“The power required to impel a vessel through the water is augmented by her submergence. If 5,000 1–h.p. are required to drive a displacement of 120 tons at 28 knots, then rather more power will be required to drive 120 tons wholly submerged at the same speed.”
This statement appeared in the Engineer in the early part of 1901, but it appears that an exactly opposite opinion is held by many eminent authorities. For instance, at the discussion which followed the reading of Mr. Nordenfelt’s paper on Submarine Boats at the Royal United Service Institution in 1886, Mr. Anderson, C.E., stated that it was well known through the late Mr. Froude’s investigation that a fish-shaped vessel under water was in much more favourable circumstances for obtaining high speed than any vessel on the surface of the water, because it had been established theoretically that a vessel of easy lines completely submarine met with no resistance at all except the skin friction of the water, no resistance, that was to say, such as that which arose from the bow wave.