"Steering on the horizontal plane while submerged is accomplished by an automatic apparatus that performed very well in one of the boat's predecessors. Steering in the vertical plane is also done automatically, and with considerable exactness, while submerged. Steering in both planes can also, at the same time, be controlled manually. There will be a steel armored turret, four feet high, to protect the pilot and smokestack, and the hull will be covered by three feet of water while the vessel runs awash to attack.
"When engaged in harbor defence duty its position will be outside the outer line of harbor defences; that is, beyond the reach of the guns defending the entrance. While performing this duty it will lie awash; that is, with only the top of its turret over the surface of the water. On the approach of an enemy's vessel the smokestack will be shipped and the aperture on top of the turret through which it passed will be quickly closed watertight. She will then run in a direction to intercept the enemy's ship, still remaining in the awash condition, until she comes near enough to be discovered by the lookouts on the ship, when she will go from the awash to the entirely submerged condition. The distance from the ship at which she will dive will depend upon the weather. In rough weather she can come quite close without being observed. Having come within a distance that the operator estimates at two or three hundred yards from the ship, the diving rudders are manipulated so as to cause the top of the turret to come for a few seconds above the surface of the water. During this short exposure of the turret—much too short to give the enemy a chance to find its distance and train a gun on it capable of inflicting any injury—the pilot ascertains the bearing of the enemy's ship, alters his course or makes another dive if necessary. If he finds that the submarine boat is within safe striking distance, say one hundred yards, a Whitehead torpedo is discharged at the ship. A heavy explosion within six seconds after the torpedo is expelled will notify the operator that his attack has been successful, and he may then devote his attention to the next enemy's ship that may be within reach. When the boat is running on the surface of the water, with full steam power, and it becomes necessary to dive quickly, the pilot gives the order, 'Prepare to dive.' The oil fuel is instantly shut off from the furnace, the valves are opened to admit water to the water-ballast tanks, an electric engine draws down the smokestack and air-shaft into the superstructure, and moves a large, massive sliding valve over the aperture on the turret through which the smokestack passes. These operations will be completed in about thirty seconds, when the boat is in the awash condition and prepared to dive. In twenty seconds more it will be running horizontally at a depth of twenty feet below the surface of the water and quite beyond reach of the enemy's projectiles."
I submitted designs of a twin-screw vessel eighty feet long, ten feet beam, and one hundred fifteen tons displacement, with 400-horsepower steam engines for surface propulsion and 70-horsepower motors for submerged work. This design introduced several new and striking features into the art of submarine navigation which have been the cause of considerable scientific discussion. The design called for a double hull vessel, the spaces between the inner and outer hulls forming water-ballast tanks; the design also called for twin screws and four torpedo tubes, two firing forward and two aft.
LAKE DESIGN AS SUBMITTED TO THE U. S. NAVY DEPARTMENT IN 1893
Novel features consisted in: (A) wheels for running on the bottom; (B) rudder forming also a steering wheel when navigating on the bottom; (C-C) propellers for holding vessel to depth when not under way; (D-D) depth regulating vanes or hydroplanes for causing vessel to change depth while under way and to accomplish the changes of depth on an even keel; (E-E) horizontal rudders or "leveling vanes" designed to automatically hold the vessel on a level keel when under way; (F) a weight automatically controlled by a pendulum; (P) mechanism to correct trim; (G) gun arranged in watertight revolving turret for defense purposes or attack on unarmored surface craft; (L) propeller in tube for swinging vessel at rest to facilitate "pointing" her torpedoes; (M) conning tower; (N) telescoping smokestack; (O) observing instrument arranged to turn down on deck when under way; (T-T) torpedo tubes, two firing forward and two aft; (W-W) anchoring weights to hold the vessel at rest at any desired depth between the surface and bottom; (X) an "emergency keel" which would be automatically released if the vessel reached an unsafe depth. She was a double-hull vessel, water being admitted to the space between the inner and outer hulls and in trim tanks forward and aft to effect submergence. A diving compartment was also provided to enable the crew to leave or enter the vessel while submerged.
The novel feature which attracted the most attention and scepticism regarding this design was—so I was later informed by a member of the Board—in the claim made that the vessel could readily navigate over the water-bed itself and that while navigating on the water-bed a door could be opened in the bottom of a compartment and the water kept from entering the vessel by means of compressed air, and that the crew could, by donning diving suits, readily leave and enter the vessel while submerged. Another novel feature was in the method of controlling the depth of submergence when navigating between the surface and the water-bed. The vessel was designed always to submerge and navigate on a level keel rather than to be inclined down or up by the bow to dive or rise. This maintenance of a level keel while submerged was provided for by the installation of four depth-regulating vanes, which I later termed "hydroplanes" to distinguish them from the forward and aft levelling vanes or horizontal rudders. These hydroplanes were located at equal distances forward and aft of the centre of gravity and buoyancy of the vessel when in the submerged condition, so as not to disturb the trim of the vessel when the planes were inclined down or up to cause the vessel to submerge or rise when under way. I also used, in conjunction with the hydroplanes, horizontal rudders, which I called "levelling vanes," as their purpose was just the opposite from that of the horizontal rudder used in the diving type of vessel. They were operated by a pendulum-controlling device to be inclined so as always to maintain the vessel on a level keel rather than cause her to depart therefrom. When I came to try this combination out in practice I found hand control of the horizontal rudders was sufficient. If vessels with this system of control have a sufficient amount of stability, they will run for hours and automatically maintain both a constant depth and a level keel, without the depth-control man touching either the hydroplane or horizontal rudder control gear. This automatic maintenance of depth without manipulating the hydroplanes or rudders was a performance not anticipated or claimed in my original patent on the above-mentioned combination, and what caused these vessels to function in this manner remained a mystery, which was left unsolved until I built a model tank in 1905, in Berlin, Germany, and conducted a series of experiments on models of submarines. I then learned that the down pull of a hydroplane with a given degree of inclination varied according to its depth of submergence, and the deeper the submergence the less down pull. This works out to give automatic maintenance of depth so long as the vessel is kept at a constant trim on a substantially level keel, and I have known of vessels running for a period of over two hours without variation of depth of one foot and without once changing the inclination of either the hydroplanes or the horizontal rudder.
The capability of this arrangement of hydroplanes and horizontal rudders to control the depth of submergence was questioned and doubted for many years. As late as 1902, nearly ten years after I first submitted this method of control to the United States Navy Department, Naval Constructor L. Y. Spear, U. S. N., testifying before the Committee of Naval Affairs, House of Representatives, in reference to the "Lake even-keel boat" and my use of hydroplanes, said, "As an expert I do not think he will make his hydroplanes work"; and strongly contended that submergence by inclining the vessel itself was the proper method.
Several years later, in 1908, in Paris, I met Captain Lauboeuf, the celebrated French naval constructor, who has perhaps done more toward perfecting the French submarines than any other designer, and he informed me that after the French Government had its sad experience in the loss of the Lutine and Farfadet with their crews, it had changed all their diving boats into even-keel boats and was now using substantially my method of even-keel submergence with hydroplane control. He also informed me that it had, at that time, thirty-five new boats under construction to operate on the even-keel principle, eighteen of which were of five hundred and fifty tons displacement. Captain Lauboeuf was kind enough to compliment me as having been the first to introduce this method of submerged control.