The Submarine Torpedo Boat
Its Characteristics And Modern Development

54 THE SUBMARINE TORPEDO BOAT surface of the water. Practically, however, that portion of the vessel above the center of buoyancy offers a consid- erably greater projected area to the thrust of the water than that portion of the hull below, and results in an un- balanced moment which must be overcome by the trim- ming rudders aft, and the boat must be trimmed to a slight inclination by the head. This type then, because of the broader and better resisting form of plane afforded by the big flat superstructure deck, unless proper vigilance is exercised, is very little removed as far as the factor of safety is concerned from the so-called diving type. The effects of this broad flat superstructure are even more accentuated by an increase of speed. To overcome these inherent tendencies to lose control at a critical speed, a method was devised and tried out on a small submarine on the Pacific Coast a few years ago. This method is illustrated by Figure 4. The system of control was essentially that of a diving boat, but involves a radical departure from the present practice in that it placed the propellers at or near the bow of the boat, and the diving rudders at or near the stern, both being equally distant from the center of buoyancy. The claim for this system was that the boat is positively controlled at all times, either when on the surface or when running submerged, and in both a horizontal and a vertical plane. When in motion the action of the vessel is inde- pendent of the metacentric height, and is submerged by inclining the diving rudders and plunging. The vessel may be plunged with a large percentage of reverse buoyancy which in this type tends to add to the controllability and not to detract from it as in the others. It was believed that the concurrent celerity of action with absolute free-