Patent GB-962116-A (GB)
Title: Control for the automatic maintenance of the depth of submersion and for the improvement of the seagoing behaviour of hydrofoils fitted to watercraft
Inventor: SCHERTEL HANNS VON
IPC: B63B1/28
Filed: 1960-10-18
Abstract: 962,116. Hydrofoil vessels. SUPRAMAR A.G. ZUG. Oct. 18, 1960, No. 35722/60. Heading B7A. Control of the depth of submarine of a fully submerged hydrofoil 1 is effected by providing Pitot nozzles 8 in the leading edge of a streamlined strut or control element 4. The nozzles are arranged some above and some below the normal waterline, and the pressure in the hollow space 7 of the strut therefore varies as the depth of submersion and the dynamic water pressure. This space 7 communicates with an operating cylinder 9 so that the pressure acts upon a piston or diaphragm 10 connected to a trailing edge flap 2 and dashpot 14, and an increase in the depth of submersion increases the load on the piston and lowers the flap 2, incresing the lift of the hydrofoil. The speed of response of the control may be reduced by a throttle valve 13, so that the control is less responsive to short waves. Rotary valves 16, 17 are provided, connected by a shaft 15 and operated by a lever 20. As the valves are rotated in one direction, the valve 17 opens, reducing the pressure in space 7 and reducing the lift of the hydrofoil. As the valves are rotated in the other direction, the valve 16 opens, permitting more water to flow in through inlet nozzle 18, increasing the pressure in the space 7 and increasing the lift of the hydrofoil. The control valves 16, 17 may be automatically controlled by devices responding to the vertical velocity of the craft, i.e. the rate of change of depth of submersion, the valves being operated by a diaphragm (Fig. 5, not shown), one side of which is pressurized directly from the space 7, the other side being pressurized from the space 7 by way of an air chamber of variable volume, so that as the depth of submersion, and hence the pressure in the space 7, changes, the pressure on one side of the diaphragm changes faster than that on the other side; by devices responding to pitching and rolling inclinations and rates of change of such inclinations, e.g. artificial horizons &c., rate gyros; by devices responding to vertical accelerations (in which a mass is restrained by a vertical spring); by being connected to the steering means of the craft, so that during turns the outside hydrofoil generates more lift and the inside hydrofoil generates less lift. The Pitot nozzles 8 may be positioned slightly away from the leading edge of the strut, on the outside, so that when sideslip occurs, during turns, the space 7 of the outside strut receives a greater pressure than that of the inside strut and more lift is generated. Two pistons, acting in opposition may be fitted to push-rod 12 (Fig. 7, not shown), a large one as already described, and a smaller one, loaded from below by pressure from a separate control device behind the strut. The depth of submersion is maintained substantially constant with forward speed by a Pitot 35, through which water pressure acts on a piston 33 causing a valve 31 to be opened as the speed rises, thus reducing the pressure in space 7 and reducing the lift. The control may be combined with the air-operated control of Specification 934,882.