Patent GB-1130179-A (GB)
Title: Hydrofoil craft with air exit apertures in the hydrofoil
Inventor: SCHERTEL HANNS FREIHERR VON
IPC: B63B1/24
Filed: 1965-12-22
Abstract: 1,130,179. Hydrofoil vessels. SUPRAMAR A.G. 22 Dec., 1965, No. 54392/65. Heading B7A. [Also in Division F2] Control of the lift produced by a hydrofoil 8 in accordance with changes in its angle of attack is effected by atmospheric air flowing into the boundary layer through a plurality of apertures or channels 16 in the uppermost surface of the hydrofoil, the flow of air being governed by a valve 1 in response to changes in pressure in a chamber 7 having a plurality of apertures or channels 9 communicating with the uppermost surface of the hydrofoil adjacent its leading edge. The valve 1 comprises an air inlet 3 and a conduit 14 connected to the channels 16 by a common chamber 15 within the body of the hydrofoil, said inlet and conduit being normally closed by a piston 4<SP>1</SP>, which is biased by an adjustable compression-spring 5 and attached to a further piston 4<SP>11</SP>. When the angle of attack increases, the corresponding reduction in pressure within the chamber 7 is transmitted to a chamber 21 containing the spring 5 through a conduit 6, whereby atmospheric pressure acting upon the piston 4<SP>11</SP> through an aperture 2a displaces the piston 4<SP>1</SP> against the action of said spring to permit air to flow into the chamber 15 and thence through the channels 16 so that the pressure on the uppermost surface of the hydrofoil rises sufficiently to keep the lift constant. The loading of the spring 5 is changed by displacement of an abutment disc 12 when a screw-threaded spindle 11 is rotated by a gear-wheel 13 coupled to control means (not shown in the drawing) situated in the control region or area of the vessel to which the hydrofoil is attached. The piston 4<SP>11</SP> can be displaced against the action of the spring 5 by a lever 23, which is connected by a cable 24 to control means in the aforesaid region. In a modification, Fig. 2 (not shown), the conduit 14 is connected to a plurality of channels (16<SP>1</SP>) in the lowermost surface of the hydrofoil through a common chamber (15<SP>1</SP>) and the spring 5 is omitted, the pistons 4<SP>1</SP>, 4<SP>11</SP> being controlled by pressure changes in chambers (7<SP>1</SP>, 711), respectively, which chambers are within the hydrofoil and communicate with areas of the hydrofoil adjacent its leading edge through upwardly and downwardly orientated channels (9<SP>1</SP>, 9<SP>11</SP>), respectively, whereby the lift effected by the hydrofoil is kept constant when the angle of attack becomes negative. Atmospheric air may be admitted to a conduit (10), through which pressure changes are transmitted from the chamber (7<SP>11</SP>) to the piston 4<SP>11</SP>, by a needle valve (17) so as to regulate the thrust exerted by the piston 4<SP>11</SP> on the piston 4<SP>1</SP>. Alternatively, the piston 4<SP>11</SP> may be biased by a compression-spring (not shown in the drawing). In a further modification, Fig. 3 (not shown), the chamber 15 and channels 16 according to Fig. 1 are provided in the hydrofoil in addition to the various chambers and channels that are provided in the modification according to Fig. 2, the chambers 15, (15<SP>1</SP>) being fed with air through separate conduits (14<SP>1</SP>, 14<SP>11</SP>), which are controlled by the pistons 4<SP>1</SP>, 4<SP>11</SP>, respectively. Compensation for pressure differences in the chambers (7<SP>1</SP>, 7<SP>11</SP>) is provided by appropriate differences in the diameters of said pistons. A compression-spring (5<SP>1</SP> or 511) engages with each piston. In another modification, Fig. 4 (not shown), the flow of air through the chamber 15 is governed by a valve-member (18) lodged therein and controlled by a spring-biased piston (4a), which is subjected to atmospheric pressure on one side and the pressure prevailing in the chamber 7 on the other side. The piston (4a) may be replaced by either a bellows or a corrugated diaphragm. The channels 9 may be screened from the regions of the hydrofoil containing the channels 16 by a pair of fins (20), Figs. 5 and 6 (not shown), so as to prevent undesirable operation of the valve 1 in response to changes of pressure caused by the air entering the boundary layer.