US 3651775 A
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llnite States Patent Mock [451 ar. 2%, 11972 54] HYDROFOIL SYSTEM 2,081,868 5/1937 Hampden ..1 14/665 H  Inventor: Helmut Kock, Woodlyn Park Apt. 0242 1 400 M CD a] e Blvd Woodlyn Pa. 19094 Primary Exammer-Andrew H. F arrell Attorney-Nolte and Nolte  Filed: Aug. 18, 1969 21 Appl. No; 850,743  ABSTRACT The present invention relates to a hydrofoil system attached to 52 US. (31.. ..ll4/66.5 H a hull vessel f Cl 1/20 The foil are attached to the hull of a vessel by means of non-  Fleld of Search ..1 l4/66.5 H lifting Struts and each foil comprises a main lifting foil portion which consists of submerged middle section and two upwardly  References Cned and outwardly inclined side sections which control the end UNITED STATES PATENTS position of the lift. In a spaced relatio and parallel to the inclined sections, two auxiliary upper lifting for] portions are 2,890,672 6/1959 Boericke ..1 14/665 h d on h ide of the hull for supporting the lifting a 3,221,697 12/1965 Allegretti.. ....1 14/665 i d bili i h l, 3,294,052 12/1966 Jones ....1 14/665 3,464,377 9/1969 Von Schertel ..1 14/665 10 Claims, 7 Drawing Figures PATENTEDMAR28 I972 SHEET 1 OF 3 INVENTOR 4 54 M117 MC/( (2 770% ATTORN EYS nvnnoron. SYSTEM BACKGROUND OF THE INVENTION The present invention relates to a front and rear lifting foils which are transversally attached by means of vertical and/or inclined struts to the hull at a certain distance from the bottom thereof. The hull can be conventional planing hull or a single stepped or multiple stepped hydroplane type hull. The known surface piercing foil systems have the disadvantage that they are extremely affected by waves. The wipe span of the foils, protruding excessively from the sides of the hull makes docking difficult, and requires special landing facilities. Besides, the prior art foil constructions disclose very heavy, large and unwieldy structures for hydrofoil crafts.
STATEMENT OF THE INVENTION Therefore, the primary object of this invention is to overcome the disadvantages of prior art foil systems.
More particularly, the object of the present invention is to reduce the effect of waves on the submerged part of the foil by shortening the leverage to the center line of the vessel, thus rendering a ride with considerably reduced lateral motions.
Another object of the present invention is to reduce the transverse span of the foils almost to the beam of the hull, thus making docking and handling of the boat much easier.
A further object of the present invention is to improve the structure, maintenance, exchange of damaged parts, and the installation of the hydrofoil system.
According to the present invention, the above objects are attained by providing front and rear foils with a main middle section which is submerged basically parallel to and at a certain distance from the water surface, and will be affected by the surface effect, losing gradually its lift force as it approaches to the surface. The middle section is extended to both sides by outward-upward inclined side sections at an angle of 30 to 35 and the tips of the side sections reach the water surface at cruising speed, limiting thus the lifting force to this point.
The length of the chord is to be kept constantover the full length of said parts or may be increased form the center line outward. The section has a straight or convex underside and a curved upper side. The angle of attack between and 1 is to be constant over the full length thereof. Said foils are of hydrodynamic, lift producing shapes which act to lift the hull clear out of the water at certain speeds, produced by the driving engine and by means of propeller or jet. The size of these foils is proportional to the load to be carried in relation to the center of gravity of the vessel.
Furthermore, two upper foil portions are attached to the hull parallel and at a distance from the inclined side foil portions to assist the lifting action of the main section and to emerge from the water during the lifting position of the vessel.
For a better understanding of the present invention, reference to the following description taken in connection with the accompanying drawings, in which:
FIG. 1A is a side elevation of a front hydrofoil attached to the bow part of the hull of the water craft;
FIG. 1B is a side elevation of a rear hydrofoil attached to the aft part of the hull of FIg. 1A;
Flg. 2 is a front elevation of the front hydrofoil of this invention as shown in FIG. 1A;
FIG. 3 is a front elevation of one modification of the rear hydrofoil of this invention for a vessel having two propellers; and
FIG. 4 is another modification of the rear hydrofoil of FIG. 3 for a vessel having a single propeller.
FIG. 5 is a bottom plan view of the front hydrofoil arrangement with parts broken away for purposes of clarity;
FIG. 6 is a perspective view of the front hydrofoil arrangement with parts thereof broken away for purposes of clarity.
Referring now to the figures of the drawing, hydrofoil boat hull l is provided with two lifting foils 2 and 3 which are transversally attached by means of vertical or inclined struts 7, 8, 9,
l0 and 11 to the hull and disposed at a certain distance from the bottom thereof.
Front foil 2 is located at the bow whereas the rear foil 3 is situated at the aft end, ahead of the rudder 12 and above propeller 14. The main components of foils 2, 3 and 4 according to this invention are submerged main lifting foil portions 2, 3, 4 and 5 which should remain at all times under the surface 15 of the water. A lift-assisting upper foil portion 6 assists in lifting the vessel out of the water when the vessel speed is increased and portion 6 will be completely out of the water when the vessel has reached its cruising speed. The connecting struts 7, 8, 10 and partially 11 attach said foils to the hull. As seen in FIGS. 2-4, the submerged main foil portion consists of a middle section 2 which can be horizontal and straight (FIG. 2) or W-shaped (FIGS. 3 and 4) or curved.
At the rear foil, as seen in FIG. 3, the horizontal middle section 2 extends over the propeller l4, and then it is inclined downwardly on each side by about 30 to form downward directed foil portions 4 each of which in turn continues upwards, taking the form of an outward inclined side foil section 3. Each of sections 3 has an inclination of about 30-35 and terminates at the water surface 15 when the vessel has attained the cruising speed.
In the front foil of FIG. 2, there is provided a straight or curved horizontal middle section 2 which is integral with the upwardly inclined side sections 3.
According to one feature of the present invention, each of the auxiliary lifting foil portions 6, which area is greater than each of half of the main foil, are mounted substantially parallel to and at a distance double or more then the mean chord length of the main under-foil 3, with the purpose of not interfering with the circulation around said lower foil 3. The portion 6 is attached to hull l by struts 7, 8 and 10 and to strut 11 in FIG. 3. The trailing edge of part 6 is located ahead of the leading edge of part 3.
The lower end of inclined portion 6 is located on the level or under the upper tips of portion 3 and connected to section 3 by a lift producing foil section 5 which is thus inclined upwards and inwards by 30 to 45 with respect to the horizontal plane. Both upper tips of portion 6 on front and rear foils are connected to the hull by non-lifting struts 7. Both the inner and lower ends of portion 6 of the front foil FIG. 2 and FIG. 4 the propeller the rear foil are connected to the hull by a nonlifting strut 8 or directly attached to strut 11, as seen in FIG. 3. A vertical strut 9 connects the middle portion 2 of front foil, as seen in FIG. 2, to the keel of the vessel. At the rear foil, one strut 11 in the case of a single propeller, as seen in FIG. 4, and two struts 11 in case of twin propellers, as seen in FIG. 3, connect the middle portion 2 with the hull. These struts ll of the rear foil 3 and 4 support the propeller shaft 13 and rudder l2 and contain the cooling water duct for the engine. Foil portions 2, 3, 4 and 5 are of hydrodynamic cross-sectional shape with a straight underside and a curved upper side to produce lift by forward motion of the vessel. Portion 6 is of a concave shape at its underside, and of a curved shape at its upper side. The struts 7, 8, 9, l0 and 11 are of a non-lifting, and of the least drag-producing shape. The angle of attack of the front and rear lift foils should be set between 0 to 1 to the base line and constant over the whole length. The areas of the front and rear foils 2 and 3 are related to the load distribution in the vessel. Since the span of the foils is limited, the length of the chord of the front foil may be different from the rear foil. At forward motion, the combined lifting forces of the boat bottom and the foils will raise the vessel. Increasing the speed, the hull will lift clear out from the water, and auxiliary foil portion 6 will emerge until the upper tips of foil portion 3 and 5 on both foils (FIGS. 2, 3 and 4) reach the surface level 15 of the water.
Beyond this point, the lifting forces at the diagonal foil parts are so reduced due to the reduction of effective area, by air braking and surface effects on the middle foil section 2, that a further elevation would be virtually impossible. The diagonal inclined portions 3 and 5 act as stabilizers, assisted by portion 6, thereby keeping the vessel in an upright position even in the event of water disturbances, waves and shifting of loads in the boat. The longitudinal trim and stability will be maintained due to the identical action and motion of the front and rear foil. The lift of the foil system depends basically upon the forward speed and it is incumbent upon the boat pilot to maintain this speed so that the foils emerge to the indicated waterline, which is the ideal condition. The effect of waves on the emerged foil portions 6 is reduced because of the much reduced leverage to the center line of the vessel. This construction permits a ride with much less motion.
Since the main foil portions 3 do not continue outward above the water level surface 15, as in conventional surface piercing foil systems, the span of the foils can be reduced almost to correspond to the beam of the boat hull thereby making docking and handling much easier.
The configuration of the foils in the present invention permits dividing them in several sections for better construction, exchange of damaged parts and simpler transportation and assembly. Furthermore, the parts are connected by means of bolts and/or hinge type connections.
The hydrofoil system of the present invention includes a front and rear foil, and both foils act in identical manner, having identical and unchanged angle of attack and foil section shape. They differ only in size and area subject to different amount of loading, shape of the hull sections and, at the rear foil to the propeller shaft bearing, attached rudder and cooling water supply duct.
What is claimed is:
1. In a hydrofoil craft having a planing hull, drive means, a front foil and a rear foil, a plurality of struts attached to the hull and being of a size proportional to the load carried in relation to the center of gravity of the craft for lifting the hull clear out of the water at a predetermined speed of the craft, each of said foils comprising a main lifting foil middle section which extends substantially parallel to and submerged at a certain distance from the water surface and which gradually loses its lifting force as it rises closer to the water surface, said front foil having side sections connected to said middle section at opposite ends thereof and inclined outward and upward at an angle of 3035 to said middle section, the upper ends thereof rising to the level of the water surface at a predetermined speed of said craft, thus limiting the lifting force to this point, and the length of the chord being kept constant from the center of the craft outward, the angle of attack being constant over the entire length of said sections, a spaced pair of auxiliary upper lifting foil portions each being parallel spaced from the adjacent lower front foil side sections, and another front foil section connecting each of the upper lifting foils and the adjacent lower front foil side sections.
2. In a hydrofoil craft as claimed in claim 1 wherein said rear foil is provided with a main lifting middle section, downwardly directed foil portions connected to opposite sides of said middle section, and side sections connected to said downwardly directed foil portions at opposite ends thereof and inclined outward and upward at an angle of 30-35 to said middle section.
3. In a hydrofoil craft as described in claim 1 wherein the area of each of the auxiliary upper lifting foil portions is larger than the area of the other of the inclined sections of said main lifting foil.
4. In a hydrofoil craft as described in claim 1 wherein the angle of attack of said auxiliary upper lifting portions is equal to the angle of attack of the main lifting foil.
5. In a hydrofoil craft as claimed in claim 1 wherein the trailing edge of each of said auxiliary upper lifting foil portions is located ahead of the leading edge of the inclined sections of said main lifting foil located below.
6. In a hydrofoil craft as described in claim 1, further comprising a front foil being an inwardly and upwardly inclined lift-producing foil portion for connecting the main lifting foil portion with the under and inner end of the upper auxiliary lifting foil portion thereby substantially increasing he stability of the vessel. I
7. A hydrofoil craft as described in claim 1 wherein said front and rear foils are substantially similar in shape and angle of attack but have different lifting foil areas according to the weight distribution on the vessel.
8. In the hydrofoil craft as described in claim 1 wherein the struts connecting the lift foils to the hull are of a non-lifting shape.
9. In a hydrofoil craft as described in claim 1 wherein the area of each of the auxiliary upper lifting foil portions is larger than the area of either of the inclined sections of said main lifting foil.
10. In a hydrofoil craft as claimed in claim 1 wherein the trailing edge of each of said auxiliary upper lifting foil portions is located ahead of the leading edge of the inclined sections of said main lifting foil located below.