Description

The present invention relates to a planing boat with a hull, having a longitudinal axis (X) and a mirror plane (S), comprising a propulsion system, a supporting hydrofoil arranged near a center of gravity of the boat, below the boat, and a stabilizer arranged near a rear end of the boat.

PRIOR ART

Planing boats are known from the prior art. Planing refers to a condition in which the boat rises out of the water and glides over the water, as it were. The boat is carried by part hydrostatic force and part hydrodynamic lift, depending on the speed. When a boat planes, it reaches its highest speed. Whether and when a boat will plane depends on several factors. This could include thrust, speed, hull shape and weight.

A major disadvantage of such planing boats is that when encountering waves, uncomfortable behavior occurs and and/or drastic stabilization measures are necessary or speed must be reduced. Such measures must be taken so quickly that it is practically impossible to carry them out manually.

The resistance of a planing boat is dictated by the frictional resistance and the extent to which hydrodynamic lift can be generated from the hull shape.

Therefore, systems have been proposed in the prior art for use with hydrofoil boats involving a front and a rear hydrofoil, these systems predicting the arrival of waves at the underwater ship and adjusting the angle of the hydrofoil accordingly. An alternative is that the force on the hydrofoils is regulated by the extent to which they split the water surface.

Although such systems work, they are costly and are associated with a relatively large effort. In addition, circumstances exist under which such systems do not operate. In such cases, a particularly uncomfortable sailing behavior will be obtained. In particular, as mentioned, these systems also see application in hydrofoil boats, instead of planing boats. A hydrofoil boat is known from, for example, US 5,448,963. Two hydrofoils are known from this publication, one hydrofoil being located near the center of gravity of the vessel and the other hydrofoil being arranged near the rear end of the vessel. The rear hydrofoil is located some distance below the hull and is fully immersed in the water under normal sailing conditions. With hydrofoil boats, the effect is achieved that when the sailing speed is increased, the vessel, with the exception of the hydrofoils, is completely lifted out of the water, as a result of which the hull surface that comes into contact with the water disappears above the water, which reduces friction. Both hydrofoils always remain completely under water. This makes it possible to achieve a higher speed with the same power.

Because a planing boat glides over the water, as it were, and is not intended to be lifted almost completely out of the water, such as a hydrofoil boat, such systems, as used in hydrofoil boats, are not applicable one-to-one to planing boats.

US 6,782,839 B1 furthermore discloses a hydrofoil boat with a hydrofoil arranged below the hull of the boat.

US 6,805,068 B1 moreover discloses a hydrofoil system for lifting a boat partially out of the water to reduce drag.

WO 2021/002744 A1 by the present Applicant addresses many of the abovementioned problems, offering effective stabilization measures to improve the boat’s behavior, in particular when encountering waves.

JP H07 267178 A discloses a vessel with a hydrofoil of which the angle of elevation can be adjusted according to sailing conditions.

JP H09 207872 A discloses a vessel with a mounting mechanism for a hydrofoil, wherein the mounting mechanism is configured in such a manner that lift can be linearly adjusted.

FR 3 073 490 A1 discloses an automated control device for a motor boat sailing on a body of water, wherein foils are provided equipped with a set of foil sensors which measure the deformations of the foil structure. The data are processed in real time in order to adjust the position of the foils underwater.

JP 2010 269723 A discloses a ship equipped with a hydrofoil for enabling smooth and safe forward/backward movement of the hydrofoil while at the same time keeping the ship stable.

US 2021/114692 A1 discloses a vessel wholly or partially supported by one or more fully or partially submerged hydrofoils. The amount of lift provided by the hydrofoils is regulated as a function of the lift itself. However, a planing boat with the abovementioned supporting hydrofoil and stabilizer can be improved even further, in particular with respect to lift, resistance and/or damping characteristics.

OBJECT OF THE INVENTION

An object of the present invention is thus to provide an abovementioned planing vessel or planing boat, wherein the performance of the boat with respect to lift, resistance and/or damping characteristics is further improved, in order to improve the overall comfort and performance of the planing boat.

SUMMARY OF THE INVENTION

According to the present invention, the planing boat is characterized in that the supporting hydrofoil comprises an asymmetric hydrofoil section, having camber, and the planing boat comprises lift regulation means for regulating the lift generated by the asymmetric foil section and/or the supporting hydrofoil. Surprisingly, the Applicant has found that such an asymmetric or cambered hydrofoil leads not only to improved lift-to-resistance ratios, in particular at zero/low angles of incidence, but also improves the damping behavior of the boat, especially when the planing boat travels at higher speeds. The lift regulation means furthermore allow the lift of the supporting hydrofoil to be optimized at all times, at any operational speed, to further improve the performance of the planing boat. The above planing boats are dubbed planing boats with “adaptive foil assist” by the present Applicant. “Adaptive” means that the lift generated by the supporting hydrofoil can be generally adapted to the requirements of the situation at hand to optimize lift, resistance and/or damping. The Applicant views “adaptive” as being different from “dynamic”, wherein e.g. the angle of incidence of the incoming flow is constantly and continuously (i.e. dynamically) influenced, for instance in view of wave motions, to constantly optimize e.g. the lift of the supporting hydrofoil.

In the context of this description, with respect to the hydrofoil, the term “supporting” is to be understood as providing a lift force or lifting force which is sufficient for causing planing of the boat during the intended sailing condition, but a lift force or lifting force which, however, is not sufficient to lift the boat completely out of the water to provide a hydrofoil boat. The lifting force is preferably 35 - 65%, for example 40 - 60%, such as 45 - 55% of the total weight of the boat, at maximum speed.

The supporting hydrofoil moreover may be connected to the hull by means of a connecting member, such as a strut or the like, as the skilled person will understand.

The planing boat may furthermore employ a stabilizer near the rear end of the planing boat, such as disclosed in WO 2021/002744 A1 by the present Applicant.

An embodiment relates to an aforementioned planing boat, wherein the lift regulation means comprise rotation means for rotating the supporting hydrofoil around a rotational axis perpendicular to the mirror plane of the planing boat. Thus, the angle of incidence can be effectively influenced, e.g. to maximize lift, minimize lift, minimize resistance, influence damping behavior, et cetera, depending on operational requirements.

An embodiment relates to an aforementioned planing boat, wherein the supporting hydrofoil is configured for being rotated around the rotational axis by the rotation means at an angle relative to the longitudinal axis (X) of the planing boat of -15° to +15°, such as -10° to +10°, or e.g. 0° to 15° or 0° to 10°, and/or 0° to -15° or 0° to -10°. In practice, this range of angles covers most of the operational requirements of the planing boat and at the same time prevents the occurrence of excessive resistance on the supporting hydrofoil, so that the constructional integrity of the supporting hydrofoil and/or for instance the strut(s) with which the supporting hydrofoil is connected to the hull is not compromised.

An embodiment relates to an aforementioned planing boat, wherein the rotational axis is situated at a perpendicular distance (DRA) from a chord of the asymmetric hydrofoil section, allowing fine adjustment of the rotational angle of the supporting hydrofoil and minimizing the force needed to effect an adjustment of the rotational angle. Of course, a strut or the like may be used to connect the supporting hydrofoil with e.g. a shaft aligned with the rotational axis.

An embodiment relates to an aforementioned planing boat, wherein the perpendicular distance (DRA) is 1.5 - 4 times, for instance 2 - 3 times, a chord length of the asymmetric hydrofoil section (i.e. at the mirror plane S). The Applicant has found this distance to be optimal when balancing constructional requirements related to the construction of the supporting hydrofoil and a connecting member connecting the supporting hydrofoil to the hull on the one hand and “force requirements”, i.e. the force needed to effect the rotational angle adjustment on the other hand. The stated perpendicular distance (DRA) also provides sufficient room/space for installing the supporting hydrofoil below the planing boat.

An embodiment relates to an aforementioned planing boat, wherein the rotational axis intersects or coincides with the hull. Thus, the rotation can be effected by arranging rotation means, such as a servo motor or the like, inside the hull, instead of outside the hull. Furthermore, the often relatively heavy rotation means can thus be placed relatively close to the center of gravity of the planing boat to prevent undesirable weight distribution and further improve the boat’s comfort and performance.

An embodiment relates to an aforementioned planing boat, wherein the lift regulation means comprise a force regulation device for counteracting pitching moments around the rotational axis due to a resultant force on the supporting hydrofoil not intersecting the rotational axis. Thus, the resultant force can thus be prevented from generating unwanted pitching moments, such as occurring when encountering a wave or another type of sudden change of flow direction/speed, such as when the planing boat “slams” on the water surface.

Preferably, the force regulation device comprises a spring. More preferably, the spring, which may be a coil/spiral spring, has a length direction aligned with the mirror plane and being perpendicular to the rotational axis for maximum efficiency, although the spring may be arranged at an angle to the rotational axis.

An embodiment relates to an aforementioned planing boat, wherein the asymmetric hydrofoil section has positive camber, to provide optimal lift. However, theoretically speaking, situations may be conceivable, wherein the asymmetric hydrofoil section has negative camber.

An embodiment relates to an aforementioned planing boat, wherein the asymmetric hydrofoil section has a maximum camber of 0.1 times a chord length of the asymmetric hydrofoil section. Otherwise, premature flow separation may occur, possibly resulting in erratic and unpredictable behavior of the supporting hydrofoil especially in the speed regime in which the planing boat operates when planing.

An embodiment relates to an aforementioned planing boat, wherein the asymmetric hydrofoil section has a maximum thickness of 0.2 times a chord length of the asymmetric hydrofoil section. In line with the preceding paragraph, flow separation can thus be postponed as much as possible. Furthermore, resistance of the supporting hydrofoil at planing speeds is further minimized.

An embodiment relates to an aforementioned planing boat, wherein the lift regulation means comprise camber adaptation means for adapting the camber of the supporting hydrofoil. Surprisingly, the Applicant has obtained very good results with changing the camber of the asymmetrical hydrofoil section (i.e. the shape of the asymmetric hydrofoil section as such) - in addition to, or instead of, changing the rotational angle of the supporting hydrofoil as a whole.

An embodiment relates to an aforementioned planing boat, wherein the camber adaptation means comprise fitting the supporting hydrofoil with a rotatable trailing edge portion configured for being rotated around a rotational axis perpendicular to the mirror plane of the planing boat. Thus, the camber of the supporting hydrofoil can be effectively influenced, for instance in situations where the supporting hydrofoil is required to provide maximum lift, wherein the rotatable trailing edge portion may be rotated downwards. In such a case, the rotatable trailing edge portion can also be advantageously used to influence the pitch angle of the planing boat.

Preferably, the rotatable trailing edge portion comprises at least 10%, but at most 50%, such as 20% to 40%, of a chord length of the of the asymmetric hydrofoil section.

An embodiment relates to an aforementioned planing boat, wherein the rotatable trailing edge portion is configured to be rotatable at an angle relative to the longitudinal axis (X) of the planing boat of -25° to +25°, such as -15° to +15° or - 10° to +10° or e.g. 0° to 25°, 0° to 15° or 0° to 10°, and/or 0° to -25°, 0° to -15° or 0° to -10°.

An embodiment relates to an aforementioned planing boat, wherein the camber adaptation means comprise fitting the supporting hydrofoil with a rotatable leading edge portion configured for being rotated around a rotational axis perpendicular to the mirror plane of the planing boat. Thus, analogous to the use of a rotatable trailing edge portion, the camber can be effectively influenced/adapted. The rotatable leading edge portion allows the incoming flow to flow more smoothly over the upper surface of the asymmetric hydrofoil when at a high angle of incidence, for instance when the supporting hydrofoil is rotated around the rotational axis perpendicular to the mirror plane of the planing boat. This allows the supporting hydrofoil to be operated effectively at higher angles of incidence, when the supporting hydrofoil is required to produce more lift.

An embodiment relates to an aforementioned planing boat, wherein the rotatable leading edge portion is configured to be rotatable at an angle relative to the longitudinal axis (X) of the planing boat of -25° to +25°, such as -15° to +15° or - 10° to +10° or e.g. 0° to 25°, 0° to 15° or 0° to 10°, and/or 0° to -25°, 0° to -15° or 0° to -10°, in order to provide optimal lift/resistance ratios and flow separation behavior.

An embodiment relates to an aforementioned planing boat, wherein the supporting hydrofoil, when seen in plan view, is symmetrically tapered from a root of the supporting hydrofoil, situated at the mirror plane of the planing boat, towards supporting hydrofoil tips situated at opposite sides of the mirror plane, wherein a chord length of the supporting hydrofoil becomes smaller from the root towards the supporting hydrofoil tips. Thus, an optimal balance between performance on the one hand and constructional limitations on the other hand is achieved.

An embodiment relates to an aforementioned planing boat, wherein a taper ratio is 0.4 - 0.6, preferably 0.5, leading to further positive effects on the maximum lift (coefficient) of the supporting hydrofoil and a reduced tendency for the flow to separate from the supporting hydrofoil. This, in turn, again increases overall comfort and performance of the planing boat.

An embodiment relates to an aforementioned planing boat, wherein, when seen in plan view, the supporting hydrofoil is provided with forward and/or aft sweep, to further decrease drag and, if applicable, reduce damage of the supporting hydrofoil when objects hit the supporting hydrofoil (in case of aft sweep).

An embodiment relates to an aforementioned planing boat, wherein a leading edge sweep angle (ALE) is 0° - 45°, such as 0°, preferably 10° - 30°, more preferably 10° - 15°.

An embodiment relates to an aforementioned planing boat, wherein a trailing edge sweep angle (ATE) is 0° - 45°, such as 0°, preferably 10° - 30°, more preferably 10° - 15°.

An embodiment relates to an aforementioned planing boat, wherein the supporting hydrofoil is provided with a shock absorber, such as a spring, wherein the supporting hydrofoil is preferably connected to the hull with the shock absorber. The shock absorber further increase comfort and overall performance of the planing boat, by absorbing shocks due to unexpected (vertical) accelerations, which are uncomfortable to passengers of the planing and also lead to (unpredictable) loss of lift on the supporting hydrofoil.

An embodiment (thus) relates to an aforementioned planing boat, wherein the shock absorber is configured for absorbing shocks in a direction perpendicular to the movement direction (M) of the boat.

An embodiment relates to an aforementioned planing boat, wherein the supporting hydrofoil is arranged to be vertically adjustable, in order to arrange the supporting hydrofoil closer to or further away from the hull, depending on operational conditions.

An embodiment relates to an aforementioned planing boat, wherein the supporting hydrofoil is configured to provide a lift force of 35 - 65%, for instance 40 - 60%, such as 45 - 55% of the total weight of the boat, at maximum speed.

An embodiment relates to an aforementioned planing boat, wherein the supporting hydrofoil is connected to the hull with a strut.

An embodiment relates to an aforementioned planing boat, wherein the strut is configured for providing minimal resistance, such as by streamlining the strut.

An embodiment relates to an aforementioned planing boat, wherein the supporting hydrofoil is connected to the hull with two, three or more struts.

An embodiment relates to an aforementioned planing boat, wherein the supporting hydrofoil is connected to the hull with two struts, wherein the two struts are symmetrically arranged at opposite sides of the mirror plane of the planing boat, at a same distance from the mirror plane, in order to provide optimal constructional strength.

An embodiment may furthermore relate to an abovementioned planing boat, wherein two or more supporting hydrofoils are arranged at a vertical distance from each other, in particular above each other, wherein the two or more supporting hydrofoils are connected to the hull with one or more struts.

An embodiment may furthermore relate to an abovementioned planing boat, wherein the hull is an unstepped hull. The Applicant is of the opinion that for the intended speed regime of the planing boat according to the present disclosure, an unstepped hull provides improved performance, as well as such a boat being easier to produce. An embodiment may furthermore relate to an abovementioned planing boat, wherein the rotation means are placed inside the hull. Thus, the rotation means are protected from exposure to water, high forces, et cetera - as opposed to various prior art disclosures, wherein the rotation means are provided behind a step in the hull, which may lead to damage, malfunctioning, et cetera.

An embodiment may furthermore relate to an abovementioned planing boat, wherein the rotation means are fully enclosed by the hull. Thus, the rotations means are optimally protected by the hull.

An embodiment may furthermore relate to an abovementioned planing boat, wherein the rotation means are placed close to or at the center of gravity of the boat. The Applicant submits that, due to the rotation means for instance often comprising a heavy servo motor, hydraulics, and the like, the rotation means can be advantageously placed close to or at the center of gravity of the boat, to improve stability.

An embodiment may furthermore relate to an abovementioned planing boat, wherein, when the lift regulation means comprise a force regulation device, the force regulation device is placed inside the hull. Thus, the force regulation device is also protected from negative outside influences.

An embodiment may furthermore relate to an abovementioned planing boat, wherein the force regulation device is fully enclosed by the hull. The force regulation device is thus fully protected from the aforementioned outside influences.

An embodiment may furthermore relate to an abovementioned planing boat, wherein the force regulation device is placed close to or at the center of gravity of the boat, to further improve stability.

An embodiment may furthermore relate to an abovementioned planing boat, wherein, when the supporting hydrofoil is provided with a shock absorber, the shock absorber is placed inside the hull. Again, the shock absorber is thus not exposed to water (resistance) and other possibly damaging external influences.

An embodiment may furthermore relate to an abovementioned planing boat, wherein the shock absorber is fully enclosed by the hull, to optimally protect the shock absorber. An embodiment may furthermore relate to an abovementioned planing boat, wherein the shock absorber is placed close to or at the center of gravity of the boat, to even further improve stability.

According to WO 2021/002744 A1 by the present Applicant, the stabilizer may be in the form of a plate-shaped profile arranged near the rear side of the vessel, such that one side influences the water flow while the other side has no effect on the water flow, resulting in stable sailing behavior. The equilibrium described above resulting from the planing of the vessel’s hull at higher speeds is no longer unstable but stable, as described in WO 2021/002744 A1.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail below, with reference to illustrative embodiments shown in the drawing. Therein:

Fig. 1 shows an example embodiment of a planing boat according to the invention with a supporting hydrofoil having an asymmetric hydrofoil section;

Fig. 2 shows an example embodiment of an asymmetric hydrofoil section according to the invention;

Fig. 3 shows an example embodiment of a supporting hydrofoil with an asymmetric hydrofoil section according to the invention, provided with life regulation means comprising rotation means;

Fig. 4 shows an example embodiment of a supporting hydrofoil with an asymmetric hydrofoil section according to the invention, provided with life regulation means comprising camber adaptation means;

Fig. 5 shows an example embodiment of a supporting hydrofoil with an asymmetric hydrofoil section according to the invention, wherein the supporting hydrofoil is provided with a shock absorber;

Fig. 6 shows an example embodiment of a supporting hydrofoil with an asymmetric hydrofoil section according to the invention, wherein the lift regulation means comprise a force regulation device.

Fig. 7 shows a perspective view of an example embodiment of a supporting hydrofoil with an asymmetric hydrofoil section according to the invention, wherein the supporting hydrofoil is provided with forward sweep and is tapered; Fig. 8 shows a plan view of an example embodiment of a supporting hydrofoil with an asymmetric hydrofoil section according to the invention, wherein the supporting hydrofoil is provided with aft sweep and is tapered; and

Fig. 9 shows a plan view of an example embodiment of a supporting hydrofoil with an asymmetric hydrofoil section according to the invention, wherein the supporting hydrofoil is tapered.

DETAILED DESCRIPTION

Fig. 1 shows an example embodiment of a planing boat 1 according to the invention with a supporting hydrofoil 4 having an asymmetric hydrofoil section 7.

More specifically, Fig. 1 shows a planing vessel or boat 1 with a hull 2. In the illustrated example embodiment, a boat 1 with a length of about 5 m is shown, but it will be understood that the length of the boat 1 can be shorter or significantly longer. Preferably, the length of the boat 1 is between 3 - 35 m, such as 5 - 20 m. The boat 1 has a longitudinal axis X and a mirror plane S. The boat 1 comprises a propulsion system 3, such as including a propeller. A rudder is also shown, although the rudder is not indicated with a reference numeral. Fig. 1 shows a fixed propeller shaft with a propeller. However, other (propeller) configurations are also conceivable, such as, but not limited to, a Z-drive, a surface propeller, a waterjet, an outboard motor or a pulling propeller, with or without single or double screws. The hull 2 preferably concerns an unstepped hull, as shown in Fig. 1.

Fig. 1 shows the position in which the boat 1 is motionless or sailing only very slowly. In this position, the longitudinal axis X of the boat 1 is generally aligned with a direction of motion M of the boat 1. However, when the boat 1 gains speed, the longitudinal axis X “pitches up” and the longitudinal axis X and the direction of motion M may therefore be at an angle (trim angle) with respect to each other (in a vertical plane), such as at angle of 0° - 8°.

According to the invention, a supporting hydrofoil 4 is arranged near a center of gravity Z of the boat 1 , below the boat 1. A stabilizer 5 is arranged near a stern or rear end 6 of the boat 1. The supporting hydrofoil 4 comprises an asymmetric hydrofoil section 7, having camber (as visible in Fig. 1 , but more clearly shown in Fig. 2 with reference numeral 8). The planing boat 1 comprises lift regulation means (generally indicated with reference numeral 9 in the Figures, although not shown in Fig. 1 for sake of clarity) for regulating the lift generated by the asymmetric foil section 7 and/or the supporting hydrofoil 4.

The vessel 1 has a hull 2 and a superstructure 21. These can be designed in any way known in the prior art. The hull 2 in particular is designed in the same way as in planing boats, i.e. it has a V-shaped appearance in cross section. Further/further transverse hull 2 shapes are conceivable, depending on the desired speed regime of the boat 1 , such as hollow (concave), convex or straight. The longitudinal hull 2 shape can also be concave, convex or straight, depending on the desired application. Spray rails (not shown) can also be used to prevent spray, create extra lift, reduce the wetted surface, prevent pitching and yawing movements, or to reduce water spray.

As mentioned in the foregoing, the boat’s 1 center of gravity is indicated by Z. The supporting hydrofoil 4 is located directly below the boat 1 , below the center of gravity Z of the boat 1 , or at a small distance in front thereof, such as 0- 15%, for instance 5-15%, of the length of the planing boat 1 in front of the center of gravity Z. Preferably, the supporting hydrofoil 4 is arranged (vertically) in the boat 1 in an adjustable or displaceable way, so that damage is prevented when sailing through shallow water.

The supporting hydrofoil 4 is configured at a vertical distance from the hull 2, when planing, of about 1 - 2 times, such as 1 - 1.5 times, a chord length L _c of the supporting hydrofoil 4. The supporting hydrofoil 4 can also be non-adjustable (i.e. fixed). Preferably, the supporting hydrofoil 4 is configured to provide a lift force of 35 - 65%, for instance 40 - 60%, such as 45 - 55% of the total weight of the boat 1 , at maximum speed.

In the example embodiment of Fig. 1 , a stabilizer 5 is provided at the rear end 6 of the boat 1 as a trim flap. The stabilizer 5 as shown is pivotable about a pivot axis by means of a hydraulic or electric jack. However, other stabilizer 5 configurations are also conceivable, as disclosed in WO 2021/002744 A1 by the present Applicant. The stabilizer 5 may for instance be attached to a propulsion system in the form of an outboard engine. The stabilizer 5 may in principle also be omitted and the propulsion system as such may be used to alter trim conditions, by rotating the propulsion system (and therefore a propulsion line) with respect to the longitudinal axis X of the boat 1. Preferably, the longitudinal distance between the stabilizer 5 on the one hand and the supporting hydrofoil 4 (and the center of gravity Z) on the other hand is about 30 - 60%, for instance 30 - 50%, such as about 40% of the length of the boat 1.

Fig. 2 shows an example embodiment of an asymmetric hydrofoil section 7 according to the invention. The asymmetric hydrofoil section 7 preferably has positive camber 8, as shown in Fig. 2 (in an exaggerated manner, to improve clarity). The asymmetric hydrofoil section 7 preferably has a maximum camber 8 of 0.1 times the chord length Lc of the asymmetric hydrofoil section 7. The asymmetric hydrofoil section 7 may have a maximum thickness t of 0.2 times the chord length L _c of the asymmetric hydrofoil section 7. For illustrative purposes, a leading edge 22 and a trailing edge 23 are also shown. In relative terms, the chord length L _c may for instance measure 5% - 10% of the boat 1’s length (i.e. when measured at the root of the supporting hydrofoil 4, normally coinciding with the mirror plane S). In absolute terms, the chord length L _c may for instance measure 0.5 - 3.5 m, such as 1 - 2 m.

Fig. 3 shows an example embodiment of a supporting hydrofoil 4 with an asymmetric hydrofoil section 7 according to the invention, such as the one shown in Fig. 2, provided with lift regulation means 9 comprising rotation means 10. The rotation means 10 are arranged for rotating the supporting hydrofoil 4 around a rotational axis R perpendicular to the mirror plane S of the planing boat 1. Thus, the supporting hydrofoil 4 may be rotated around the rotational axis R by the rotation means 10 at an angle relative to the longitudinal axis X of the planing boat of -15° to + 15°. Preferably, the rotational axis R is situated at a perpendicular distance DR.A from the chord 11 of the asymmetric hydrofoil section 7, such as about 1.5 - 4 times, for instance 1.5 - 3 times or 2 - 3 times, the chord length L _c of the asymmetric hydrofoil section 7. Preferably, the rotational axis R intersects or coincides with the hull 2, as shown in Fig. 3. Typically, the rotation means 10 will rotate a shaft (not shown) to which the supporting hydrofoil 4 is connected. The rotation means 10 may comprise servo motors, hydraulically powered devices, et cetera. The rotation means 10 are preferably placed inside the hull 2, more preferably are fully enclosed by the hull 2, and/or are preferably arranged close to or at the center of gravity Z.

Fig. 4 shows an example embodiment of a supporting hydrofoil 4 with an asymmetric hydrofoil section 7 according to the invention, provided with lift regulation means 9 comprising camber adaptation means 14 for adapting the camber 8 of the asymmetric hydrofoil section 7. The camber adaptation means 14 may comprise fitting the supporting hydrofoil 4 with a rotatable trailing edge 23 portion 15 configured for being rotated around a rotational axis Ri perpendicular to the mirror plane S of the planing boat 1. The rotatable trailing edge 23 portion 15 may be configured to be rotatable at an angle Pi relative to the longitudinal axis X of the planing boat of -25° to +25°. Preferably, the rotatable trailing edge 23 portion 15 comprises at least 10%, but at most 50%, such as 20% to 40%, of the chord length L _c of the of the asymmetric hydrofoil section 7. In addition to the above, or in place thereof, the camber adaptation means 14 may comprise fitting the supporting hydrofoil 4 with a rotatable leading edge 22 portion 16 configured for being rotated around a rotational axis R2 perpendicular to the mirror plane S of the planing boat 1. The rotatable leading edge 22 portion 16 may be configured to be rotatable at an angle relative P2 to the longitudinal axis X of the planing boat of -25° to +25°. Again, rotation may be achieved by means of a suitable servo motor, by means of hydraulic power, et cetera. Such rotation means are preferably placed inside the supporting hydrofoil 4, inside the strut 20, or inside the hull 2, to protect the rotation means from damage (not shown). In the latter two cases, such rotation means may be connected to the camber adaptation means 14 by an appropriate mechanical linkage (not shown), which is also preferably to be enclosed by the supporting hydrofoil 4, the strut 20, the hull 2 or otherwise.

Fig. 5 shows an example embodiment of a supporting hydrofoil 4 with an asymmetric hydrofoil section 7 according to the invention, wherein the supporting hydrofoil 4 is provided with a shock absorber 19, such as a spring 13 or a piston- cylinder-type (hydraulic) shock absorber. The supporting hydrofoil 4 is preferably connected to the hull 2 with the shock absorber 19. The shock absorber 19 is preferably configured for absorbing shocks in a direction perpendicular to the movement direction M of the boat 1. Preferably, the supporting hydrofoil 4 is arranged to be vertically adjustable, such as over a distance/range DVA, as explained in the foregoing. The shock absorber 19 may, of course, play a role in the vertical adjustment of the supporting hydrofoil 4. From a vertically “neutral position” the supporting hydrofoil 4 may be moved over a (maximum) vertical distance/range DVA of for instance 0.2 - 0.5 times the chord length L _c of the asymmetric hydrofoil section 7, i.e. a movement of for instance 0.1 - 0.25 times the chord length L _c of the asymmetric hydrofoil section 7 upwards and/or 0.1 - 0.25 times the chord length L _c of the asymmetric hydrofoil section 7 downwards. The shock absorber 19 is preferably placed inside the hull 2, more preferably the shock absorber 19 is fully enclosed by the hull 2. The shock absorber 19 may also be placed close to or at the center of gravity Z of the boat 1 .

Fig. 6 shows an example embodiment of a supporting hydrofoil 4 with an asymmetric hydrofoil section 7 according to the invention, wherein the lift regulation means 9 comprise a force regulation device 12 for counteracting pitching moments MP around the rotational axis R due to a resultant force F on the supporting hydrofoil 4 not intersecting the rotational axis R. The force regulation device 12 may comprise a spring 24. Preferably, the force regulation device 12 is placed inside the hull 2, more preferably the force regulation device 12 is fully enclosed by the hull 2. The force regulation device 12 may also be placed close to or at the center of gravity Z of the boat 1 .

Fig. 7 shows a perspective view of an example embodiment of a supporting hydrofoil 4 with an asymmetric hydrofoil section 7 according to the invention, wherein the supporting hydrofoil 4 is provided with forward sweep and is tapered, i.e. when seen in plan view, the supporting hydrofoil 4 is symmetrically tapered from a root 17 of the supporting hydrofoil 4, situated at the mirror plane S of the planing boat 1 , towards supporting hydrofoil 4 tips 18 situated at opposite sides of the mirror plane S, wherein the chord length L _c of the supporting hydrofoil 4 becomes smaller from the root 17 towards the supporting hydrofoil 4 tips 18. A taper ratio may be 0.4 - 0.6, preferably 0.5. Preferably, the supporting hydrofoil 4 is connected to the hull 2 with one or more struts 20, such as two, three or more struts 20. The example embodiment shown in Fig. 7 for instance comprises two struts. Preferably, the struts 20 are so configured as to provide minimal resistance, which can be achieved by streamlining the struts 20, minimizing frontal surface area, et cetera.

As shown in Fig. 7, the two struts 20 may be symmetrically arranged at opposite sides of the mirror plane S of the planing boat 1 , at a same distance from the mirror plane S.

Fig. 8 shows a plan view of an example embodiment of a supporting hydrofoil 4 with an asymmetric hydrofoil section 7 according to the invention, wherein the supporting hydrofoil 4 is provided with aft sweep and is tapered.

Fig. 9 shows a plan view of an example embodiment of a supporting hydrofoil with an asymmetric hydrofoil section according to the invention, wherein the supporting hydrofoil is tapered. Generally referring to the example embodiments shown in Figures 7- 9, when seen in plan view, the supporting hydrofoil 4 may be provided with forward and/or aft sweep ALE, ATE. A leading edge 22 sweep angle ALE may be 0° - 45°, such as 0°, preferably 10° - 30°, more preferably 10° - 15°. A trailing edge 23 sweep angle ATE may be 0° - 45°, such as 0°, preferably 10° - 30°, more preferably 10° - 15°.

Although the invention has been described above with reference to example embodiments, variants within the scope of the present invention will readily occur to those skilled in the art after reading the above description. Such variants are within the scope of claim 1 and the dependent claims. In addition, it is to be understood that express rights are requested for variants as described in the dependent claims of independent of claim 1. It should also be noted that the example embodiments shown in the Figures, or features thereof, may be combined to yield embodiments not explicitly shown in the Figures. For instance, Figures 7-9 show possible variations regarding the amount of struts that can be used, the use of forward sweep or aft sweep, et cetera. Although Fig. 7 shows a supporting hydrofoil 4 with two struts 20 and forward sweep, embodiments are conceivable wherein the example embodiment of Fig. 7 is provided with aft sweep, such as shown in Fig. 8, although such an embodiment is not explicitly shown in one of the Figures. Furthermore, the example embodiments shown in Figures 7-9 may of course be provided with any one of the features of the embodiments shown in Figures 1-6, such as the rotation means 10, camber adaptation means 14 or shock absorber 19, although such resulting embodiments are not explicitly shown in an individual Figure.

LIST OF REFERENCE NUMERALS

1. Planing boat

2. Hull

3. Propulsion system

4. Supporting hydrofoil

5. Stabilizer

6. Read end of boat

7. Asymmetric hydrofoil section

8. Camber

9. Lift regulation means

10. Rotation means

11. Chord

12. Force regulation device

13. Spring (shock absorber)

14. Camber adaptation means

15. Rotatable trailing edge portion

16. Rotatable leading edge portion

17. Root

18. Tip

19. Shock absorber

20. Strut

21. Superstructure

22. Leading edge

23. Trailing edge

24. Spring (force regulation device)

Z. Center of gravity

R. Rotational axis of hydrofoil

Ri . Rotational axis of rotatable trailing edge portion

R2. Rotational axis of rotatable trailing edge portion

X. Longitudinal axis of the boat

M. Direction of movement

S. Mirror plane of the boat DR.A. Distance between rotational axis and chord

DVA. Vertical adjustability distance

L _c . Chord length

F. Resultant force on hydrofoil Mp. Pitching moment t. Thickness of asymmetric hydrofoil section p. Angle of hydrofoil relative to the longitudinal axis (X) of the planing boat

Pi. Angle of rotatable trailing edge portion relative to the longitudinal axis (X) of the planing boat 2. Angle of rotatable leading edge portion relative to the longitudinal axis

(X) of the planing boat