TECHNICAL FIELD

The present invention relates to a device for use in water sports and a method for using same. The invention has particular application to hydrofoil bikes, although it could be applied to other vehicles as appropriate.

BACKGROUND ART

Hydrofoil vehicles are those which are provided with hydrodynamic foils (which, for ease of reference, will now be referred to as foils) in a manner similar to aerofoils, such as those found on fixed-wing aircraft. A foil is a wing-like structure which is suspended horizontally under the hull of the vehicle (usually a boat such as a racing yacht or speedboat) and beneath the water surface. Typically, a hydrofoil vehicle will have at least two foils. When the vehicle is in motion at a sufficient speed, the foils generate lift and the bulk of the vehicle will rise out of the water as it moves. The foils may remain fully submerged or pierce the water surface (the latter is more common for larger vehicles such as passenger ferries).

Being lifted largely out of the water, water resistance and drag along the hull is reduced and thus greater travelling speeds can be achieved with a reduced thrust or power output. Furthermore, because the foils move beneath the surface of the water, the vehicle is less susceptible to waves and thus can achieve a smoother ride. Foils have been used on boats such as ferries for many decades as a means for efficient and timely transportation of people and cargo. Publicity generated by the foil- equipped yachts used in the 2013 America's Cup has also increased awareness of foils. However, the use of human powered hydrofoil vehicles in water sport activities is becoming increasingly common. Many of these types of hydrofoil vehicles are custom built by enthusiasts, but there is increasing commercial activity in the industry.

Human powered hydrofoil vehicles can be classified into two main groups. The first group are those which are buoyant. This type of vehicle has foils which are attached to the hull of a conventional water craft such as a kayak or canoe. When not being powered by the person using the device, the water craft will remain buoyant.

The second group of human powered hydrofoil vehicles are those that lack buoyancy, and which will sink if insufficient lift is generated by its foils. Essentially, this latter type of hydrofoil vehicle needs to be in continual motion in order to remain substantially out of the water.

However, human powered hydrofoil vehicles such as that described above can require considerable effort to drive the vehicle at a speed sufficient to generate enough lift for it to be raised at least partially out of the water. Thus users need to be relatively fit individuals and this can limit the popular appeal of these types of vehicles.

This type of hydrofoil vehicle requires lift to be generated through the use of an input device operated by the user. The input device can be configured to be operable by physical movement such as a rowing, pumping or pedalling action.

Additionally, existing hydrofoil vehicles have a number of design issues which also limit their appeal.

Hydrofoil vehicles with pedal-driven propellers tend to be less strenuous to operate than those requiring a pumping or rowing action. Such vehicles often resemble bicycleswith foils in place of the front and rear wheels. The user will operate the pedals to drive a propeller proximate the foils, thus moving the machine forward in the water. If sufficient forward momentum can be sustained, the foils generate lift to raise the vehicle substantially out of the water.

These types of vehicles shall now be referred to as hydrofoil bikes. Existing hydrofoil bikes tend to be relatively complicated assemblies. For most manufacturers, a key design focus is to keep the hydrofoil bike as light as possible. However, this can compromise the structural integrity of the bike.

Thus, hydrofoil bikes may be prone to breakage when the foils strike the ground, both in and out of water. They also tend to be relatively difficult to assemble and disassemble for transportation or storage purposes. Some hydrofoil bikes come in a multitude of parts, which require extensive and time consuming assembly with specialist tools. Others come in relatively few, but large, components but these can be difficult to transport in a passenger car.

Hydrofoil bikes also require good timing and coordination when launching as the user has to be able to generate sufficient and immediate forward momentum for the foils to generate lift. Above-water launching usually requires the person using the device to start from a jetty, dock or the like, with the vehicle momentarily suspended above the water, and is lowered simultaneously with a forward lunge or push-off motion followed by prompt pedal strokes. When both the bike and its user are in a stationary position and fully immersed in the water, under-water launching usually proves too difficult achieve. Consequently if the user loses balance or otherwise forced to dismount the hydrofoil bike, they run the risk of getting stranded far from shore. They may be forced to abandon the bike in order to return to shore. If not retrievable, this may mean the loss of the bike and endanger the user who has to then swim back to shore.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

Throughout this specification, the word "comprise", or variations thereof such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF THE INVENTION

The present invention preferably relates to a hydrofoil vehicle in the form of a pedal- operated hydrofoil bike. The bike includes any one, or a combination, of inventive features described herein and which provide advantages over existing hydrofoil bikes. The overall invention is designed to enhance the appeal of hydrofoil bikes to the general public, with the inventive features contributing to increased safety and improved ease of use.

According to one aspect of the present invention, there is provided a hydrofoil bike, wherein the bike includes: a front frame, a rear frame, a linking beam for the front frame and the rear frame, wherein the beam has a front end and a rear end, characterised in that the front frame includes a sleeve for the front end of the beam, and the rear frame includes a sleeve for the rear end of the beam, wherein the sleeves include apertures complementary to apertures in the front end and rear end of the beam.

The main frame of the hydrofoil bike is configured as a two-part assembly, connected via a linking beam. The two parts of the bike frame are specially adapted to receive the linking beam, which can come in a variety of lengths to allow the distance between the two parts of the frame to be adjustable according to the requirements of the user.

According to another aspect of the present invention there is provided a hydrofoil bike, wherein the bike includes: a frame, a propeller assembly, and characterised in that the propeller assembly is mounted to the frame via a horizontal axle to allow pivotal movement of the propeller assembly relative to the frame.

The bike includes a propeller assembly which is pivotal relative to the frame of the bike. This helps minimise the risk of damage to the components of the propeller assembly should it contact rocks or shallow ground when in use.

According to a further aspect of the present invention, there is provided a hydrofoil bike, wherein the bike includes: a frame, wherein the frame includes a steering assembly, a tiller, wherein the tiller is pivotally mounted to the steering assembly, characterised in that the tiller is fabricated from a plastics material having shape memory.

The front part of the frame of the bike includes a forwardly extending tiller mechanism, which is designed to be deformable in the event of contact with an object in the water.

According to yet another aspect of the present invention, there is provided a hydrofoil bike, wherein the bike includes: a frame, a front hydrofoil, characterised in that the bike includes an actuator for the hydrofoil, wherein the actuator is configured to pivotally move the hydrofoil relative to the frame about a substantially horizontal axis. The hydrofoil bike includes a steering assembly that allows pivotal movement of the front hydrofoil of the bike about a substantially horizontal axis. This allows the user of the bike to adjust the lift effect that is generated by the foil.

Reference throughout this specification will now be made to a hydrofoil bike which includes all of the inventions described above. However, it should be appreciated that some or all of the inventions may also be applied to existing hydrofoil bikes independently of each other.

The major components of the preferred embodiment of the hydrofoil bike are:

• the frames (front and rear); · the linking beam

• the hydrofoils;

• the steering assembly;

• the tiller (which may be considered to be part of the steering assembly);

• the drive unit; and · the propeller assembly.

These components, and the inventive features associated with them, shall now be described by way of example only.

Frames

The bike should be understood to have a front frame and a rear frame. The material selected for forming the frames should ensure that they are structurally sound and able to be formed in aesthetically pleasing shapes.

Preferably, the front and rear frames are formed from plastics material such as high density polyethylene (HDPE), acrylonitrile butadiene styrene (ABS), polycarbonate (PC) or another material readily identified by a person skilled in the art as being suitable for the purpose.

The frames may be moulded with sealed air cells in the interior of the frames. It is preferable that the frames have some buoyancy such that the bike does not sink should the user fall off when in relatively deep water. However, the buoyancy should not be such that the bike turns upside down, with the foils floating on the surface. Nor should the buoyancy result in the bike turning on its side such that both the front and rear frames float on the surface. If this was to occur, it would be extremely awkward for a user to be able to manipulate the bike into a position where they could keep the bike stable and be able to remount. Preferably, the buoyancy is such that the user, sitting on the bike in a submerged condition, has their head above water.

Persons skilled in the art will appreciate that because of the weight of the user, the rear frame is preferably more buoyant than the front frame. In use, this may mean that when it is in a submerged condition, the bike is orientated such that the front frame is directed somewhat downwards.

However, in some embodiments of the invention, the front and rear frames may be formed from more dense materials, for example a fibre reinforced composite material such as fibreglass or carbon fibre. The frames may also be formed from aluminium. It will be appreciated that the recited materials for the frame are just examples, and are not meant to be limiting.

When formed from denser materials such as fibreglass, preferably the front and rear frames include a buoyant material.

This may vary depending on the manner of manufacture, but in preferred embodiments of the present invention the buoyant material is foam.

It will be appreciated that the size and shape of the frames determine their buoyancy. The use of foam is preferred as it is a space filler; should there be a leakage, there is nowhere for water to enter and thus buoyancy may not be compromised. For composite constructions, the foam can add strength and stiffness. Foam also deadens vibrations that may occur in an otherwise hollow frame.

In some embodiments, the frames may be configured with a means to allow entry of water into certain sections or the entire interior of the front and rear frames. For example, the frames may be moulded with internal compartments sealed with plugs or the like which can be removed by the user. Thus water may be allowed to enter select compartments of the frame, which can subsequently act as ballast. This allows buoyancy of the bike to adjusted according to the preferences of the user.

Furthermore, in some embodiments, the compartments may be arranged at the upper portions of the frames; thus when the bike is raised above the surface of the water, the water is allowed to drain away. Thus, the weight penalty is not permanent. Alternatively, in other embodiments, particularly those where the frames are made of a denser material, the internal compartments could allow a light-than-air gas to be introduced into the frame to enhance its buoyancy. However, persons skilled in the art will appreciate that the plugs to seal the compartments will need to be suitably engineered.

Preferably, the frames are shaped with a generally hydrodynamic and streamlined form. This is preferred not only for improving water flow around the bike when it is being pedalled, but also for aesthetic reasons. A more professional looking hydrofoil bike, in some aspects similar in appearance to road racing bikes, may have greater market acceptability.

The rear frame should be understood to either include a seat for the user or at least means to attach a seat.

Preferably, the rear frame is configured with a seat tube into which a seat, mounted to a seat post, is inserted. A clamp may be then be used about the seat tube to lock the seat post in place. This form of seat attachment method is similar or identical to that used to attach a seat to a conventional bicycle. Thus, off-the-shelf seats and clamps may be readily used with the invention.

However, this is not meant to be limiting and alternative ways of attaching a seat to the rear frame will be readily envisaged. This may include a seat integrally formed with the rear frame.

Linking beam

The front and rear frames are connected via a linking beam.

The linking beam should be understood to mean an elongate tubular structure having a first end and a second end. The first end is configured to engage with the front frame and the second end is configured to engage with the rear frame.

It will be appreciated that the linking beam is a load bearing structure which has to support the weight of the user. Therefore, the linking beam may be fabricated from any suitably robust material. For example, the linking beam may be an aluminium extrusion. However, this is not meant to be limiting and it could also be fabricated from carbon fibre or fibreglass or even toughened plastics material. The beam may be provided in a number of shapes and cross-sections; the preferred embodiment is a substantially rectangular cross-section with an arched top side to provide some torsional and bending strength. An asymmetrical cross-section is preferred as it may prevent the front and rear frames from twisting out of alignment in relation to each other along their respective housings against the linking beam. However, this is not meant to be limiting, the linking beam could just as easily have a substantially circular or oval profile.

Like the preferred embodiment of the frames, at least a portion of the interior of the linking beam may include foam or the like for buoyancy purposes.

The front and rear frames are provided with structures that act as a sleeve for the linking beam. The linking beam may be inserted into the sleeves, or the sleeves may be dimensioned such that they may be inserted into the ends of the linking beam. It will be appreciated that this arrangement may be thought of as a bayonet-type mounting.

The use of a sleeve to engage with the beam is preferred as it provides a more positive and secure fit. This type of arrangement requires the respective parts to have relatively close tolerances, which may be prone to corrosive seizing or premature wear from repeated assembly and disassembly.

In preferred embodiments, one or both of the contact surfaces of the linking beam and sleeve may be provided with a sleeve liner made from a sacrificial plastics material. It will be understood that the contact surfaces of the linking beam are its exterior surface while those of the sleeve is its interior (or vice versa depending on the nature of the engagement between these parts).

As the sleeve liner is formed from a material that is less durable than the linking beam or housings, it will deteriorate first and can be replaced once a positive fit between the linking beam and sleeves can no longer be achieved due to excessive wear. The sleeve liner may also help minimise friction and corrosion and acts as a protective layer between the mating surfaces of the linking beam and sleeves.

However, this is not meant to be limiting. It is possible that in some embodiments, the sleeves may have an open track which engages with pegs or the like provided on the exterior surface of the ends of the linking beam. Detents are another possibility although it should be recognised that this may complicate manufacture of the frames and linking beams and therefore impact production costs.

The sleeves are provided on the surfaces of the frames that oppose each other when the bike is assembled, i.e. the sleeves are provided on the forward facing surface of the rear frame and on the rearward facing surface of the front frame.

The sleeves include a plurality of apertures complementary to apertures provided on the linking beam. In use, the linking beam is fixed to the sleeves using fasteners such as threaded or quick release bolts or latching devices that do not need tools to operate. The position of the apertures are such that they allow the distance between the front and rear frames to be adjusted according to the preference and body size of the user.

Another way in which the distance between the front and rear frames may be adjusted is to provide the linking beam in a variety of sizes. This also provides a degree of flexibility in the customisation of the bike to the preferences of the user. The use of the linking beam to connect the front and rear frames also mean that if one or the other is damaged, only that part needs to be replaced. In prior art devices with a unitary frame, the entire frame may need to be replaced. Thus, the use of a linking beam provides a degree of modularity to the bike, which may increase market acceptability.

It will be appreciated that this aspect of the invention may also be used with more conventional hydrofoil bikes, rather than the preferred embodiment described herein.

Hydrofoils

The bike should be understood to have a front hydrofoil and a rear hydrofoil (referred to throughout the remainder of this specification as foils). The front foil is associated with the front frame and the rear foil is associated with the rear frame.

A foil should be understood to be a substantially horizontal wing-like structure suitably configured to generate lift and has an upper surface and a lower surface.

The foil is contoured to create a pressure differential from the laminar flow of the fluid passing above and below the foil surfaces. Depending on the contour of the foils, a desired lift characteristic can be achieved. Foils with a profile suitable for generating lift will be readily apparent to a person skilled in the art.

Reference will be made in some sections of this specification to the foils having an angle of attack. This should be understood to mean the angle of the foil relative to the flow of fluid around it, wherein the angle is determined by the chord of the foil. The chord is the straight line running between the leading edge of the foil and the trailing edge of the foil. If the chord is such that the leading edge is higher than the trailing edge, the foil is raised (inclined) or has a positive angle of attack. If the trailing edge is higher than the leading edge, the foil is lowered (declined) and has a negative angle of attack.

The foils of the bike are one of the largest, if not the largest, components of the bike.

In preferred embodiments of the invention, the rear foil is larger than the front foil. It will be appreciated that this is to compensate for the weight distribution of the invention in use, as the rear foil is substantially beneath the user.

With a relatively wide span, the foils extend well to the sides of the bike in use. Thus, they are relatively exposed and vulnerable to impacts with both floating and submerged objects, which may not always be visible to the person riding the bike. Therefore, the foils need to be appropriately engineered and formed from robust materials that provide an acceptable degree of resilience against bending, impacts and abrasions.

In preferred embodiments of the invention, the foils are formed as an extrusion of aluminium. However, other suitable materials for the foils include fibre reinforced composite materials such as fibreglass or carbon fibre or indeed toughened plastics material. Having the foils made from a denser material, such as aluminium, relative to the frames will not only help the user keep the bike in a relatively upright orientation when it is stationary, but also assists in keeping the centre of gravity as low as possible.

However, the use of aluminium is not meant to be limiting and other materials may be used. For example, the foils may be formed from carbon fibre or fibreglass. They may also be moulded from toughened plastic.

In preferred embodiments of the present invention, detachable tips may be provided for the outer ends of the foils as separate attachments. These "foil-ends" can simply be replaced if damaged rather than replacing the entire foil. There are also advantages for storage and transportation as the size of the foils can be reduced with the use of foil- ends.

The foil-ends may be fabricated from any suitable material such as toughened plastics material or, in some embodiments, soft plastics material, such as rubber or a similar elastomeric material, for greater safety and protection.

The use of foil-ends may also allow the user to improve or otherwise customise the hydrodynamic performance of the bike to match their skill and fitness level. For example, the foil-ends may be shaped or otherwise profiled to enhance lift or, if the person using the bike is doing so for fitness and wants a harder workout, may slightly counteract the lift. It will be appreciate that the user may be required to use more energy input to overcome the effect of the foil-ends.

However, it should be appreciated that an important aspect of the invention is the modularity of the components, which offers the user the ability to customise the entire bike. The hydrodynamic performance of the bike may be adjusted through replacement of the foils themselves.

In some embodiments of the invention, the foils may be formed such that foam material, for buoyancy, may be inserted or otherwise introduced into their interior. This can be useful to improve the overall buoyancy of the bike.

The foils are suitably configured to engage with the front and rear frames of the bike, or in some embodiments, intermediary members connected or otherwise linked to the front and rear frame.

In preferred embodiments of the present invention, the upper surfaces of the foils are provided with a recess into which a portion of the frame or an intermediary member may be inserted and secured with bolts inserted through the lower side of the foil and into the frame or member. Alternatively, the upper surface of the foil may be configured with a protrusion or strut which engages with a recess in the frame.

It will be understood that these are just examples of the ways in which the foils may be mounted to the bike and are not meant to be limiting. Persons skilled in the art will appreciate that the foils may be mounted to the bike in a number of ways through the appropriate use of fasteners, apertures, recesses and housings or any combination of these.

Steering assembly The bike should be understood to have a steering assembly, which can be manipulated by the user while the bike is in motion. This provides a means of controlling the general path of travel of the bike as well as making it easier for the bike to be started from a stationary and submerged position.

In preferred embodiments of the invention, the steering assembly is associated with the front frame.

Preferably, the front frame is formed from two sections, an upper or first section and a lower or second section. The second section may be thought of as a strut to which the front foil is mounted. The strut also acts as a rudder for the invention in use, allowing the user to control the direction of the bike. It is possible that in some embodiments of the present invention that the front frame is a unitary, one-piece, structure. However, it will be appreciated that this may compromise the ease of use and manufacture of the invention.

Preferably, the front frame includes a steering fork. This should be understood to mean an elongate member with two ends. In use, the steering fork will be in a substantially vertical orientation, and thus one end can be thought of as the upper end and the other end as the lower end.

In preferred embodiments, the upper end of the steering fork is configured to allow the attachment of handle bars for the user. This will be achieved in a number of ways readily apparent to persons skilled in the art.

In preferred embodiments, the handlebars are attached to a horizontal stem, which in turn is attached to the upper end of the steering fork. The stem can come in a range of lengths so the handlebars can be customised to the user's preference. This method of attaching handlebars is also used for conventional bikes, and thus suitable handle bars and stems may be readily sourced from manufacturers of conventional bikes and may be used with minimal or no modifications

However, this is not meant to be limiting and other ways of mounting handlebars to the steering fork are envisaged. For example, the handle bars may include a clamping mechanism that fits about the upper end of the steering fork. Alternatively, bolts may pass through apertures in the handle bars and the upper end of the steering fork or bushings or the like may be used.

The handle bars and steering fork are configured to have a restricted range of movement which may be referred to as a steering arc. The steering arc should be understood to mean the extreme limit of the range of movement that may be achieved when turning the handle bars side to side.

It is not desirable to have an unrestricted steering arc as an abrupt or otherwise significant and uncontrolled change of direction can result in loss of frontal lift generated by the front foil. The laminar flow of fluid above and below the foil will no longer be substantially perpendicular to the leading edge of the foil.

In preferred embodiments of the invention, a steering lock is employed to restrict the steering arc.

In its simplest form, the steering lock is a bolt which is threaded through a suitably configured aperture in the front frame and into a horizontal slot provided in the steering fork. The portion of the bolt that enters the slot is non-threaded and therefore does not grip the slot, the length (width) of which determines the steering arc. It will be appreciated that the bolt is fixed relative to the front frame. When the steering fork is moved to one side, the degree of movement is defined by the length of the slot. When the bolt contacts one end of the slot, further movement of the steering fork in that direction is prevented.

Preferably, the steering lock is provided on the upper rear side of the front frame but it can just as easily be positioned elsewhere. Other ways of restricting the steering arc will be readily apparent to persons skilled in the art. The lower end of the steering fork is configured to pivotally engage with the second section (the strut) of the front frame such that some movement of the second section, together with the foil attached to it, is permitted. This movement is about a generally horizontal axis, such that the foil can be inclined or declined to increase or decrease its angle of attack. In preferred embodiments, the lower end of the steering fork is configured as a pair of prongs, with a recess there between. At least a portion of the second section of the frame is positioned within the recess and connected to the steering fork by passing an axle, such as the shaft of a bolt, through apertures in the prongs and the second section. It will be understood that the axle has a generally horizontal orientation in use. However, this is just one way of connecting the steering fork to the second section of the frame and is not meant to be limiting.

In embodiments where the front frame is a unitary structure, it will be appreciated that the front foil will need to be mounted to the steering fork in such a way to allow movement of the foil about a generally horizontal axis.

Preferably, the steering fork is a length of aluminium tubing or a similar material readily apparent to a person skilled in the art as being suitable for the purpose. The steering fork will be subject to torsional and bending loads and thus needs to have structural integrity. In preferred embodiments, the steering fork passes through the interior of the front frame. This improves the aesthetic appeal of the bike rather than having external tubing which may be detrimental to its appearance. However, this is not meant to be limiting.

In preferred embodiments of the present invention, the steering assembly includes an actuator which is operable by the user to adjust the angle of attack of the foil (i.e. the incline or decline of the foil). This allows lift to be manually manipulated as required.

In preferred embodiments of the present invention, the actuator is a lever, mounted to the handle bars, to which one end of a wire cable or the like is connected. However, this is not meant to be limiting and the actuator may be positioned elsewhere on the front frame or, in some embodiments, on the rear frame. However in the latter scenario, it will be appreciated that the actuator should still be within easy reach of the user when the bike is in operation.

The other end of the cable is connected to the second section of the frame (or directly to the foil). The second section of the frame should be understood to have an operational bias. This may be an inherent bias to either incline or decline, depending on its centre of gravity and weight distribution. The way in which the cable and levers operate the second section may reflect the operational bias of a particular bike or user's preferences.

In instances where the second section of the front frame has a tendency to be inclined, the cable shall be configured to pull the second section, and therefore the front foil, into a decline (a negative angle of attack). Alternatively, if the operational bias is such that the second section and front foils are declined, the cable is configured to pull the second section upwards.

It will be appreciated that this means that the cable needs to be connected or otherwise attached to the second section (or foil) in an appropriate position, for example, proximate the forward facing portion of the second section or the rearward facing portion of the second section, depending on the operational bias. When launching the bike from a stationary and submerged position, the front foil may get over-inclined, presenting a large portion of the underside of the foil forwards. This could generate drag instead of lift. Pulling the cable in this instance to decline the foil will allow this condition to be corrected. This restores the lift characteristics that are more conducive to raising the bike and user above the surface of the water. By pulling on the lever, the cable is tensioned which pulls on the second section. The length of the cable may vary but when no longer tensioned it should not be so short as to impede the pivoting movement of the second section.

In some embodiments of the invention, the same principle described above with respect to control of the front foil may be used to adjust the rear foil, either with the front foil or on its own. Persons skilled in the art will appreciate that this may mean that the rear foil needs to be mounted to the rear frame to allow pivotal movement about a horizontal axis.

In some embodiments of the invention, the actuator may include a locking mechanism or the like to hold it in position and make it easier for a user to maintain a certain foil orientation.

In preferred embodiments of the present invention, the second section (and/or the front foil) is configured to have a restricted range of movement which may be referred to as the tiller arc. An unrestricted tiller arc is not desirable as an abrupt transition in the angle of attack of the front foil may lead to an unrecoverable stall (when lift ceases and the bike sinks beneath the water surface) or a nose dive. The lower end of the steering fork also functions to limit the tiller arc as will become apparent from the ensuing discussion of the tiller.

It will be appreciated that this aspect of the invention may also be used with more conventional hydrofoil bikes, rather than the preferred embodiment described herein.

Tiller

The steering assembly may also include a tiller. A tiller should be understood to mean a structure that extends forward of the front frame of the bike and provides a means of activating the tiller arc. In preferred embodiments, the tiller is mounted to the second section (the strut discussed above with respect to the steering assembly) of the frame (together with the lower end of the steering fork in particularly preferred embodiments) such that they have a common axis of movement. Therefore, the second section moves in synchrony with the tiller.

The tiller and the second section (and therefore the front foil) is effectively a unitary unit, which shares a common horizontal axis.

The tiller is formed from plastics material having a shape memory. This should be understood to mean that the tiller may be deformed upon the application of force to an area of the tiller, but restores its shape when that force is removed.

It will be appreciated that the plastics material needs to have an appropriate amount of elasticity and resilience to both be deformable but capable of returning to its original shape. A plastics material appropriate for this purpose will be readily recognised by persons skilled in the art. For example, the plastics material may be HDPE or PC; however, this is not meant to be limiting.

The tiller may take a variety of forms, but should be understood to include a nose cone. The nose cone is the forward portion of the tiller and is formed as a substantially streamlined shape having an upper surface and a lower surface. Preferably, the lower surface has the largest surface area of the nose cone when compared to its sides and the upper surface. The lower surface heavily influences the path of the nose cone when it skims on top of, or pierces below, the surface of the water.

The upper surface is relatively elongate and ultimately leads to a mounting end by which the tiller is attached to the second section of the front frame.

To assist in the deformation of the tiller, the cross-sectional profile of the upper surface is substantially arched. This is an important aspect of the tiller as its deformation is most likely to result in a portion of the tiller being bent or otherwise deformed. The arched profile of the upper surface of the tiller changes shape in the area where it is bent, becoming substantially flattened.

The lower surface of the nose cone also seeks to maintain a skimming travel path along the water surface, and acts in a manner similar to a surfboard. In use, the nose cone of the tiller will always act to migrate to this 'default' position. If the front foil travels too low in relation to the water surface, the orientation of the tiller will migrate to an incline. As the second section moves in synchrony with the tiller, the front foil, attached to the second section, will be orientated to a positive angle of attack.

Alternatively, if the front foil travels too high in relation to the water surface, the orientation will migrate to a decline, shifting the front foil to an orientation having a negative angle of attack.

The tiller arc is the pre-defined range of movement that is related to this automatic self- levelling operation.

The frontal surface area of the nose cone is preferably streamlined with no sharp edges. It will be recognised that the tiller is one part of the bike that may strike a person in the water. However, as the tiller is formed from plastics material and has a particular streamlined profile, it can deform upon impact, which may help minimise any injury or damage.

It will be appreciated that this aspect of the invention may also be used with more conventional hydrofoil bikes, rather than the preferred embodiment described herein.

Drive unit

In preferred embodiments of the invention, the bike includes a drive unit which transfers the energy of the user to the propeller assembly. Thus, it will be appreciated that in preferred embodiments of the present invention the drive unit and propeller assembly work together.

Preferably, the drive unit includes a main sprocket, which should be understood to be a toothed wheel. The size of the sprocket may depend on the requirements of the user. In preferred embodiments of the invention, the main sprocket may be removable and interchanged with readily available conventional sprockets.

The sprocket includes a hub (similar to the bottom bracket of a conventional bike) with a generally horizontal axle.

Preferably, the hub of the sprocket is configured to pass through a complementary aperture in the rear frame. The hub may include bushings with flanges to provide a lip about the apertures of the rear frame.

However, it is not beyond the scope of the present invention that the drive unit is associated with the front frame rather than the rear. For example, the bike may be relatively reclined. It will be appreciated that this may mean that the geometry of the drive unit and propeller assembly may be suitably arranged to allow this and this may mean mounting the drive unit to the front frame. However, this may complicate manufacture and assembly due to the presence of the steering fork.

The sprocket includes a means by which it can be rotated. In preferred embodiments, the sprocket includes a pair of cranks and pedals, one for either foot of the user. It will be appreciated that the reciprocating motion of the user's legs is converted into rotational movement of the sprocket.

However, in some embodiments of the invention, the cranks of the sprocket may include a pair of oscillating levers or the like which may be actuated by the user's arms in a manner similar to a hand cycle (or legs, in a manner similar to a fitness step machine). It will be appreciated that the geometry of the drive unit and propeller assembly may need to be suitably configured to allow this.

Additionally, it is not beyond the scope of the present invention that the drive unit includes an electric motor or a combustion engine or the like. However, in such an embodiment, the motor would need to be appropriately sealed and adapted to operate in the environment in which the invention is to be used.

The cranks and pedals are connected to the hub and sprocket in a manner that will be readily apparent to persons skilled in the art. In preferred embodiments of the invention, the teeth of the sprocket engage with a drive chain. Reference shall now be made to the drive chain being a chain.

In preferred embodiments of the invention, the chain is a continuous chain in the form of a plurality of individual links. It will be appreciated that given the environment in which the bike is to be used, a suitable chain with anti-corrosive properties may be used. However, it is not beyond the scope of the present invention that the chain is in the form of a continuous toothed belt or the like.

Rotation of the sprocket drives the chain, which is linked to the propeller assembly.

However, it is not beyond the scope of the invention that a rotary driveshaft with pinion gears or the like on each end be used to transmit the user's energy to the propeller assembly. In this embodiment, the sprockets may be replaced with bevel gears or the like which mesh with the pinion gears of a rotary drive shaft. Alternatively, a worm gear may be used. The rotary drive shaft may be positioned internally within the frame or externally. However, it will be appreciated that when positioned externally of the frame, housings may be provided to cover the intermeshing regions of the gears for safety and aesthetics.

Propeller assembly

The bike has a propeller assembly which converts the energy transferred from the user via the drive unit into rotation of a propeller.

In preferred embodiments of the present invention, the drive unit described above interacts with the propeller assembly. However, it is not beyond the scope of the present invention that the propeller assembly and drive unit are a unitary assembly, with the user directly operating a sprocket mounted to the propeller assembly. Preferably, the propeller assembly includes a second sprocket. This should be understood to be a toothed wheel.

It will be appreciated that the chain of the drive unit engages with the teeth of the second sprocket. Thus, the reciprocal movement of the user's legs is converted via the chain into rotational movement of the second sprocket. In preferred embodiments, the second sprocket is substantially smaller (or has less teeth) than the main sprocket of the drive unit similar to conventional bicycles. However, in some embodiments, the sprocket of the drive unit may be smaller than that of the propeller assembly.

In preferred embodiments of the invention, the second sprocket may be removable and interchanged with readily available conventional sprockets. As with the main sprocket, the ability to interchange the sprockets may be useful in optimising propeller performance with users of varying fitness levels. Persons skilled in the art will appreciate that the size of the main sprocket and second sprocket, and the number of teeth present on both sprockets, affect the gearing ratio of the bike. It is also possible that the bike may include several additional sprockets with any number of teeth (grouped in sprocket clusters) and a gear shifting mechanism to adjust the gearing ratio while riding. It will be appreciated that the bike may need to be suitably configured to allow this by, for example, having a cable operated gear shifting mechanism. Such a system may be useful when an individual bike is to be used by several people who may be of varying fitness levels.

In the preferred embodiments of the invention, the second sprocket should be understood to have a generally horizontal axle. The entire propeller assembly is configured to pivot about this axle.

The propeller assembly should be understood to include a substantially hollow housing which has an upper end and a lower end.

In preferred embodiments of the present invention, the upper end of the housing of the propeller assembly is connected to mounting plates, which in turn are fixed to the rear frame. Thus the propeller assembly is linked to the rear frame (or in the alternative embodiment previously noted, the front frame).

The axle of the second sprocket passes through the mounting plates and an aperture in the housing. In preferred embodiments, sealed bearings are utilised between the contact surfaces of the mounting plates and the second sprocket axle. In some embodiments, rubber O- rings, bushings, or washers may be provided between the contact surfaces of the mounting plates and the sides of the second sprocket. A portion of the mounting plates include a plurality of apertures or a slot through which fasteners may pass in order to fix the mounting plates to the rear frame.

The use of slots is preferred as this allows a degree of flexibility with respect to the position of the propeller assembly on the frame. Depending on its placement, tension on the chain may be increased or decreased as appropriate. However, a plurality of apertures arranged in series will likewise allow some flexibility in placement of the propeller assembly relative to the frame.

In preferred embodiments of the present invention, the mounting plates are configured to be positioned on the housing of the rear frame that is provided for the linking beam. Thus, the fasteners used to secure the mounting plates also fix the linking beam to the rear frame. This helps reduce the number of fasteners that may be required for assembly of the bike.

The propeller should be understood to engage with the lower end of the housing of the propeller assembly. In some embodiments, the lower end may be suitably profiled with a housing or the like for the base of the propeller itself.

The propeller assembly is arranged relative to the rear frame such that the propeller is ahead of the rear foil. The propeller itself faces rearwards towards the foil and is located behind the propeller assembly housing. Thus, the propeller faces rearwards.

Preferably, the axle of the propeller is substantially at the same height as the chord of the rear foil. This is to ensure that the propeller generates fluid flow over both the upper and lower side of the rear foil in substantially equal proportions.

However, this is not meant to be limiting. A longer propeller assembly housing may be used to accommodate a propeller with a larger diameter. In this instance, it is possible that the axle of the propeller is located below the chord of the rear foil so that the tips of the propeller do not break above the surface of the water.

It will be recognised that the geometry and placement of the propeller housing is such that when the propeller assembly pivots, the propeller itself does not contact the rear foil.

The propeller may be any propeller suitable for the purpose of generating propulsion. It will be understood that the propeller has a plurality of blades arising from a central hub and axle.

Preferably a five-bladed propeller is used with the propeller assembly as this has been found to be adequate for generating propulsion but this is not meant to be limiting.

It will be appreciated that the axle of the propeller is substantially at right angles to the axle of the second sprocket.

Therefore, the propeller assembly includes a movement transfer mechanism to convert the rotation of the horizontal axle of the second sprocket to rotation of the axle of the propeller.

Preferably, the mechanism is located within the interior of the housing of the propeller assembly.

This mechanism may be in a number of forms. For example, bevel gears may be used at either end of a shaft extending between the axle of the second sprocket and the axle of the propeller. However, this example is not meant to be limiting and persons skilled in the art will readily appreciate other ways in which the rotation of the axle of the second sprocket can be transferred to the propeller. The manner of engagement of the axle of the second sprocket with the housing is such that the propeller assembly and its housing can be pivoted about the axle.

However, in some embodiments of the invention, the propeller assembly may be mounted to the rear frame to allow pivotal movement independent of the axle of the second sprocket.

Allowing pivotal movement of the propeller assembly is an important safety feature of the invention. As noted above, the propeller at least, and in some embodiments, a portion of the housing of the propeller assembly extends beneath the horizontal plane of the foils. Should the forward facing surface of the housing come into contact with submerged objects such as the substrate, rocks or even swimmers, the propeller assembly will pivot back and upwards about the axle of the second sprocket. This helps prevent or minimise damage to the propeller assembly.

However, it will be recognised that the geometry and placement of the propeller housing is such that when the propeller assembly pivots, the propeller itself does not contact the rear foil.

It will also be appreciated that this aspect of the invention may also be used with more conventional hydrofoil bikes, rather than the preferred embodiment described herein.

Using the Hydrofoil bike

Operating the hydrofoil bike is an acquired skill. Essentially, it can be launched in two different ways; from a stationary, fully submerged position (where there is clearance between the foils and the underlying substrate) or from a structure above water such as a jetty or dock.

In the former situation, the user simply starts pedalling until enough forward momentum is achieved for the foils to take effect and raise the bike out of the water.

In the latter situation, launching from a jetty, the user ideally will stand behind the bike, which should be balanced on the edge of the jetty by the rear portion of the rear frame (which may be suitably configured with an overhang, protrusion or other suitable surface for this purpose). The user will straddle the rear frame while holding the handle bars. The bike will be gradually lowered.

The user will then push off from the jetty and mount the hydrofoil bike in a continuous motion. As the bike carries the user forward through the momentum of the push off, the user starts pedalling in order to rotate the propeller and generate forward propulsion. When at a sufficient speed, the foils begin to generate enough lift to raise the user and the bike out of the water. It will be appreciated that there needs to be sufficient clearance between the substrate and the surface of the water; otherwise the user and the bike may make heavy contact with the substrate.

It will be appreciated that the present invention provides a number of advantages over prior art devices, as discussed throughout the preceding section of the specification. Essentially, these include:

• easy to assemble and disassemble;

• able to be launched, or re-launched from a submerged stationary position;

• safety features to reduce the risk of physical injury in the event of a collision; · safety features to reduce the risk of damage to the bike should it come into contact with submerged objects and terrain; or

• at the very least, offers the public a useful choice. BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which: Figure 1 is a front perspective view of one embodiment of the Hydrofoil Bike;

Figure 2 is a side perspective view of the Hydrofoil Bike of Figure 1 in use;

Figure 3 is a second side perspective view of the Hydrofoil Bike of Figure 1 in use;

Figure 4 is an exploded view of the main components of the Hydrofoil Bike of

Figure 1 ; Figure 5 is a perspective view of the mount for the rear foil of the Hydrofoil Bike of

Figure 1 ;

Figure 6 is a top perspective exploded view of the Hydrofoil Bike of Figure 1 ; Figure 7 is a side view of the Hydrofoil Bike of Figure 1 ;

Figure 8 is an exploded view of the propeller assembly of the Hydrofoil Bike of

Figure 1 ;

Figure 9 is an exploded view of the tiller mechanism of the Hydrofoil Bike of Figure

1 ;

Figure 10 is a rear perspective view of the steering lock of the Hydrofoil Bike of

Figure 1 ; Figure 11 is a side perspective view of the tiller mechanism of Figure 9. Figure 12 is a side rear perspective view of the tiller of the tiller mechanism of Figure 9

Figure 13 is a front perspective view of the tiller of Figure 12.

BEST MODES FOR CARRYING OUT THE INVENTION The invention is a hydrofoil bike (generally indicated by arrow 1) as depicted in Figure 1. As will be apparent from the following discussion, the hydrofoil bike has a number of distinctive features which collectively work to make it relatively easy for a person to use.

The bike (1) includes a front (2) and rear frame (3). Handle bars (4) are mounted to the front frame and a seat (5) is mounted to the rear frame. Both are mounted in such a way that they are adjustable to be suitable for the height of the person (not shown) using the bike. Also associated with the front frame are a tiller mechanism (6) and a front foil (7). Associated with the rear frame is a rear foil (8), a drive unit (9), and a propeller assembly (10).

Part of the rear frame (3) is configured with an overhang (11). This can assist in the launching of the hydrofoil bike (1) from a stationary object such as a jetty or dock (12) such as is depicted in Figure 2. The user (not shown) will stand behind the hydrofoil bike, straddling the overhang (more confident users may stand slightly to one side) while holding the handle bars (4) and balancing the hydrofoil bike on its overhang. The bike is gradually lowered substantially level, facing the water (not shown). At this point, the user (not shown) will push off from the jetty (12) and mount the hydrofoil bike (1) in a continuous motion. As the hydrofoil bike carries the user forward through the momentum of the push off, the user will begin operating the drive unit (9) in order to activate the propeller (13) and generate further forward motion sufficient for the foils (7, 8) to generate lift.

The overhang (11) also serves as a stand by which the hydrofoil bike (1) can be placed in a position of rest while on flat ground (not shown) as shown in Figure 3. This essentially parks the hydrofoil bike, and the user (not shown) can then begin disassembling the hydrofoil bike for transportation and storage. It will be appreciated that this encourages bottom-up assembly (by first mounting the rear foil (8) to the rear frame (3), and then the remaining components of the hydrofoil bike) and top-down disassembly (by first removing the tiller mechanism (6) or the front foil (7) and then the remaining components of the hydrofoil bike). Figure 4 depicts the main components of the hydrofoil bike in an exploded view. The front frame (2) is formed in two main sections, the first section (2a) bearing the handle bars (not shown) and the second section (2b) bearing the tiller mechanism (6). The front foil (7) is fitted to the second section of the front frame.

The rear frame (3), in use, is linked to the front frame (2) by the linking beam (14). The rear frame also bears the propeller assembly (10) and it will be noted that an aperture (15) is provided for the drive unit (not shown in this view). The rear frame includes a strut (3a) to which the rear foil (8) is mounted.

The front (2) and rear frame (3) as well as the front (7) and rear foils (8) can be made from a variety of suitable materials. For example, the front and rear frame may be moulded from plastics material or another suitable material and include cavities (not shown) that may be filled with foam (not shown) for buoyancy.

The hydrofoils (7, 8) are formed as an extrusion of aluminium into which foam material (not shown), for buoyancy, may be inserted or otherwise introduced. While the hydrofoil bike (1) will not be able to float above the surface of the water (not shown), the use of buoyant materials (not shown) for the interior of the frames (2, 3) and foils (7, 8) provide sufficient buoyancy that the hydrofoil bike does not sink.

It will be seen that the upper surface (7a, 8a) of the front (7) and rear foils (8) are configured with a recess (7b, 8b) into which a peg (2c, 3b) of the second section (2b) of the front frame (2) and the strut (3a) of the rear frame (3) may be inserted. This is more easily seen in Figure 5.

The rear foil (8) is shown in cross-section and it will be seen that the interior includes ribs (8c) defining a channel (8d) between them. The recess (8b) for the peg (3b) of the strut (3a) of the rear frame (not shown) corresponds with this channel, and essentially acts as a socket. Fasteners (16) pass through the underside (not visible in this view) of the foil and into the peg of the strut in order to fix the foil in place.

Turning now to Figure 6, it will be appreciated that the distance between the seat (5) and the handle bars (4) of the hydrofoil bike (1) may need to be altered to allow persons (not shown) of different heights (and therefore arm lengths) to use the hydrofoil bike.

It will be seen that the front (2) and rear frames (3) each include a sleeve (2d, 3c) for the linking beam (14). The housings have a series of apertures (17a, 17b) which correspond to apertures (18) provided in the linking beam. By passing fastening devices such as bolts (19) through the apertures, the linking beam can then be secured to the front and rear frames. For protection, the mating surfaces of the beam and sleeves may be protected with plastic sleeve liners (not shown).

Depending on how far the linking beam (14) is inserted into either the front (2) or rear frame (3), the distance between the two can be adjusted. Alternatively, the linking beam may be an interchangeable component, and will also allow the frame size to be adjusted by replacing a short linking beam with a longer one (or vice versa).

The linking beam (14) is an important aspect of the hydrofoil bike (1) as it eliminates the need to manufacture a single unified frame in different sizes to accommodate riders of various heights. The only major component that may need to be provided in a variety of sizes is the linking beam.

Figure 7 illustrates the manner in which the propeller assembly (10) can be pivoted. The drive unit (9) includes pedals (20) linked to a main drive sprocket (21). A chain (22) links the main sprocket to a second sprocket (23) on the propeller assembly. It will be appreciated that the second sprocket of the propeller assembly serves as a fulcrum about which it is able to be pivoted relative to the rear frame (3).

This is useful in the event the forward facing surface (10a) of the propeller assembly (10) comes into contact with an object (not shown) in the water (not shown). It will be apparent from Figure 1 that the propeller assembly is the lowest part of the hydrofoil bike (1) and therefore, is likely to be the first part of the hydrofoil bike to make contact (ground strike) with the bed of the body of water in which it is being used. To restore the propeller assembly to its substantially vertical, in-use, configuration, the user simply needs to start pedalling.

Therefore, being able to pivot in the limited arc direction (24) shown in Figure 7 can help reduce the potential for damage of the propeller assembly (10). When the propeller assembly is pivoted back and upwards while not being used, it also allows the hydrofoil bike (1 ) to rest on its foils (7, 8) on the ground (not shown) without risking damage to the propeller assembly.

The propeller assembly (10) is shown in an exploded view in Figure 8 and includes a pair of mounting plates (25) which, through the use of fasteners (19), is fixed to the rear frame (not shown). The plates that secure the propeller assembly to the rear frame include the elongate slots (17a) that are also shown in Figure 6.

This provides the user (not shown) with a degree of flexibility in the positioning of the propeller assembly (10) for the user, by allowing it to be moved in a horizontal plane relative to the rear frame (not shown). It also allows the chain of the drive unit (not shown) to be tensioned. The same fasteners (19) used to secure the mounting plates (25) may also pass into or through the linking beam (not shown) once it is inserted into the sleeve of the rear frame (not shown).

Each mounting plate (25) also includes an aperture (26) for the axle (23a) of the second sprocket (23). The axle of the sprocket acts as the pivot about which the propeller assembly (10) is moveable. To provide a little frictional resistance to the pivoting movement of the propeller assembly, friction washers (27) may be deployed. These act to dampen the movement of the propeller assembly.

Rubber stops (28) are provided to make contact with the underside of the rear frame (not shown) to restrict the movement of the propeller assembly (10) about the axle (23a) of the second sprocket (23). The range of this movement is the propeller assembly arc (24 in Figure 7) such that the propeller (30) does not contact the rear foil (not shown). It also constrains forward movement of the propeller assembly so that it does not move beyond its most efficient position for thrust delivery. The propeller assembly (10) includes a housing (29) which contains the necessary movement transfer mechanism (not shown) to convert the rotation of the sprocket to rotation of the five-bladed propeller (30). This may be achieved through the use of bevel gears (not shown) or the like.

The housing (29) includes a removable and replaceable propeller protector fin (29a), which extends past the lowest point of the propeller (30) in use. The protector fin would make contact with the ground, rocks or other submerged objects (not shown) with which the propeller assembly (10) may make contact.

Figure 9 is an exploded view of the tiller mechanism (6), which can be considered to include a tiller (31) which is connected to the top (32) of the second section (2b) of the front frame (2). The tiller mechanism also includes the front foil (7) which is connected to the second section in a manner similar to that previously described with respect to Figure 5. The second section of the front frame is effectively a rudder for the hydrofoil bike (not shown). The first section (2a) of the front frame (2) has a channel (not shown) passing therethrough into which a steering fork (33) is inserted. A bushing or bearing (34) on the lower (33a) and upper (33b) end of the steering fork allows it to be pivotally attached to the first section of the front frame. The steering fork is securely held in place at its upper end by a locking collar (34a). The handle bars (4) are mounted to the upper end (33b) of the steering fork (33) which passes through the first section (2a) of the front frame. The upper end (32) of the second section (2b) is connected to the lower end (33a) of the steering fork by a fastener (35) on which the tiller mechanism (6), comprising the tiller (31), the rudder (2b) and the front foil (7), will pivot. The user (not shown) can steer the hydrofoil bike (not shown) in the desired direction by moving the handle bars (and thus the rudder/tiller mechanism) along its restricted steering arc.

The front frame (2) may include a steering lock (36) for the steering fork (33) as shown in Figure 10. The steering fork is provided with a horizontal slot (37). A partially threaded bolt (38) passes through a threaded aperture (39) in the front frame. The slot defines the range of movement of the steering fork, and therefore the handle bars (4) whenever the end (38a) of the bolt meets the ends of the horizontal slot.

The tiller mechanism (6) is allowed to pivot in a limited vertical direction referred to as the tiller arc (39) as indicated in Figure 11. In this view, it will be appreciated that the tiller (31) is arc-like profile in a side view, and includes a nose cone (40). The underside (40a) of the nose cone is wider than its upper surface (40b), and this is to act as a skid plate which skims on top of the water surface (not shown) when the hydrofoil bike (1) is in forward motion.

The tiller mechanism (6) functions as an automatic self-levelling and self-correcting mechanism for the front foil (7) of the hydrofoil bike (1).

Thus, if the front of the hydrofoil bike (1) is too high as it moves forward in the water, such as may be the case when it passes over the crest of a wave, the underside (40a) of the nose cone (40) loses contact with the water (not shown). The tiller mechanism (6) will then dip, which in turn pivots (41) of the front foil (7) downwards so that the underside of the nose cone restores contact with the water. Should the nose cone become fully submerged in the water, such as may be the case when it penetrates a wave, the tiller mechanism will be raised which in turn pivots the front foil (7) upwards until the underside of the nose cone resumes skimming the water surface.

This may also be manually controlled through the use of a user operable cable (42, partially in dashed lines 43) passing through the steering fork (shown in dashed lines 34). At one end (42a), the cable is linked to a lever (44) mounted to the handle bars (4). At the other end (42b), it is connected to the tiller mechanism (6) via the upper end (32) of the second section (2b) of the front frame (2). By actuating the lever (44), thus tightening the cable (42), the tiller mechanism (6) can be tilted and this causes a decline in the plane of the front foil (7). This is useful when correcting an overly inclined front foil as the hydrofoil bike (1) moves forward underwater, to make it easier for the user (not shown) to pedal it up and out of the water.

The tiller (31) is formed from plastics material having a shape memory such that it is deformable in the manner illustrated in Figure 12. Should the tiller come into contact with a submerged object or even a person in the water (not shown), it will temporarily yield and deform from the impact (dashed lines show the tiller prior to deformation). However, because of its shape memory, once the impact force has been removed, it will return to its original shape.

The cross-section of the tiller (31) is in a substantially arched form, and thus when the tiller is bent, the central portion (31 a) of the tiller will spread out, flatten and bend as shown. It can also deform in a sideways orientation. The deformable nature of the tiller reduces the risk of physical injury in the event of a collision.

The cross-section of the tiller (31) will change along its length as shown in Figure 13. This view also shows the broad lower surface (40a) of the nose cone (40) and the narrow upper surface (40b)

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope of the appended claims thereof.