Background of the Invention

[0001] The present invention generally relates to hydrofoil watercraft, and in particular to a craft or board with a hydrofoil and an electric motor and battery.

Description of the Prior Art

[0002] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

[0003] Recent developments in battery technology have started to make electric watercraft more practical, where high power requirements and the size and weight of batteries previously prevented this. These watercraft tend to be relatively small, such as for use as a backup on a small sail boat or as the primary propulsion source on a rigid inflatable boat, tender, or similar. The propulsion systems are generally in the form of an outboard motor connected to a battery located within the craft.

[0004] One particular form of watercraft that is growing in popularity is the electric hydrofoil surfboard, created by the attachment of a hydrofoil and a motor to a surfboard, with the battery typically housed within the board. These systems include an electric motor and a hydrofoil in combination, where the hydrofoil elevates the board clear of the water when under power from the motor, reducing drag and providing high speed travel over the water.

[0005] The hydrofoil and motor are positioned towards a lower end of a mast, while an upper end of the mast is bolted to an underside of the board. One method of developing such a system has been to take an existing hydrofoil surfboard and insert a motor to part of the mast. Many components required for operation of the motor may be housed in the board, such as batteries and/or control circuitry. These components must then be connected to the motor at the lower end of the mast by wires that are routed internally down the mast. Control of the motor may be achieved via a hand controller communicating wirelessly with the control circuitry located in the board.

[0006] Despite the significant advances in battery technology, the weight and power density limitations of batteries still remains a key design challenge. As the batteries are located in the board, which is being elevated above the water during use, any reduction in weight is desirable for performance characteristics and range or time of use available per charge.

[0007] Similarly, the efficiency and performance of the propulsion unit are also core considerations of electric hydrofoil surfboards. Making the most efficient use of the available power ensures maximum run time and/or lower weight and cost, depending on the priorities of a particular application.

[0008] At the same time, however, the performance characteristics of the propulsion unit can have a significant impact on the usability of the watercraft. Different applications may have different priorities, such as maximum thrust in contrast to smooth power delivery, for example. These priorities may also vary for the experience level of the user as well as other factors, such as use on smooth water as opposed to wave riding, for example. Accordingly, it is desirable to provide a propulsion unit that is efficient while also being suitable for a wide range of users, riding styles and/or situations.

Summary of the Present Invention

[0009] In one broad form an aspect of the present invention seeks to provide a hydrofoil watercraft, comprising: a board; a battery module locatable in the board; a hydrofoil and a motor that are connected to the board by a mast, wherein the motor is powered by the battery module; and a first propulsion module operatively coupled to the motor; wherein the first propulsion module is removable from the motor, allowing a second propulsion module to be fitted so that it is operatively coupled to the motor in place of the first propulsion module.

[0010] In one embodiment, the first propulsion module comprises a propeller.

[0011] In one embodiment, the first propulsion module comprises a gearbox that couples to an output shaft of the motor. [0012] In one embodiment, the gearbox reduces the rotational speed of the propeller relative to the motor.

[0013] In one embodiment, the ratio of motor rotational speed to propeller rotational speed is at least one of: 2: 1; 3: 1; and greater than 4: 1.

[0014] In one embodiment, the second propulsion module comprises a propeller.

[0015] In one embodiment, the propeller of the second propulsion module comprises at least one of: an outer diameter that is different to an outer diameter of the propeller of the first propulsion module; a blade pitch that is different to a blade pitch of the propeller of the first propulsion module; a blade shape that is different to a blade shape of the propeller of the first propulsion module; and a ratio of motor rotational speed to propeller rotational speed that is different to a ratio of motor rotational speed to propeller rotational speed of the first propulsion module.

[0016] In one embodiment, the second propulsion module comprises a water pump comprising an inlet, an axial flow pump, and a nozzle.

[0017] In one embodiment, the water pump couples directly to an output shaft of the motor without any gearbox to reduce or increase a rotational speed of the axial flow pump relative to the motor.

[0018] In one embodiment, the propulsion modules couple to the motor using a threaded fitting.

[0019] In one embodiment, the motor is housed within a fuselage and the propulsion modules couple to the fuselage using a threaded fitting.

[0020] In one embodiment, the hydrofoil is attached to the fuselage and the fuselage is attached to the mast.

[0021] In one embodiment, the threaded fitting further comprises a locking mechanism.

[0022] In one embodiment, the threaded fitting does not comprise any additional locking mechanism. [0023] In one embodiment, the thread direction is chosen to be opposite to a torque direction of the motor, such that torque applied by the motor to the fitted propulsion module causes the threaded fitting to be tightened.

[0024] In one embodiment, the first propulsion module comprises an adapter configured to engage the motor and/or a component fixed thereto, the adapter being fixed relative to an internal component of the first propulsion module and rotatable within a module housing, the module housing comprising a thread that couples the first propulsion module to the motor.

[0025] In one embodiment, the adapter comprises one or more recesses shaped to receive one or more corresponding protrusions extending from the motor or an associated component, wherein the protrusions are located in the recesses when the first propulsion module is coupled to the motor, thereby rotationally fixing the internal component of the first propulsion module relative to the motor.

[0026] In one embodiment, the adapter comprises a ramp surface extending between each of the one or more recesses.

[0027] In one embodiment, a slope of the one or more ramp surfaces substantially matches a pitch of the thread.

[0028] In one embodiment, the first propulsion module can be removed from the motor and the second propulsion module fitted in place of the first propulsion module without the use of any tools.

[0029] In one embodiment, the watercraft comprises a controller and an input device, the input device allowing inputs to be received from a user and corresponding signals to be provided to the controller, and the controller performs functions to operate the motor based on the signals received from the input device, wherein the controller is programmed to moderate the operation of the motor in relation to the signals received based on whether the first propulsion module or the second propulsion module is fitted.

[0030] In one embodiment, the controller receives information regarding which of the propulsion modules is fitted from the input device. [0031] In one embodiment, the controller determines which of the propulsion modules is fitted automatically from one or more sensors and/or other feedback.

[0032] In one embodiment, the controller can detect if the propulsion module is incorrectly fitted or no propulsion module is fitted.

[0033] It will be appreciated that the broad forms of the invention and their respective features can be used in conjunction and/or independently, and reference to separate broad forms is not intended to be limiting.

Brief Description of the Drawings

[0034] Various examples and embodiments of the present invention will now be described with reference to the accompanying drawings, in which: -

[0035] Figure 1 is an isometric view of a watercraft according to an embodiment of the invention;

[0036] Figure 2 is an exploded side view of the hydrofoil system of the watercraft from Figure 1, illustrating two interchangeable propulsion modules;

[0037] Figure 3 is an isometric view of the hydrofoil system from Figure 2;

[0038] Figure 4 is an isometric view of the hydrofoil system with a propulsion module fitted that includes a water pump; and

[0039] Figure 5 is an isometric view of the hydrofoil system with a propulsion module fitted that includes a gearbox and a propeller;

[0040] Figure 6 is a cross sectional side view of coupling portions of a propulsion module and a hydrofoil system;

[0041] Figure 7 is a side view of the system from Figure 6 where the propulsion module is no longer shown in cross section;

[0042] Figure 8 is an isometric view of an adapter;

[0043] Figure 9 is a side view of the adapter from Figure 8; and [0044] Figure 10 is an isometric view of coupling portions of a propulsion module and a hydrofoil system, with a portion of a motor housing removed or transparent for illustrative purposes.

Detailed Description of the Preferred Embodiments

[0045] The following modes, given by way of example only, are described in order to provide a more precise understanding of the subject matter of a preferred embodiment or embodiments.

[0046] In the Figures, incorporated to illustrate features of an example embodiment, like reference numerals are used to identify like parts throughout the Figures.

[0047] An example of a hydrofoil watercraft according to an embodiment of the invention will now be described. The watercraft includes a board, a hydrofoil and a motor that are connected to the board by a mast. The motor is electric powered from a battery module locatable in the board. The battery module may include a housing and any necessary components for storing and supplying power, such as a battery.

[0048] A first propulsion module is operatively coupled to the motor, so that rotational power provided by the motor can be transferred to the first propulsion module, which in turn creates thrust in the water to propel the watercraft. The first propulsion module is also removable from the motor, allowing a second propulsion module to be fitted so that it is operatively coupled to the motor in place of the first propulsion module.

[0049] Throughout this specification, unless otherwise indicated the term “board” is used in a broad sense and is intended to include any suitable form of flotation device. For example, the board may be a rigid structure made from fibreglass, carbon fibre, or other similar materials. It may or may not include a foam or other type of core, similar to a surfboard for example. Alternatively, the board may be softer, such as made primarily from a rigid foam or similar. In still another example, the board may be inflatable or collapsible in some other way, so that it can take a rigid or at least semi-rigid form during use, but can be deflated or otherwise packed down for transport.

[0050] The watercraft as described is advantageous because it allows for propulsion modules with different performance characteristics to be used in different situations without the need for completely separate watercraft. This can reduce the cost for the user or allow variety where they would otherwise be forced to choose one or the other.

[0051] For example, some propulsion modules may be designed to provide smooth power and high top speed, potentially at the expense of maximum thrust or fast response. Such a propulsion module may be well suited for use on relatively flat water and/or leisurely activities. Meanwhile, other propulsion modules may be better suited to catching waves, performing tricks and/or riding in rough conditions.

[0052] Accordingly, the present invention can allow the user to change the propulsion module to suit their riding style, the conditions on a particular day and/or the location where they are planning to ride. Where it would have previously been necessary to have access to a completely different watercraft, or at least a separate complete hydrofoil and motor system, significant cost and convenience benefits can be realised by being able to change only the propulsion module.

[0053] Some other example embodiments of a watercraft will now be described.

[0054] In one example embodiment of a hydrofoil watercraft, the first propulsion module has a propeller. This propeller may be driven directly by the motor, or the first propulsion module may preferably also include a gearbox that couples to an output shaft of the motor. Use of a propeller in general is advantageous as being a highly efficient means of propulsion in water.

[0055] The gearbox if used could increase or more preferably reduce the rotational speed of the propeller relative to the motor. For example, the ratio of motor rotational speed to propeller rotational speed could be 1 :2, 2: 1, 3: 1, or even greater than 4: 1. Cases where the propeller speed is reduced relative to the motor may be particularly advantageous, because it can allow a narrower, high speed motor that may create less drag in the water, while still providing a propeller that is capable of operating with high torque.

[0056] Having multiple propulsion modules that include propellers may be advantageous by allowing the use of propellers with different diameter, blade shape and/or pitch angles, for example. Each of the propellers may have fixed pitch angles for simplicity and cost reasons, for example, but could therefore be altered in different situations as necessary by changing the propulsion module. Such changes may also optionally be accompanied with changes to gearbox ratios, for example, or some may be provided without a gearbox.

[0057] In another example embodiment of a hydrofoil watercraft, the second propulsion module has a water pump, which may alternatively be referred to at least in some forms as a pump jet, fully shrouded propeller, water jet or hydro jet. This water pump may include an inlet, an axial flow pump, and a nozzle. Preferably, the axial flow pump includes one or more propellers, impellers or sets of impeller blades and one or more sets of stator vanes, all housed within a duct or shroud that connects the inlet to the nozzle. Alternatively, it will be appreciated that in some embodiments a different type of pump could be used, such as a radial flow pump or positive displacement pump, for example . The duct preferably narrows at the nozzle, thereby increasing the velocity of the water as it exits the nozzle during use.

[0058] The water pump may include a gearbox similar to that described with relation to the first propulsion module, but preferably the water pump couples directly to an output shaft of the motor without any gearbox to reduce or increase a rotational speed of the axial flow pump relative to the motor. In this way, a narrow, high speed motor may be used, resulting in high rotational speed for the axial pump in the water pump.

[0059] The use of a water pump may be advantageous for its performance characteristics, such as smooth power delivery, lower rotational thrust component than a propeller and/or an improved ability to operate through the water at high speeds. The water pump may be quieter than a propeller and may also be safer in the event that accidental contact is made with the propulsion module during use, both in terms of potential injury as well as damage to the module itself. It may also be possible for thrust vectoring to be used to assist with control in some situations.

[0060] In another embodiment, the propulsion modules couple to the motor using a threaded fitting. The propulsion modules may couple directly to a threaded portion of the motor, or alternatively the motor may be housed within a fuselage and the propulsion modules couple to the fuselage.

[0061] Use of a fuselage may be advantageous and it will be appreciated that the hydrofoil and connected components could take a range of forms, provided it includes one or more components for providing lift, as well as necessary components for providing propulsion. For example, the hydrofoil wings may be integrated with the motor, similar to the present Applicant’s earlier design as described in publication number WO2019/104378. In this way, the wings are not connected directly to the mast, but rather the wings are connected to the motor housing, which in turn is connected to the mast. Alternatively, the hydrofoil and motor may take a different form, such as some other known designs where a mast has wings mounted at one location and a motor mounted at a separate location.

[0062] A threaded fitting is advantageous because it is allows for extremely simple removal and attachment of the propulsion modules to the motor, while also requiring minimal space and being relatively simple to manufacture. It will be appreciated, however, that many alternative attachment means could be used, such as a bayonet or twist-lock fitting and/or simple slide fit with securing clips or standard fasteners such as screws, for example.

[0063] In one example, the threaded fitting may also include a locking mechanism. This locking mechanism may be a simple compressible seal or washer, grub screws in the fuselage, motor and/or propulsion module that can be tightened once fitted, one or more clips or latches, a ramp and teeth arrangement, or any other suitable locking mechanism that may be known in the art for use with a threaded fitting.

[0064] In yet other examples, the threaded fitting may not have any additional locking mechanism, relying instead simply on friction of the threaded fitting to secure the propulsion module. Once again, such an arrangement may be advantageous for its simplicity of packaging and ease of manufacture, provided the threaded fitting is designed in a way that ensures it is unlikely to come loose during regular use.

[0065] In these or other examples, one means of helping to ensure the threaded fitting remains secure during use may be to choose the thread direction to be opposite to a torque direction of the motor. In this way, torque applied by the motor to the fitted propulsion module causes the threaded fitting to be tightened.

[0066] In one example embodiment, the first propulsion module may have an adapter that engages the motor and/or a component fixed thereto, such as a motor end cap and/or part of a fuselage or motor housing in which the motor is located. In this example, the adapter may be fixed relative to an internal component of the first propulsion module, such as a shaft, gearbox, or gearbox components, yet rotatable within a housing of the module.

[0067] The module housing may have a thread that couples the first propulsion module to the motor, but because the adapter is rotatable within the housing, this means it does not necessarily need to rotate while the module is being threaded on or off the motor. This can be advantageous when designing the interface between the module and the motor, for example, because it allows for alignment of features of the module and motor even though a rotational position can’t be guaranteed when a thread is used for securing the parts together.

[0068] In one specific example, the adapter may have one or more recesses shaped to receive one or more corresponding protrusions extending from the motor or an associated component. These protrusions may be in the form of bolts, bolt heads, nuts, tabs, flanges, or any other similar feature, including specifically designed protrusions. The recesses may be substantially identical in shape to the protrusions, or they may be different or enlarged in some ways to account for tolerances, assembly and disassembly, or any other requirement.

[0069] The protrusions can be located within the recesses when the first propulsion module is coupled to the motor, thereby rotationally fixing the internal component of the first propulsion module relative to the motor. For example, in the case where the internal component is a gearbox or gearbox subassembly, the recesses and protrusions act to hold the gearbox in place when torque from the motor is applied, even though the gearbox may be rotatable when the module is removed from the motor. This therefore allows the gearbox to be rotated within the housing during assembly or disassembly, yet fixed in place once assembly is complete.

[0070] In one exemplary but non-limiting example, the adapter has a ramp surface extending between each of the one or more recesses. Preferably, a slope of the ramp surface(s) substantially matches a pitch of the thread. It will be appreciated that the ramp surface may be used with a greater or lesser pitch than the thread, however the identical or at least similar pitch is advantageous because it has been found to significantly reduce the likelihood of jamming or locking when assembling or disassembling the module onto or off the motor.

[0071] In particular, it has been found that a pitch lower than that of the thread can cause jamming during assembly, while a pitch higher than that of the thread can cause jamming during disassembly. By matching these pitches, however, it is most likely that the protrusions will never contact the ramp surfaces of the adapter, only ever contacting the inside of the recesses. It is this potential contact of the protrusions with the ramp surfaces that has been found to cause jamming, so avoiding this possibility is advantageous for assembly and disassembly.

[0072] In a preferred embodiment, one of the propulsion modules can be removed from the motor and the other propulsion module fitted in place of the originally fitted propulsion module without the use of any tools. Such a system ensures that changing of the propulsion modules is as quick and easy as possible, and may even allow this task to be achieved immediately before or after use at the side of a water body, for example.

[0073] In yet other embodiments, however, a simple tool may be provided that has protrusions corresponding to indents on the propulsion modules, so that this tool can be accessible and easily used when necessary. For example, the tool may be stored in a case that is also used for storing components of the watercraft when not in use, and thereby always transported with the watercraft and readily available for use when needed.

[0074] In any of the embodiments described above, the output shaft of the motor may connect to an input shaft of the propulsion modules using any of a range of connection means. In one example, the output shaft of the motor may have splines around the outer circumference or similarly may have a pinion gear. Each of the propulsion modules can then have a corresponding input shaft that includes a bore with internal splines to couple with the output shaft or pinion gear. Alternatively, for propulsion modules that include a gearbox, the pinion gear may couple directly to planetary gears of the gearbox, thereby creating a more compact assembly.

[0075] As the propulsion module is threaded onto the motor or fuselage, the output shaft is received within the bore of the input shaft or within the gears (if used). This in turn can allow torque to be transferred from the motor to the propulsion module once secured through the locking action of the splines or gears.

[0076] Such an arrangement is advantageous because it allows the attachment of the propulsion module to the motor to be as simple as possible. That is, connection of the shafts is not necessarily an extra step or procedure that requires specific attention but may simply happen naturally as the propulsion module is connected to the motor.

[0077] In some example embodiments, additional means may be provided to aid with successful coupling of the motor output shaft to the propulsion module input shafts. In one specific example, one or more tapers may be used on one or both of the shafts to assist with engagement of the shafts as the threads are engaged. In yet another example, the coupling portions of the shafts may be long enough that they can begin to be engaged before threads of the motor or fuselage and propulsion module engage.

[0078] It will be appreciated that a range of alternative mechanisms for coupling the shafts could also be used. For example, the shafts may be keyed in a different manner to that described above. In another example, each of the shafts may have an end plate with faces that abut one another, these abutting end faces having splines, notches, ramps, fingers, or some other engaging features, optionally further including rubber inserts or pads to absorb vibration and/or allow for slight misalignment. In yet other examples, a coupling mechanism could be used that includes more complex features, such as a one way ratchet or bearing, or another form of clutch that can be useful in the operation of the propulsion module.

[0079] In an embodiment, the watercraft may include a controller and an input device. For example, these components may be similar or based on those described in the Applicant's earlier patent publications WO 2022/174296 Al or WO 2019/183668 Al. In particular, the input device can allow inputs to be received from a user and corresponding signals to be provided to the controller. The controller can then perform functions to operate the motor based on the signals received from the input device.

[0080] The input device may be in the form of a hand controller, which receives inputs through one or more buttons and/or a trigger. The hand controller can then send a signal to the controller to choose the level of thrust to be produced by the motor, for example. The hand controller may also optionally be sent information from the controller for display to a user, such as a charge level of the battery, temperature, speed, warnings and any other relevant parameters.

[0081] In one example, the controller is programmed to moderate the operation of the motor in relation to the signals received from the input device at least in part based on whether the first propulsion module or the second propulsion module is fitted. For example, the different propulsion modules will typically have different torque and power profiles, so it may be desirable for the mapping of the throttle to the motor output to be adjusted to better suit each of the different types of propulsion module.

[0082] In one specific implementation of the different throttle mapping, for example, the first propulsion module with a propeller may be matched to a relatively linear throttle-motor output relationship, while for the second propulsion module with a water pump this may be significantly altered. This is due to the nature of a water pump that may require high power to allow the user to begin hydrofoiling, but then significantly reduced power while hydrofoiling at speed. As such, the throttle mapping can be adjusted to make this process more easily controlled by the user.

[0083] In another specific implementation, there may be different responses to the user dramatically reducing the throttle. The user may do this when they catch a wave, for example, not only when they wish to stop moving. In this situation, if the first propulsion module is fitted the motor power may be simply reduced to zero, while if the second propulsion module is fitted a small motor power may be provided to allow the water pump to continue rotating without creating excessive drag. Various additional detection means may also be employed to differentiate between the user catching a wave rather than wishing to stop, such as GPS data and/or feedback from the motor.

[0084] In one example, the controller may receive information regarding which of the propulsion modules is fitted from the input device. That is, the user may select a propulsion module option on the input device using buttons and a screen, with this information being conveyed to the controller so that the controller knows which propulsion module is fitted.

[0085] In another example, the controller may be able to determine which of the propulsion modules is fitted automatically from one or more sensors and/or other feedback. For example, when the controller is activated it may briefly rotate the motor, with a relationship between measurable parameters such as motor power, torque, speed, etc., being used to automatically determine the type of propulsion module that is fitted. Alternatively, this determination may be made soon after the user begins riding the watercraft. In another example, a dedicated sensor or switch may be used. In such a case, one of the propulsion modules may have a tab or other device that activates the sensor when fitted, with this tab being absent on the other one of the propulsion modules.

[0086] Preferably, the controller can also detect if the propulsion module is incorrectly fitted or no propulsion module is fitted. In such a situation, the controller may then be able to take a mitigating action like preventing operation of the motor or notifying the user via the input device or some other warning or feedback means. This can be done according to certain rules pre-programmed in the controller.

[0087] An example embodiment of a watercraft 100 will now be described with reference to the Figures.

[0088] Referring to Figure 1, the watercraft 100 has a board 110 with a deck 111 that is suitable for a user to he or stand on when in use. A mast 114 extends from a lower surface of the board 110 and a motor 115 with propulsion module 116 is connected to a lower end of the mast 114. A main hydrofoil wing 118 and a tail wing 119 are each connected to a body of the motor 115. A battery module 120 is located within the board 110 below a deck cover 121.

[0089] Referring to Figure 2 and Figure 3, a first propulsion module 130 is shown as being removable from the motor 115, allowing a second propulsion module 140 to be fitted in its place. When either the first propulsion module 130 or the second propulsion module 140 are fitted (as shown in Figures 4 and 5), they operatively couple to the motor 115 so that the motor 115 can drive the propulsion module 130, 140 and thereby produce thrust when in water.

[0090] The first propulsion module 130 has a propeller 131 connected by a central shaft 132 to a gearbox 133. The gearbox 133 couples to an output shaft 150 of the motor 115 (shown in Figure 3) and allows the rotational speed of the motor 115 to be reduced, with the propeller 131 rotating at a lower speed but higher torque relative to the motor 115. The ratio of motor rotational speed to propeller rotational speed is preferably about 2: 1, but may be adjusted depending on particular situations and motor or propeller design, such as 3: 1 or even greater than 4: 1. [0091] Looking now also at Figure 3, the second propulsion module 140 has an inlet 141 and a nozzle 142. An axial flow pump 143 includes a shroud 144 housing an impeller 145 and one or more sets of stator vanes 146. The axial flow pump 143 couples directly to the output shaft 150 of the motor 115 without any gearbox to reduce or increase a rotational speed of the axial flow pump 143 relative to the motor 115.

[0092] Referring to both Figure 2 and Figure 3, the propulsion modules 130, 140 couple to the motor 115 in the embodiment shown using a threaded fitting. That is, the first propulsion module 130 includes a male thread 136 and a seal 137, while a housing 151 in which the motor 115 is located includes a female thread 152. Similarly, the second propulsion module 140 has a male thread 147 and a seal 148.

[0093] The housing 151 forms part of a fuselage 154, with the main hydrofoil wing 118, the tail wing 119 and the mast 114 all being connected to the fuselage 154. The threaded fitting couples one of the propulsion modules 130, 140 to the housing 151 and thereby the motor 115 is secured simply by a friction fit with no additional locking mechanism. However, it may be preferable in an alternative embodiment to use a retention ring to ensure the motor is not accidentally removed from the fuselage when there is no propulsion module attached.

[0094] The thread direction is opposite to the rotational direction of the motor 115 so that torque applied by the motor 115 to the propulsion module 130, 140 acts to tighten the threaded connection. It will be appreciated, however, that in some alternative embodiments there may be a locking mechanism provided to reduce any risk of the threaded connection coming loose, such as when the user is slowing down or catching waves.

[0095] Due to the lack of any locking mechanism and the use of a simple threaded connection, it will be appreciated that in the embodiment shown the first propulsion module 130 can be removed from the motor 115 and the second propulsion module 140 fitted in place of the first propulsion module 130 without the use of any tools. Similarly, the reverse process can also be completed without the use of any tools.

[0096] The output shaft 150 has splines around the outer circumference, with each of the propulsion modules 130, 140 having a corresponding input adapted to mate with the splines of the output shaft 150. In the second propulsion module 140 this input is in the form of a shaft that includes a bore with internal splines to couple with the output shaft 150. In the first propulsion module 130 this input is in the form of planetary gears 134 (see Figure 6) that mesh with the output shaft 150. Accordingly, as the propulsion module 130, 140 is threaded onto the motor 115, the output shaft 150 is received within the bore of the input shaft or between the planetary gears 134 and thereby allowing torque to be transferred from the motor 115 to the propulsion module 130, 140 once secured.

[0097] Referring now to Figures 6 and 7, more detail is shown of the connection of the first propulsion module 130 to the motor 115. The first propulsion module 130 has an adapter 135 fitted to the gearbox 133 that engages an end cap 160 of the motor 115. More specifically, the adapter 135 couples with protrusions 161 that are in the form of heads of bolts that are partially threaded into holes in the end cap 160 at the end of the motor 115. Using bolts to form the protrusions 161 may be advantageous by allowing a degree of adjustability to account for tolerances, for example, however it will be appreciated that the protrusions 161 could be formed as an integral part of the end cap 160 in an alternative embodiment or formed in some other suitable way.

[0098] The adapter 135 is fixed to the gearbox 133 using bolts 138. This subassembly of the gearbox 133 and adapter 135 is rotatable within a housing 139 of the module 130. The thread 136 and seal 137 are part of the housing 139 and are used to couple the module 130 to the motor 115 as described previously.

[0099] Referring now to Figures 8 and 9, the adapter has a number of recesses 162 that are shaped to receive the bolt heads 161 that extend from the motor end cap 160. The bolt heads 161 are located in the recesses 162 when the module 130 is coupled to the motor 115, thereby rotationally fixing the adapter 135 and gearbox 133 relative to the motor 115.

[0100] As noted previously, the module 130 is designed to be readily removed from the motor 115. To enable this, however, there needs to be a way for the bolt heads 161 to seat correctly in the recesses 162 as the module 130 is threaded on or off. To achieve this, the adapter 135 has a ramp surface 164 extending between each of the recesses 162. This creates a high side 165 and a low side 166 for each recess 162. [0101] As the module 130 is threaded onto the motor 115 and the adapter 135 moves towards the bolt heads 161, the bolt heads 161 will at some point contact the high sides 165 of the recesses 162 as they rotate with the module 130. At this point, the bolt heads 161 will prevent the adapter 135 and gearbox 133 from rotating, instead remaining stationary within the rotating module housing 139. The module 130 can continue to be threaded onto the motor 115 until the bolt heads 161 a fully seated within the recesses 162, with both the low side 166 and high side 165 of the recesses preventing rotation of the adapter in either direction.

[0102] To prevent sticking or jamming of the module 130 as it is threaded on or off, the slope of the ramp surfaces 164 is chosen to match the pitch of the threads 136, 152. While it may not be essential for this to be the case, the matching of the pitches provides the greatest likelihood that the bolt heads 161 will only contact the recesses 162 and never the ramp surfaces 164 themselves.

[0103] The watercraft 100 has a controller and an input device. In the preferred embodiment, the input device is in the form of a hand controller that allows inputs to be received from a user, such as via a trigger and/or buttons. Corresponding signals are then provided wirelessly from the input device to the controller, with data optionally also being relayed in the reverse direction for communication to the user.

[0104] The controller includes the relevant components for allowing the watercraft 100 to function, including a microprocessor, a memory, an input/output device in the form of one or more wireless communication devices to exchange instructions with the hand controller and battery module, and a logic level motor controller, interconnected by a bus. These components function together to allow the controller to perform tasks including battery management, motor operation, and data output to be displayed to the user.

[0105] The nature of the controller and in particular the physical form factor of the device, as well as the components used, can vary depending on the preferred implementation. For example, the microprocessor and communication device can be formed from a custom integrated circuit, such as a Bluetooth system on a chip (SOC), coupled to, or including an integrated antenna and other optional components, such as the memory. [0106] The controller performs functions to operate the motor based on the signals received from the input device. For example, the user provides an input such as depressing the trigger, with a corresponding signal being relayed to the controller and the controller then increasing power to the motor 115.

[0107] The controller is also programmed to moderate the operation of the motor 115 in relation to the signals received based on whether the first propulsion module 130 or the second propulsion module 140 is fitted. For example, the mapping of the throttle input to the motor power can be modified to better suit the performance characteristics of the particular propulsion module 130, 140 that is fitted at a given time.

[0108] More specifically, when the first propulsion module 130 with the propeller 131 and gearbox 133 is fitted, the throttle to motor power mapping may be relatively linear, as this is suitable for the efficiency and performance of this propeller setup which does not change significantly across its use range.

[0109] In contrast, a water pump may vary significantly in performance and/or efficiency across its use range, particularly depending on the speed the watercraft is moving through the water. This is particularly relevant for a hydrofoil watercraft, because such a watercraft requires high power at low speeds when the board is on the water. When hydrofoiling, however, not only does the speed increase, but the power requirement can decrease, or at least the watercraft becomes more efficient. This corresponds to an increase in the efficiency of the water pump as well, which can create challenges in throttle control for the user.

[0110] Therefore, a throttle map that makes control easier, particularly during the transition from the water to hydrofoiling, is particularly advantageous for use of a water pump. As such, when the second propulsion module 140 with the axial flow pump 143 is fitted, the throttle to motor power mapping is changed to better suit this propulsion module 140.

[oni] In the preferred embodiment, the controller receives information regarding which of the propulsion modules is fitted from the input device. That is, the user selects a propulsion module from available options using the hand controller, or another optionally connected device, such as a smartphone application. [0112] Alternatively, in another example embodiment, the controller can determine which of the propulsion modules 130, 140 is fitted automatically from one or more sensors and/or other feedback. Preferably, in either of these embodiments, the controller can also detect if the propulsion module 130, 140 is incorrectly fitted or no propulsion module is fitted, producing an error signal or warning to the user and/or preventing the motor 115 from operating.

[0113] In the foregoing description of preferred embodiments, specific terminology has been resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as “front” and “rear”, “inner” and “outer”, “above” and “below” and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms

[0114] Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers. As used herein and unless otherwise stated, the term “approximately” means ±20%.

[0115] Persons skilled in the art will appreciate that numerous variations and modifications will become apparent. All such variations and modifications which become apparent to persons skilled in the art, should be considered to fall within the spirit and scope that the invention broadly appearing before described.