Technical Field

[0001] The present disclosure relates to apparatuses for water sports, such as surfboards, kiteboards, wakeboards, foil boards, and the like. Embodiments include a jet system for powering a board, and boards comprising the jet system.

Background

[0002] Boards used in water sports typically require a user or an external system to propel the board to a sufficient speed to perform the relevant water sport. For example, a surfer paddles whilst lying on their surfboard to increase their speed in anticipation of catching a wave travelling at a similar speed. Boards with a propulsion system (which may be referred to as powered boards) can be used to provide an initial acceleration and/or velocity so that there is less reliance on the user or the relevant external system (e.g. a boat) to propel the board, and less reliance on external conditions such as suitable waves (and catching them at an appropriate angle).

[0003] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims.

[0004] Throughout this specification the word "comprise", or variations 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. Summary

[0005] Some embodiments relate to a jet system body for a board, the jet system body comprising: a first inlet conduit comprising: a first inlet end defining a first inlet opening; a first outlet end defining a first outlet opening; a first lumen extending from the first inlet opening to the first outlet opening; a second inlet conduit comprising: a second inlet end defining a second inlet opening; a second outlet end defining a second outlet opening; a second lumen extending from the second inlet opening to the second outlet opening; a manifold in fluid communication with the first outlet opening and the second outlet opening; and an outlet in fluid communication with the manifold and configured to receive an impeller for drawing fluid through the first and second inlet conduits, through the manifold and into the outlet; wherein the first inlet conduit and the second inlet conduit extend from the manifold such that the first inlet end and the second inlet end are spaced apart.

[0006] The first inlet conduit may be spaced apart from the second inlet conduit along a first length of the first inlet conduit. The first length may extend from the first outlet end to the first inlet end, and the second length may extend from the second outlet end to the second inlet end.

[0007] The first inlet conduit may comprise a first arcuate portion defining an arcuate portion of the first lumen; and/or the second inlet conduit may comprise a second arcuate portion defining an arcuate portion of the second lumen. [0008] The first and/or second inlet conduit may comprise a respective first and/or second flow guidance structure. The first and/or second flow guidance structure may comprises one or more of: a winglet, fin, baffle, ridge, and groove. The first and/or second flow guidance structure may be disposed on an internal wall of the respective first and/or second inlet conduit.

[0009] The jet system body may comprise: a first grille disposed at the first inlet end; and/or a second grille disposed at the second inlet end. The first grille and/or the second grille may be integrally formed with the respective inlet ends. The first grille and/or the second grille may be removably connected to the respective inlet ends.

[0010] The first and/or second inlet opening may have a cross sectional area that is larger than a cross sectional area of the respective first and/or second outlet opening.

[0011] The first lumen may have a cross sectional area that decreases from the first inlet opening to the first outlet opening. The first lumen may taper from the first inlet opening to the first outlet opening.

[0012] The second lumen may have a cross sectional area that decreases from the second inlet opening to the second outlet opening. The second lumen may taper from the second inlet opening to the second outlet opening.

[0013] The manifold may comprise a first manifold inlet in fluid communication with the first inlet conduit. The manifold may comprise a second manifold inlet in fluid communication with to the second inlet conduit. The manifold may comprise a manifold outlet in fluid communication with to the outlet of the jet system body. The manifold may comprise a plenum in fluid communication with the first manifold inlet, the second manifold inlet, and the manifold outlet.

[0014] The manifold may comprise a drive conduit. The drive conduit may comprise a drive conduit inlet end defining a drive conduit inlet opening. The drive conduit may comprise a drive conduit outlet end defining a drive conduit outlet opening. The drive conduit may comprise a drive conduit lumen extending from the drive conduit inlet opening to the drive conduit outlet opening, the drive conduit lumen being configured to receive a part of a drive shaft.

[0015] Some embodiments relate to a jet system comprising: the jet system body as described above; a propulsion system, the propulsion system comprising an impeller and a drive system to drive the impeller; wherein the drive system is configured to drive the impeller to move fluid from at least one of the first inlet end and the second inlet end through the outlet of the jet system body.

[0016] The jet system may further comprise: a controller for controlling the propulsion system, the controller comprising a sensor system; wherein the controller is configured to: determine a speed estimate that is indicative of a speed of the board using sensor data determined using the sensor system; compare the speed estimate to a speed threshold; and activate the drive system to drive the impeller in response to the speed estimate being equal to or greater than the speed threshold.

[0017] The jet system may further comprise a controller for controlling the propulsion system, the controller being configured to: receive a propulsion system activation delay input that is indicative of a time delay duration associated with activation of the propulsion system; and activate the drive system to drive the impeller after a time period corresponding to the time delay duration elapses.

[0018] The jet system may further comprise a controller for controlling the propulsion system, the controller being configured to: receive a thrust time window input that is indicative of a duration of a thrust time window; activate the drive system to drive the impeller for an activation duration that is equal to the duration of the thrust time window; and deactivate the drive system after the activation duration elapses.

[0019] The drive system may be configured to connect to the drive conduit and the impeller is disposed adjacent to the manifold outlet. The drive system may comprise a motor, the motor being disposed outside of the manifold and between the first and second inlet conduits. The drive system may further comprise a drive shaft, wherein the drive shaft extends from the motor through the drive conduit lumen to the impeller.

[0020] The outlet of the jet system body may comprise a nozzle connected to a flange, the flange configured to enable the outlet of the jet system body to be connected to the manifold outlet. The nozzle and the flange may be integrally formed. The nozzle may have an inner diameter that is larger than an outer diameter of the impeller.

[0021] The jet system body may define a Y shape, the Y shape comprising: the first and second inlet ends in spaced apart relation; and the outlet disposed between and offset from the inlet ends.

[0022] The jet system body may be symmetrical about a plane of symmetry. The propulsion system may be intersected by the plane of symmetry. The outlet of the jet system may be intersected by the plane of symmetry. The plane of symmetry may be between the first and second inlet ends.

[0023] The manifold may be contained within a cartridge. The drive system may be contained within the cartridge. The cartridge may comprise a cartridge body that defines first and second cartridge conduit apertures in opposed side walls of the cartridge body. The first outlet end of the first inlet conduit may be configured to fluidly connect to the first manifold inlet through the first cartridge conduit aperture; and the second outlet end of the second inlet conduit may be configured to fluidly connect to the second manifold inlet through the second cartridge conduit aperture. The manifold may be integrally formed with the cartridge body. [0024] Some embodiments relate to a kit for a jet-powered board, the kit comprising: a board defining a cavity, a first inlet aperture, and a second inlet aperture; and the jet system body as described above; wherein the cavity is configured to at least partially receive the jet system body; and the first and second inlet openings of the jet system body are configured to be in fluid communication with the first and second inlet apertures respectively, when the jet system body is received by the cavity.

[0025] Some embodiments relate to a kit for a jet-powered board, the kit comprising; a board defining a cavity, a first inlet aperture, and a second inlet aperture; and the jet system as described above; wherein the cavity is configured to at least partially receive the jet system; and the first and second inlet openings of the jet system body are configured to be in fluid communication with the first and second inlet apertures respectively, when the jet system body is received by the cavity.

[0026] The board may comprise: a bottom surface defining an underside of the board; a front end and a rear end; and a longitudinal axis; wherein the jet system body is configured to be received by the cavity such that the first inlet end and the second inlet end are: (i) spaced apart; (ii) disposed on opposite sides of the longitudinal axis; and (iii) configured to ingest fluid from the underside of the board.

[0027] The board may further comprise: a mast mount; a mast configured to be connected to the mast mount; and a hydrofoil configured to be connected to the mast. [0028] The first inlet end and the second inlet end of the jet system body may be configured to be disposed on opposite sides of the mast mount. The propulsion system and the mast mount may be configured to be disposed along an elongate centreline of the board.

[0029] The cartridge may be configured to be removably received in the cavity of the board.

[0030] The jet system may further comprise a shroud configured to cover a recess of the board. The shroud may have an exterior surface which is configured to be flush with the bottom surface of the board when the shroud is in use. The bottom surface of the board may be substantially flat at the rear end of the board when the jet system body is received in the cavity and covered by the shroud.

[0031] Some embodiments relate to a jet-powered board, the jet-powered board comprising an assembly of the kit as described above. In use, a centre of mass of the jet system may be positioned over the hydrofoil.

Brief Description of Drawings

[0032] Embodiments are described in further detail below, by way of example, with reference to the accompanying drawings, in which:

[0033] Fig. 1 is an exploded view of a hydrofoil board;

[0034] Fig. 2 is a simplified example of a powered foil board;

[0035] Fig. 3 is an underside view of a board comprising a jet system, according to some embodiments. Fig. 3 also comprises an inset which shows a cross section view of a nozzle of the jet system;

[0036] Fig. 4A is an exploded view of the jet system of Fig. 3, as seen from above; [0037] Fig. 4B is a perspective view of the jet system of Fig. 4, as assembled and as seen from underneath;

[0038] Fig. 5A is a perspective view of an impeller of the jet system of Fig. 3, as received in the nozzle;

[0039] Fig. 5B is an exploded view of Fig. 5A, viewed from a reverse angle;

[0040] Fig. 6A is a perspective view of a cartridge of the jet system of Fig. 3, according to some embodiments;

[0041] Fig. 6B is a section view of Fig. 6A, as taken along the line 6B-6B;

[0042] Fig. 6C is an exploded view of Fig. 6A;

[0043] Fig. 7 is a section view as shown in Fig. 6B, as viewed from above; and

[0044] Fig. 8 is a perspective view of an embodiment of the jet system comprising a cartridge housing for receiving the cartridge of Figs. 6A-6C.

Detailed Description

[0045] The present disclosure relates to apparatus for water sports, such as surfboards, kiteboards, wakeboards, foil boards, and the like. Embodiments include a jet system for powering a board, and boards comprising the jet system. Reference is drawn to the Australian Provisional Patent Application entitled “Water sport apparatus, control systems and methods” filed on 3 November 2021, the entire content of which is fully incorporated by reference herein.

[0046] Fig. 1 shows an exploded view of a water sport apparatus 100. The water sport apparatus 100 comprises a board 110. The board 110 has a front end 112. The board 110 has a rear end 114. The board 110 may be substantially elongate, extending from the front end 112 to the rear end 114. The front end 112 of the board 110 may be raised relative to the rear end 114 so that in use, water is guided under the board 110 towards the rear end 114.

[0047] The board 110 comprises a core and an outer shell. The shell comprises a top surface (or topside) and a bottom surface (or underside). The board 110 is suitable for one or more water sports. The board 110 may be a surfboard, kiteboard, wakeboard, or any similar type of board.

[0048] The water sport apparatus 100 has a centre of mass 102. The water sport apparatus 100 is configured to roll (tilt side-to-side) about a roll axis 104 which passes through the centre of mass 102. The roll axis 104 may be referred to as a longitudinal axis of the board 110. The water sport apparatus 100 is configured to pitch (tilt frontrear) about a pitch axis 106 which passes through the centre of mass 102. The water sport apparatus 100 is configured to yaw (turn left or right) about a yaw axis 108 which passes through the centre of mass 102.

[0049] In some embodiments, the water sport apparatus 100 comprises a mast 120. The mast 120 is connected to the board 110 at a mast mount 116. The mast mount 116 is typically positioned towards the rear end 114 of the board 110. That is, the mast mount 116 is closer to the rear end 114 of the board 110 than to the front end 112. For stability, the mast mount 116 is typically aligned with the roll axis 104 of the board 110. The roll axis 104 is preferably collinear with a longitudinal centreline 118 of the board 110. The board 110 is symmetrical about the longitudinal centreline 118, which extends between the front end 112 and rear end 114.

[0050] The mast 120 comprises a first end 122 which attaches to the mast mount 116. The mast 120 comprises an opposed second end 124. A foil (hydrofoil) 130 is configured to connect to the second end 124. The mast mount 116 comprises at least one rail or track along which the first end 122 of the mast 120 can be received and slid into a desired position. The mast mount 116 may also be referred to as a “track box” or “Tuttle box”. [0051] The position of the mast 120 may be selectively varied depending on the wind and water conditions as well as the rider’s skill, weight, or surfing style. For example, moving the mast 120 towards the front end 112 of the board 110 may make the assembled water sport apparatus 100 easier to control but be less responsive to the foil 130. Conversely, moving the mast 120 towards the rear end 114 of the board 110 may make the assembled water sport apparatus 100 more responsive to the foil 130 but harder to control. Moving the mast 120 forward may enable the foil 130 to generate more lift compared to moving the mast 120 (and foil 130) rearward.

[0052] The foil 130 comprises a front wing 132. The foil 130 comprises a rear stabiliser 134. The rear stabiliser 134 may take the form of a wing or winglet. The foil 130 comprises an elongate fuselage 136. The front wing 132 and the rear stabiliser 134 are disposed at opposite ends of the fuselage 136.

[0053] The location of the centre of mass 102 (and consequently, the ability to roll, pitch, or yaw the water sport apparatus 100) is affected by the distribution of weight across the water sport apparatus 100. The board 110, the mast mount 116, the mast 120, and the foil 130 each have respective masses such that when these components are attached to each other, they cumulatively shift the position of the centre of mass 102.

[0054] The water sport apparatus 100 shown in Fig. 1 is unpowered. In use, the water sport apparatus 100 relies on the movement of the board and/or water interacting with the foil 130 to lift the water sport apparatus 100. The wing 132 generates a lift force in response to relative movement of the water sport apparatus 100 and water around the wing 132. Preferably, the centre of mass 102 of the water sport apparatus 100 is positioned over the wing 132. This means that the lift force vector passes through the centre of mass 102, so that the water sport apparatus 100 is lifted in a balanced way (i.e. the lift force does not cause the water sport apparatus 100 to roll, pitch, or yaw).

[0055] The wing 132 has an aerofoil shape to generate lift with movement of water around the wing 132. Water flow around the foil 130 may be caused by the user propelling the water sport apparatus 100 onto a wave, after which, movement of the water sport apparatus 100 by the wave may cause the water flow. Alternatively, the user (rider) riding the water sport apparatus 100 may be connected to a kite which catches the wind, thereby towing the user and the board through the water and causing water to flow around the foil 130. A similar tow can be achieved using a motorboat in wakeboarding.

[0056] The rear stabiliser 134 stabilises the foil 130 by providing a balancing force that counteracts the lift generated by the wing 132. When the lift force is larger than the weight of the water sport apparatus 100 and its rider, the foil 130 raises the board 110 out of the water, thereby reducing drag. This allows the user (rider) to ride smaller, less energised waves compared to a board without a foil. Alternatively, where the board 110 is a kiteboard, the user can use a kite of a particular size to take advantage of wind speeds that are lower than those ordinarily useable with that particular kite if the user were to be using a board without a foil.

[0057] When waves are weak, or when wind speeds are low, the rider of an unpowered foil board can find it difficult to propel the unpowered foil board to a sufficient speed to provide sufficient water moving past the foil 130 to generate lift. To address this, foil boards can include a propulsion system which propels the board 110 through the water to generate the initial lift using the foil 130. The propulsion system may comprise a motor connected to an impeller to generate thrust (a jet of water) which propels or pushes the board 110 through the water.

[0058] Fig. 2 shows a simplified example of a water sport apparatus 200. The water sport apparatus 200 may comprise a jet system 210. The jet system 210 comprises a propulsion system 220. The propulsion system 220 includes an impeller 222 that is driven by a drive system 230. The jet system 210 may be applied to surfboards, kiteboards, wakeboards, and the like where a hydrofoil is not present. The jet system 210 may be applied to hydrofoil boards. The jet system 210 may be installed with a board to form a jet-powered board. [0059] The water sport apparatus 200 may also comprise the board 110, mast 120, and foil 130 described with reference to the unpowered water sport apparatus 100 of Fig. 1, except as detailed herein as different. For example, the board 110 described with reference to Fig. 1 may be modified to enable the provision of the jet system 210. To reduce drag, the impeller 222 and drive system 230 may be embedded within the board 110 so that the underside of the board 110 remains smooth and consistent. Changes in profile, such as a step, are more likely to generate turbulence as water flows over the surfaces of the board 110. This may make the water sport apparatus 100 unpredictable and/or unsafe to ride.

[0060] In some embodiments, the jet system 210 comprises a jet system body 212. The jet system body 212 may comprise a single intake conduit or inlet conduit 240 connected to, or in fluid communication with, an outlet 250 of the jet system body 212. In some embodiments, the jet system body 212 may comprise two or more intake conduits or inlet conduits 240 connected to, or in fluid communication with the outlet 250 of the jet system body 212. The impeller 222 is disposed at the outlet 250 of the jet system body 212. The inlet conduit 240 is connected to an inlet aperture 241 which is defined in the underside of the board 110.

[0061] In some embodiments, the core of the board 110 defines a cavity 270. The cavity 270 is wholly contained within the board 110 and is not accessible from an outer surface of the board 110. In some embodiments, the board 110 defines a recessed portion 272. The recessed portion 272 may extend from the underside of the board 110 into the core of the board 110. In some embodiments, the recessed portion 272 is connected to the cavity 270. As shown in Fig. 2, the cavity 270 and the recessed portion 272 may be connected to form a tunnel or passage in which the inlet conduit 240 may be received, for example. A shroud or cover (not shown) may be provided to cover the recessed portion 272. The shroud (not shown) may be configured to be flush with the underside of the board 110 when the shroud is in place covering the recessed portion 272. The underside of the board 110 at the rear end 114 may be substantially flat when the shroud is in place over the cavity 270 or the recessed portion 272. [0062] The cavity 270 or the recessed portion 272 may be defined in or toward the rear end 114 of the board 110. The cavity 270 or the recessed portion 272 may be configured to at least partially receive the jet system 210. In particular, the cavity 270 or the recessed portion 272 may be configured to at least partially receive the inlet conduit 240. In Fig. 2, the inlet conduit 240 is shown in dotted lines as an example of its positioning when the inlet conduit 240 is received in the cavity 270 or the recessed portion 272.

[0063] The drive system 230 comprises a power supply 232. The drive system 230 comprises a controller 234. The controller 234 controls a motor 236 to spin the impeller 222 at the desired speed. The spinning impeller 222 draws fluid (air or water) from the underside of the board 110 through the inlet aperture 241, into the inlet conduit 240, and into the outlet 250 where it meets the impeller 222. The fluid passing through the impeller 222 is accelerated and expelled through the outlet 250 as a jet, providing thrust. By way of example, the position of at least part of the drive system 230 (e.g. the controller 234 and/or motor 236) is shown as a dash-dot line.

[0064] Similar to the water sport apparatus 100, the water sport apparatus 200 has a centre of mass 202. The water sport apparatus 200 is configured to roll about a roll axis 204 which passes through the centre of mass 202. The water sport apparatus 200 is configured to pitch about a pitch axis 206 which passes through the centre of mass 202. The water sport apparatus 200 is configured to yaw about a yaw axis 208 which passes through the centre of mass 202.

[0065] To improve ride predictability and safety of the water sport apparatus 200, it is desirable to align the centre of mass of the jet system 210 with the roll axis 204 of the water sport apparatus 200, or to at least balance this weight about the roll axis 204.

This means that the drive system 230, impeller 222, inlet conduit 240, and outlet 250 are each aligned closely with the roll axis 204 of the board 110. The roll axis 204 may be collinear with the longitudinal centreline 118 of the board 110. [0066] As previously described, the mast mount 116 allows the position of the mast 120 to be adjusted along the longitudinal centreline 118. The size of the mast mount 116 limits the amount of space available along the longitudinal centreline 118 at the rear end 114 of the board 110.

[0067] The mast mount 116 typically needs to be able to accommodate the mast 120 in a rearmost position (at or close to the rear end 114 of the board 110). This means that for the inlet conduit 240 and the jet system 210 to also be on the centreline 118, at least some of these parts are likely to be forward of the mast 120.

[0068] Positioning the inlet conduit 240 and the drive system 230 forward of the mast 120 results in the centre of mass 202 being shifted forward, towards the front end 112 of the board 110 (and further forward than the centre of mass 102 of the water sport apparatus 100, that is, the board without the jet system 210). This means that the centre of mass 202 may no longer be aligned with the lift force generated by the wing 132, and accordingly the lift force may be likely to cause the water sport apparatus 200 to pitch. In contrast, the centre of mass 102 of the water sport apparatus 100 is positioned over the wing 132, meaning the lift force generated does not cause the water sport apparatus 200 to pitch.

[0069] Fig. 3 shows an underside view of a water sport apparatus 300 comprising a jet system 310, according to some embodiments. The jet system 310 may be applied to surfboards, kiteboards, wakeboards, and the like where a hydrofoil is not present. In some embodiments, the water sport apparatus 300 is a jet-powered board 300. The jet system 310 may be referred to as a twin- intake jet system.

[0070] In some embodiments, the water sport apparatus 300 also comprises the same board 110, mast 120, and foil 130 as the water sport apparatus 200, except as detailed herein as different. However, the mast 120 and the foil 130 are not shown in Fig. 3 for clarity. Similar to the jet system 210, the jet system 310 comprises a propulsion system 320. The propulsion system 320 includes an impeller 322 driven by a drive system 330. The impeller 322 has a plurality of blades 324 which move fluid when the impeller 322 is rotated. The blades 324 may be attached to a hub 326 (see Fig. 3, inset; see also Fig. 5A).

[0071] Similar to the water sport apparatus 100 and 200, the water sport apparatus 300 has a centre of mass 302. The water sport apparatus 300 is configured to roll about a roll axis 304 which passes through the centre of mass 302. The water sport apparatus 300 is configured to pitch about a pitch axis 306 which passes through the centre of mass 302. The water sport apparatus 300 is configured to yaw about a yaw axis 308 which passes through the centre of mass 302. As Fig. 3 is an underside view of the board 110, the yaw axis 308 runs into the page and is not shown.

[0072] Compared to the jet system 210, the jet system 310 is a more longitudinally- compact configuration. When installed in the board 110, the jet system 310 may allow weight to be distributed more towards the rear end 114 of the board 110. This enables repositioning of the centre of mass 302 so that it is aligned with the lift force generated by the wing 132. As a result, the lift force generated is less likely to cause the water sport apparatus 300 to pitch.

[0073] The features which allow the jet system 310 to be more longitudinally- compact than the jet system 210 will now be described in detail.

[0074] In some embodiments, the jet system 310 comprises a jet system body 312. The jet system body 312 comprises a first inlet conduit 340. The first inlet conduit 340 may be referred to as a first intake conduit. The first inlet conduit 340 is configured to be fluidly connected to, or in fluid communication with, an outlet 350 of the jet system body 312. The first inlet conduit 340 is in fluid communication with a first inlet aperture 341 defined by the underside of the board 110.

[0075] The jet system body 312 further comprises a second inlet conduit 360. The second inlet conduit may be referred to as a second intake conduit. The second inlet conduit 360 is configured to be fluidly connected to, or in fluid communication with, the outlet 350. The second inlet conduit 360 is in fluid communication with a second inlet aperture 361 defined in the underside of the board 110.

[0076] In some embodiments, the core of the board 110 defines a cavity 370. The cavity 370 is wholly contained within the board 110 and is not accessible from an outer surface of the board 110. In some embodiments, the board 110 defines a recessed portion 372. The recessed portion 372 may extend from the underside of the board 110 into the core of the board 110. In some embodiments, the recessed portion 372 is connected to the cavity 370. As shown in Fig. 3, the cavity 370 and the recessed portion 372 may be connected to form a tunnel or passage in which at least one of the inlet conduits 340, 360 may be received, for example.

[0077] The cavity 370 and/or the recessed portion 372 may be defined in the rear end of the board 110. The cavity 370 and/or the recessed portion 372 may be configured to at least partially receive the jet system 310. In particular, the cavity 370 and/or the recessed portion 372 may be configured to at least partially receive the first inlet conduit 340 and the second inlet conduit 360. In Fig. 3, the first and second inlet conduits 340, 360 are shown in dotted lines as an example of their positioning when the conduits 340, 360 are received in the cavity 370 and/or the recessed portion 372.

[0078] A shroud or cover may be provided to cover the recessed portion 372. The shroud may be configured to be flush with the underside of the board 110 when the shroud is in place covering the recessed portion 372. The underside of the board 110 at the rear end 114 may be substantially flat when the shroud is in place over the cavity 370 and/or the recessed portion 372. The shroud may protect the first and second inlet conduits 340, 360 from debris. The shroud may have a seal to reduce or prevent water ingress into the cavity 370 and/or the recessed portion 372. All seals on the jet system 310 may have a minimum dust and water resistance IP rating of 68, unless noted otherwise.

[0079] In some embodiments, the impeller 322 is disposed at the outlet 350. The drive system 330 comprises a power supply 332. The drive system 330 comprises a controller 334. The controller 334 controls a motor 336 to spin the impeller 322 at the desired speed. The spinning impeller 322 draws fluid (air or water) from the underside of the board 110 through the inlet apertures 341 and 361. The fluid flows through the respective inlet conduits 340, 360 into the outlet 350 where it meets the impeller 322. The fluid passing through the impeller 322 is accelerated and expelled through the outlet 350 as a jet, providing thrust. Fig. 6B and Fig. 7 show an example layout of the power supply 332, the controller 334, and the motor 336.

[0080] To improve ride predictability and safety of the water sport apparatus 300, it may be desirable to align the weight of the jet system 310 along the roll axis 304 of the water sport apparatus 300, or to at least balance this weight about the roll axis 304. In some embodiments, the drive system 330, impeller 322, and outlet 350 are each aligned closely with the roll axis 304 of the board 110. In some embodiments, the roll axis 304 is collinear with the longitudinal centreline 118 of the board 110.

[0081] The inclusion of the first inlet conduit 340 and the second inlet conduit 360 in the jet system 310 allows for greater flexibility with packaging and weight distribution, compared to a jet system configuration with the single inlet conduit 240 (as present in jet system 210). For example, the inlet conduits 340, 360 may be positioned either side of the roll axis 304. The inlet apertures 341, 361 may also be positioned either side of the roll axis 304.

[0082] By positioning the inlet conduits 340, 360 and the inlet apertures 341, 361 on opposite sides of the roll axis 304, the weight of one conduit can counterbalance the weight of the other conduit. This can provide a net zero (or close) roll moment about the roll axis 304, meaning that the roll stability of the water sport apparatus 300 is not adversely affected by the positioning of the inlet conduits 340, 360.

[0083] In some embodiments, the inlet conduits 340 and 360 and the inlet apertures 341, 361 are positioned on opposite sides of the mast mount 116. As previously described in relation to the water sport apparatus 100 and 200, the mast mount 116 is aligned with the roll axis 304 to provide stability. The inlet conduits 340, 360 and the inlet apertures 341, 361 are thus positioned on opposite sides of the roll axis 304, with the mast mount 116 positioned between the inlet conduits 340, 360 and the inlet apertures 341, 361.

[0084] Positioning the inlet conduits 340, 360 and the inlet apertures 341, 361 on opposite sides of the mast mount 116 allows the inlet apertures 341, 361 to be closer to the outlet 350. With the inlet apertures 341, 361 positioned closer to the outlet 350, the drive system 330 can also be positioned closer to the outlet 350. This allows the centre of mass 302 of the water sport apparatus 300 to be positioned over the wing 132, which can reduce the extent to which the lift force generated may cause the water sport apparatus 300 to pitch. Positioning the inlet apertures 341, 361 to be closer to the outlet 350 may also allow the inlet conduits 340, 360 to be made shorter in length, thereby saving weight. Shortening the inlet conduits 340, 360 may reduce the amount of energy lost as the fluid moves through the inlet conduits 340, 360. This may improve the efficiency and power output of the jet system 310, compared to the jet system 210.

[0085] The inclusion of two inlet conduits and inlet apertures may also provide redundancy in the event that fluid flow is impeded (or otherwise reduced) through one of the inlet conduits 340, 360 or one of the inlet apertures 341, 361.

[0086] The jet system 310 may be provided as part of a kit, which can be assembled to obtain the water sport apparatus 300. The kit for the water sport apparatus 300 may comprise the board 110. The board 110 may comprise a core made from a foam material. The shell of the board 110 may be made from layers of fibreglass or carbon fibre. The first and second inlet apertures 341, 361 are formed in the shell. The jet system body 312 is configured to connect to the first and second inlet apertures 341, 361 through the cavity 370 and recess 372 formed in the core of the board 110.

[0087] The cavity 370 is configured to at least partially receive the jet system body 312. When the jet system body 312 is received by the cavity 370, the first and second inlet conduits 340, 360 are configured to be in fluid communication with the first and second inlet apertures 341, 361 respectively. The kit may also comprise the shroud to cover the jet system body 312 when in the cavity 370. The shroud may also be made from layers of fibreglass or carbon fibre.

[0088] The board 110 may be approximately Im to 2m in length. In some embodiments, the board may be approximately 1.2m to 1.6m (4ft to 5ft) in length. The board 110 may be approximately 0.3m to 0.8m wide. The board 110 may be approximately 0.3m to 0.6m wide. In some embodiments, the board may be approximately 0.45m to 0.5m (18in to 20in) wide. In some embodiments, the board 110 may be about 69cm wide.

[0089] The kit for the water sport apparatus 300 may further comprise the mast mount 116, the mast 120, the foil 130, the propulsion system 320, and the drive system 330. The cavity 370 may be sized to receive the propulsion system 320. The cavity 370 may be sized to receive the drive system 330. The cavity 370 may be sized to receive both the propulsion system 320 and the drive system 330. The cavity 370 may also receive the mast mount 116 (for attaching the mast 120 and the foil 130 thereto). The shroud may also cover these components when they are received in the cavity 370.

[0090] By way of example, the position of the drive system 330 in the board 110 is shown as a dash-dot line in Fig. 3. In some embodiments, the drive system 330 is positioned above the mast mount 116. In other words, the drive system 330 may be positioned between the first end 112 and the mast mount 116. As previously described, the mast mount 116 comprises at least one rail or track. The mast mount 116 occupies a small portion on the underside of the board 110, allowing room in the board 110 to receive the drive system 330 above the mast mount 116 and between the inlet apertures 341, 361. In some embodiments, the mast mount 116 comprises two parallel tracks which are spaced apart. Spacing apart the two parallel tracks of the mast mount 116 may create more space in the board 110 to receive the drive system 330. In this configuration, at least part of the drive system 330 may be positioned between the two parallel tracks of the mast mount 116. [0091] The drive system 330 may comprise the power supply 332. The drive system 330 may comprise the controller 334. The drive system 330 may comprise the motor 336. The drive system 330 may further comprise a gearbox 338 connected to the motor 336. The power supply 332 is connected to the controller 334 and the motor 336. The power supply 332 may be a rechargeable battery, such as a lithium-ion battery. The controller 334 may comprise memory 337 and one or more processors 335 to execute code or instructions stored in the memory 337. The controller 334 may execute the code or instructions to draw power from the power supply 332 to operate the motor 336. The controller 334 may operate the motor 336 at a specified speed corresponding to a user-selected setting. For example, the user may select a speed corresponding to their weight when on the water sport apparatus 300.

[0092] The user may select the settings via a user interface, such as a control panel. The user interface may be situated on the board 110. In some embodiments, the board 110 comprises a user interface lumen 325 that extends between the user interface recess 327 and the cavity 370. One or more components of the controller 334 (e.g. the one or more processor(s) 335) may be contained in the cavity 370. Electrical wires configured to enable communication between the user interface and the one or more processor(s) 335 of the controller 334 may extend through the user interface lumen 325. Alternatively, in some embodiments, the user interface is configured to wirelessly communicate with the one or more processor(s) 335 of the controller 334.

[0093] The user interface may comprise a handheld remote. The remote may be configured to wirelessly communicate with the controller 334. The user interface may communicate with a display unit on the board 110 and/or on the remote. The display unit may display information such as battery life, usage data, and/or performance of the water sport apparatus 300 (such as top speed). The display unit may be a touchscreen. The display unit and/or the user interface may have physical buttons or dials to enable the user to easily operate the display unit and/or the user interface with wet hands or without looking at the display unit and/or the user interface. For example, the display unit and/or the user interface may include a propulsion system activation button. When the button is operated, the controller 234 may activate the propulsion system 320. [0094] In some embodiments, the controller 334 comprises a timer and at least one sensor. The sensor may comprise an accelerometer, and/or a gyroscope. The controller 334 may be configured to process sensor data obtained using the at least one sensor and may store the sensor data in memory 337. The controller 334 may automatically reduce or shut down power to the jet system 310 after a certain amount of time. The controller 334 may automatically reduce or shut down power to the jet system 310 if the accelerometer detects acceleration within a specified threshold and/or if the gyroscope is in a non-upright position for a certain amount of time. This may correspond to the water sport apparatus 300 not requiring the initial acceleration/boost provided by the jet system 310 (for example, if the water sport apparatus 300 is already moving), or not being in use (for example, accidentally switched on during storage). The timer may also cooperate with the controller 334 to operate the motor 336 for a specified time period, for example if the user/rider only requires a short burst of power to get the water sport apparatus 300 moving. The timer may also have a delay function to allow the rider time to start paddling before the jet system 310 operates.

[0095] The one or more processor(s) 335 of the controller 334 may be configured to determine a value of one or more operational parameter(s), for example, using the sensor data and/or other data (e.g. other operational data).

[0096] The operational parameter(s) may comprise a thrust estimate parameter, the value of which may be indicative of a thrust of the propulsion system 320. In particular, the value of the thrust estimate parameter may be indicative of the thrust provided by the propulsion system 320 at a particular time. The value of the thrust estimate parameter may be referred to as a thrust estimate. The operational parameter(s) may comprise an acceleration estimate parameter, a value of which may be indicative of an acceleration of the water sport apparatus 300. In particular, the value of the acceleration estimate parameter may be indicative of the acceleration of the water sport apparatus 300 at a particular time. The value of the acceleration estimate parameter may be referred to as an acceleration estimate. The accelerometer estimate is indicative of acceleration in one or more of the first acceleration direction, the second acceleration direction and the third acceleration direction at a particular time. The value of the acceleration estimate parameter may be referred to as an acceleration estimate. In some embodiments, the acceleration estimate comprises an acceleration estimate vector.

[0097] The operational parameter(s) may comprise a velocity estimate parameter, a value of which may be indicative of a velocity of the water sport apparatus 300. In particular, the value of the velocity estimate parameter may be indicative of velocity of the water sport apparatus 300 at a particular time. The velocity estimate is indicative of velocity in one or more of a first velocity direction, a velocity acceleration direction and a third velocity direction at a particular time. One or more of the first velocity direction, the second velocity direction and the third velocity direction may be orthogonal. The value of the velocity estimate parameter may be referred to as a velocity estimate. In some embodiments, the velocity estimate comprises a velocity estimate vector.

[0098] The operational parameter(s) may comprise a speed estimate parameter. A value of the speed estimate parameter is indicative of a speed of the water sport apparatus 300. In particular, the value of the speed estimate parameter is indicative of the speed of the water sport apparatus 300 at a particular time. The value of the speed estimate parameter may be referred to as a speed estimate. In some embodiments, the controller 334 is configured to determine a speed estimate that is indicative of a speed of the board using sensor data, which may, for example, be determined using the sensor system. The controller may be configured to compare the speed estimate to a speed threshold and activate the drive system to drive the impeller in response to the speed estimate being equal to or greater than the speed threshold.

[0099] In some embodiments, the controller 334 is configured to receive a propulsion system activation delay input that is indicative of a time delay duration associated with activation of the propulsion system and to activate the drive system to drive the impeller after a time period corresponding to the time delay duration elapses. In some embodiments, the controller 334 is configured to receive a thrust time window input that is indicative of a duration of a thrust time window activate the drive system to drive the impeller for an activation duration that is equal to the duration of the thrust time window and to deactivate the drive system after the activation duration elapses.

[0100] The jet system 310 may comprise a cooling system for dissipating heat generated from operation of the jet system 310 and/or the drive system 330. The cooling system may be a passive cooling system which provides cooling by the movement of fluid. The cooling system may comprise at least one of a vent, a fan, a heatsink, or a radiator. The heat generated may be dissipated by the cooling system being in communication with the surrounding air or water. In embodiments where the cooling system comprises a heatsink or a radiator, the heatsink or radiator is disposed within the inlet conduits 340, 360 or is in contact with an exterior portion of the inlet conduits 340, 360. In this way, the heat is transferred into the fluid moving through the inlet conduits 340, 360.

[0101] The kit may be supplied in a completely unassembled state or in a partly assembled state. Some embodiments of the kit may be combined or replaced with other parts. For example, the jet system 310 may be combined with the user’s own board, or with the user’s own foil 130.

[0102] Figs. 4A and 4B show further detail of the jet system 310 and the jet system body 312, according to some embodiments. Fig. 4A is an exploded view of the jet system 310 as seen from above. Fig. 4B is a perspective view of the jet system 310 as assembled and as seen from underneath. The mast mount 116 is shown in Figs. 4A and 4B for reference positioning, and is not intended to suggest that the mast mount 116 is part of the jet system 310.

[0103] Fig. 4A shows parts of the first and second inlet conduits 340, 360 in phantom to allow viewing of various sub-features in the same drawing. The first inlet conduit 340 comprises a first inlet end 342 defining a first inlet opening 343, shown in phantom. The first inlet conduit 340 comprises a first outlet end 344 defining a first outlet opening 345, shown in phantom. The first inlet conduit 340 comprises a first lumen 346, shown in phantom, extending from the first inlet opening 343 to the first outlet opening 345.

[0104] The first inlet opening 343 is configured to be fluidly connected, or in fluid communication with, to the first inlet aperture 341. When fluidly connected or communicable, fluid entering the first inlet aperture 341 may then flow through the first lumen 346, passing through the first inlet end 342 towards the first outlet end 344. The fluid may then pass through the first outlet end 344 and out of the first outlet opening 345.

[0105] The second inlet conduit 360 comprises a second inlet end 362 defining a second inlet opening 363. The second inlet conduit 360 comprises a second outlet end 364 defining a second outlet opening 365. The second inlet conduit 360 comprises a second lumen 366 extending from the second inlet opening 363 to the second outlet opening 365.

[0106] The second inlet opening 363 is configured to be fluidly connected to, or in fluid communication with, the second inlet aperture 361. When fluidly connected or communicable, fluid entering the second inlet aperture 361 may then flow through the second lumen 366, passing through the second inlet end 362 towards the second outlet end 364. The fluid may then pass through the second outlet end 364 and out of the second outlet opening 365.

[0107] The first and second inlet apertures 341, 361 are disposed on either side of the mast mount 116. That is, the first and second inlet apertures 341, 361 are disposed on opposing sides of the mast mount 116. This allows the distance between the outlet 350 and the inlet conduits 340, 360 to be reduced, compared to the distance between the outlet 250 and the single inlet conduit 240 in the jet system 210.

[0108] In some embodiments, the jet system body 312 further comprises a manifold 410. The manifold 410 fluidly connects the inlet conduits 340, 360 to the outlet 350 so that fluid passes from the inlet apertures 341, 361 to the impeller 322. In other words, the manifold 410 is fluidly connected, or in fluid communication with, to the first outlet opening 343 and the second outlet opening 363. The outlet 350 is configured to receive the impeller 322, which draws fluid through the first and second inlet conduits 340, 360 through the manifold 410 and into the outlet 350.

[0109] The exploded view of Fig. 4A shows the manifold 410 and the inlet conduits 340, 360 as separate components for clarity. In some embodiments, the manifold 410 and the inlet conduits 340, 360 may be formed as a single piece. The manifold 410 and the inlet conduits 340, 360 may be moulded or cast as a single piece (or as separate pieces to be joined together) using metal casting or plastic moulding. A composite material, such as carbon fibre or fibreglass may also be layered over a mould to form the manifold 410 and the inlet conduits 340, 360 as a single piece or as separate pieces to be joined together.

[0110] The manifold 410 may comprise a first manifold inlet 412 fluidly connected, or in fluid communication with, to the first inlet conduit 340, and a second manifold inlet 414 fluidly connected to, or in fluid communication with, the second inlet conduit 360. That is, the first manifold inlet 412 is fluidly connected to or is in fluid communication with the first lumen 346 and the second manifold inlet 414 is fluidly connected to or is in fluid communication with the second lumen 366. The manifold 410 may comprise a manifold outlet 416. The manifold outlet 416 is fluidly connected to or is in fluid communication with the outlet 350 of the jet system body 312. The manifold 410 may further comprise a plenum 418. The plenum 418 is fluidly connected to or is in fluid communication with the first manifold inlet 412, the second manifold inlet 414, and the manifold outlet 416. The manifold inlets 412, 414 and the manifold outlet 416 may be disposed at opposite ends of the plenum 418. Fluid is configured to enter the manifold 410 via the manifold inlets 412, 414, and transit the plenum 418, before being discharged through the manifold outlet 416.

[0111] In some embodiments, the manifold 410 comprises a drive conduit 420. The drive conduit 420 comprises a drive conduit inlet end 422 defining a drive conduit inlet opening 424. The drive conduit 420 (and in particular, the drive conduit inlet opening 424) may be disposed between the first manifold inlet 412 and the second manifold inlet 414.

[0112] The drive conduit 420 comprises a drive conduit outlet end 426 defining a drive conduit outlet opening 428. The drive conduit 420 comprises a drive conduit lumen 430 extending from the drive conduit inlet opening 424 to the drive conduit outlet opening 428. At least part of the drive conduit 420 may be fluidly connected, or in fluid communication with, to the plenum 418.

[0113] The drive system 330 may be configured to connect to the drive conduit 420, such as at the drive conduit inlet opening 424. The drive conduit lumen 430 may be configured to receive a part of a drive shaft 440 connecting the drive system 330 to the impeller 322. The impeller 322 may be disposed adjacent to the manifold outlet 416. In some embodiments, the plenum 418 is arranged between the drive system 330 and the impeller 322. The drive shaft 440 may thus extend through the manifold 410 and/or plenum 418 to connect the drive system 330 and the impeller 322.

[0114] As previously described, the drive system 330 comprises the power supply 332, the controller 334, the motor 336, and/or the gearbox 338, for example as shown in Fig. 6B and Fig. 7. The power supply 332, the controller 334, the motor 336, and/or the gearbox 338 are arranged along the longitudinal axis 118 so that their respective centres of mass are aligned with the roll axis 304. In some embodiments, at least one of the power supply 332, the controller 334, the motor 336, and the gearbox 338 is disposed outside of the manifold 410. At least one of the power supply 332, the controller 334, the motor 336, or the gearbox 338 may be positioned away from the inlet apertures 341, 361. The drive shaft 440 may extend from the motor 336 through the drive conduit lumen 430 to the impeller 332.

[0115] The drive system 330 is configured to drive the impeller 322 to move fluid from at least one of the first inlet end 342 and the second inlet end 362, into the manifold 410, and into the outlet 350 of the jet system body 312 via the manifold outlet 416. [0116] In some embodiments, the outlet 350 of the jet system body 312 comprises a nozzle 450. The nozzle 450 may comprise a nozzle body 452, a nozzle inlet end 454, and a nozzle outlet end 456. The nozzle inlet end 454 and the nozzle outlet end 456 may be fluidly connected, or in fluid communication, through the nozzle body 452. The nozzle inlet end 454 and the nozzle outlet end 456 may be disposed at opposite ends of the nozzle body 452. The nozzle body 452 may be tubular and define an internal surface 453. The nozzle body 452 may have an internal diameter sized to receive the impeller 322 therein. For clarity, the impeller 322 is not shown in Figs. 4A and 4B to allow the internal surface 453 to be more clearly seen.

[0117] Fig. 5A is a perspective view of the impeller 322 as received in the nozzle 450. Fig. 5B is an exploded view of Fig. 5A, viewed from a reverse angle. The impeller 322 has a plurality of blades 324 which move fluid when the impeller 322 is rotated. The blades 324 are mounted to the impeller hub 326. The impeller hub 326 defines a hub lumen 328 which is configured to receive and connect to the drive shaft 440 so that the drive shaft 440 can rotate the impeller 322. To transmit torque and rotate the impeller 322, the drive shaft 440 may be a keyed shaft or a splined shaft that engages with the hub 326 via a corresponding shaft key or spline. This allows the impeller 322 to be removed from the drive shaft 440 for ease of repair or replacement. As the impeller 322 rotates, the tips of the blades 324 define an envelope of the impeller 322. The envelope is defined by the outer diameter/sweep of the blades 324.

[0118] The inner diameter of the nozzle body 452 is larger than the outer diameter or sweep of the blades 324 of the impeller 322. At least part of the internal surface 453 of the nozzle body 452 is preferably closely fitted around the impeller 322, such as shown in Fig. 5A. A closely fitted nozzle body 452 directs more fluid through the envelope of the impeller 322, rather than outside the outer diameter of the blades 324. The reduced gap between the tips of the impeller blades 324 and the inner diameter of the nozzle body 452 thereby allows the impeller blades 324 to draw more fluid through the impeller 322 (compared to an impeller and nozzle with a larger gap therebetween). [0119] The nozzle 450 may direct the ejected fluid in a particular direction. In some embodiments, the nozzle body 452 comprises flow guidance structures 459 which help to direct the flow of fluid through the nozzle 450 after it passes through the impeller 322. The flow guidance structures 459 may assist with conditioning or guiding the flow of fluid as it exits the nozzle 450 at the nozzle outlet end 456. The flow guidance structures 459 may comprise at least one fin or wing. The nozzle body 452 may taper at the nozzle outlet end 456 to increase the speed of the ejected fluid.

[0120] Continuing to refer to Figs. 5A and 5B, with further reference to Figs. 4A and 4B, the nozzle 450 may further comprise a flange 458. The flange 458 may be configured to enable the outlet 350 of the jet system body 312 to be connected to the manifold outlet 416. The manifold outlet 416 may have a matching flange 417 to allow the flange 458 to be connected thereto to form a flanged connection. The flanges 417, 458 may be connected by removable fasteners, such as bolts. The flanged connection allows the nozzle 450 to be easily removed and cleaned or replaced. For example, the internal surface 453 of the nozzle body 452 may become worn through use, particularly when the nozzle body 452 and impeller 322 are closely fitted. The wear on the internal surface 453 of the nozzle body 452 may be caused by the blades 324 of the impeller 322 eroding or abrading the internal surface 453. The nozzle 450 may also become damaged from external impact. The flanged connection of the flanges 417, 458 allows the nozzle 450 to be replaced without having to replace the impeller 322 as well.

[0121] The flange 458 may be integrally formed with the nozzle 450. The flange 458 may be connected to the nozzle 450 by welding or by removable means such as a threaded connection. For example, the flange 458 may be a substantially ring-shaped with a threaded connection on the inside of the ring, and this threaded connection is configured to mate with a corresponding threaded connection on the outside of the nozzle body 452. The flange 458 may be connected to the nozzle 450 at the nozzle inlet end 454.

[0122] Referring again to Figs. 4A and 4B, the manifold 410 may be fluidly connected to, or in fluid communication with, the first outlet opening 345 of the first inlet conduit 340. The manifold 410 may be fluidly connected, or in fluid communication with, the second outlet opening 365 of the second inlet conduit 360. The first inlet conduit 340 and the second inlet conduit 360 may extend or branch out from the manifold 410 such that the first inlet end 342 and the second inlet end 362 are spaced apart. The first inlet end 342 and the second inlet end 362 may be spaced apart and disposed on opposite sides of the longitudinal axis of the board 110 or on opposite sides of the roll axis 304. In some embodiments, the first inlet end 342 and the second inlet end 362 are spaced apart while the first outlet end 344 and the second outlet end 364 are not spaced apart, so that the outlet ends 344, 364 are fluidly connected, or in fluid communication with, the same portion of the manifold 410.

[0123] By spacing apart the first inlet end 342 and the second inlet end 362, the jet system body 312 defines a gap 400 between the first inlet end 342 and the second inlet end 362 in which at least part of the propulsion system 320 or drive system 330 can be received. For example, the motor 336 may be disposed in the gap 400.

[0124] The length of the gap 400 can be increased by spacing apart the first inlet conduit 340 and the second inlet conduit 360 beyond their inlet ends 342, 362. For example, the first inlet conduit 340 may be spaced apart from the second inlet conduit 360 along a first length of the first inlet conduit 340. The first length extends from the first outlet end 344 to the first inlet end 342. The first length may correspond with a length of the first lumen 346.

[0125] Similarly, the second inlet conduit 360 may be spaced apart from the first inlet conduit 340 along a second length of the second inlet conduit 340. The second length extends from the second outlet end 364 to the second inlet end 362. The second length may correspond with a length of the second lumen 366.

[0126] In some embodiments, the first and second inlet conduits 340, 360 are spaced apart along their lengths so that the first inlet end 342 and the first outlet end 344 are spaced apart from the second inlet end 362 and the second outlet end 364. In this way, the outlet ends 344, 364 are fluidly connected to, or in fluid communication with, different portions of the manifold 410.

[0127] In some embodiments, the first inlet conduit 340 may extend from a first side portion of the manifold 410. The second inlet conduit 360 may extend from a second side portion of the manifold 410. The second side portion of the manifold 410 may be opposed to the first side portion of the manifold 410. The first and second side portions may, for example, be left and right side portions of the manifold 410, as divided by a notional reference plane such as a plane of symmetry.

[0128] The first body side portion of the jet system body 312 may comprise the first inlet end 342. The second body side portion of the jet system body 312 may comprise the second inlet end 362. The first body side portion may be an opposing side portion of the jet system body 312 to the second body side portion.

[0129] The jet system body 312 may be symmetrical about a plane of symmetry. The plane of symmetry is a notional reference plane and may be between the first and second inlet ends 342, 362. The propulsion system 330 may be intersected by the plane of symmetry. In some embodiments, the outlet 350 of the jet system body 312 is intersected by the plane of symmetry. The plane of symmetry may coincide with the centreline of the outlet 350 so that the first and second inlet ends 342, 362 are mirror images of each other. In other words, the outlet 350 may be bisected by the plane of symmetry. In some embodiments, the first and second inlet conduits 340, 360 are mirror images of each other about the plane of symmetry.

[0130] In some embodiments, the jet system body 312 defines a Y shape. The Y shape comprises the first and second inlet ends 342, 362 in spaced apart relation (forming the gap 400), with the outlet 350 disposed between and offset from the inlet ends 342, 362. The Y shaped jet system body 312 may be asymmetrical. In some embodiments, the Y shaped jet system body 312 is symmetrical so that the first and second inlet conduits 340, 360 are mirror images of each other. The Y shape may orient at least part of the inlet conduits 340, 360 at an obtuse angle (marked 470) to the direction of fluid flowing through the outlet 350. In some embodiments, such as shown Figs. 4A and 4B, the outlet ends 344, 364 of the inlet conduits 340, 360 are at an obtuse angle 470 to the direction of fluid flowing through the outlet 350. In this way, the change of direction of fluid as it enters the manifold 410 is relatively gradual, compared to an acute angle configuration.

[0131] In some embodiments, the first inlet conduit 340 comprises a first arcuate portion defining an arcuate portion of the first lumen 346. In some embodiments, the second inlet conduit 360 comprises a second arcuate portion defining an arcuate portion of the second lumen 366. The first and second arcuate portions may increase the width of the gap 400 between the first and second inlet conduits 340, 360 when traversing along their length, away from the manifold 410, thereby enabling a reduction in the length of the jet system body 312. This allows the jet system 310 to be longitudinally compact and facilitates aligning the weight of the jet system 310 close to the lift force vector generated by the wing 132, which may improve the balance of the water sport apparatus 300. A longitudinally compact jet system 310 may also allow the jet system 310 to be more easily removed from the board 110 as the mast 120 does not get in the way.

[0132] The shape of the inlet conduits 340, 360 may affect the characteristics of the fluid flowing through the first lumen 346 and the second lumen 366. This may affect the speed, direction, and turbulence of the fluid flow encountered by the impeller 322. For example, tapering or narrowing the inlet conduits 340, 360 may cause the fluid flowing through the first lumen 346 and the second lumen 366 to accelerate as it moves into the manifold 410. The taper may occur consistently over the length of the conduits 340, 360, or over only a part of the length. The first inlet opening 343 may have a cross sectional area that is equal to a cross sectional area of the first outlet opening 345. Any change in shape or curvature of the inlet conduits 340, 360 and lumens 346, 366 may be gradual. A sudden change in shape or curvature may impede the fluid flowing through the inlet conduits 340, 360 and lumens 346, 366. This may reduce the speed, direction, and/or turbulence of the fluid entering the manifold 410. [0133] In some embodiments, the first inlet opening 343 has a cross sectional area that is larger than a cross sectional area of the first outlet opening 345. A larger area at the inlet opening enables more fluid to enter the first inlet conduit 340. A smaller area at the first outlet opening 345 may enable improved control of the amount and rate of fluid flowing out of the first inlet conduit 340.

[0134] The cross sectional area of the first lumen 346 may accordingly reduce in size or taper along the length of the first inlet conduit 340. Alternatively, the cross sectional area of the first lumen 346 may vary along the length of the first inlet conduit 340, such as increasing in size before reducing towards the first outlet opening 345.

[0135] Similarly, the second inlet opening 363 may have a cross sectional area that is larger than a cross sectional area of the second outlet opening 365. The cross sectional area of the second lumen 366 may accordingly reduce in size or taper along the length of the second inlet conduit 360. Alternatively, the cross sectional area of the second lumen 366 may vary along the length of the second inlet conduit 360, such as increasing in size before reducing towards the second outlet opening 365.

[0136] The fluid flow through the jet system body 312 may in some embodiments be regulated by a valve or a plurality of valves. The valve may be a oneway valve to prevent or reduce reverse flow through the jet system body 312. The one-way valve may, for example, comprise a flap which is configured to open in only one direction when there is a sufficient fluid pressure differential across the valve. In some embodiments, the valve is disposed in at least one of the inlet conduits 340, 360. In some embodiments, the valve is disposed in the manifold 410, such as in the plenum 418.

[0137] To further affect the characteristics of the fluid flowing through the first lumen 346 and the second lumen 366, the first inlet conduit 340 and the second inlet conduit 360 may comprise respective flow guidance structures. The flow guidance structures may assist with conditioning or guiding the flow of fluid through the first and second inlet conduits 340, 360. For example, the flow of fluid through the first and/or second inlet conduits 340, 360 may be too fast, too slow, too turbulent, too laminar, or not focused in the desired direction. The flow guidance structures may be similar to the flow guidance structures 459 present in some embodiments of the nozzle body 452.

[0138] The first and/or second flow guidance structures may comprise one or more of: a winglet, fin, baffle, ridge, vane, and groove. The type, size, and orientation of the first and second flow guidance structures may be different or identical to each other depending on the type and amount of flow conditioning desired.

[0139] For example, at least one of the flow guidance structure(s) may be disposed on an internal wall of the first inlet conduit 340 and/or on an internal wall of the second inlet conduit 360. In this way, fluid passing through the first lumen 346 and the second lumen 366 may be guided towards the outlet 350 of the jet system body 312 with the desired speed and direction. This may also improve the performance of the impeller 322.

[0140] The performance of impeller 322 may be adversely affected by contact with debris. To reduce the likelihood of large debris entering the first and second inlet conduits 340, 360 and impacting the impeller 322, the jet system body 312 may comprise at least one grille 460 to filter such debris.

[0141] As shown in Fig. 4B, the grille 460 comprises bars or wire spaced apart to allow fluid to pass through, while inhibiting the passage of debris that is larger than the grille spacing. The jet system body 312 may comprise a first grille 462 disposed at the first inlet end 342, and a second grille 464 disposed at the second inlet end 362. The bars of the grille 460 (e.g. the first grille 462 and/or the second grille 464) may be received in slots 466 formed in the first and second inlet openings 343, 363 respectively. For clarity, Fig. 4B shows the second grille 464 installed to cover the second inlet opening 363, with the first grille 462 removed to show the slots 466. The grilles 462, 464 may be secured in their respective slots 466 by a clamp arrangement, by adhesive, or by removable fasteners. [0142] The first grille 462 and the second grille 464 may be removably connected to the respective inlet ends 342, 362 to allow easy access into the first lumen 346 and the second lumen 366 for maintenance. Alternatively, the first grille 462 and the second grille 464 may be integrally formed with the respective inlet ends 342, 362 to reduce the likelihood of the grilles 462, 464 inadvertently not being attached after maintenance.

[0143] The inlet ends 342, 362 may be rectangular shaped or circular shaped. The size of the inlet ends 342, 362 may be adjusted to control the amount of fluid ingested into the manifold 410 and subsequently directed through the impeller 322. The inlet apertures 341, 361 formed in the underside of the board 110 are shaped to correspond with the shape of the inlet ends 342, 362.

[0144] Turning now to Figs. 6A, 6B and 6C, some embodiments of the jet system 310 comprise a cartridge 600. Fig. 6B is a section view of Fig. 6A, as taken along the line 6B-6B. Fig. 6C is an exploded view of Fig. 6A.

[0145] The cartridge 600 comprises a cartridge body 610 having a head end 620 and an oppositely disposed tail end 630. The tail end 630 of the cartridge 600 is configured to be connected to the outlet 350.

[0146] The cartridge body 610 comprises a plurality of cartridge body walls which define a cartridge cavity 640. As shown in Fig. 6B, the cartridge cavity 640 is configured to contain at least part of the manifold 410. The manifold 410 may be integrally formed with the cartridge body 610. The cartridge cavity 640 is configured to contain at least part of the drive system 330. In some embodiments, one or more of the power supply 332, the controller 334, and the motor 336 are contained within the cartridge cavity 640. The cartridge body 610 may comprise a panel or lid 645 which is removable to allow access to the cavity 640.

[0147] The cartridge body 610 comprises a first cartridge body wall 622 disposed at the head end 620, and a second cartridge body wall 632 disposed at the tail end 630. The outlet 350 is configured to be attached to the second cartridge body wall 632. The manifold plenum 418 and the nozzle 450 are disposed on opposite faces of the second cartridge body wall 632. The second cartridge body wall 632 defines a cartridge body wall aperture 634 which fluidly connects or communicates the manifold 410 to the outlet 350. In some embodiments, the manifold outlet 416 extends through the cartridge body wall aperture 634. The cartridge body 610 may comprise a cartridge body flange 636 which surrounds the cartridge body wall aperture 634. The flange 417 of the manifold outlet 416 may connect to the cartridge body flange 636 so as to be connected with the flange 458 of the nozzle 450. The second cartridge body wall 632 may define a plurality of flange holes to allow bolts or other fasteners to pass therethrough for connecting the flanges 636, 417, 458.

[0148] The cartridge body 610 further comprises a first cartridge body side portion 650 and a second cartridge body side portion 660. The first and second cartridge body side portions 650, 660 connect the head end 620 and the tail end 630. The first and second cartridge body side portions 650, 660 may be oppositely disposed. The first cartridge body side portion 650 comprises a first cartridge body side wall 652. The second cartridge body side portion 660 comprises a second cartridge body side wall 662. As best shown in Fig. 6C, the first cartridge body side wall 652 defines a first cartridge conduit aperture 654. The second cartridge body side wall 662 comprises a second cartridge conduit aperture 664.

[0149] In some embodiments of the jet system 310, such as shown in Fig. 6B, the manifold 410 is contained within the cartridge cavity 640. The manifold inlets 412, 414 may abut the cartridge conduit apertures 654, 664. The manifold inlets 412, 414 may be approximately the same size as the cartridge conduit apertures 654, 664.

[0150] In some embodiments, the first and second inlet conduits 340, 360 (not shown in Figs 6A-6C for clarity; refer Fig. 7) are separate pieces to the manifold 410 and are configured to fluidly connect to or communicate with the manifold 410 through the first and second cartridge conduit apertures 654, 664 respectively. Specifically, the first outlet end 344 of the first inlet conduit 340 is configured to fluidly connect to or communicate with the first manifold inlet 412 through the first cartridge conduit aperture 654. Similarly, the second outlet end 364 of the second inlet conduit 360 is configured to fluidly connect to or communicate with the second manifold inlet 414 through the second cartridge conduit aperture 664.

[0151] Fig. 7 is the section view as shown in Fig. 6B, as viewed from above and now showing the first and second inlet conduits 340, 360 as attached to the cartridge 600.

To minimise fluid leakage as it flows from the inlet conduits 340, 360 into the manifold 410, in some embodiments the outlet ends 344, 364 of the inlet conduits 340, 360 may each include an extension portion 700. The extension portion 700 may be configured to pass through the cartridge conduit apertures 654, 664 and enter the manifold inlets 412, 414 to guide fluid from the inlet conduits 340, 360 into the manifold 410. The extension portion 700 may form a lip around the perimeter of the first and second outlet openings 345, 365 which protrudes to bridge any gap with the cartridge conduit apertures 654, 664. This may reduce or prevent fluid seepage through the cartridge conduit apertures 654, 664.

[0152] Fig. 7 shows the compact packaging provided by the twin-intake arrangement of the jet system 310. The first and second inlet conduits 340, 360 are adjacent to the mast mount 116, which provides a shorter configuration than if the inlet conduits 340, 360 were to be placed forward of the mast mount 116 instead. A shorter, longitudinally compact configuration may provide weight and/or balance advantages as previously discussed herein.

[0153] The first inlet conduit 340 and the second inlet conduit 360 are arranged to extend from the manifold 410. The first inlet conduit 340 and the second inlet conduit 360 are spaced apart from each other. The inlet conduits 340, 360 are spaced apart along an axis that is substantially perpendicular to a thrust direction. The thrust direction is the direction in which fluid is ejected from the jet system 310 through the nozzle 450. [0154] Fig. 8 shows an embodiment of the jet system 310 comprising a cartridge housing 800. The cartridge housing 800 may be embedded within the board 110 to provide a rigid surface with which the cartridge 600 can engage and be locked in place.

[0155] The cartridge housing 800 comprises a body 810 having a head end 820 and an oppositely disposed tail end 830. The body 810 comprises a plurality of walls defining a cavity 840 configured to receive the cartridge 600. The cartridge 600 and the cartridge housing 800 may be elongate. Installation of the cartridge 600 into the cartridge housing 800 may involve sliding the head end 620 of the cartridge 600 into the cartridge housing 800 until the cartridge head end 620 engages with the cartridge housing head end 820. The cartridge tail end 630 may then engage with the cartridge housing tail end 830. The inlet conduits 340, 360 may then be positioned over the cartridge conduit apertures 654, 664 so as to be in fluid communication with the manifold 410 (via manifold inlets 412, 414 as previously described).

[0156] In some embodiments, the cartridge housing tail end 830 comprises a hood 832 configured to extend over the outlet 350. When the cartridge 600 is properly received in the cartridge housing 800, the outlet 350 may be partly covered by the hood 832. The hood 832 may protect the outlet 350, particularly the nozzle 450, from damage.

[0157] The cartridge housing 800 may comprise side portions 850, 860 configured to engage with the first and second cartridge body side portions 650, 660. The side portions 850, 860 facilitate the installation and removal of the cartridge 600 by providing a guide which appropriately positions the cartridge 600 when slid into the cartridge housing 800. The side portions 850, 860 may respectively comprise a step or rail 852, 862 which restricts lateral and vertical movement of the cartridge 600 when slid into the cartridge housing 800. The cartridge housing cavity 840 may also be sized to fit snugly around the outer surfaces of the cartridge 600, thereby also limiting the amount of movement of the cartridge 600 when inside the cartridge housing 800. [0158] The cartridge 600 (whether alone or in combination with the cartridge housing 800) provides a modular arrangement which allows the jet system 310 to be removed from the board 110. This allows the board 110 to potentially be used without the jet system 310. This also allows the jet system 310 to be utilised over multiple boards. The modular arrangement allows the jet system 310 to be easily removed from the board 110, for example for maintenance.

[0159] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.