Abstract:
Conventional unpowered surfboards enable riders to catch and ride waves towards a shoreline and experience the thrill and power of ocean waves. An electric powered surfboard has been developed to assist novice riders or riders who have suffered injuries or impairments which limit their ability to paddle are effectively prevented, or at least impaired from enjoying this activity. The surfboard comprises one or more propulsion systems which each comprise an electric motor, a drive shaft and a rotor. The rotor may be a propeller mounted in a fin of the board, or it may be an impellor in a water jet. The surfboard also comprises a power control system for controlling power to the propulsion system and comprises a speed controller and a battery as well as a cooling system for cooling the motor and speed controller. The surfboard may also comprise a monitoring system which comprises a power monitor and an output device for indicating the remaining capacity to the rider. This has the advantage of improved reliability as well as informing the user of their use and remaining capacity to ensure they are able to safely return to the shore.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to Australian Provisional Patent Application No. 2011904784 entitled “Electrically powered surfboard” and filed on 16 Nov. 2011, the entire content of which is hereby incorporated by reference. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to surfboards. In a particular form the present invention relates to an electrically powered surfboard for assisting riders in riding waves. 
       BACKGROUND 
       [0003]    Conventional unpowered surfboards enable riders to catch and ride waves towards a shoreline and experience the thrill and power of ocean waves. However in order to catch a wave, the surfer must first paddle through the surf zone and out to the point where the waves begin to form crests which can be caught and ridden. Once the rider is in a suitable position to catch an incoming wave, the rider must quickly accelerate in order to catch the wave as it passes the rider. Such activities are both time consuming and exhausting, and require the rider to have considerable upper body strength in order to pass through the surf zone to reach the waves, and then to rapidly accelerate and actually catch a wave. Accordingly persons who have suffered injuries or impairments which limit their ability to paddle are effectively prevented, or at least impaired from enjoying this activity. Similarly novice riders often lack the necessary combination of strength and skill to catch waves. 
         [0004]    Whilst various powered watercraft and electric surfboards have been developed which such persons could utilise, such watercraft and surfboards do not typically replicate the feel and handling characteristics of conventional surfboards, nor are they suitably adapted to the needs of such riders. One example uses a pod containing a battery and water jets which is fitted in the rear section of the board. However the size and weight of this pod adversely affect the feel and handling of board it is fitted to, or requires the construction of a specialised board. Further for injured, impaired or novice riders, reliability and safety is a significant concern, and it is important that riders do not become stranded in the surf zone or beyond and are able to safely return to shore. 
         [0005]    There is thus a need to provide a powered surfboard with the feel and handling of conventional surfboards that is adapted to assist injured, impaired, or novice riders to experience the joy of surfing or to at least to provide such riders with a useful alternative. 
       SUMMARY 
       [0006]    According to a first aspect of the present invention, there is provided an electric powered surfboard comprising: 
         [0007]    at least one propulsion system comprising an electric motor and a rotor assembly; 
         [0008]    a power control system for controlling power to the at least one propulsion system comprising a speed controller and at least one battery; and 
         [0009]    a cooling system for cooling the motor and speed controller. 
         [0010]    In a further aspect the electric powered surfboard further comprises a monitoring system comprising a power monitor and an output device for indicating a remaining capacity to the rider. In one aspect the power monitor provides real time, or near real time monitoring of the battery usage and remaining battery capacity. The power monitor may also monitor and report other parameters such as current amps, battery voltage, power, battery temperature, motor temperature or RPMs. In one aspect the battery capacity is defined and reported in milli-Amp hours (mAh). In one aspect the remaining capacity is indicated as an estimate of the time remaining determined from the predefined battery capacity. The estimate of remaining capacity remaining time may be based upon the current usage level or it may be based upon historical values or averages (ie past usage). Alternatively or additionally the remaining capacity is indicated as a percentage of total capacity determined from the predefined battery capacity. 
         [0011]    In one aspect the output device is a digital display device mounted in or on the board. The display device may be mounted on the surface of the board, within a compartment with a viewing window. In one aspect the output device is a remote display device, which may be worn by the user, which is in wireless communication with the power monitor. In one aspect the monitoring system further comprises one or more warning indicators. In one aspect the one or more warning indicators comprises a low power indicator and/or a low voltage indicator and/or an over temperature indicator, in which case the monitoring system further comprises a temperature sensor. In one aspect the one or more warning indicators are provided on the top surface of the board. These may be via a display device or via separate indicators, such as LEDs or other lights. 
         [0012]    The surfboard may comprise one, two, three or four independent propulsion systems. In one aspect the electric motors are brushless DC motors which are rated with a power rating in excess of 500 W. The motors may be in-runner or out-runner motors. 
         [0013]    In a further aspect the rotor assembly is a drive shaft and a propeller located in a fin. In one aspect the drive shaft exits the lower surface of the surfboard and enters the forward edge of the fin, and the propeller is located in a cut out portion in the rear of the fin. In one aspect the fin further comprises a propeller guard. 
         [0014]    In a further aspect the rotor assembly is a drive shaft and water jet, and the drive shaft drives an impellor in the water jet. In one aspect the at least one propulsion system further comprises a scoop and a thruster tube, wherein the scoop projects from the bottom surface of the board to draw water into the water jet and the thruster tube directs water from the water jet to the rear of the board where it is expelled. In one aspect the jet pump is an all plastic jet pump. 
         [0015]    In a further aspect the cooling system is a closed loop system, an open loop system or a passive cooling system. The cooling system facilitates the use of high power motors, such as those with ratings in excess of 500 W which can provide the output required to catch waves. The cooling system may be a liquid cooling system. In one aspect the cooling system is a closed loop system comprising a pump and a heat exchange region. In one aspect coolant is pumped around the speed controller and motor and then through a heat exchange region located on an upper surface of the board where it exchanges heat with the surrounding environment (eg seawater). In one aspect the cooling system is an open loop system comprising an intake port and an exhaust port. In one aspect the intake port is located on the lower surface in the front half of the board, and the exhaust port is located on the upper surface in the rear of half of the board. Seawater is drawn in and passed over the speed controller and motor before being expelled. A pump may be used. In one aspect a passive cooling system is used. In one aspect the speed controller and motor are mounted in a metal heat sink box located near or flush with a surface of the board, such as the top surface, to exchange heat with the surrounding environment (eg seawater), or in a housing or box containing the motor and/or other components and one or more openings in the top surface to allow water to flow into and out of the housing and over the motor so that the natural flow of water is used to cool the motor. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]    A preferred embodiment of the present invention will be discussed with reference to the accompanying drawings wherein: 
           [0017]      FIG. 1A  is a top view of an electric powered surfboard according to an embodiment of the present invention; 
           [0018]      FIG. 1B  is a rear view of an electric powered surfboard according to an embodiment of the present invention; 
           [0019]      FIG. 1C  is a side view of an electric powered surfboard according to an embodiment of the present invention; 
           [0020]      FIG. 2A  is a top view of an electric powered surfboard according to an embodiment of the present invention; 
           [0021]      FIG. 2B  is a rear view of an electric powered surfboard according to an embodiment of the present invention; 
           [0022]      FIG. 2C  is a side view of an electric powered surfboard according to an embodiment of the present invention; 
           [0023]      FIG. 3  is a perspective view of fin housing a propeller and propeller guard according to an embodiment of the present invention; 
           [0024]      FIG. 4  is a top view of a compartment including the speed controller and motor according to an embodiment of the present invention; 
           [0025]      FIG. 5  is a top view of a closed loop cooling system according to an embodiment of the present invention; 
           [0026]      FIG. 6  is a side view of a closed loop cooling system according to an embodiment of the present invention; 
           [0027]      FIG. 7  is a schematic view of display for monitoring the power control system according to an embodiment of the present invention; 
           [0028]      FIG. 8  is a block diagram of the various functional systems according to an embodiment of the present invention; 
           [0029]      FIG. 9  illustrates cross sectional and underside views of several embodiments of scoops located on the underside of the board; 
           [0030]      FIG. 10A  is a perspective view of a motor housing to allow passive cooling of the motor; 
           [0031]      FIG. 10B  is a a top view of the motor housing of  FIG. 10A ; 
           [0032]      FIG. 10C  is a side view of the motor housing of  FIG. 10A ; 
           [0033]      FIG. 10D  is another top view of the motor housing of  FIG. 10A ; 
           [0034]      FIG. 10E  is an exploded top view of another embodiment of a motor housing; 
           [0035]      FIG. 10F  is a top view of yet another embodiment of a motor housing including a plurality of circular holes on the top surface thereof; 
           [0036]      FIG. 10G  illustrates a top view of yet an embodiment of a motor housing including a plurality of diamond shaped openings on the top surface thereof; 
           [0037]      FIG. 11A  is another perspective view of a motor housing to allow passive cooling of the motor in accordance with the embodiment of  FIG. 10A ; 
           [0038]      FIG. 11B  is a side view of the motor housing of  FIG. 11A ; 
           [0039]      FIG. 11  C is a reverse perspective view of the motor housing of  FIG. 11A ; 
           [0040]      FIG. 11D  is perspective view of the motor housing of  FIG. 11A  as it is positioned with respect to a cavity in the surfboard to receive the motor housing; 
           [0041]      FIG. 11E  is another perspective view of the motor housing of  FIG. 11A  as it is installed in the cavity in the surfboard shown in  FIG. 11D ; 
           [0042]      FIG. 11F  is an perspective view of the motor housing of  FIG. 11A  installed in the cavity in the surfboard shown in  FIG. 11D ; 
           [0043]      FIG. 11G  is a partial perspective view of the surfboard showing the motor housing of  FIG. 11A  installed so that the top surface thereof is flush with the top surface of the board, and further showing a speed controller and an open housing cover for the speed controller; 
           [0044]      FIG. 11H  is another partial perspective view as shown in  FIG. 11G , but with the speed controller housing cover closed; 
           [0045]      FIG. 12A  is a perspective view of another embodiment of a motor housing with a motor housing cover open, and the motor housing located flush with the top surface of the board to allow passive cooling of the motor; 
           [0046]      FIG. 12B  is another perspective view of  FIG. 12A  showing the motor housing cover closed; 
           [0047]      FIG. 13A  illustrates a perspective view of a compartment for housing a battery and components of the power control system being installed into a surfboard; 
           [0048]      FIG. 13B  is an enlarged perspective view of the battery of  FIG. 13A ; 
           [0049]      FIG. 14  illustrates an electronics module encased in fibre glass resin; 
           [0050]      FIG. 15  illustrates a side view of the rear of an embodiment of an electric powered surfboard; 
           [0051]      FIG. 16A  is a top view of an embodiment of an electric powered surfboard; 
           [0052]      FIG. 16B  is a top view of another embodiment of an electric powered surfboard; 
           [0053]      FIG. 16C  is a top view of another embodiment of an electric powered surfboard using a single propeller based propulsion system 
           [0054]      FIG. 17A  is a top view of a flexible drive shaft and mount; and 
           [0055]      17 B is a perspective view of the drive shaft, fins and propeller of embodiments of an electric powered surfboard; and 
           [0056]      17 C is another perspective view of the drive shaft, fin and propeller of embodiment of the electric powered surfboard of  FIG. 17A . 
       
    
    
       [0057]    In the following description, like reference characters designate like or corresponding parts throughout the figures. 
       DESCRIPTION OF EMBODIMENTS 
       [0058]    Embodiments of a modular electric powered surfboard  10  will now be described. The surfboard  10  is a conventional surfboard with a centre of mass  11  and fins  12 , which includes a series of modular components located in compartments and conduits distributed throughout the surfboard so as to preserve the ride and handling characteristics of the surfboard. Preferably the modules are distributed both longitudinally and laterally to maintain the centre of mass of the board, or to or substantially preserved). The modules include one or more propulsion systems, a power control system and a cooling system and may also comprises other modules such as a monitoring system. The one or more propulsion systems comprise an electric motor and a rotor assembly with the power control system controlling power to the propulsion system. The power control system comprises a speed controller and at least one battery. The motor and speed controller are cooled by a cooling system.  FIGS. 1A ,  1 B and  1 C, illustrate top  100 , rear  110  and side  120  views of an electric powered surfboard according to an embodiment of the invention. In this embodiment the rotor assembly  80  comprises a draft shaft and a water jet, with the drive shaft driving an impellor in the water jet. Embodiments of an electric powered surfboard are further illustrated in  FIGS. 16A and 16B .  FIGS. 2A ,  2 B and  2 C, show top  200 , rear  210  and side  220  views of an electric powered surfboard according to another embodiment of the invention. In this embodiment the rotor assembly  80  comprises a drive shaft and a propeller located in the fin. Embodiments  10   a    10   b    10   c  of an electric powered surfboard are further illustrated in  FIGS. 16A ,  16 B and  16 C. 
         [0059]    Top  100 , side  110  and rear  120  views of an embodiment of an electric powered surfboard are illustrated in  FIGS. 1A to 1C . In this embodiment the surfboard  10  comprises a throttle  20 , one or more batteries  30 , a display  40 , a speed controller  50 , a motor  60 , a cooling system  70 , a rotor assembly  80  and a thrust tube  90 . The components may be grouped into a plurality of functional systems.  FIG. 8  illustrates a block diagram of the overall system  800  arranged into a propulsion system  810  comprising one or more propulsion units  812 , a power control system  820 , a cooling system  830  and a monitoring system  840 . Each propulsion unit  812  comprises an electric motor  60  and a rotor assembly. In this embodiment the rotor assembly comprises a water jet  83  in which an impeller  84  is driven by a drive shaft  62  which draws water in via a scoop  82  and propels the water out the rear of the board via thrust tubes  90 . Embodiments of an electric powered surfboard are further illustrated in  FIGS. 16A and 16B . In another embodiment, the rotor assembly  80  comprises a drive shaft  62  and a propeller  86  located in the fin  12 . The fin  12  may be provided with a propeller guard  87 .  FIGS. 2A ,  2 B and  2 C, show top  200 , rear  210  and side  220  views of an electric powered surfboard according to this embodiment of the invention.  FIG. 3  shows a perspective view of the fin and  FIGS. 17B and 17C  are rear perspective views of embodiments of an electric powered surfboard. 
         [0060]    The power control system comprises a throttle  20 , one or more batteries  30  and a speed controller  50  for providing and controlling power to motors in the propulsion system in response to the throttle. The cooling system provides cooling to the motors and speed controller and the monitoring system includes a power monitor and an output device for monitoring and reporting power usage and remaining capacity to the rider. Preferably the output device is a display  40 , such as a LCD or LED display. The monitoring system may also comprise one or more warning indicators. Multiple output devices or indicators may be used such as a combination of a display, warning lights and/or sounds. In addition to power usage and capacity, the monitoring system may include sensors for detecting high temperatures, low power, low voltage and/or loss of the rider. 
         [0061]    The propulsion system  810  is used to assist riders, and in particular impaired or unskilled riders to conserve energy when moving through the water, to assist them when moving though the surf zone where waves are breaking and attempting to push the rider back to shore, as well as provide the quick impulsive high thrust needed to catch a passing wave. Each propulsion unit  812  includes electric motor  60  which drives a shaft  62  which in turn drives a rotor such as an impeller  84  in a water jet or a propeller  86  which may be located in the fin. A combination of the two (ie a propeller and water jets) could also be provided. These components are distributed along and throughout the board to ensure the board&#39;s original centre of gravity can be maintained. The choice of the number of propulsion units  812  to include depends upon factors such as available space, choice of motors, intended use and/or required thrust. As will be discussed speed controllers and cooling systems (and in particular liquid cooling systems) may be used to enable the use of small light weight and powerful motors. Typically between 1 and 4 propulsion systems will be used, although more could be provided if space and battery power permits. In the case of a single propulsion system this should be aligned along the longitudinal centreline. In the case of multiple propulsion systems these should be distributed to preserve symmetry about the longitudinal centreline. Providing multiple propulsion systems improves the redundancy of the system should one of the individual propulsion systems fail. 
         [0062]    Propeller systems generate approximately 40% more thrust than water jet systems and thus a single propeller based propulsion system can be used with the propeller located in the main central fin. The fin provides a convenient mounting or housing for the propeller and a guard can also be provided to both protect the propeller and prevent injury to a rider (or others) as shown in  FIGS. 2A to 2C , and  FIG. 3 . In the embodiment shown in  FIGS. 2A to 2C  the guard in the plane of the fin, but other guard arrangements which project radially (or laterally), and which enclose, cage or shroud the propeller, whether fully or partially can be used. For example a sphere shaped cage guard with (ie with apertures to allow water flow) could be used or a circular shroud or ring around the propeller could be used. A flexible drive shaft is used to drive the propeller. In one embodiment a mount  64  is used to orient the drive shaft from the motor down through the board so that the drive shaft exits the lower surface of the board and enters the forward end of a fin to drive a propeller.  FIG. 17A  illustrates a top view of the drive shaft  62  and mount  64 , and  FIG. 17B  illustrates a view of the underside of a surfboard comprising multiple fins  12   a - 12   e , in which the drive shaft  62  exits the lower surface of the board and enters the rear of central fin  12   a  to drive a propeller  86 .  FIG. 17C  shows another embodiment in which the underside of the board comprises a single fin  12  which receives the drive shaft  62  to drive a propeller  86 . As shown in  FIGS. 2A to 2C  and  FIG. 16C  the single propeller based propulsion system is distributed along the centreline. Systems with multiple propeller based propulsion systems may also be used. 
         [0063]    In the case of water jet systems, a single water jet may be used. However using two water jets provides similar thrust levels to a single propeller system and has additional redundancy should one of the propulsion systems fail in use. For example as shown in  FIGS. 1A to 1C  the two propulsion systems as distributed symmetrically about the centreline so that they are mirrored about the centreline. 
         [0064]    Catching waves requires high thrust for the short duration when the wave is passing the rider, and thus in order to assist impaired or unskilled riders in catching waves (and thus being able to enjoy the surfing experience) it is desirable that high power motors are used in the propulsion system. Thus preferably electric motors capable of providing high power are selected. In one embodiment brushless DC motors which are rated with a power rating in excess of 500 W were selected. However electric motors with higher ratings such as 1000 W, 2000 W or even as high as 5000 W or more may be used. Lower power motors such as 250 W, 300 W, or 400 W may be used depending upon the system and the riders capabilities. The electric motors may be in-runner or out-runner type motors. In-runner motors tend to be more compact and easier to cool than outrunner motors. However in-runner motors also tend to be less efficient and produce less torque than out-runner motors. Thus the choice of motor may be dictated by the type of board the motor is to be installed in, with in-runner motors preferred when weight sensitivity and room are key considerations (i.e. small boards) and out-runner motors selected for us in larger stand up boards where there is more room or when greater efficiency is a key requirement. 
         [0065]    A large variety of suitable motors from a range of manufacturers have been tested with weights ranging from 200 g up to 800 g in mass selected to meet a desired thrust level of efficiency. Suitable motors can be sourced from a hobby supplier such as Hobby King (www.hobbyking.com).These include HET (High End Technology) motors such as the 600 and 700 series can-in-run brushless motors with rpm ratings from 400 up to 2000 KV (rpm/v) or Scorpion brushless outrunner motors with stators in the 30-50 mm size range and with rpm ratings from 300 to 2000 KV (rpm/v). The motor is used to drive the rotor assembly such as a propeller or an impeller in a jet pump which draws water up from scoops or intakes located on the underside of the board. 
         [0066]    The propeller may be mounted in a fin. A portion may be cut out of the fin and a bore provided to receive the drive shaft. The size of the propeller can be chosen based upon the size of the fin, and can range from sizes of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm or higher to obtain the desired thrust levels of efficiency. The propeller may be manufactured from brass or other suitable materials. Suitable propellers may be those sold under Prop Shop Props™ or ABC Prop™ brands sourced from model boat suppliers (eg www.hobbysupplies.com.au). 
         [0067]    A conventional jet pump may be used or a jet pump manufactured from all plastic or non metal composite materials to reduce the risk of corrosion of the jet pump. Jet pump sizes can vary size and thrust depending on the internal impeller system which can range from impeller size of 30 mm, 40 mm, 45 mm, 50 mm or higher to obtain the desired thrust levels of efficiency. One suitable jet pump is a jet power 40 mm jet unit available at http://www.jet-drive.de/index.php?option=com_virtuemart&amp;page=shop.browse&amp;category_id=11&amp;Itemid=17. 
         [0068]    Water is drawn into the water jet/impeller via a scoop  82  located on the underside of the board and projects below the board. Whilst an intake with a flat (non projecting) or a cavity (eg a scoop is taken out of the bottom of the board) may be used to draw water into the jet pump, it has been found that the use of a scoop which projects into the water flow helps to ram water into the water jet and significantly increases the efficiency of the water jet compared to the use of a flat or cavity intake. Whilst the scoop projects into the water, and thus may create extra drag, it increases the volume of water reduces the amount of cavitation that can occur when a flat intake is used. The intake may take various configurations such as those illustrated in the sectional and underside views shown in  FIG. 9 . The intake may comprise solely of a scoop  910  which projects outward from the underside of the board  912 . Alternatively a scoop  910  may be used in conjunction with a cavity  922  in the board located forward of the scoop  910 . Further the cavity may take a range of shapes such as a half cone shape  932 . Preferably the scoop has a relatively low profile and is shaped to minimise drag and cavitation effects. In one embodiment the inlet size has (cross sectional) dimensions of approximately 40 mm (width) by 120 mm to 160 min in length. The scoop may be constructed from plastic or rubber or other materials with sufficient strength to hold their shape whilst moving through the water and which are resistant to corrosion. 
         [0069]    A thrust tube is provided after the output of the jet pump to direct the water to the rear of the board where it can be used to propel the surfboard forward. Preferably the thrust tubes exit at the rear of the board and are located in the plane of the board as illustrated in  FIG. 1C . In some cases the boards may thin towards the rear in which case the thrust tubes may extend above and beyond the board surface. Using a thrust tube and placing the exhaust point in the rear helps to prevent the back end from being pulled into the water which can occur if the exhaust point is located a short distance from the intake point on the underside of the board. Placing the exhaust at the rear provides for a smoother bottom surface and thus doesn&#39;t disturb the water flow on the bottom of the board thus helping to preserve the natural ride and performance of the board. Rear thrust tubes allow the output to be efficient directed and can be adjusted in length or shape to suit individual boards and lengths.  FIG. 15  illustrates a close up side view of the rear of an embodiment of an electric powered surfboard. A scoop  82  projects out from the underside board and draws water into the water jet/impeller module which projects slight above the board surface. A thrust pipe  90  is embedded in the board (extending slightly above the top surface of the board) and projects from the rear of the board with a slight downward inclination. 
         [0070]    The power control system  820  comprises a throttle  20 , one or more batteries  30  and a speed controller  50  for providing and controlling power to motors in the propulsion systems in response to the throttle. In the case of multiple propulsion units, and thus multiple motors, a single speed controller may be used to all of the motors or a separate speed controller may be used to control each motor separately. A range of brushless electric speed control (ESC) units may be used. One suitable brushless ESC unit is the Turnigy 120A water-cooled brushless motor controller (http://www.hobbyking.com/hobbyking/store/ — 8946_Turnigy_Marine — 120A_Brushless_Boat_ESC.html). Lower amp versions may also be used (eg the 35 A). The throttle  20  may be provided on the surface of the board near the front to allow the user to control power whilst leaning on the board in a prone or paddling position. This is the typical position the user will be in when assistance is required. A control line  21  may send the control signals to the speed controller where they are used to control the motor to produce the desired thrust level. Alternatively a wireless signal could be used to transmit throttle commands to a receiver associated with the speed controller. 
         [0071]    The throttle may be a fully proportional throttle (eg 0-100% power) and throttle/power selection may be received through the use of a rotatable dial or dowel, a slider, a rocker switch (increase/decrease), or series of buttons (increase/decrease). Alternatively or additionally buttons or other inputs may be used to select predetermined power levels (eg 25%, 50%, 75% 100%) or programs which provide a predefined power level for a predefined time period (unless terminated early by a user). For example a surf zone program which provides constant thrust at a low to moderate power level (eg 40%) for a period of 5 minutes to allow the rider to transit through the surf zone could be provided and/or a wave catching program that provides 100% thrust for 30 seconds to allow the rider to catch a wave. The buttons may be provided in large sizes, or otherwise provided as easy to activate inputs to facilitate ease of activation of the desired power level or program. The speed controller may then translate these inputs into power levels or commands to the motor or motors. The speed controller may control how power is distributed across the motors. For example if three propulsion units are used, more power may be provided to the central unit. Controls to allow thrust vectoring may also be provided. 
         [0072]    An on off switch may be provided on the board or on a remote device  24  such as watch which is wearable by the user to allow them to remotely switch off the surfboard in the event that they fall off. Alternatively a proximity based approach could be used in which a proximity sensor detects if an appropriate device worn or associated with the rider (eg watch, magnetic keycard, RFID tag located in angle cuff etc). If contact is lost for a defined period of time (eg 10 seconds) the motors can be configured to automatically shut off. Similarly a detachable ankle cord with a snap fit arrangement which is designed to snap apart if the rider falls off could be utilised. The snap fit arrangement can incorporate a sensor, such as continuity sensor which when broken triggers an engine shut down. Similarly a gravity switch may also be provided detect when the board is upright or upside down, so that the motors may be shut down when the board is upside down. The watch or remote device could also include throttle controls if desired, although this is less preferable than on the board surface where they are more easily accessible when riding the board. 
         [0073]    One or more batteries  30  may be located in a compartment, which will typically be provided in the front half of the board to offset the motors and jets in the rear.  FIGS. 13A and 13B  illustrate an embodiment of a compartment  1300  for housing a battery  30  and components of the power control system being installed into a surfboard. The compartment is a box with a clear acrylic lid to allow viewing of a display  40  contained within the compartment. The batteries may be high energy density cells having high discharge/recharge rates such as Lithium based batteries including Lithium polymer, lithium ion and lithium phosphate which have high energy density and low weight characteristics. The internal surfboard battery voltage can range from 11 V up to 50 V depending on the desired power levels and efficiencies for the system. The capacity of the batteries can range from 5000 mAh hours to as many as 100,000 mAh hours of capacity in the main operating battery system. Batteries may be joined in series to increase capacity. An example of a suitable battery is the Turnigy 5.0 battery which has a 5000 mAh capacity. Providing two such batteries provides 10000 mAh capacity. A waterproof recharging connector  32  may be provided on the board to allow recharging of the batteries. Alternatively a cover for the battery compartment may be provided to allow removal and recharging of the batteries. A battery controller may be provided as a module in the speed controller or as a separate module. The battery controller may control charging and battery balancing and additional electronics may be provided to allow recharging from 240V AC or 12V DC supply. The speed controller receives on/off commands, input throttle requests and sends control signals to control the power generated by the motor or motors. The speed controller, along with other electronics may be encased in fibre glass resin or other materials to protect them from water.  FIG. 14  illustrates an embodiment of an electronics module (including an electronic speed controller)  50  encased in liquid fibre glass resin. 
         [0074]    High power electric motors and speed controllers can generate significant heat, which if not dealt with may lead to a failure or reduce the motor life and thus a cooling system may be included to prevent or minimise this risk. This provides greater reliability and thus a safer system for use by novice, impaired or injured riders. Suitable cooling systems  830  include liquid cooled loop systems which may be arranged as either open loop or closed loop systems, or systems using heat sink compartments which may be cooled by the seawater or environment surrounding the board, or some combination of the two. Liquid cooled loop systems direct a fluid around specific components such as the motor, speed controller and any other electronics or heat generating parts. A single loop or multiple loops may be used. To more efficiently cool the motor, a jacket may be provided through which a coolant can flow. Intermediary materials may be used to draw heat away from the components which are then cooled. The specific choice of cooling system used will depend upon the number, type and power of electric motors used. 
         [0075]    In an open loop system seawater is drawn in through one or more intake ports and passed over the speed controller and motors before being expelled through one or more exhaust ports. The intake and exhaust ports may be located on any surface, with the intake preferably being located on the lower surface to provide improved access to seawater during normal use. The seawater may be forced through the coolant system through active components such as pumps or through passive design features, or a combination of the two. For example the design and location of the intake may be chosen so that water will be forced (or rammed) into the coolant intake through motion of the board through the water. Additionally or alternatively a pressure differential may be set up between the intake and exhaust based upon their respective locations (for example by locating the intake on the lower surface and the exhaust on the upper surface) or as a result of heating of the water whilst in the system. Preferably the intake port(s) are located on the lower side in the front half of the board, and the exhaust port(s) are located on the upper surface in the rear half of the board. The cooling requirements are typically such that the ports have a small diameter in the range 5-25 mm, although bigger or smaller ports may be used as required. A mesh or grill or other filter (including a removable filter) may be provided to prevent fouling of the intake. Additionally the design and location of any intake or exhaust ports may be shaped to reduce cavitation caused by water being drawn into the intake or flowing around the ports. 
         [0076]    In a closed loop system no input and exhaust ports are required and liquid coolant is pumped around the speed controller and motor and then through a heat exchange region. The heat exchange region maybe located in an upper region (ie near the surface) of the board where the coolant can exchange heat with the surrounding environment such as air or seawater flowing across the top surface of the board. Further a non corrosive high thermal capacity (ie efficient heat exchange) coolant can be used. 
         [0077]    An embodiment of an open loop cooling system  70  is illustrated in  FIGS. 1A to 1C . The intake  71  is located on the underside of the board and a tube  72  passes water to the motor and then the speed controller before being expelled through exhaust  73  located on the upper side of the board. A top view  500  and a side view  600  of an embodiment of a closed loop cooling system are illustrated in  FIGS. 5 and 6 . A pump  510  pumps a coolant around the motor  60  after which it is directed around the speed controller  50  before being directed to the heat exchange region  540 . As illustrated in  FIG. 6 , the heat exchange region may be just below the upper or top surface  610  of the board  610  whereas the motor and speed controller may be located more centrally between the upper surface  610  and the lower surface  620  of the board. 
         [0078]      FIG. 4  shows a top view of a compartment which contains a speed controller  50  and a motor  60 . In this case the motor and the speed controllers are both provided with cooling jackets which surround the components. Such cooling jackets may be used in either open loop or closed loop systems. 
         [0079]    In another embodiment a passive (ie pump free) cooling system may be used in which the flow or presence of surrounding sea water is used to cool electronics components such as the speed controller and motor, or housings containing such components. In one embodiment the speed controller and motor are placed or mounted in a metal heat sink box using thermally conductive paste which is then sealed. The metal heat sink box is then mounted or located near or flush with a surface of the surfboard (such as the upper surface) to exchange heat with the surrounding environment (eg by seawater washing over the board).  FIGS. 12A and 12B  illustrate an embodiment of a metal motor housing  1200  which is located flush with the top surface of the board to allow passive cooling of the motor  60 .  FIG. 12A  illustrates an open housing (ie prior to sealing) containing the motor and electronic speed controller, and  FIG. 12B  illustrates the housing with the cover  1210  in place. 
         [0080]    In other embodiments, a housing  1000  for containing a motor  60  may be constructed with one or more openings in the top surface to allow the seawater to penetrate into (and out of) the box to cool the motor. This will be referred to as the motor housing although it is to be understood that the housing may contain other components. In these embodiments the movement of the board, or the natural wave movement of seawater (when the board is stationary) will naturally force flow through cooling in which seawater flows into the box, around the can of the motor and then out of the box. The one or more openings may a series of grills, holes, or apertures, and may be of different sizes.  FIGS. 10A to 10G  illustrate various views and embodiments of a motor housing  1000  to allow passive cooling of the motor.  FIG. 10A  illustrates a perspective view  1010  of a housing in the shape of a rectangular box;  FIG. 10B  illustrates a top view  1020 ; and  FIG. 10C  illustrates a side view  1030 . The housing houses a motor  60  connected to a shaft  62  and front drive coupling which connects the motor to the electronic speed controller. A plurality of openings  1022  allow water to flow in (arrows  1034 ), circulate and cool the motor  60 , mix with water in the rear of the housing and then exiting via an opening (or openings) in the rear of the housing (arrows  1035 ). In this embodiment the openings  1022  comprise a plurality of narrow elongate openings (ie a grill) over the motor and a rear section which extends from the rear of the motor to form a pool with a large opening in the top surface to allow water to easily flow out from the housing box. In  FIG. 10B  the top surface is shaded, and portions of the motor and shaft are visible through openings  1022 . Hidden portions of the motor  60 , motor coupling wires  23  and shaft  62 , openings  1022  and wall  1033  are shown as dotted lines in  FIGS. 10B and 10C . 
         [0081]    In one embodiment the housing is constructed from a box  1031  with a removable top surface  1040  (ie a lid). In one embodiment the box is constructed out of acrylic. In this embodiment the box includes an internal wall  1033  which divides the box into a rear section (or portion)  1032  though which water can flow via openings in the top surface, and a front section (or portion)  1034  which houses the front drive coupling of the motor which couples the motor to the electronic speed controller via wiring  23  and which is sealed to prevent the ingress of water. In other embodiments this also houses the electronic speed controller, and may house other electronic components and wiring. The wall  1033  contains an opening for receiving the front portion or section of the motor so that the motor spans the front and rear sections. The wall may act as a mount for the motor, or other elements maybe used to securely mount the motor in place. Once the motor is received in the opening in internal wall  1033 , the front section is sealed to prevent water ingress in to the front section. An access panel can be provided in the top surface of the front section to provide for simple access to the front drive coupling so that maintenance can be performed as required. In another embodiment the front section is not sealed and instead the motor coupling is sealed against water ingress through the use of sealant such as encasing the motor coupling in fibre glass resin. 
         [0082]    The top surface  1040  may be divided into different potions or sections. In one embodiment these comprise a rear portion  1044  with a single large opening, a mid portion  1046  located over the middle of the motor with openings comprises of a plurality of narrow elongate openings to form a grill, and a front portion  1048  with no openings which covers at least the front section  1034  (ie forward of internal wall  1033 ). In one embodiment the top surface  1040  is formed from a plurality of panels.  FIG. 10E  illustrate an exploded top view of an embodiment of a top surface  1050  having a separate rear panel  1052 , a separate middle panel  1054  and a separate front panel  1056 . The rear panel has a single opening  1052  and the middle panel has a plurality of openings  1055 . Each panel can be separately removed to allow internal access to the box, such as to allow for motor maintenance or replacement/upgrade as required. 
         [0083]      FIG. 10F  illustrates a top view of an embodiment of a housing  1060  in which the openings (apertures) are in the form of a plurality of circular holes  1062 . Similarly  FIG. 10G  illustrates a top view of an embodiment of a housing  1070  in which the top surface is a grid (or mesh) in which the openings (apertures) are in the form of a plurality of diamond shaped openings  1072  between the structural members forming the grid. 
         [0084]      FIGS. 11A to 11H  illustrate installation of an embodiment of motor housing  1000  shown in  FIG. 10A  into a surfboard.  FIGS. 11A to 11C  show various views of housing constructed from acrylic. The top surface is provided in 3 panels, with the middle panel located over the motor and including three elongate openings (which extend along the shaft axis) to allow water to flow in, and a rear panel with a large central rectangular opening to allow water to flow out of the housing.  FIGS. 11D to 11F  illustrate placement of the housing in a cavity made in the surfboard which has been cut to size to receive the housing.  FIG. 11G  shows the motor housing located in the surfboard so that the top surface is flush with the top surface of the board, along with a further metal housing for the electronic speed controller which is located forward (to the right in  FIG. 11G ) of the motor housing. The speed controller circuit board is also shown just prior to installation in the metal housing.  FIG. 11G  shows the completed housings for the motor and electronic speed controller which are located flush with the top surface of the board to allow passive cooling of these components. 
         [0085]    Such passive or natural cooling systems provide an abundant and endless supply of cooling liquid without the need for tubing, piping and high-pressure water cooling jackets to cool the brushless motor system. This increases efficiency in build times and improves overall simplicity and reliability of the entire jet board. In particular, this cooling system may be used effectively with larger boards using out-runner motors where space is less of an issue and provides an efficient and low maintenance cooling system (although it is to be understood that passive cooling systems can be used with in-runner motors as well). 
         [0086]    The monitoring system  840  includes a power monitor which provides real time, or near real time monitoring of the battery usage and remaining battery capacity. The power monitor may also monitor and report other parameters such as current (amps), battery voltage, power, battery temperature, motor temperature or even motor RPM. The battery capacity may be reported in milli-Amp hours (mAh) or reported as a percentage of total capacity and/or estimated time remaining based upon known battery capacity. The remaining capacity is effectively a fuel gauge indicating to the user how much available power there is remaining. The estimate of remaining capacity may be based upon the difference between known capacity and actual usage. This may be expressed as the remaining capacity or as an estimate of the time remaining at the current usage level. A memory may be used to store historical values or averages of past usage to allow estimates of the remaining capacity based upon past use. The reporting system may use a digital display device  40 . The display device may be mounted on the surface of the board, within a compartment with a viewing window, or the display device may be in a remote device in wireless communication with the power monitor. An example of a display device is shown in  FIG. 7  in which the display  700  is split into 4 portions  710   720   730  and  740 , and separately reports current, temperature, power and remaining capacity. 
         [0087]    The monitoring system may include additional warning sensors and indicators. These warning sensors may include temperature sensors and low voltage or low power sensors. The display device  40  may display warnings or separate indicators such as LED&#39;s or audible alarms may be used. Other sensors such as pressure sensors, gravity sensors, or proximity sensors may be may be used to determine if the rider is on the board or the board is upright, to allow deactivation of motors in case the rider comes off the board. 
         [0088]    An example of a compartment including a motor, speed controller and power monitor and display is illustrated in  FIG. 4 . The speed controller  50  receives power via electrical connectors  21  from the batteries (or a battery controller) and controls motor  60  via electrical connectors  52 . The temperature of the speed controller is measured by sensor  53  and reported by display  54 . A power sensor  55  measures battery usage which is also provided to the display for reporting instantaneous power usage and remaining capacity. The speed controller also includes a wireless receiver  56  for receiving on/off commands from a remote device  24 . A suitable power monitor and display is the eloggerV4 and PowerPanel LCD display manufactured by Eagletree systems. The elogger monitors the capacity and usage of the batteries and the motor, and has inputs for sensors such as temperature and power and can display the results in the PowerPanel LCD display. However other microcontrollers and displays may be used. 
         [0089]    The electric surfboard may be constructed from a conventionally constructed surfboard from which compartments and conduits have been cut out to receive the various components. To preserve the ride and handling of the assembled board, the components are distributed throughout the board (ie both longitudinally and laterally) so as to maintain the centre of gravity. The components may be sealed in place or provided with access panels as required. 
         [0090]    The electric surfboard may be constructed by obtaining a conventionally constructed surfboard (eg polyurethane or polystyrene foam covered with layers of fibreglass, cloth and polyester or epoxy resin) and cutting out compartments and conduits for receiving various components, or the compartments and conduits may be included during manufacture. The compartments may empty when installed, or may be preloaded with components. A combination of the techniques may be used. Once the various components are inserted into the components, the compartments may then be sealed within the board, or provided with externally accessible plates to allow access to the components. Preferably the components are distributed around the board to preserve the original centre of mass and to preserve the ride and handling characteristics of the board. Preferably the batteries are placed near the front and the motor is toward the rear of the board. 
         [0091]    The electric surfboard described herein is well suited to use by impaired or unskilled riders as it allows them to conserve energy and assists them when getting to the waves and to catch them. The use of a cooling system allows high power motors to be provided to assist in catching waves where rapid acceleration (ie a short impulse) is required. High power motors can use significant power and thus a monitoring system and displays can also be provided to allow the rider to continuously monitor how much power they are using and how much power is left. This is very important to allow riders with impairments or little skill to control power management and remaining energy levels and ensure they have sufficient power to safely return to the shore. Various other sensors and reporting systems can be used to ensure independent propulsion systems are used and are constructed using modular distributed components. A range of thrust levels can be obtained through selection of the number and type of motors. Further the modular design offers greater reliability as each part of the system is separate allowing for individual parts to be replaced or upgraded at any time without having to remove the entire system. Also the use of modular compartments allows for accurate spacing of the jet pumps and equipment to maintain existing centre of gravity for all individual board designs so the ride and handling is not significantly affected. Further multiple independent propulsion systems provides redundancy so that if one propulsion system (or part thereof) fails, other independent systems can continue to operate and ensure the rider can safely return to shore. 
         [0092]    More generally the modular compartment design allows all the parts to be located into any board exactly where they are needed to be to ensure the board&#39;s original centre of gravity can be maintained. This ensures the ride remains as natural as possible with power ON or OFF. Also different motor power options can be selected to achieve different power options, thrust levels and run times. This allows customisation of the power system to an individual, the board and the intended surf conditions. Further individual parts can be selected as required based on the board and replaced as required. Finally all this can be provided in such a way that the ride and handling characteristics are preserved so that unskilled or impaired riders can more fully enjoy the surfing experience. 
         [0093]    Those of skill in the art would understand that information and signals may be represented using any of a variety of technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
         [0094]    Those of skill in the art would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. 
         [0095]    Throughout the specification and the claims that follow, unless the context requires otherwise, the words “comprise” and “include” and variations such as “comprising” and “including” will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. 
         [0096]    The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general knowledge. 
         [0097]    It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the invention is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims.