Background Art With the increasing popularity in recreational water activities the sit-on-top kayak has become increasingly popular due to its stability and ease of use.

Typically, kayaks are of the conventional sit-in kayak construction wherein the operator sits in an enclosed cockpit within the shell of the kayak, entering through an opening in the upper deck of the kayak. Modifications on this type of kayak have the additional features of water jet propulsion.

Sit-on-top kayaks, which include surf-skis and wave-skis, have become very popular for those people who do not enjoy being confined in a traditional kayak, preferring a floating platform that gives the operator easy access to board the craft, particularly after the craft has capsized, and relative case to disembark from the vessel.

Typically, a sit-on-top kayak is characterised by a watertight shell having an upper and lower skin, and an open cockpit area with seating and footrests moulded or provided on the upper skin of the shell.

Several types of sit-on-top kayaks are much wider across the beam and do not possess the narrow bow and streamlined hull dynamics of the traditional enclosed kayak, resulting in a more stable, user-friendly kayak for all to enjoy.

All kayaks typically use a double-ended paddle to power and manoeuvre the kayak-the greater the force placed on the paddle blade in the water the greater the rate of travel of the kayak.

As with many kayaks and manually propelled watercraft, the operator will eventually tire due to the physical demands of paddling the craft, this being particularly prevalent with sit-on-top kayaks. This may be overcome by providing a motor to propel the kayak, however, with more stringent environmental regulations being imposed on the use of powered watercraft, such as jet skis, an alternative having a reduced environmental impact is needed for recreational activities particularly at waterside resorts.

The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia as at the priority date of the application.

It is an object of this invention to provide a sit-on-top kayak having a propulsion means, enabling an operator to enjoy propulsion assistance if and when required.

Disclosure of the Invention The present invention provides a watercraft comprising: a shell having an upper skin adapted to support at least one person, a lower skin defining a hull for contact with the water, an aperture extending through the upper and lower skin and defined by a sidewall enclosure between the lower skin and the upper skin to maintain the integrity of the shell, wherein the aperture removably secures a propulsion means for propelling the watercraft, such that a cavity within the shell remains watertight to allow for practical functioning when the propulsion means is removed.

Preferably the watercraft is in the form of a sit-on-top kayak.

The need exists for a sit-on-top kayak designed to support one or more occupants and adapted to accommodate a removable propulsion means such that, when the propulsion means is removed the watercraft is capable of practical functioning.

The kayak should also provide recreational enjoyment without any detriment to the environment in the form of noise, bank-wash erosion or pollution, whilst greatly reducing the chance of injuries to other people.

Preferably the propulsion means is aft of the rearmost operators position.

Preferably the aperture is in the aft portion of the watercraft, adjacent the most rearward point of the stern.

The propulsion means may be easily removed from the watercraft to facilitate ease of handling when loading and unloading the watercraft from storage and ease of handling at the waters edge.

Preferably the propulsion means has an intake for receiving water and an outlet for discharging water.

The propulsion means may be positioned relative to the watercraft to ensure the intake of the propulsion means has a continuous supply of water.

Preferably the aperture is configured to provide easy positioning and securing of the propulsion means.

Preferably when the propulsion means is in place, a lower end of the propulsion means is substantially flush with an under-side of the hull, therefore reducing the impact on the environment, particularly when passing across coral outcrops, weed banks and riverbanks.

The propulsion means may comprise a pump and a motor to drive the pump.

The motor may be powered by a fuel source such as a battery system, solar power, fuel cell, or photovoltaic cells. Preferably the fuel source is in the form of one or more batteries.

Preferably the motor is an electric motor.

The electric motor may be mounted transverse to the longitudinal axis of the kayak.

In one aspect of the invention the pump and motor are integral.

In another aspect of the invention a coupling means may separate the pump from the electric motor.

The coupling means may be in the form of a belt drive.

In one aspect of the invention the pump may be an impeller type pump.

In another aspect of the invention the pump may be a centrifugal pump.

A shroud may be fitted over the propulsion means.

The shroud may be fitted to the pump to direct the water discharged into a central rearward position, substantially aligned with the longitudinal axis of the watercraft.

The inlet of the pump through which the water is drawn may be protruding below or substantially flush with the under side of the hull. The water discharged from the propulsion means may be discharged substantially below the surface of the water.

Preferably the water discharged from the propulsion means is propelled rearward, substantially parallel to the longitudinal axis of the watercraft.

The watercraft may be fitted with an activation means to activate and deactivate the propulsion means when required.

The propulsion means fitted to the watercraft, is preferably driven by a DC electric motor, which in turn is provided with a compact power source in the form of one or more on-board batteries. The source of power may come from a rechargeable storage battery or any other means of producing electrical energy such as photovoltaic cells or fuel cell technology etc. The further environmental advantage of such an electrical driven motorized watercraft is that the pollution emission levels are negligible. This clean, eco friendly form of propulsion is not intended to be of high speed but more inclined to appeal to the general populous of people enjoying the usage at beach side resorts, coral outcrops, ocean adventure tours, inland lakes and harbours, eco wilderness tours and general leisure activities.

The propulsion means may be positioned in a holding compartment integral with the upper skin and protected from the elements by way of a hood, lid or hatch cover.

The fuel source may be positioned in a holding compartment integral with the upper skin and protected from the elements by way of a hood, lid or hatch cover.

The watercraft may be fitted with a steering means for steering the watercraft when being propelled by the propulsion means.

Preferably the steering means directs the body of water discharged from the propulsion means.

In one aspect of the invention the steering means takes the form of the shroud.

Preferably the shroud is rotatable in the horizontal plane, allowing angular redirection of the water discharged to facilitate turning of the watercraft.

In another aspect of the invention the steering means takes the form of an aft fitted rudder arrangement.

The hull may have a profile consisting of at least one keel or stepped hull formation. Preferably the at least one keel or stepped hull formation runs from the stern of the kayak towards the bow.

Preferably the hull has a recessed portion centrally located along the longitudinal axis, and at the stern of the kayak, wherein the recessed portion induces and helps maintain the flow of water to the propulsion means, whilst reducing the drag upon the watercraft. The recessed portion may be in the form of a channel.

The at least one keel or stepped hull formation may be designed to extend deeper into the water than the propulsion means. This will provide protection to the propulsion means from underwater contact particularly in shallow depths, without impeding the flow of water towards the propulsion means.

At least one floatation assembly may be located in an aft position of the shell.

The at least one floatation assembly may be removable.

Preferably there are two floatation assemblies.

Preferably each flotation assembly comprises an adjustable element such that each assembly is variably adjusted between an extended position and a retracted position.

Preferably each floatation assembly is releasably mounted with respect to the watercraft and comprises at least one support pontoon attached to a support arm.

Preferably the support arm defines the adjustable element.

Preferably each floatation assembly is located on opposed sides of the longitudinal axis of the watercraft, and being symmetrical with respect to each other about said axis.

When fitted to the watercraft the floatation assemblies assist in transferring any unstable rolling action of the watercraft back to the semi submersed pontoons to

increase the stability of the overall watercraft. The pontoons may provide an additional buoyancy effect on the watercraft to provide some compensation for the weight of the propulsion means. Preferably the additional buoyancy effect of the flotation assemblies is equal to the weight of the propulsion means.

The kayak may incorporate at least one storage compartment. The at least one storage compartment may be integral with the upper skin.

In another aspect of the invention the propulsion means is provided by a screw propeller and motor. Preferably a cage surrounds the propeller to protect the environment and other swimmers.

The cage may be integral with the propulsion means.

The cage may be removably attached to the lower skin of the shell.

Preferably the screw propeller is of a diameter that will allow for the overall draft depth of the watercraft to be minimal so as to avoid underwater obstacles whilst giving consideration to properties of propeller efficiency.

The motor may take the form of a fully immersed electric drive.

In a further aspect of the invention the propulsion means is provided by a paddle wheel and motor.

Preferable the motor is an electric motor.

The paddle wheel may be positioned within the aft section such that the outer most extremity of the paddle wheel is adjacent the most rearward point of the stern, providing a forward thrust to the watercraft.

The electric motor may be integral with or positioned within the inner perimeter of the rotating paddle wheel so as the unit acts as one in respect of mounting and dismounting from the watercraft.

The paddle wheel may be provided with rotational torque capabilities from the electric motor mounted with its axis parallel to the rotational axis of the paddle wheel.

The electric motor may be attached to the paddle wheel by a coupling or belt drive means.

A cage may encapsulate the under water portion of the paddle wheel for the protection of the environment and swimmers. The cage may be removably attached to the underside of the hull or be integral with the propulsion means.

A cage may surround the exposed portion of the paddle wheel. The cage also provides protection for the motor from the elements.

The upper skin may also provide footrests and a seat for each of the at least one person. The seat may have a support surface raised slightly above the portion of cockpit flooring immediately forward of the seat so as to keep the at least one person above the lowest point any water may collect.

Apertures may be provided in the shell. The apertures may be capable of accepting posts to aid in the transport of the watercraft across land.

The watercraft may also incorporate an underwater viewing window for the enjoyment of the occupants.

The cockpit floor space may have an opening which may receive a viewing window for viewing underwater objects. The opening may have a raised rim extending around the entire perimeter. The raised rim aids in keeping the top of the viewing glass dry and clean for underwater viewing purposes.

To maintain a single shell type hull, and for an added safety feature in the event of damage to the transparent window, the window aperture is moulded with integral side walls so that the underside hull moulding will be integral with the upper hull deck cockpit floor, whereby the aperture receives the window.

The present invention further provides a watercraft comprising: a shell having an upper skin adapted to support at least one person, a lower skin defining a hull for contact with the water, wherein the shell accommodates a propulsion means for propelling the watercraft, such that the watercraft is configured to maintain a cavity within the shell watertight to allow for practical functioning when the propulsion means is removed.

Preferably the propulsion means is removably secured within an aperture in the aft portion of the watercraft, adjacent the most rearward point of the stern.

The aperture may extend through the upper and lower skin.

Preferably the aperture is defined by a sidewall enclosure between the lower skin and the upper skin to maintain the integrity of the shell.

The present invention further provides a watercraft comprising: a shell having an upper skin adapted to support at least one person, a lower skin defining a hull for contact with the water, an aperture extending through the upper and lower skin and defined by a sidewall enclosure between the lower skin and the upper skin to maintain the integrity of the shell, at least one floatation assembly comprising an adjustable element such that the at least one floatation assembly is adjustable between an extended position and a retracted position, allowing the person to increase or decrease the degree of stability added to the shell, wherein the aperture removably secures a propulsion means for propelling the watercraft, such that a cavity within the shell remains watertight to allow for practical functioning when the propulsion means is removed, the at

least one floatation assembly providing an increase in buoyancy to the watercraft.

Preferably there are two floatation assemblies, each being located in an aft position of the shell, and on opposed sides of the longitudinal axis of the watercraft, and being symmetrical with respect to each other about said axis.

The assemblies may be located sufficiently aft so as not to interfere with the paddling motion.

The present invention further provides a watercraft formed by an upper skin and a lower skin whereby one or more operators are seated upon an open cockpit area formed as part of the upper skin with the shell capable of receiving and supporting at least one floatation assembly aft of the most rearward seating position and able to receive and retain a propulsion means aft of the most rearward seating position.

Typically, the watercraft is capable of functioning practically when the propulsion means is removed The present invention still further provides a watercraft comprising a shell having an upper and lower skin which define a cavity, and an aperture within the shell to accommodate a propulsion means, the aperture extending between the upper and lower skins and being separated from the cavity by a sidewall such that no water may pass through the aperture into the cavity.

The present invention further provides a watercraft comprising a shell having a lower skin defining a hull for contact with the water and an upper skin having a cockpit adapted to support a first occupant and a second occupant, whereby the first occupant is in face to face relation with the second occupant, the shell being capable of receiving and supporting at least one floatation assembly aft of the most rearward seating position and able to receive and retain a propulsion means aft of the most rearward seating position.

The present invention further provides a watercraft comprising:

a shell having an upper skin adapted to support a first occupant and a second occupant, whereby the first occupant is in face-to-face relation with the second occupant, and a lower skin defining a hull for contact with the water, an aperture extending through the upper and lower skin and defined by a sidewall enclosure between the lower skin and the upper skin to maintain the integrity of the shell, wherein the aperture removably secures a propulsion means for propelling the watercraft, such that a cavity within the shell remains watertight to allow for practical functioning when the propulsion means is removed.

The present invention further provides a watercraft comprising: a shell having an upper skin adapted to support a first occupant and a second occupant, whereby the first occupant is in face-to-face relation with the second occupant, and a lower skin defining a hull for contact with the water, an aperture extending through the upper and lower skin and defined by a sidewall enclosure between the lower skin and the upper skin to maintain the integrity of the shell, at least one floatation assembly comprising an adjustable element such that the at least one floatation assembly is adjustable between an extended position and a retracted position, allowing the person to increase or decrease the degree of stability added to the shell, wherein the aperture removably secures a propulsion means for propelling the watercraft, such that a cavity within the shell remains watertight to allow for practical functioning when the propulsion means is removed, the at least one floatation assembly providing an increase in buoyancy to the watercraft.

The rotational moulded kayak has many features that make the craft very user friendly and functional for the purpose of recreational usage. The upper skin cockpit area may have a shallow sidewall that forms the surround. The backrest may rise to a point higher than any deck portion forward of the most rearward seating position.

Brief Description of the Drawings The invention will be better understood by reference to the following description of several specific embodiments thereof as shown in the accompanying drawings in which: Figure 1 is a plan view of the watercraft according to a first embodiment; Figure 2 is a view similar to figure 1 showing an aperture; Figure 3 is a perspective sectional view of figure 2; Figure 4 is a perspective view similar to figure 1; Figure 5 is a perspective sectional view of the underside of the watercraft showing the propulsion means; Figure 6 is a bottom view of Figure 5; Figure 7 is a plan view of the watercraft according to a second embodiment; and Figure 8 is a perspective view according to the second embodiment; Figure 9 is a side view of figure 7; Figure 10 is a plan view of figure 7 with room for two operators; Figure 11 is a side view of figure 7 with two operators;

Figure 12 is a plan view of the watercraft according to a third embodiment; Figure 13 is a plan view of the watercraft according to a fourth embodiment; and Figure 14 is a plan view of figure 13 with the aperture showing.

Best Mode (s) for Carrying Out the Invention Referring to Figures 1 to 6, the invention according to the first embodiment is a watercraft in the form of a sit on top kayak 11 comprising an upper skin 13 and a lower skin 15 to define a sealed cavity.

The upper skin 13 provides a support area in the form of a cockpit 19 to receive an operator 21 (not shown). The lower skin 15 defines a hull 23 which contacts the water when the kayak 11 is in use.

The kayak 11 has a stern region 25 aft of the cockpit 19. The stern region 25 incorporates an aperture 24 extending from the upper skin 13, through to the lower skin 15, with a side wall 100 extending from the upper skin 13 to the lower skin 15.

The aperture 24 is configured to removably retain a propulsion means 31 such that the propulsion means 31 is easily fitted or removed by the operator.

The kayak 11 is configured such that, upon removal of the propulsion means 31, the kayak 11 can be used in a conventional manner for practical use.

The propulsion means 31 comprises a pump 33 and an electric motor 30 to assist in the propulsion of the kayak 11.

The pump 33 has an intake 49 for receiving water, and an outlet 51 for discharging water, to propel the kayak 11. The outlet 51 is positioned such that the water discharged therefrom is substantially aligned with the longitudinal axis of the kayak 11.

The pump also has a shroud 53 located over the outlet 51, and is rotatable in the horizontal plane. The shroud 53 has a nozzle 56 from which discharged water may accelerate from the shroud 53. The shroud 53 may be controlled by the operator to direct the water discharged from the pump in order to assist in manoeuvring and steering the kayak 11.

The propulsion means 31 is positioned such that it does not protrude below the hull 23 adjacent the propulsion means 31. This limits the damage that may be caused by underwater obstacles when the kayak 11 is in use.

The stern region 25 incorporates a hood 54 which is contoured with the shape of the kayak 11. The hood 54 is located over the propulsion means 31, providing protection from the elements.

The propulsion means 31 may be activated by an activation means in the form of an on/off switch 55 located near the cockpit 19.

The cockpit 19 incorporates footrests 57 moulded into the upper skin 13, and a seat 59. The seat 59 is raised above the floor 61 of the cockpit 19 so that each operator 21 does not sit in a pool of water which may splash onto the kayak 11.

The hull 23 has a profile to induce water towards the pump 33 whilst protecting the pump 33 from any underwater obstacles. For this purpose, the hull 23 incorporates two keels 45 substantially parallel to the longitudinal axis of the kayak 11, and running along the length of the kayak 11, and a recessed portion 47 located in the stern region 25.

Referring to figures 7 to 11 the invention according to a second embodiment comprises essentially the same features with the addition that the kayak 11 comprises two floatation assemblies 37. Each floatation assembly 37 comprises a pontoon 39 and pontoon arm 41. The pontoon arm 41 is received in a socket in the form of a blind bore, not shown, located in the kayak 11. The pontoon arm 41 is capable of variable adjustment between a retracted and an extended condition.

When the floatation assembly 37 is fitted it is locked into place and provides increased stability and buoyancy to the kayak 11.

Figures 12 shows a third embodiment of the invention wherein the propulsion means 31 comprises a screw propeller 63 which is driven by a submersible electric motor 65. The propeller 63 is of a diameter which minimises the draft depth of the kayak 11 whilst giving due consideration to propeller efficiency.

In order to protect people from the propeller a cage 67 (not shown) is fitted around the propeller 63 to shield the blades.

The kayak 11 also incorporates compartments, not shown, which enable the operator to store items within.

Referring to Figure 13 and 14, the invention according to a further embodiment is a watercraft in the form of a sit on top kayak 11 comprising an upper skin 13 and a lower skin 15 to define a sealed cavity.

The upper skin 13 provides a support area, in the form of a cockpit 19, to a first occupant (not shown) and second occupant (not shown). The lower skin 15 defines a hull 23 which contacts the water when the kayak 11 is in use.

The cockpit 19 has a first seat support 59a and a second seat support 59b. The first seat support 59a provides seated support for the first occupant, the second seat support 59b provides seated support for the second occupant.

The first seat support 59a is located aft of the second seat support 59b, and is positioned such that the first occupant has a forward view from the kayak 11.

Each seat 59a, 59b is raised above the floor 61 of the cockpit 19 so that the occupants do not sit in a pool of water which may result from water splashing into the kayak 11.

The first occupant operates the kayak, whilst the second occupant is a passenger.

The cockpit also provides footrests 57 for the first occupant. The footrests 57 are located in spaced apart relation along each side of the cockpit 19. When the first occupant is seated in the kayak 11 he/she can place a leg adjacent either side of the cockpit 19 and gain support from the footrests 57.

The cockpit 19 also has a flat surface 24. The flat surface 24 is located forwardly of the first occupant and between the footrests 57. the flat surface 24 provides an area where the second occupant may place his/her legs when seated in the second seat support 59b without interfering with the first occupant.

The cockpit also provides a viewing window 26 allowing the occupants to view underwater.

In a further embodiment, not shown, the propulsion means 31 is provided by a paddle wheel in combination with an electric motor. The paddle wheel is positioned such that rearmost portion of the wheel does not extend beyond the rearmost stern region 25 of the kayak. Again a cage is used to protect the exposed sections of the paddle wheel in order to prevent injury to a person.

In this embodiment the electric motor is positioned within the paddle wheel and parallel with the longitudinal axis of the paddle wheel. This enables the propulsion means 31 of this embodiment to be removed easily.

In use the operator 21 may position the kayak, minus the propulsion means 31 upon the waters edge before retrieving and positioning the propulsion means 31 in the aperture. Whilst paddling the operator may activate the propulsion means 31 using the on/off switch 55, and allow the propulsion means 31 to propel the kayak 11 or to assist the operator 21 whilst the operator continues to paddle in a conventional manner.

If the operator wishes to use the kayak 11 without the assistance of the propulsion means 31, the propulsion means 31 need not be fitted and the kayak 11 can still be used in a conventional manner.

It is believed that the introduction of this invention will provide recreational enjoyment without any detriment to the environment in the form of noise, bank- wash erosion or pollution, whilst greatly reducing the chance of injuries to other people.

The kayak so described by this invention is primarily for recreational use in and around populated holiday beaches and waterways. For reasons of safety and ease of use in recreational areas, it is preferred that the speed range of the craft may be limited to 2-6 knots. At these low speeds, kayaks are equipped with a hand held paddle for the operator to enjoy the tranquil moments of kayaking without the engagement of the propulsion means. When the operator requires assistance or some relief from paddling, he or she simply engages the electric drive through a simple on/off button or switch.

Modifications and variations such as would be apparent to the skilled addressee are considered to fall within the scope of the present invention.

Throughout the specification, unless the context requires otherwise, the word "comprise"or variations such as"comprises"or"comprising", 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.