TITLE

AMPHIBIOUS MARINE CRAFT

FIELD OF THE INVENTION

The present invention relates to objects including marine craft and more particularly to a boat or light fastship. or other marine craft, such craft being made amphibious by having an elongate hull provided with a flexible track apparatus for enabling the craft to move in both forward and backwards directions to enable the craft to move on to and off land, or up to and back from the land's edge (beach) or on the sea bottom (or river or lake bottom) or on any other firm relatively surface. The track apparatus being so arranged as not to adversely affect the shape and "lines" of the hull of the craft so that the hull has the same hydrodynamic performance on the water as a hull that does not have the track apparatus. The track system also being relatively simple in construction, strong and safe.

BACKGROUND OF THE INVENTION Prior art vehicles which are capable of moving from water onto land and vice versa include hovercraft and certain track type military vehicles. t is also known to add drivable wheels to the hull of a water going craft.

A disadvantage of these types of systems of making a craft amphibious is that the hull loses its aesthetic appeal and its hydrodynamic performance and in fact ceases to become a genuine marine craft.

Other prior art attempts to make an amphibious marine craft include International Patent Xo, WO 89 04261 by Lindberg which discloses a marine craft into the bottom of which is adapted two flexible and endless type belts on track rollers. This has the disadvantage that the track compromises the boat's aesthetics and performance and structural simplicity _. , as wells as compromising the boat ^' s safety and integrity. Also, internal space is lost and excessive weight is added by the track.

Similar track assemblies exist attached to the sides of land based vehicles and again these are not suitable for the same basic reasons.

Such prior art track type craft are focuses on the purpose of enabling high land speed and long distance travel on land; they are not concerned with efficiency of travel on water. For these prior art craft water is an obstacle to be traversed rather than a medium of efficient travel.

The amphibious marine craft of the present invention is properly a marine craft of the true type, such as a boat or ship, including ones known as landing craft, boats, multi-hulled

boats, and sailing boats. The apparatus of the present invention is suitable to be used in both new boat construction and to be retro-fitted to boats already built and in use.

SUMMARY OF THE INVENTION

Therefore it is an object of the present invention to provide an amphibious marine craft which is efficient in travel on the water and can move itself onto and off land.

In accordance with one aspect of the present invention there is provided an apparatus for moving a water borne craft on land, the apparatus comprising: a flexible elongate track means which can be moved along the length of the bottom of tlie hull of the craft, at least a portion of tlie track means being guided along said hull for inhibiting lateral movement of the track means with respect to tlie hull, tlie track means being capable of bearing a substantial portion of tlie force of the weight of the craft when the craft is at least partly supported the land, including on a beach or sea bottom, the track means being retractable into the said hull in a water borne mode of operation for maintaining the hydrodynamic efficiency of the hull, and the track means being extendible onto and along the hull in a land borne mode of operation for engaging with tl e land; and, a drive means attached to the track means for applying a force to the track means for moving tlie track means with respect to tlie said hull for propelling the craft onto and off the land when tlie track means engages with the land.

In accordance with another aspect of the present invention there is provided an amphibious marine craft which incorporates the said apparatus for moving a water bonie craft onto and off land.

Typically, the track means is in the foπn of a belt and the drive means includes a motor for moving the belt with respect to the hull.

Advantageously, a guide is provided on the outer surface of the hull for guiding the belt. Typically, a material having a low coefficient of friction with the belt, such as a composite, plastic material or roller bearings (small), is provided in connection with said guide for minimising friction between tlie belt and the outer surface of tlie hull when in the land borne mode of operation.

In one embodiment said belt is an endless belt, a first length of the belt extending along said outer surface of the hull, and the remainder of the belt returning tlirough to an interior or deck area of said hull, having means such as a suitable motor or manual mechanism to drive said belt.

In another embodiment said belt is of finite length and said means for moving the belt comprises first and second motors provided at respective ends of the belt for drawing the

belt in first and second directions respectivel> along the longitudinal extent of the craft.

Preferably said flexible elongate track has a ground engaging surface provided with means for gripping the ground. In one embodiment, advantageously said ground engaging surface is proλ'ided on a portion only of the total length of the elongate track, said portion being retractable when tlie craft is in a water borne mode, and additional elongate non-belt type means preferably provided, such as at least one cable to connect to the belt, and to apply a force to one end of the belt for moving the belt relative to tlie craft's required direction of movement on land.

The present invention was developed with a view to providing an apparatus that allows a water craft to move itself onto and off land from the water. Although the invention will be described with particular reference to rigid hull monohull vessels, it is to be und rstood that the apparatus of the invention is equally applicable to objects other than vessels and to multi-hull vessels of the rigid or semi-rigid type, including water craft with inflatable hulls

BRIEF DESCRIPTION OF THE DRAWINGS In order to facilitate a more comprehensive understanding of tl e nature of tl e invention, several presently preferred embodiments of the apparatus for moving a water craft onto and off land will be described in detail, by wa> of example only, with reference to the accompanying draλvings in which:

Figure 1 is a longitudinal section view through a boat hull and a track apparatus showing a first embodiment of the apparatus according to the present invention;

Figure 2 is a transverse section view of the boat hull and track apparatus of Figure 1;

Figures 3 A and 3B are lower plan views of the boat hull of Figure 1 showing die boat with tlie track in a refracted and extended position respectively;

Figure 4 is an elongate section λ'iew tlirough a boat hull similar to that of Figure 1 showing a second embodiment of the track apparatus according to the present invention;

Figure 5 is a transverse section λ'iew through the track apparatus employed in the apparatus of Figure 4 or as an option for use in Figure 1 ;

Figure 6A and 6B are lower plan λ'iews of the boat hull of Figure 4 showing tlie boat with the track in an extended and a retracted position respectively; Figure 7 is a lower plan λ'iew of a boat hull showing a third embodiment of the track apparatus according to the present invention; and.

Figure 8 is an elongate section λ'iew tlirough a boat hull showing a fourth embodiment of the track apparatus according to the invention, in which tlie track is endless.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT. S .

In Figures 1 to 3B there is shoλλ a first preferred embodiment of a propulsion apparatus 8 for moving a water craft 9 on land in accordance with the present invention. The propulsion apparatus 8 includes an elongate track in the form of a flexible belt 10 and a drive unit 11 in the foπn of two motors.

The principle of operation of the propulsion apparatus 8 of the present i -ention is that the belt 10, when in contact with the land, is stationary with respect to the land and so force applied from the driλ'e unit 11 to the belt 10 causes the craft 9 to react by moλ'ing with respect to the belt 10. This reaction causes the craft 9 to move onto or off the land depending on the direction in which the force of the driλ'e unit 1 1 is applied to tl e belt 10.

A portion of the belt 10 is slideably received on an outer bottom surface region 12 of a hull 14 of the λλ'ater craft 9, which in the examples is a monohull (single hull) type craft. The belt 10 may be of rubber or a suitable synthetic rubber type material, reinforced and constructed to give the necessary tensile strength to enable the λλ'ater craft 9 to be slipped onto and off land. The belt 10 is also made so as to be capable of bearing a substantial portion, if not all, of the force of the λλ'eight of the water craft 9 as it is slipped.

In tlie preferred exemplary embodiments of Figures 1 to 3B, a portion of the belt 10 extends lengthλvise oλ'er tl e hull 14 along the centre line region generally. Preferably, a guide 16 is provided, particularly as shown in Figure 2, extending lengthwise along the centre line of the outer surface 12 for guiding the belt 10. A component 18 of material, having a high wear resistance and low coefficient of friction such as a plastic composite bearing surface may be applied to the outer sides of the under side surface of the guide 16 for minimising friction between tlie belt 10 and the hull 14 particularly when the craft 9 is moved on land on the belt 10. The purpose of the guide 16 is to confine tlie belt 10 to movement along tlie length of tlie hull 14 for inliibiting fransverse slip or bending of the belt 10.

The low friction material 18 enables tlie belt 10 to slide with greater ease, requiring a lower motor size and energy use to be used, and loλλ' λvear within tlie guide 16 eλ'en λvhen tlie f ill weight of the craft 9 is resting, and moved on the belt 10. The guide 16 is provided also to inhibit foreign material from coming into contact λvith tlie bearing surface 18.

In order to inhibit the belt 10 from slipping on the ground, in situations when the craft 9 being moλ'ed onto the land is particularly heaλy. the belt 10 or a portion of the length of the belt 10, ma)' be provided with a ground engaging surface formed with elements such as transλ'erse ribs 20 (see Figure 3B). The ribs 20 also assist in proλiding for extra grip when the craft 9 is being moved on the land which has a modest angle of slope. In some embodiments of the track apparatus for use for moving the water craft on land a further

distance, comprises first and second motors 22 and 24 for moving the belt 10 relative to the outer surface 12 of the hull 14. Belt 10 may be moλ'ed either in a foπλ'ard or backward direction, relevant to the craft for moving the craft 9 on land when the belt 10 is held to the land by the craft's weight. The first motor 22 is located in the bow 26 of the vessel, and the second motor 24 is located in the stem 28. The first and second motors 22 and 22 may. for example, be electric or hydraulic motors which may be poλvered by the main engine(s) of the vessel, or they may be provided with their own independent: power source, or manual means may be proλided in place of the motors or means such as an anchor λvi ch and motor, even one adapted to move the anchor and belt. In each case, by such as a drive shaft (not illustrated) of the motor is connected to such as a spool or cable drum, proλ'ided for gripping and moving the belt 10 relative to the outer surface 12 of the hull, and for moving the hull 14 relevant to the belt, so that the craft moλ-es on land.

In one embodiment, a first end of the belt 10 may be connected to such a spool on and driλ'en by the first motor 22 in the boλλ' 26 of the λ'essel. and a second end of the belt 10 is connected via a cable(s) 30 to a second spool on second motor 24 positioned in the stem 28 of the λ'essel. Preferably, such cable or cables run right tlirough the belt 10. and preferably on in each side which thereby run in grooves in guide 16 sides provided.

In its fully or partly, and place of storage retracted position, the belt 10, commencing at the first end is wound onto the spool connected to tlie first motor 22, and a portion of the cable(s) 30 from motor spool 24. will extend beneath the hull 14, preferably on or within grooves in the hull bottom, or within the guide mechanism 16 on the outer surface 12 of the hull 14 of the craft. In order to moλ'e the belt 10 to its fiilly or partly extended position the second motor 24 is activated in order to wind the cable 30 onto tlie motor spool 24 located in the stem 28 of the hull so as to draw the belt 10 along the outer surface 12 tlirough guide 16 or alternatively to cause the boat to slide on tlie belt 10. Whether the belt moλ'es freely on the hull 14 of the boat moλ'es and belt remains stationary relatiλ'e to the land depends on whether or not the belt 10 is held by the weight of the craft to the land. The position of the belt 10 beneath the hull 14 is by λvay of example in Figure 3B.

The operation of the apparatus for moving the water craft from the water onto land will noλv be described, as one example of one amphibious operation.

During normal use of the water craft 9 in water borne mode the belt 10 is kept preferably in its fully retracted position remoλ-ed from the hull bottom as shoλvn in Figure 3 A and only the cable(s) 30 will be beneath the craft 9 along the centre line of the outer bottom surface 12 of the hull 14. When it is desired to bring the craft 9 onto land, or over otherwise too shallow water depth shoals the belt 10 is first moved to a partly extended position from storage to beneath the boλv end of the hull 14 bottom, (not shown). The positioning of the belt to this first stage is preferably executed while the boat is free

floating. As cable 30 is wound onto the spool 24 provided in the stem 28 of tlie craft, belt 10 is simultaneously unwinding from tl e spool 22 proλ ded in the boλv 26 of the craft.

The second stage of operation concerns moving tlie craft 9 until tlie bow- end 26, with the belt 10 under it, is supported on tlie water bottom or beach edge or such like land. In order to then move the craft 9 further on the water bottom or onto the beach or land, tlie cable 30 is pulled in by the motor 24 at the stern 28 of the hull 14 by applying a force in a steπiwards direction to tlie belt's 10 second end beneath the bow 26. The result of applying this force because tlie belt 10 is held stationary by the weight of the craft 9 causes an opposite reaction in tlie opposite direction of the force being applied, consequently tlie craft 9 moλ'es in a fonvard direction and moλ'es sliding on the belt 10 in guides 16 moλ'es relative to tlie sea bottom, beach or land.

The inλ'ention proλ des as an optional feature that the belt 10 unwinds freely from the motor spool 22 in the bow 26 of the craft 9 as the belt 10 is being drawn up by the motor spool 24. More preferably tlie motor spool 22 unwinds faster than the cable 30 is being drawn beneath the hull 14. Accordingly the load of moving the craft 9 on tl e belt 10 is reduced.

When the belt 10 reaches an unwound position extending for essentially tlie length of the bottom 12 of the hull 14, as shown in Figure 3B, the λvater craft will noλv be beached for the relative distance of the length of belt 10 so extended. The ground engaging surface λvith the ribs 20 of the belt 10 inhibit slip on the sand, soil or grass on the shore and so the craft 9 is more efficiently propelled onto the land..

If it is desired to moλ'e the craft further out of the λvater onto tl e land the second motor 24 in the stem 28 of the craft is again activated, drawing further belt length from tlie boλv end 26 storage spool motor 22 as H e craft slides on tlie belt 10. To re-enforce the explanation of how the boat moves on land tlie following is provided. The ribs 20 of the ground engaging surface on belt 10 grip into the sand, grass or ground or tlie shore due to the weight of tlie craft 9 pressing down on tlie belt 10 so that tlie belt 10 remains substantially stationary relative to the ground. Therefore, by winding tlie belt 10 onto tlie spool provided in the stem 28 the craft is effectively drawn up onto tlie beach slideably supported on the belt 10. The distance that the craft 9 can traλ'el up tlie beach in this manner is of course determined by the length of the belt 10 and the amount of grip which the belt 10 has on the land.

In some cases tlie distance tlie craft 9 is able to travel on land is set by the length of the ground engaging surface proλided on belt 10 in its fully extended position beneath the craft 9.

In order to moλ'e the craft back down the beach in a backward direction on belt 10. the first

motor 22 is now activated and the second motor spool 24 is allowed to free wheel. This action applies a force to the belt 10 beneath the craft 9 in a fonvard direction which causes the craft 9 to move in the opposite direction sliding on the belt 10. As the craft 9 moves backλvards the cable 30 and the belt 10 is unwound from the spool motor 24 and is draλλ'ii along the guide 16 on the hull bottom 12.

In some situations and λvith certain types of craft 9 it may be preferred to moλ'e the belt 10 to a more fully extended position beneath the hull bottom 12 than just beneath the bow end 26 of the hull bottom 12 prior to beaching. Further movement of the craft 9 onto the land is then accomplished by the motor 24 at the stem 28 of the craft 9 winding Hie belt 10 onto the spool causing the boat to moλ'e forward. The substantial and extra length of the belt 10 first moved under the hull 14 prior to land engaging ensures extra grip of tlie belt 10 on tlie land, thereby enabling the craft 9, eλ-en though of substantial λveight, to moλ'e onto and' or off tlie land.

In a further optional λ'ariation to moλ'e the craft 9 onto the land or on the sea bottom across shallow shoals, the belt 10 is first extended to beneath the bow 26, following which tl e craft 9 is driλ'en towards tlie land. The ground engaging surface of the belt 10 grips the sand or shore as the hull 14 rides onto the beach. Because of the momentum of tl e craft 9. the craft 9 will continue its forward movement, traλ'elling easily and freely a limited distance up tlie beach. The distance travelled then depends on the angle of incline of the beach and the initial speed of the craft 9. Simultaneously, the belt 10 is allowed to unwind freely by disconnecting the motor 22 from the spool so as to not impede the momentum of the craft 9 by being stationary with respect to the craft 9 and gripping into the land.

Typically, some breaking control is applied to limit the speed at which tlie spool freely umvinds so as to not exceed the take-up speed of the motor 24 by too much The craft 9 can then move a substantial distance up the beach easily and using very small amount of energy as it has the belt 10 under and consequently minimal resistance due to tlie loλλ' friction material 18 located between the guide 16 and belt 10. The belt 10 will remain substantially stationary relatiλ'e to the beach, due to the λveight of the craft 9 and the friction and grip to tlie beach to the underside of tlie belt 10. Due to the forwards movement of the craft 9 the belt 10 will unwind from the spool 22 proλided in the boλv 26 of the craft 9. A brake mechanism may be provided to the motors 22 and 24 and or to the belt 10 to control the speed of umvinding of the belt 10.

Propulsion of the craft 9 with respect to the belt 10. once engaged with the land, could alternately be achieλ'ed using such as a water jet propulsion, or by manual pushing or pulling on small boats, or by the use of stem or bow end placed anchors and lines to tlie craft 9 or tlie like.

When it is desired to reverse the boat off the beach, it is a simple matter of activating motor

22 in the bow 26 of the craft 9 to rewind the belt 10, tlie belt 10 being able to be rewound because the craft 9 is moving reaπλ'ard relative to it, sliding in guide 16. In this arrangement the belt 10 is played off the spool of the motor 24 and stored onto the spool of motor 22 located in H e bow 26 of the craft 9. A further embodiment of the apparatus for moving a water borne craft on land in accordance with the present invention is illustrated in Figures 4, 5, 6, & 6A. This embodiment is similar to that illustrated in Figures 1 to 3B and therefore similar parts have been identified with tl e same reference numerals and will not be described in detail again. In this embodiment, tl e belt 10 does not extend the full length of the hull 14 when in tlie land borne mode of operation. Instead, the belt 10 in its fully extended position is slideably received along tlie centre line of tlie outer surface 12 of the hull 14 for less than the full length of tl e hull 14. In order to moλ'e the belt 10 relative to tlie outer surface 12 of the hull 14 or to move tlie craft 9 on the belt 10 the second motor 24 is provided approximate!;* midship rather than in the stem 28 of the craft as in the embodiment of Figures 1 to 3, However, in other respects tlie belt 10 of this embodiment is similar to the first embodiment in both structure and operation.

In order to move tlie belt 10 to its fully extended position cable 30 is wound onto a spool at motor 24 proλ'ided in the mid section of the craft 9, and in order to moλ'e tlie belt 10 to its fully refracted position the belt is wound onto the spool of the motor 22 at tlie bow 26. A means such as an opening in the foπn of a fransverse slot 32 is proλ'ided in the outer surface 12 of the hull 14 tlirough which the belt 10 can be positioned and cable 30 located. The slot 32 extends upλvards to a safe distance aboλ'e the water line as a sealed compartment to tl e hull 14 interior. If preferred tlie sealed compartment may extend through the interior of hull 14 to the deck or floor aboλ'e to eliminate any danger of the craft 9 flooding. Alternatively, a sealing device could be provided between the belt 10 and the slot 32.

A further difference between this embodiment and that of Figures 1 to 3 is tl e manner in which the guide track 16 is recessed into tlie outer surface 12 of the hull 14 as can be seen in Figure 5. In Figure 2 it can be seen that the guide track 16 is formed by an appropriately shaped guide member, which may be made for example from pressed metal, λλ'hich is attached to and protrudes from the outer surface 12 of tlie hull 14. However, in the embodiment of Figure 5 the guide track 16 is recessed into die surface 12 of the hull 14 and therefore is less obstructive and so reduces drag in tlie water, in some circumstances and at certain speeds. A feature of the invention in several embodiments shown relates to tl e outer edges of the guide 16 being shaped to house the cables and or sides of the belt 10 by returning inwards to create a track or groove such track or εroove beine arranged as well to contain at

planing speeds a portion of water flow from the hull 14 centre line region area, therein creating higher lift of a modest amount. In one form the guide sides may be in the approximate shape of planing sfrakes of a lift increasing type.

It will be appreciated that many variations of the same basic apparatus can be conceived without departing from the context of the invention, for example, for different sizes and shapes of water craft 9, by using one or a plurality of propulsion apparatus 8 as herein described. Figure 7 illustrates one such possible variation in which three separate belts 10 are proλ'ided and are able to be extended to the position on the outer bottom surface of the hull 14 of the craft 9 for moving tlie craft 9 on land, or just towards tlie land on the sea bottom, (where the λ'essel is particularly large or The belts 10 are spaced apart along the length of tl e hull 14 and across _*_• width. The lengthwise spaced belts 10 can be operated consecutively to assist in land based propulsion.

In each of the Figure 7 embodiments each belt 10 may be of finite length and requires two motors. Alternatively, tlie stem end 28 motor 24 may be eliminated by the addition of a second spool coupled to the motor 22 by an extension of the belt 10 from tlie stem end 28 back to the position of the motor 22 in the bow end 26. Alternatively, the extension could be by a cable back to the motor 22. Additional appropriate control mechanisms could be added to the motor 22 and the spools to control the pay out and take up of the cable 30 and the belt 10. Alternatively, in tlie embodiment of Figure 7 endless belts 10 could be used with only one motor 22 each or the two stem end belts may be driλ'en by one motor 22 shared between them.

Figure 8 shows a further embodiment in λvhich the flexible elongate track is in the form of an endless belt 40. The embodiment of Figures 6 A and 7 could also have the same endless belt variation as Figure 8. In the embodiment of Figure 8 the endless belt 40 has a first length 42 shown extending along tlie outer hull bottom surface 44 of the hull 46, while the remainder of the belt 40 extends tlirough into tlie craft over rollers and return through for example, each end of the craft 9. and into tlie interior of tlie hull 14 and across the deck.

In Figure 8 the ground engaging portion of tlie belt 40 is shown in the position of the first length 42 λvhich extends along the outer surface 44 of the hull 46. This is the position in which the belt 40 would be in relation to the bottom 44 of the hull 46 when tlie craft 9 has travelled on land, or over the deck (inside or out) or around, or portions »f the belt 40 onlv extending over such interior or upper areas. OptionallyΛthe belt 40 can be provided with transλ'erse ribs to better grip the land. Hoλλ'eλ-er. during tl e λvater borne mode of operation where fravel and speed are involved, it is undesirable to have the ribs 48 in this position due to the additional drag they λvould create. Therefore, in the λvater borne mode the ground engaging portion of belt 40 is refracted into the hull 46 by rotating the endless belt

40 over a plurality of rollers 50 provided to and within the hull 46 until a purpose provided smooth portion of the belt 40 replaces the ground engaging portion. Preferably, the special belt poi lion 40 is of only sufficient length to cover the hull bottom 44 frack length portion

A further variation of this special belt embodiment feature concerns the section of belt 40 used when the craft 9 is in water borne operation, having a section of tlie belt 40 able to be accessible to the interior of the craft able to be easily remoλ'ed, such as by remoλing pins from eyelets at end of fee belt at joins. Cables may replace the removed belt section and in either case the belt 40 can be rotated and the hull bottom 44 is free from any and the belt sections used for land travel mode. One important adλ'antage of employing an endless belt is that only a single motor is required to move the belt relative to the outer surface 44 of tlie hull. For example, a single motor 52 may be proλ'ided in tl e bow of the craft 9 as shown in Figure 8. Alternate ^r ely the motor may be located in the stem of the craft 9 as shown at 54. A suitable guide frack be proλ'ided on the outer surface of the hull 44 as in the preλious embodiments, if required. A further advantage of employing an endless belt 40 is that theoretically there is no limit on how far the craft can traλ'el oλ'er land, λvhereas in the previous embodiments the distance is limited by tl e finite length of the belt 10.

In any of the embodiments, the elongate frack may be of any suitable λvidth releλ'ant to the width of the particular craft 9 depending on the size and shape of the particular marine craft. However, it is preferred that the frack be of only sufficient width adequate to support most of the full weight of the craft 9 and so that tlie main hull 14 bottom surface remaining alongside the belt 10 is held away from the land, so that minimal surface area of the hull is in contact with land, both to reduce drag and friction. For example, a 100 tonne craft 9 can be propelled on a beach by a belt 10 which has a width of at least 300 mm. That is. such a belt 10 has sufficient grip to propel the craft 9.

One λ'ariation could be the apparatus in the fonn of a flat cross section of flexible form or rigid segments linked together, including segments which may be spaced apart extending laterally across such as a cable or chain extending preferably centrally along the hull 14 centre line, preferably but not essentially held to the hull 14 bottom in a central groove or track or such like particular cable chain guide.

Alternatively tlie apparatus may include a flexible belt which is not held up to tl e hull 14 by the guides 16 but is secured in its mid centre line to a cable or chain. Such a belt being essentially flat whilst the hull 14 above may be \ee angled or rounded (or flat also for the width of the belt) in which case the belt 10 has upward extending protrusions to contact the hull 14 above positioned on tlie belt 10 outer edge region (not shown)

The invention has been described as applied to a mono or single hull type water craft to

which mav be added (not shown), additional means to balance the craft 9 when tl e belt 10 is en essentially centre line position. Altematiλ-ely. the propulsion apparatus 8 may be in two parts spaced a small distance either side of the centre line extending longitudinally beneath the hull 14 and of depth suitable to be leλ'el with the hull 14 bottom at the centre line distance. Alternatively, the belt 10 could be rounded on the centre line and may have spaced apart downward protruding components added to engage the ground leλ'el with the keel depth when the craft is moved on the land.

Tlie invention is also applicable to multi hulled craft such as catamarans, or trimarans or variations thereof, where an elongate frack apparatus is applied to each appropriate portion of each hull, or on some trimaran types applied only to the central hull,

Each of the described embodiments of the invention have tlie advantage when compared to common prior art. such as land tractor type tracked amphibious vehicles, including amphibious marine craft, that it requires a smaller size motor, substantially reduced power requirements, and lower torque and energy requirements. Also, due to the relatively limited distance of fravel onto the land that is required and the relatively low speed required the belt 10 can be of substantially smaller dimensions, particularly in weight and width than is used in prior art land based vehicles.

It will be seen that the described embodiments of the apparatus for moving a λλ'ater bonie craft 9 on land provide a simple yet effective means for enabling a water craft, such as a modem or traditional designed craft or ship water craft to travel out of the λλ'ater on land, also only advantageously, when compared to existing art requiring minimal extra work and components to apply to water craft manufacturing. The propulsion apparatus 8 is suitable also to retro-fitting to existing water craft 9. Furthermore, the propulsion apparatus 8 does not interfere or substantially affect tlie normal operation of the λλ'ater craft 9 in its λvater bonie mode even for high speed performance boats.

Tl e provision of a loλλ' friction composite plastic material may be replaced by other loλλ' friction mechanisms, such as rollers in the guide 16 or hull bottom 12 or to tlie upper surface of tlie belt 10. Such low friction further reduces tlie size and energy used of the motors 22 and 24. The speed of the motor(s) 22 and 24 may be kept constant by tlie use of suitable λ'ariations in belt speed as the diameter of the spool on λλ'hich the belt 10 is λvound varies as it empties and fills. The guide 16 on the hull bottom 12 may be provided according to the invention with a remoλ'able material which slides in and out of the guide 16 depending on the different operating modes of the craft 9. Further to the invention the ground engaging ribs 20 may be remoλ'able ie clip on and off, and accessible easily from inside the craft and bearing surface material may be arranged and provided in such a form as to be extended into the guide 16 λλiien the belt 10 is to be used and retracted λλ'hen not.

Further to the invention it is not essential that the ground engaging surface be provided with gripping means as a smooth surface may be sufficient due to the weight of the boat and the high ground engaging friction of beaches, land, grass, sea bottom and such like and the area of belt able to be used. Other forms of belt may be provided achieving the same affect provided always that the propulsion apparatus 8 is able to be deployed and remoλ'ed from the hull bottom of the craft such as a boat enabling it to move easily onto land whilst retaining its inherent and valuable water borne mode operations and aesthetics.

Numerous variations and modifications will suggest themselves to persons skilled in tlie marine arts, in addition to those already described, without departing from the basic inventive concept. For example, although tlie flexible elongate frack in each of tlie described embodiments is in the form of a continuous belt, the flexible elongate frack may be of any suitable form. For example, a series of rigid linked elements joined end to end to foπn a flexible elongate track or even a cable haλing a suitable ground engaging surface provided in connection therewith, may perform the same function. All such variations and modifications are to be considered within the scope of the present invention, the nature of which is to be determined from the foregoing description, and illustrations.

The iiiλ'ention has been described as applied to mono hulls and in one of the λ'ariations to tlie land apparatus to the centre line apparatus of the craft, accordingly means, not shown, to hold the craft up-right and leλ'el laterally may be needed and provided to or in the boat such as inflatable rollers which are placed under the outer side area of tlie hull 14. Such means carry a small portion only of the craft weight.

Alternatively, devices fixed to tlie hull 14 sides or stem or through from inside may be proλ'ided and apparatus Figure 7 of two stem end tracks may be arranged to be able to be moved down and up veitically as needed to contact the land and balance tlie boat and be remoλ'ed λλ'hen λvater borne. Alternatively, frack belt 10 Figure 2 may be located on down to the ground hull 14 permanent hull extensions.

Additionally according to the invention the craft to λλ'hich track apparatus for on land t -el is added may have secondary means such as a rolled up device (not shown) able to be laid out in front of and beneath tlie belt 10 when moving onto land.