This invention relates generally to marine crafts and more particularly to marine craft hull stabilisation. More specifically, although not exclusively, this invention relates to marine craft hull stabilisation elements and direction control systems.

High performance marine crafts that operate in challenging environments are subject to extreme external forces that often cause a reduction or even loss of effective direction and manoeuvring control. This can be dangerous for the crew, particularly in military applications.

Existing stabilisation systems often include stabilisation elements in the form of tubes that extend along at least a portion of either side of the craft. While these elements are generally quite effective, the means by which they are mounted to the hull of the craft are generally cumbersome and are prone to damage or failure.

Such known systems generally consist of a pneumatic tubular element fastened to a boat hull by inserting shaped parts of the tubular elements in linear guides that run longitudinally of the boat hull and follow the hydrodynamic profile of the periphery of the hull. These tubular elements extend along the flank of the hull and are designed to increase safety and stability of the craft as well as mitigating shock and/or damage that may result from minor collisions. The linear guides must therefore be shaped to conform with the hull of the marine craft, which can be difficult where such guides are manufactured separately and installed on the hull after its manufacture.

EP1514793 seeks to address these drawbacks by providing a process of embedding the guide within the hull as it is moulded. Whilst this approach simplifies the manufacturing process, installation of the tubular elements in use can be difficult and time consuming.

It is therefore a first non-exclusive object of the invention to provide a marine craft stabilisation system that is simplifies the installation of stabilisation elements.

Hydrojet propelled marine crafts, which are increasing in popularity, provide many advantages over propeller driven crafts. They provide higher power density thereby facilitating the provision of smaller units, increased manoeuvrability especially in shallow- water operations, reduced noise and improved safety because the rotor is protected. However, hydrojet propulsion systems rely on the force generated by the jet to turn and therefore suffer from poor manoeuvrability at lower jet flow rates.

It is therefore a second non-exclusive object of the invention to provide a marine craft control system with improved directional control.

It is a further non-exclusive object of this invention to at least mitigate the aforementioned issues associated with known stabilisation systems. It is a more general non-exclusive object of the invention to provide an improved stabilisation system and hull that incorporates such a stabilisation system.

Accordingly, one aspect of the invention provides a marine craft stabilisation system comprising a buoyancy element with first and second elongate connection elements extending along at least a portion, preferably most or substantially the whole of, the buoyancy element and a substantially flat and/or planar plate for incorporation in or securement to a recess in the side of the hull of a marine craft, the plate having upper and lower elongate and substantially straight connection elements extending along the plate, wherein the first and second connection elements are configured to cooperate, in use, with a respective one of the upper and lower connection elements to retain the buoyancy element within the recess of the marine craft.

The provision of a flat and/or planar plate facilitates substantially the installation and removal of the buoyancy element when replacement or repair is required.

One of the upper and first connection elements and/or one of the lower and second connection elements preferably comprises a female connection element and/or includes or incorporates a guide or slot or keyway with or within which the other cooperates or is received, such as in a sliding manner or engagement. The other of the upper and first connection elements and/or the other of the lower and second connection elements may comprise a male connection element and/or a bolt rope, for example an extruded section with a web or neck portion and an enlarged portion or free end such as a flange or cord or head, e.g. a continuous enlarged portion or free end or flange or cord or head, e.g. for receipt within and/or engagement with the guide or slot or keyway.

The connection elements may be configured as a snap fit, but in a preferred embodiment each of the upper and lower connection elements of the plate comprises a guide or slot or keyway within which a respective one of the first and second connection elements of the buoyancy element is received, e.g. slidably received. Each of the upper and lower connection elements more preferably comprises an open end or interruption or gap in the guide or slot or keyway at or adjacent one end, for example a front end with respect to the hull, e.g. for insertion of a respective one of the first and second connection elements. The upper and lower connection elements may be formed integrally with the plate, but are preferably connected or fixed or secured thereto, for example by one or more or a plurality of fasteners such as screws, e.g. along its length. The first and second connection elements may be secured to or formed integrally with the buoyancy element.

Preferably, the buoyancy element is tubular and may be inflatable, for example by an inflation means or compressor or accumulator in or of the marine craft, and may comprise an inflation valve or connector such as for connection with or to an inflation connector of the marine craft, e.g. for inflation after the buoyancy element is installed in the recess.

In some embodiments, the buoyancy element comprises an unconstrained cross-section that is substantially circular, wherein the buoyancy element may deform, in use, to correspond substantially to the shape of the recess. In other embodiments, the buoyancy element may comprise a flattened or straightened portion or a substantially flat or planar plate portion that may be stiffer or more rigid than the rest of the buoyancy element, e.g. between or interconnecting the first and second connection elements, for example to cooperate with or correspond to the plate. In such embodiments, the buoyancy element may also comprise substantially flat upper and lower portions and/or the buoyancy element may have an unconstrained cross-section that is substantially in the shape of a D or rectangular.

The plate is preferably rigid, although it may be flexible, and/or may be formed integrally with the hull or as a separate part and secured to the hull, for example by one or more fasteners.

A second aspect of the invention provides a marine craft comprising a stabilisation system as described above. The marine craft may comprise any one or more of the preferable or optional features described above. The marine craft preferably comprises a hull with a recess in a side or flank of the hull within which the substantially flat and/or planar plate is incorporated or secured, for example at an innermost position of the recess, e.g. on or to form a base of the recess. Preferably, the recess is substantially rectangular and/or includes one or a pair of right angles at or adjacent its base and more preferably comprises a right angle along one or each of upper and lower edges of the plate. The recess may comprise an upper portion or wall, e.g. for engaging or contacting an upper portion or surface of the buoyancy element, which upper portion or wall may be outboard of a lower portion or wall thereof, for example such that a lower portion or surface of the buoyancy element is at least partially exposed.

In a particularly preferred embodiment, the upper portion or wall of the recess extends beyond a central point or plane of the buoyancy member and/or is configured to engage or contact most of the upper portion of the buoyancy element, such as more than 50%, for example more than 55%, e.g. more than 60% or 65% or 70% or 75% or 80% or 85% or 90% or 95% thereof.

The marine craft may further comprise a hull extension that may extend from a portion of the hull adjacent the recess, for example the upper portion or wall of the recess, and/or may extend outwardly and/or downwardly such as to at least partially surround or encase the buoyancy member. The hull extension may be configured to provide a low radar return.

The marine craft may comprise a pump jet or hydrojet and/or a rudder, which pump jet or hydrojet may comprise a steering or adjustable nozzle that may be configured for directing, in use, a jet of water. The rudder may be spaced from the pump jet or hydrojet positioned substantially outside of the path of the jet and/or positioned to redirect the hydrodynamic flow across the hull and/or substantially outside of the jet of pumped water directed by the nozzle, for example to provide improved manoeuvrability.

A third aspect of the invention provides a marine craft propulsion and direction control system comprising a pump jet or hydrojet and a rudder, the pump jet or hydrojet comprising a steering or adjustable nozzle for directing, in use, a jet of water, wherein the rudder is spaced from the pump jet or hydrojet and/or positioned substantially outside of the path of the jet and/or positioned to redirect the hydrodynamic flow across the hull.

The use of both a pump jet or hydrojet and a rudder provides a synergistic improvement in the manoeuvrability of the marine craft, particularly when it is coasting. Preferably, the system further comprises a controller or control unit, for example that is operatively connected to a user or driver input, which may include an accelerator and/or a steering element or wheel. The controller or control unit may be operatively connected to the pump jet or hydrojet and/or to the rudder, e.g. to control simultaneously the steering or adjustable nozzle and/or the rudder. More preferably, the controller or control unit comprises an electrical or electronic controller or control unit. The controller or control unit may be configured to control simultaneously the motion and/or direction of the steering or adjustable nozzle and the rudder according to a predetermined relationship that may vary, e.g. with a speed of the marine craft or with a flow rate through the nozzle.

In some embodiments, the controller or control unit may be configured to prevent or reduce the movement or adjustment of the nozzle and/or use or rely on adjustment of the rudder, e.g. in response to a command received by the input element, for example in conjunction with a measured speed or an accelerator input, e.g. when the measured speed and/or accelerator input increases or decreases or is below or above a particular threshold.

Additionally or alternatively, the controller or control unit may be configured to control the nozzle and rudder independently, for example to enhance the maneovrability of the marine craft.

The propulsion and direction control system may comprise two or more pump jets or hydrojets and/or two or more rudders.

A fourth aspect of the invention provides a marine craft comprising the propulsion and direction control system described above. The pump jet or jets or hydrojet or hydrojets preferably extend from the rear or a rear portion or stern of the hull or craft, for example rearwardly. The rudder or rudders preferably extend from the rear or a rear portion or stern of the hull or craft, for example downwardly.

The marine craft may comprise a pair of pump jets or hydrojets that may be positioned side by side, for example with the rudder extending downwardly from the hull laterally therebetween. In some embodiments, the marine craft comprises a pair of rudders extending downwardly and/or outwardly from the hull and/or positioned laterally outwardly of the pump jet or jets or hydrojet or hydrojets. The or each pump jet or hydrojet preferably comprises a tail pipe, for example to which the nozzle is movably or pivotably mounted, and/or a jet deflector element or bucket, which may be movably or pivotally mounted to either the tail pipe or the nozzle, e.g. for movement between a retracted or raised position and/or a deployed or lowered position. The jet deflector element or bucket may be substantially outside the path of the jet when in the retracted or raised position and/or may deflect the jet when in the deployed or lowered position, for example to provide the craft with reverse thrust. The jet deflector element may comprise two portions, e.g. for deflecting respective portions of the jet, e.g. in different directions.

Further aspects of the invention provide a method of manufacture and/or installation of the systems or buoyancy member described above.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a partial perspective view of a marine craft incorporating a stabilisation system according to a first embodiment of the invention;

Figure 2 is a partial perspective view corresponding to portion A of Figure 1 of the elongate connection elements illustrating the insertion of the bolt rope into the guide;

Figure 3 is a partial cross-sectional view of the stabilisation system of Figure 1 with the buoyancy element installed;

Figure 4 is a partial cross-sectional view of a stabilisation system according to a second embodiment of the invention;

Figure 5 is a rear perspective view of a marine craft incorporating a propulsion and direction control system according to an embodiment of the invention; and

Figure 6 is a rear perspective view of a marine craft incorporating a propulsion and direction control system according to an alternative embodiment of the invention.

Referring now to Figures 1 to 3, there is shown a marine craft 1 with a stabilisation system 2 according to one embodiment. The stabilisation system 2 includes a buoyancy element 3 and a substantially flat and/or planar plate 4 incorporated in a recess 10 in the side of the hull 1 1 of the marine craft 1.

The buoyancy element 3 is tubular and includes first and second elongate connection elements 30, 31 extending along substantially the whole of its length and an inflation valve (not shown) for connection to an inflation connector 12 of the marine craft 1 when the buoyancy element 3 is installed in the recess 10. The marine craft 1 includes a compressor (not shown) for providing high pressure air to inflate the buoyancy element 3. Each connection element 30, 31 is a bolt rope in this embodiment that is in the form of an extruded section having a web or neck portion 32 and an enlarged head portion 33.

The plate 4 includes upper and lower elongate and substantially straight connection elements 40, 41 extending along its length adjacent respective upper and lower edges thereof. Each connection element 40, 41 includes a mounting plate 42 and a guide 43 in the form of a C-shaped channel section for receiving the head portion 33 of a respective bolt rope 30, 31. The mounting plate 42 includes a plurality of holes 44 along its length for receiving screw fasteners 45 that secure the connection elements 40, 41 to the plate 4. The guide 43 of each connection element 40, 41 also includes an interruption or gap 46 in a portion thereof adjacent the front end of the hull 1 1 .

The plate 4 is incorporated in the recess 10 in the hull 1 1 such that it forms an innermost base thereof. The recess 10 is substantially rectangular in shape with a right angle along each of upper and lower edges of the plate 4 and includes a lower wall 46 extending perpendicularly from the lower edge of the plate 4 and an upper wall 47 extending perpendicularly from the upper edge of the plate 4 and outboard of the lower wall 46.

In use and with the buoyancy element 3 in a deflated condition (not shown), a rear end of the bolt ropes 30, 31 are inserted into the gap 46 in the guide 43 and slid therealong so that the head portion 33 of a respective bolt rope 30, 31 enters and engages the guide 43 to the rear end thereof. With the bolt ropes 30, 31 fully installed in the connection elements 40, 41 of the plate 4, the inflation valve (not shown) is connected to the inflation connector 12 of the marine craft 1 and the buoyancy element 3 is inflated.

In this embodiment, the buoyancy element 3 has an unconstrained cross-section that is substantially circular as illustrated by line 34 in Figure 3. However, the shape of the recess 10 causes the buoyancy element 3 to deform to correspond substantially thereto. Thus, the upper wall 47 contacts and engages an upper portion of the buoyancy element 3 with the majority of the lower portion of the buoyancy element 3 exposed by virtue of the upper wall 46 being outboard of the lower wall 47. As shown in Figure 3, the upper wall 47 of the recess 10 extends beyond the central vertical plane of the buoyancy member 3 and is configured to contact and engage most of the upper portion of the buoyancy element 3, which provides improved stability in use.

Figure 3 shows an optional hull extension 12, illustrated by dashed lines, that is configured to provide a low radar return. The hull extension 12 extends from the upper wall 47 of the recess 10 outwardly and downwardly to surround or encase an outer portion of the buoyancy member 3.

Referring now to Figure 4, there is shown a stabilisation system 102 according to a second embodiment of the invention similar to the first embodiment, wherein like references depict like features and will not be described further. This stabilisation system 102 differs from the stabilisation system 2 according to the first embodiment in that the buoyancy member 103 includes a plate portion 140 that is stiffer than the other walls thereof such that it has an unconstrained cross-section that is substantially in the shape of a D.

The bolt ropes 30, 31 are also replaced with rigid connection elements 130, 131 configured to provide a snap fit with the guides 40, 41 of the plate 4. As with the bolt ropes 30, 31 of the first embodiment, each of the rigid connection elements 130, 131 is in the form of an extruded section having a web or neck portion 132 and an enlarged head portion 133.

Referring now to Figure 5, the marine craft 1 includes two pump jets or hydrojets 5 in combination with a rudder 6 to provide a more stable propulsion and direction control system. The hydrojets 5 extend rearwardly from the stern of the hull 1 1 , while the rudder extends downwardly from a rear portion of the stern of the hull 1 1 in a position that is spaced from the hydrojets 5 and substantially outside of the paths of the jets.

Each hydrojet 5 includes a steering nozzle 50 pivotally secured to a tail pipe 51 and a deflector element or bucket 52 pivotally mounted to the tail pipe 51 for movement between a retracted or raised position as shown in Figure 5 and a deployed or lowered position (not shown) in which the jet is deflected to provide the craft 1 with reverse thrust. The deflector element 52 includes two portions 52a, 52b that deflect respective portions of the jet in different directions.

The hull includes a cockpit 13 on an upper deck 14 and a base portion 15 with a substantially V-shaped lateral cross-section defining a pair of flanks 16a, 16b. The rudder 6 is a hydrofoil that is substantially rectangular in plan with a longitudinal shaft 60 that is rotatably secured to the lowermost point of the V-shaped base portion 15 of the hull 1 1 . The rudder 6 extends downwardly from the base portion 15 for selectively redirecting the hydrodynamic flow across the hull 1 1 to change the direction of the craft 1 in use.

In use, the jet of water from the pump jet 5 is diverted by pivoting the nozzle 50 to propel and manoeuvre the water craft as with known pump jet water crafts, but the inclusion of the rudder 6 provides improved manoeuvrability. In fact, the inventors of the present invention have observed that spacing the rudder 6 away from the pump jet 5 and outside of the path of the jet emitted therefrom improves significantly the manoeuvrability of the marine craft 1 when it is coasting.

Referring now to Figure 6, there is shown a marine craft 100 incorporating a propulsion and direction control system that is similar to that of Figure 5, wherein like references depict like features that will not be described further herein. The marine craft 100 according to this embodiment differs from that of the first embodiment in that it includes two rudders 106a, 106b positioned laterally outwardly of the hydrojets 5.

Each rudder 106a, 106b extends substantially orthogonally from a respective one of the flanks 16a, 16b, extending at an angle of substantially 45 degrees with respect to the vertical. This arrangement provides greater manoeuvrability than the single rudder arrangement and is able to operate in shallower waters.

The marine crafts 1 , 100 both include an electronic controller (not shown) operatively connected to an accelerator (not shown) and a steering wheel (not shown) in the cockpit 13, the hydrojets 5 and the rudder 6 or rudders 106a, 106b. The controller (not shown) is configured to control simultaneously the motion of the steering nozzle 50 and rudder 6 or rudders 106a, 106b according to a predetermined relationship that varies with the speed of the marine craft 1 , 100 and with a flow rate of the water jet exiting through the nozzles 50.

It will be appreciated by those skilled in the art that several variations to the above specific embodiments are envisaged without departing from the scope of the invention. For example, the connection elements 30, 31 , 40, 41 and 130, 131 , 140, 141 may be of any suitable form or configuration, the buoyancy element may be of any suitable shape, the propulsion system may comprise only one or a plurality of pump jets 5 and/or a plurality of rudders 6.

It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.