AU767485B2 - Further improvements to marine hull - Google Patents

Description

Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant: LFoiA~R JEFI-Fk5OrI 3

-LE

Actual Inventor s: EL E(VtA~ R J E r RSIV &4ft~SS FOR SERVICE_ *Address for Service: 6 6 i4?-'Aff A,1' re :P Asa 4Riq& Invention title: 10 'D:PQ~ AA RE Details of Associated Provisional Application No(s): PPR 59q87 The following statement is a full description of this invention, including the best method of performing it known to me/us.

FIELD OF THE INVENTION This invention relates to improved marine hull designs to give improved sea worthiness and efficiencies.

BACKGROUND OF THE INVENTION In my previous patents, namely Australian Patent No. 574872 entitled Marine Hull, Australian Patent No. 610094 entitled Improvements to Marine Hull, and US Patent No. 5031556 entitled Marine Hull, novel improvements are described and claimed for craft incorporating at least one pair of downwardly facing channels which diverge horizontally and rearwardly with respect to its vertical longitudinal plane.

While such craft are much superior to conventional, further experimentation and sea testing with prototypes has revealed some areas needing improvement.

15 Patent No. 574872 claimed a hull wherein the diverging channels impart lift over a major portion of the hull and this is of great value in still water.

However, because higher channels must be always located forward of the lowest set in contact with water while in motion it follows that when the craft meets a wave, the 20 lift distribution is changed such that the forward and usually lighter portion of the craft gains more lift than the stern. As most craft have ample lift available in the form of added buoyancy on meeting a wave, any additional lift is undesirable and eeeee can result in the craft being forced airborne.

25 Patent 574872 also indicated that the forward sections of the channels forced the exiting water very much "downwardly close to the hull so it cannot be blown back inside the boat".

Sea tests generally substantiated this principle most of the time but on some occasions, not necessarily windy, spray would enter the craft in very large quantities.

This clear distinction between no spray and extreme quantities of water with little in between was researched at length and finally with the aid of high speed cameras it was revealed that water leaving upper channels near the bow travelled downwardly to the sea surface where it appeared to be reflected upward with great efficiency, sometimes to a height of tens of metres.

On reflection this discovery is believed to be similar in principle to the effect observed when a drop of water falls onto a still water surface, initiating a rising drop of similar magnitude.

I realised that this occurrence needed to be stopped in the bow area and in general wherever the craft's surfaces diverged greatly or were capable of displacing large volumes of water, in order to minimise spray.

However, I realised that the lowest channel pair active or in contact with the water surface might be possibly arranged to generate a similar phenomenon.

I reasoned that if the diverging channels of my first prototypes could be modified such that water forced downward resulted in water rising vertically to impact the craft and give up energy, greater lift might be attained for no additional input power.

20 Further, I reasoned that if the rising water could be arranged to occur just in front of an approaching hull surface, the channel might, in effect, reuse its spray many times and the process might be regenerative provided the channels were not allowed to eeeee choke with water.

25 A prototype was constructed to utilise and demonstrate the effect and many failures and much sea testing has recently revealed the geometry required. A prototype craft indicated efficient use of power whilst physical location of water deflecting surfaces was well in front of the centre of gravity of the craft indicating aft lift is obtained without conventional deflection of water. It is found that once the phenomena has been initiated, any surface under the stern of the craft spaced a short distance above the sea surface can be utilised to capture some of the lift with minimal drag and while a generally horizontal surface gives good results, arranging for this water to enter a channel is more effective.

I have found that a certain combination of channel divergence, angle, operational height of the channel above the sea surface, channel cross-section shape and water departure angle is required to maximise the lift.

Also, if the channel pair and essentially the uppermost downwardly curved portion of surface of that channel pair rises slightly from front to rear the channel is not only less likely to choke with water but the craft's motion through choppy water is smoothed greatly by allowing peak pressure water to escape rearwardly. A limiting and optimum rate of rise is affected by the angle of divergence of the channel pair.

In one form the invention is said to reside in a water vehicle wherein a water engaging region thereof has a forward portion, a rearward portion and intermediate surfaces between the forward and rearward portions; the forward portion including at least some forward surfaces being operable in use to at least in part minimise lifting forces generated by water displaced by the forward surfaces when the vehicle is in motion; 20 the rearward portion including at least some rear surfaces having at least S some portions thereof in contact with water and operable in use to define a constant lateral cross-sectional area of water displaced when taken along a longitudinal centre line of said vehicle; the intermediate surfaces between the forward and rearward portions at least in part being operable in use to define an increasing lateral cross-sectional area of water displaced by the intermediate surfaces when taken from front to rear of the vehicle when the vehicle is in motion, and the intermediate surfaces being bounded by at least one channel pair, each S. channel of the channel pair comprising at least in part a downwardly facing concave surface.

BRIEF DESCRIPTION OF THE DRAWINGS To assist with understanding of the invention reference will now be made to the drawings in which: Fig. 1 shows a bottom view of a hull according to one embodiment illustrating channels and fluid flow paths; Fig. 2 is a side view of the embodiment shown in Fig. 1; Fig. 3 shows a lateral part cross-section of the channels of the embodiment shown in Fig. 2; Fig. 4 shows a preferred part cross-section of the forward portion of the embodiment shown in Fig. 2; Fig. 5 shows a bottom view of a boat hull of an alternative embodiment illustrating one stern arrangement; Fig. 6 shows a stern view of the embodiment shown in Fig. Fig. 7 shows a side view illustrating a forward portion, an intermediate portion and a rearward portion of a boat hull of an alternative embodiment of the invention; Fig. 8 shows a bottom view of the embodiment shown in Fig. 7 illustrating a S• recessed mounting for a motor; *0 Fig. 9 shows a stem view of Fig. 7 illustrating flooding chamber apertures; Fig. 10 shows side and plan views of an aperture in a channel surface with conduit, valve means and sensor responsive control means; Fig 11. shows a side and plan view of an aperture in a hull surface; Fig 12 shows a part of a boat hull in plan, cross section and elevation views of a hole arranged to provide lift; Fig 13 shows an alternative part of a boat hull in plan, cross section and elevation views of a hole arranged to provide lift; Fig 14. shows a lateral part cross-section of a boat hull with a channel aperture, conduit and flooding chamber; Fig 15. shows a lateral part cross-section of a boat hull with a channel aperture with connecting chamber; Fig 16. shows a lateral part cross-section of a boat hull with a channel "gill" 15 aperture and connecting chamber; Fig 17 shows a part side view of a hull with a "gill" aperture; Fig 18. shows a bottom view of a hull of an alternative embodiment of the invention with conventional motor mounting; Fig 19. shows a part side view of a hull with a channel in side view with 20 surface interruptions; Fig 20. shows a top view of a hull having "gill" apertures; Fig 21. shows a top view of Fig. 20 with accommodation layout; :"Fig 22. shows a side view of a hull including a perimeter deflecting surface and a flooding chamber arrangement; S" 25 Fig 23. shows a stem view of prior art; Fig 24. shows the hull of Fig. 23 modified to have a rear downwardly facing surface and a buoyancy chamber; Fig 25. shows a side view of a conventional craft equipped with a rear downwardly facing surface; Fig 26. shows a stern view of the embodiment shown in Fig. 25; and Fig 27. shows a stern view of the embodiment shown in Fig. 26 with valves.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS To minimise excessive bow lift, my improvements incorporate a forward section of the craft where the angle of divergence of the craft's surfaces in a horizontal plane is deliberately kept minimal and are initiated by a generous curved surface to aid tracking ability rather than the typical fine bow of conventional craft.

Instead of channels being used in this portion of the hull, surfaces much like that shown in Figs. 1, 2 and 4 excel and can include "exit notches" if desired. However, an important departure from that as depicted in US Patent 5031556 is that surfaces 41 do not greatly diverge or meet sharply at the bow Fig. 2 and are generally straight and sharp edged.

The previously patented "exit holes" in the channels if utilised, also smooth the craft's progress especially in random or "lumpy" seas. Should the exit hole be also positioned so that it is not directly associated with an exit hole in a neighbouring channel, smoothness and minimal spray is achieved. This arrangement also enhances mechanical strength.

An improved exit hole 161 is shown in Fig. 19. The previous leading edge 162 shown :i 20 dotted, is replaced by an upwards curvature 163 which simplifies and improves trailer design.

o$°•e Also, the edges of surfaces 41 in Fig 1 may be rounded, such that displaced water is held against the hull by air pressure (a coanda effect) until it loses momentum. In this way, the volume of uncontrolled water is minimised with consequent spray reduction. Craft may not require exit notches if the rounded concave and convex surfaces 41 are generous and flowing as in cross-sectional view Fig. 4.

To aid the bow to recover when deep into a wave the surfaces 41 can rise as they approach the bow with spray and shock being minimised if this is achieved in a continuous three-dimensional curvature or multiple smaller curved surfaces. The application of the coanda effect in a novel way makes the craft easier to manufacture and trailer.

The transition from small divergence to large can be achieved by ending a surface 41 in line horizontally level and suitable width with the open portion of a channel 17 which then diverges rearward and may incorporate an air inlet hole as previous patents describe. This is shown in Figs. 1 and 2. All forward surfaces should have generous curvature with special attention to areas 42 which may need an escape slot 43 with depth increasing rearwardly and ending at an external surface or a channel to dissipate peak forces.

The forwardmost point of each channel can include an exit hole 13 and subsequent ones placed along the channel. The forward end of the channel curve 18 can slope upwards to an air conduit to aid and ease fluid flow as shown at 9 in Fig. 2.

In my first Patent 574872 I recognised the potential benefit of water leaving the channels in a near vertical downward direction to recover maximum kinetic energy of the displaced water, and proposed angling surfaces inwardly and downwardly.

Such a device can also aid in positioning the rebounding water with respect to the "20 approaching hull surfaces to maximise the regenerative effect. However, this arrangement makes production difficult and more expensive tooling is required.

°o..oi I have found that an arrangement shown in Figs. 1 and 3 will also produce the result with less difficulty. By increasing the radius of curvature of the surface 16 between channels and decreasing distance between exit holes, a surface 15 can be generated which is essentially diverging less than the channels and can be made parallel or converge with respect to the centre line of the hull in plan. This returns water to the surface which rebounds near vertically with respect to the craft's centre line to facilitate and maximise the phenomenon.

It should be noted that the surfaces 49 in Fig. 2 of Patent No. 5031556 are restricted to a small portion of the channel wall between exit holes and were incorporated to guide water in the channels as it flowed rearward and minimise its escape through aperture 47 when the channels were choked at slow vessel speed.

The previous V-shaped central stern area can be omitted or simplified for some hull applications. In Fig. 1 it is replaced by a rearward rising channel 21 which can open at a rearward step in the hull or at the transom. It preferably contains a step at its forward end incorporating a hole which connects to atmosphere. Multiple steps and/or holes can be of benefit at slow speed and to reduce pounding.

Alternatively, to reduce draught and preserve ride softness, the stern section may comprise a plurality of curved surfaces 51a, as shown in Figs. 5 and 6. Air conduits may be installed as indicated.

Referring to Figs. 7, 8 and 9 a boat hull 61 can be defined a classification of function of sections of a channel or part of the hull at design attitude and speed according to: A-B Maximum buoyancy, minimum divergence and minimum dynamic lift Minimum disruption and water maintained in contact with hull B-C Maximum divergence by increasing cross-section in horizontal or •vertical plane, or both, directly resulting in lift Water displaced into inverted channels to be redirected downwards C-D Minimal variation in cross-sectional area for minimum dynamic displacement of water Captures energy in displaced and reflected water to give lift Concentrates buoyancy to outer hull sections Acts to reduce energy loss at transom The classification may differ for surfaces at different heights at a particular crosssection.

To minimise overall storage length on trailer while maximising seakeeping ability and deck space the motor can be mounted in a recess 63. This forms two pods 79 in Fig. 8 giving buoyancy either side of the motor which greatly enhances stability. At high speed, these surfaces can become non-displacing but at low speeds actively displace and capture energy of displaced water. In this way, the normal extension of the water line forward at lower speeds is matched with aft low speed extension of lift over the pod area allowing heavier four-stroke motors to be used.

The pods may extend sufficiently aft to negate the use of an "over length" flag and light on the tilted motor when trailering. The craft may incorporate trailer lights and number plate pre-wired to a connector in the bow to mate with the towing vehicle.

The forward section is rounded with minimal divergence and contains some recessed portions 64 allowing greater lateral cross sectional curvature of the hull to reduce dynamic reaction to water. Areas 64 may be spray deflecting chines but preferably have large convex and concave rounded edges (Fig. 4) to utilise the coanda effect to constrain and deliver water to inverted perimeter strake or channel 62.

In section B-C these can merge in to inverted diverging channels 60 mounted high in the :.2D hull and exiting the side perimeter at point C or to the transom. These are positioned to capture water from the peaks of highest wave intended to be regularly encountered and lift is generated in section B-C which can locate the centre of gravity. Lower main channels diverge in plan over section B-C and tend to be more parallel over C-D to exit the rear of the craft. The channels can rise rearwardly upward and contain one or more exit holes 66 and can positioned to be just above sea level at speed. Again, maximum lift is over B-C with some from C-D.

Inner rear channels 67 can run near parallel and can rise rearwardly in section C-D. Note area 68 contains a cross-sectional area increasing in plan and/or elevation rearwardly o* J (actively displacing) and area 69 is of essentially constant cross-section (non-displacing).

At speeds channels 671 act as exit relief paths and may serve to limit the rate of rotation when the craft is given full rudder turns and may make a varying angle to the centre line to achieve this. Lift from area 68 can be increased at the expense of some degree of ride softness by decreasing the transverse curvature of this lower surface. This tends to increase the velocity of escaping water and giving increased lift efficiency (Lift 1mV 2 Lift efficiency is also improved by using a deeper section in this curve to act on deeper water that has less ease in moving into the surface areas.

Thus in this configuration, displaced water containing maximum energy will tend to emerge near point C and conveniently may enter the more parallel and efficient channel portions over C-D. Also, this arrangement helps maintain the position of centre of lift with differing speeds and loads.

It may be required to vary the lift generated by a channel along its length to improve 15 balance of lift at a particular speed range.

To decrease lift less angle of divergence can be used so that less lift in the bow has S" channels closer to parallel or at the stern channels curve in plan to run more nearly 99 9° parallel. Conversely, increased lift is given by a section of the channel having an 20 increased divergence angle over that portion and displacing more water into the channel.

9 Also, the water exit direction from the channel provides maximum lift when angled vertically downwards and a minimum when allowed to exit upwardly.

The rate at which channels rise vertically as they extend rearwardly can also be varied and increased rate of rise gives less lift. Any rise rearwardly must be compensated by increased divergence for lift to be maintained.

Another lift enhancing technique is to increase the cross-sectional area and bulk of the hull between each inverted channel towards the stem.

This can be achieved by rearwardly lowering the bottom channel edge with respect to its top curvature resulting in the top of the next lower channel to appear more recessed or by successively increasing divergence between successive channels towards the stern giving more bulk in the cross-section or a combination of both.

For instance, the top curvature of a channel may rise rearwardly while the lower edge may lower rearwardly, displacing more water into the next channel giving more lift.

This can occur over a portion of or over the whole channel length.

Much interest has been given to an apparent increase in outboard motor efficiency when mounted on an extension or pod rather than the normal transom mount.

e 15 My research has indicated this phenomenon is due to a change in propeller efficiency Deeo which is decreased if variations in water velocity (fore to aft) occur over the blade swept area.

De 0 At the transom, water which preferably should support the craft or emerge at the 20 chines takes an easier escape route which is essentially aft. To do this it gains aft velocity (and thus kinetic energy) in relation to boat motion and also to the static water. This occurs in the thin volume of water immediately adjacent to the hull aft underside of the craft which emerges at the surface. Thus by increasing the length of the escape route by employing the non-displacing portion C-D, a resistance to high 25 speed surface flow is generated in cooperation with the greater water mass.

This not only minimises energy otherwise lost by water escaping rearwards, but encourages a new escape path near point C and leading into the efficient parallel channel portions.

This is further enhanced by the shape of intersecting surfaces 100 of B-C and C-D if the transverse curvature of B-C is flatter than C-D which can be near semi-circular, Fig. 18. In conventional marine design any curvature or variation of running surfaces mid to aft B-D) is strictly avoided as it acts to reduce speed and may result in porpoising.

My recent research indicates hull surface drag has minor effect when compared to the volume of water disturbed by the hull. This is in contrast with my previous Australian Patent No. 574872 which describes a modification to the shape of 13 in Fig. 8 "to prevent excess water which would not be caught by curve 18 (Figs. from being forced upward", and in which Fig. 6 shows a shelf 24 forward of the transom arranged to clear the water and reduce wetted area at speed.

The new parallel portion C-D is different in that it is much longer than that of the previous patent's requirement and in direct contrast to reducing wetted area of the hull at speed.

1. 0 High speed photography has shown mist or spray can be generated by exit holes of patent 5031556 under infrequent conditions or should the craft be overloaded.

An improved and novel arrangement to soften the ride is shown in Figs. 14, 15, 16 20 and 17.

At least one aperture 142 is included in the channel 141 such that water moving freely upward does not normally enter. It may take the form of round holes but a slot has advantages in minimal interruption to water flow and ease of manufacture.

The apertures may connect with chamber 143 running lengthwise and if extending to the stem, may include an aperture which can pass air, water, or both.

It may also connect via one or more conduits 144 to the flooding chamber 145, allowing fluid passage and structural stiffness.

On hitting a wave, water and spray pass at a controlled rate through the aperture 142 as the lower open face of channel 141 becomes closed off by the wave. However, unlike exit holes, spray is contained within the craft and in the case where the craft is rising from deep in a wave, fluids can pass from chamber 143 or 145 and conduit 144 through 142 to reduce suction effects on the lower hull surfaces.

Similarly, a gill-like vertical opening in the channel surface at 142 in Fig 17, rearwardly fairing into that surface can be utilised to pass fluid.

In Figs. 7,8 and 9 a flooding chamber 71, which may be similar to my previous patents, admits water through holes 72 and 74 at rest with air passing holes 73. A one-way valve 75 replacing orifices 73 can prevent return air flow into the flood chamber and water loss while holes 72 and 74 are submerged. At rest, movement of the craft in waves encourages water entry only into chamber 71 even above the static water line. This can enhance stability and can simplify support of the floor. The valve 75 can be fitted with an override which can usefully be operated when the motor is in a tilted position. Thus water can exit freely when loading on to the e trailer. An arm connected to the valve and moving with motor tilt may be used.

S 20 In Fig. 22 holes 72 and 74 can be improved by angling and/or recessing the hull near the transom. This allows the holes to be vertically moulded instead of cutting the ooeoe S. transom after manufacture. Hole 74 allows air entry at speed and holes 72 can act as a venturi and suck water from a flooding chamber 57, 58. Recess 76 can mate with a eooee mount on the trailer for secure positioning when on land.

It can be usual and of no major detriment for water to flow out holes 72, 74 during normal operation.

If the flooding chamber is of generous width near the fore and aft midpoint it can be used as a pivot to counter any change in bow or stem height with load. In this case the height of the chamber at the stern is at or just below sea level at rest. A drop in bow or stern height transferred through the midpoint pivot tends to raise the opposite end of the chamber which loses the support through buoyancy and raises a mass of water. This is novel over previous use to set up fore and aft trim.

To maximise this concept the flooding chamber may take the form in Fig. 27 (stern view) where an upper portion of the chamber 201 extends over the beam of the craft.

If the floor 202 is to be self draining through one way ball valve 203, a shield 204 can be used to confine any air brought in, and buoyancy chambers 205 can be used. The floor 202 extends across the craft at water level or just above and can usefully have a depressed centre.

One way valves 206 purge air from chamber 201 during normal movement at rest and conduits 207 prevent water entry internal to the craft.

Should increased load be placed on one side, some lateral lean is initiated and using the buoyancy on that side and centre of the craft as a pivot, the opposite side tends to rise bringing some water upward. The extra weight of this water cooperating with increased lift from buoyancy on the other side greatly enhances the lateral stability of the craft.

20 A similar effect can be produced longitudinally to enhance fore to aft stability.

.000.: S A similar effect can be retrofit achieved or used with dissimilar materials e.g. plastic and aluminium by making the chamber modular and providing drain connections S 208 through the parent hull. In this case the chamber portion 209 may not join the .ee..i hull surfaces at the bottom and chamber portion 201 may consist physically of 0. lengthwise chambers at the periphery connected by conduits to a central chamber portion 209..

However, in craft such as shown in Figs. 1 through 9 it is especially convenient within the plan area 111 of the flooding chamber, holes 113 with edges and sides arranged to reduce entry of water during motion may be placed at points of peak pressure, i.e. where the hull appears to hit the water hard, to soften the ride. A hole is shown in Figs. 11 where the pipe 112 can be added to usefully rise to the static water level to reduce water flow. Elsewhere the hole may connect via a conduit to exterior. The hole may take the form of a slot or a groove leading to a conduit or opening as shown by 43 in Fig. 1.

If the hole is required to be in a surface portion of the hull that generates direct lift, the hole can take the form of that shown in Fig 12 where an inclined surface 150 is located to intercept and redirect water flowing from an edge 151 which can be a portion of the major hull surface 152. Preferably orientation should be such that a stream line would connect the mid-point of edge 151 and the mid-point of trailing edge 153 at high speed (which may not be directly fore and aft).

Hull edge 151 may include an upwardly curved surface 154 which ends in a sharp edge of an aperture 155 connecting with atmosphere. Curvature 154 acts to decrease water velocity which focuses the water stream to intercept forward portions of surface 150 to enhance lift. Fig 13 shows part bottom and lateral cross sectional views of an enhanced version of Fig 12. Intercepting surface 150 is of a downwardly convex longitudinal shape as indicated by the curved aft intersecting edge 153 with major hull surface 152 which adds strength and softens water impact. The longitudinal vertical edges 156 of Fig 12 are revised into concave surfaces connecting surface 150 with the edge of surfaces 157 which are recessed from major hull surface 152.

Aperture 155 may connect with a flooding chamber or a conduit which allows air to freely pass through the aperture at speed. In operation water over hull surface 151 is redirected by surface 154 such that it intercepts surface 150 which redirects it laterally to surfaces 156 which redirect the water downwardly to generate lift. On impact with the water at a slight lateral angle it is reflected upwardly to impact surfaces 157 to further enhance lift. Benefit is obtained from efficient lifting forces and by shock dissipation should the craft impact the water surface.

The trailer should preferably be no wider than the beam of the craft and by locating the motor in a recess the centre of gravity is moved forward, allowing the trailer wheels forward where the underside of the craft is narrower. The hull may thus sit as low as possible on the trailer and a drop axle or other suspension may allow this.

One application of particular benefit of my invention is to a trailer mounted boat with outboard motor.

Changing lifestyles of the last decade have led to residential houses being constructed on smaller blocks of land leading to people having less room to store a boat.

Referring to the standard minimum dimensions of garages being 2.1 metres high, 2.4 metres wide and 5.5 metres long, allowing 0.5 metres for motor protrusion from stemrn and 0.5 metres for trailer hitch and winch at the bow, a maximum practical boat length of 4.5 metres is obtained. To maximise deck space, a maximum practical width on trailer of 2.3 metres is obtained.

A craft with theses dimensions would be in demand but has never been successfully built with conventional marine technology due to disadvantages of rough ride or deep V instability at rest which increases as the length: beam ratio approaches 2:1.

A boat of one embodiment of my technology to this size is shown in Figs. 20, 21 and 22.

At deck height the hull has a blunt rounded bow of some 1.4 metres beam to maximise forward storage capacity and giving high inherent buoyancy needed in a small craft and increases to 2.3 metres near midpoint and thence to the stern. This large area has a windscreen mounted well forward allowing two seating positions in front of a central helm position and two more slightly further aft. This arrangement has advantages of keeping the load near the fore/aft centre of gravity with easy communication between crew, allowing easy access to anchor from the helm when used single handed, and facilitates seating for three people to fish over the stern.

A lower set of channels 50 containing apertures similar to 142 in Figs 14 through 17 begin near midpoint and diverge rearwardly before becoming parallel and eventually opening out to a short area of large divergence 51 which serves to enhance stability in turns whilst limiting the maximum rate of rotation or turn diameter.

A second channel pair 53 commences higher and slightly more forward and continues to diverge rearwardly and upwardly with increasing cross-section. Several gill slots 142 are spaced along its length and connect fluidly with a central flooding compartment. The channels tend to deepen in proximity with conduits 90, 91 and a surface groove 62, connects with channels 50 to soften ride.

The operation and construction of this flooding compartment shows novelty and improvement of function over previous design. A central longitudinal rib 55 extends from transom to the channel start point where it comprises a T-shape 56 from one hull side to the other. Holes 54 situated in the vertical sides can allow fluid passage 0 to chambers 57 or 58 and the top surface strengthens a floor.

The width of the rib 55 can be about 150 mm and at the transom it can flare outward with increased thickness to join to the transom between the motor mounting holes. If the rib 55 is hollow its lower rearward junction opens rearwardly in front of the motor cavitation plate and allows passage of fluid forward to the T-junction where it communicates with two hollow chambers 57 of changing height, sealed at the rib, Tshape and hull at the upper channel and the inner channel and to rear chambers 58 which can open to the stern.

.:•to The rib provides a central support for the floor and motor, braces the transom and hull, provides with the floor and T-shape torsional stiffness, allows air to replace water at the forward end to provide early air to conduits 90, 91 and the gills 142. The height and volume of the chambers 57, 58 allows the attitude of the craft at rest and its draught to be modified and apertures 54 precisely positioned in rib 55 prioritise drainage in motion. Check valves 59 situated in floor recesses can open to the chamber provide self-drainage of the floor.

The channels 50, 53 can rise at their forward end to join conduits 90, 91 which can be fitted with valve means 93 operable to prevent fluid from passing in order to adjust the attitude of the craft to load or to provide limited steerage function which may be controlled manually or automatically by direction sensing and control equipment 92 to make correction to the craft's course or by sensors and associated equipment responding to sea conditions as shown in Fig. Should minimum draught be required valves can seal the flooding chamber from water entry.

The lower forward hull sections comprise two sets of three-dimensional curvatures either side of a rounded keel section 66 in a gradual rise to an inverted channel 68 at the craft's perimeter to control spray.

oo o On either side a curvature 67 of more horizontal orientation assists in down sea progress and reacts to larger waves by smartly raising the bow.

On either side storage 69 exists between fore and aft seating suitable for a removable ice box.

Fig. 23 shows a stern view of a craft referred to in my previous patents. With an outboard motor cavitation plate at height 80 any steering movement will increase the S" depth of water flowing over that motor plate with an end result that large steering efforts may be required.

Fig. 24 shows a method of minimising any increase in steering effort with steering angle. If the hull bottom had simply been flattened at height 80, drag would increase as a result of the change in effective cross sectional area of the water passing.

If flattened at height 81, a suction would be created. To maintain the overall crosssectional area new protrusions 82 are faired in to increase in cross-section rearwardly as height 80 progresses to height 81 thus compensating for loss of cross sectional area between 80 and 81.

Surface 81 may be concavely contoured to raise motor height and efficiency whilst minimising steering effort and enhancing ride softness.

To enhance a self-righting tendency, a significant buoyancy chamber 85 can be installed on one side of the craft above water line and to coaming height.

This technique can be used with benefit in conventional marine craft to reduce the loss of energy by rearwardly escaping high velocity water.

~In the embodiment shown in Figs. 25 and 26 a conventional monohull 100 has a lower portion 106 removed to leave a somewhat flatter or laterally curved surface 105 Z which may be convex or concave and of shape approximating a triangle. This surface is orientated such that at speed and "on the plane" it is generally parallel to the static water surface. In some craft it may be beneficial to arrange the apex or leading surface portion to be slightly higher than the rear transverse edge to improve overall response.

S

If using outboard power, the cavitation plate should be positioned horizontally near level to the rearward surface edge. When in motion this arrangement can produce a flatter wash, reduced steering load, less power required, reduced draft at speed and greater clearance between power head exhaust ports to water level at rest.

Claims (19)

1. A water vehicle wherein a water engaging region thereof has a forward portion, a rearward portion and intermediate surfaces between the forward and rearward portions; the forward portion including at least some forward surfaces being operable in use to at least in part minimise lifting forces generated by water displaced by the forward surfaces when the vehicle is in motion; the rearward portion including at least some rear surfaces having at least some portions thereof in contact with water and operable in use to define a constant lateral cross-sectional area of water displaced when taken along a longitudinal centre line of said vehicle; the intermediate surfaces between the forward and rearward portions at least in part being operable in use to define an increasing lateral cross-sectional area of water displaced by the intermediate surfaces when taken from front to rear of the vehicle when the vehicle is in motion, and the intermediate surfaces being bounded by at least one channel pair, each channel of the channel pair comprising at least in part a downwardly facing concave surface.

2. A water vehicle as in Claim 1 wherein the forward portion includes more than one pair of convex surfaces defining an outwardly convex lateral cross- section taken normal to the vehicle stem or keel profile at that point, said convex surfaces being connected by forward joining surfaces.

3. A water vehicle according to Claim 1 or 2 wherein the intermediate g surfaces intercept and displace water when the vehicle is in motion, said displaced water entering the channel pair wherein said displaced water is redirected downwardly such that lift is imparted to the vehicle.

4. A water vehicle according to any one of claims 1 to 3 wherein one channel of said channel pair defines a rearwardly divergent angle with a second of the channel pair over some portion of the channel pair length.

5. A water vehicle according to any one of claims 1 to 4 wherein at least one said channel pair opens rearwardly to stern or sides such that water is free to discharge unimpeded.

6. A water vehicle according to Claim 4 wherein said rearwardly divergent angle varies over some part of said channel pair length.

7. A water vehicle according to any one of claims 1 to 6 wherein the downwardly facing surfaces of the channel pair define a rearwardly increasing angle with respect to the water surface over some portion of the channel pair length when the vehicle is in motion.

8. A water vehicle according to Claim 2 wherein at least some of the forward convex surfaces and forward joining surfaces define a shape operable in use to maintain the displaced water in contact with said vehicle surfaces.

9. A water vehicle according to Claim 8 including a redirecting surface, said redirecting surface extending over at least some perimeter surface of the vehicle, said redirecting surface being operable to limit the rise of said displaced water in contact with the vehicle.

A water vehicle according to Claim 1 or Claim 2 including at least one chamber, said chamber having at least two apertures. 0:6:

11. A water vehicle according to Claim 10 wherein the chamber is defined by walls and at least a portion of said walls include a structural member.

12. A water vehicle according to Claim 11 wherein at least some portion of said walls is operable to structurally locate propulsion means.

13. A water vehicle according to Claim 10 wherein the lateral cross-section of said chamber varies from fore to aft to determine static vehicle trim.

14. A water vehicle according to Claim 10 wherein said chamber and said apertures are operable to admit water at rest and allow water to drain when in motion.

A water vehicle according to Claim 1 or Claim 2 wherein the intermediate surfaces include at least one aperture having at least one adjacent surface co- operable with the aperture to restrict water ingress into the aperture when the vehicle is in motion.

16. A water vehicle according to Claim 1 or Claim 2 wherein the at least one channel includes at least one aperture having at least one adjacent surface co- operable with the aperture to restrict water ingress into the aperture when the vehicle is in motion. :.0

17. A water vehicle according to Claim 1 or Claim 2 wherein the rear surfaces include at least one aperture having at least one adjacent surface co-operable with the aperture to restrict water ingress into the aperture when the vehicle is in motion.

18. A water vehicle according to Claim 15, 16 or 17 wherein the at least one S aperture connects to a chamber.

19. A water vehicle according to any one preceding claim including a power unit mounting structure, said structure being located within the static water line plan of said vehicle at rest. A water vehicle according to any one preceding claim including a central helm position and accommodation surrounding. Dated this 11 th day of September, 2003. LEONARD JEFFERSON BLEE By his Patent Attorneys MADDERNS 0* S 'S