TECHNICAL FIELD

The invention relates to a watercraft with at least one hull using narrowing concave channels with water propulsion.

BACKGROUND OF THE INVENTION

A goal of naval engineering is to achieve higher speeds and achieve greater fuel efficiency. Usually this is achieved by reducing hydrodynamic drag in the water and one of the best known ways to do this is to decrease wetted surface of the hull which implies hydrodynamic lift is required.

Prior art on planing hulls achieve hydrodynamic lift by presenting a surface angled slightly upward to horizontal which forces water downward thereby creating hydrodynamic lift as the said hull moves forward through the water. This concept of hydrodynamic lift is proven only to work efficiently for relatively small watercraft with low displacement hulls. Presenting an inclined surface as the hull moves forward through the water has two components of force: the first component pushes water downward and results in a reactionary upward force on the said hull; the second component pushes water forward which creates a 'bow wave' which larger planing vessels are unable to climb over without massive amounts of propulsive power. In fact, propulsive power required to plane increases exponentially as hull displacement increases.

Large planing watercraft able to carry large payloads and capable of much higher speeds than any displacement craft would be of great economic benefit. However, large planing watercraft designs of prior art need to achieve high speeds in order to overcome the bow wave their hulls generate to be able to plane. These watercraft designs of prior art unfortunately cannot achieve the required speed unless they are already planing. The initial answer to this dilemma was the hydrofoil.

Although hydrofoils were once favoured to produce hydrodynamic lift for larger watercraft, the disadvantages associated with their use led to their decline in use over the years. SUMMARY OF THE INVENTION

The invention is a watercraft which uses a novel method of achieving hydrodynamic lift using concave channels to bring a large watercraft to plane safely, efficiently and at a relatively lower speed and requiring much less power than planing watercraft of prior art.

Watercraft of prior art using a hull with concave channels do offer certain advantages over traditional 'V shaped planing hulls in terms of planing efficiency in that the concave channels direct water under the hull as opposed to allowing the water to displace to the sides of the hull. However, prior art on concave channel hulls still present an inclined surface as the said hull moves through the water to create hydrodynamic lift and hence still create a bow wave as in prior art on 'V shaped hulls. The invention achieves hydrodynamic lift in a totally different manner in that no inclined surface is required to produce hydrodynamic lift. The invention uses a similar principle of providing hydrodynamic lift as hydrofoils but without the associated disadvantages commonly found in systems using hydrofoils. A key advantage of the invention compared to watercraft of prior art is that prior art requires the planing hull to achieve a relatively high speed to plane which is impeded by the bow wave which it creates whilst the invention only requires water flow within the said channels to create the required hydrodynamic lift to plane. The invention is a hull with channels at the underside of the said hull where dynamic pressure is created to lift the watercraft to a planing state quickly and efficiently using strategically placed water based propulsion. Besides propelling the watercraft of the present invention, the propulsion also draws water through the channels which gradually narrow towards the the stern of the said watercraft of the present invention thereby creating hydrodynamic pressure within the channels instead of pushing an inclined surface towards a body of water as in prior art.

The invention is envisioned to be the only commercial viable means to bring a large marine watercraft to a planing state efficiently and continue to safely operate on plane; a feat that is currently not possible with prior art. BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be more readily understood and put into practical effect, a preferred example of the invention will now be described with reference to the accompanying drawings which are as follows :

Figure 1. Underside view of the invention illustrating the narrowing channels, planing pad and its position with respect to the centre of gravity (CG)

Figure 2. Side view of a channel 1 illustrates the slight inclined surface with respect to the centre of gravity (CG)

Figure 3. Frontal view of the invention illustrating the concave shape of the channels

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The channels 1 narrows as they pass the design longitudinal centre of gravity CG as illustrated in Figure 1. This narrowing of the channel creates hydrodynamic lift by virtue of increasing dynamic pressure in the said channels on the underside of the hull. In the preferred embodiment the concave channels narrow towards the stern gradually so that hydrodynamic resistance is kept to a minimum whilst providing the necessary hydrodynamic lift.

The gradual narrowing of a water channel on the underside of the hull 1 to create dynamic pressure under the hull may seem so simple that it is should be common knowledge to those skilled in the craft, but, most prior art on traditional 'V shaped planing hulls do not use any such water channels under the hull. Furthermore, most prior art on water channels on the underside of a hull specifically keep the channel width constant but decrease the channel's depth from bow to stern to provide a traditional inclined surface which is known to result in a bow wave. Furthermore, prior art on hulls with concave water channels do not claim or disclose propulsion effects on dynamic pressure within the said narrowing concave channels. Thus, the invention is indeed unique as it uses principles and methods which are uncommon to those skilled in the craft.

How the narrowing channels work may be explained by the Bernoulli principle. Assuming the flow rate is uniform across the said channel, the velocity of a fluid such as water is highest in the narrowest part of the said channel and lowest at the widest part. Following the Bernoulli principle, the pressure exerted by the fluid is thus highest at the widest part of the channel and lowest in the narrowest part. With the widest part of the channel positioned at or forward of the longitudinal centre of gravity of the watercraft (CG) and the said channel narrowing from this point towards the stern of the hull, a positive pressure to efficiently lift the hull to a planing state without having to overcome a bow wave as required by a traditional planing hull is created. It is possible to have a wide channel over the entire length of the underside of the hull where this said channel only narrows near to the stern such that dynamic pressure applies to almost the entire length of the hull. This is not practical in the preferred embodiment because longitudinal instability will result the moment there is insufficient water flow through the channel. For practical purposes, the longitudinal centre of gravity is best located between the narrowest point and the widest point of the channels.

The preferred embodiment of the invention uses dual narrowing concave channels 1 on the underside of the hull both having an entrance la, an exit lb and propulsion 3 in the water flow of each channel. These channels 1 are placed longitudinally side by side such that hydrodynamic lift for both port and starboard sides of the hull can be individually controlled. This particular variant of the invention is thus also expected to turn well even without the use of rudders since a difference in flow rates between the port and starboard channels 1 will result in the invention turning but also rolling into the turn i.e roll and yaw. Control of water flow in each channel can also be further enhanced through the use of the hinged flaps 6a,6b,6c. Hinged flap 6c works in the same plane as a rudder but instead controls the difference in flow rates in the two channels 1. When hinged flap 6c is in the closed position it does not impart any change to the flow rates of the two channels.

The height of the channels 1 reduce slightly from the said entrance la to a point slightly forward of the longitudinal centre of gravity (CG) as illustrated in Figure 2. Although this does provide a traditional planing surface it is not the primary motivation. This is done to reduce the wetted surface when the hull is already planing. Thus the angle presented is much less inclined than that which is required for traditional planing.

Once the invention is on plane, slamming then becomes an issue as in all planing hulls in rough seas. The invention inherently solves this problem. Hinged flaps 6a,6b are usually open and allow water to flow unimpeded through the channels 1, however when the hull has separated from the surface of the water, hinged flaps 6a,6b close and the concave channels 1 become channels of trapped air. The concave channels of trapped air provide an air cushion effect to reduce the effects of slamming. The concave shape within the channels allows progressive compression of the trapped air further improving the cushioning effect. Figure 2 illustrates hinged flaps 6a and 6b in their closed state. Hinged flap 6b is at an angle such that debris is deflected downward and outward in its closed state and thus prevents debris from entering the propulsion 3. In Figure 1, the planing pad 4 formed between the channels supports the said watercraft of the present invention while it is in a planing state. The narrowing channels 1 on both sides of this planing pad 4 quickly bring the invention to a planing state. However, once the invention is planing, the concave channels 1 can no longer provide the same hydrodynamic lift as most of the channels 1 are already out of the water. It is the planing pad 4 which dynamically supports the invention while it is on plane at high speed. For the sake of longitudinal stability the design centre of gravity (CG) lies above the planing pad 4 and to the rear of the widest point of the channels 1. The side of the planing pad 4 forms part of the concave walls of the channels 1.

The wave piercing stem of the bow 2 acts to pierce through an incoming wave thus the stem comes to a point at the front. The stem of the bow does not need to generate any upward component of force because the concave channels 1 provide all the hydrodynamic lift that is required and thus the stem of the bow can be vertical or inclined. In the preferred embodiment the bow stem directs water into the channels. The function of control surfaces 7a and 7b is to control the invention especially in pitch and roll and may be deployed under or above the design waterline. Control surfaces 7a are air based control surfaces and are larger than the water based control surfaces 7b.

Concave channels give the hull of the invention the unique ability to plane more efficiently than prior art whilst the control surfaces and the wave piercing bow enable safe and comfortable operation in high sea states at speeds not possible for craft of prior art with hulls of the same displacement.

Figure 3 illustrates the frontal view of the preferred embodiment where the superstructure 5 is preferably aerodynamic. The channel entrances la illustrate the concave cross-sectional shape of the channels 1 on the underside of the hull of the watercraft in the preferred embodiment of the invention. Also illustrated are the positions of air based control surfaces 7a and water based control surfaces 7b. Propulsion 3 may be in the form of waterjets, surface drive propellers, podded propulsion or any other type of water based propulsion. Propulsion 3 has a means to direct their thrust where rudders, hinged flaps and any other means to direct propulsion may be used. The invention also works well to provide hydrodynamic lift to non planing watercraft such as submarines.

While the invention has been shown and described with reference to the preferred embodiment thereof, it will be understood by those skilled in the art that various change in form and detail may be made therein without departing from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: