HK1019218B - Surface effect vessel hull - Google Patents

Description

Surface effect ship hull

The present invention relates to a hull which employs a compressed air cushion mounted in an air cushion accommodating groove formed on a portion of the bottom of the hull in order to reduce resistance of water thereto and thereby improves the speed of a ship and the fuel efficiency of the ship. In particular, the invention relates to a vessel with a catamaran structure, wherein each of the monohulls of the catamaran has a compression cushion.

One of the main issues in ship design is to reduce the amount of drag caused by the interface between the hull and the water surface. Earlier designs of planing hulls were such that the forward motion of the hull raised the boat so that it ran on the surface of the water by virtue of a small portion of its hull surface. As a result, the frictional force between the hull and the water is reduced. The design structure of the hydrofoil boat further reduces the contact surface between the boat body and water by installing hydrofoils for high-speed running of the boat on the boat body. Some watercraft introduce a film of air between the hull and the water to reduce the friction between the hull and the water. An example is described in US3191572 to h.a. wilson, where a three-hull boat introduces air along the bottom of each hull and allows said air to flow freely off the stern. US4031841 to blatt also describes air foil hull technology. The blatt and wilson hull is still driven with the hull lower in the water, with the result that most of the hull sides are still in contact with the water, but the resistance between the water and the bottom part of the ship is more or less reduced by the air film mixed with the water.

A surface effect craft is an improvement over a gas film hull in that the hull of the craft is lifted out of the water by means of a compressed gas cushion which is partly enclosed in the hull. Past hovercraft hulls have been designed with the air cushions arranged so that the flexible seals (via rubberized curtains) surround the entire hull in the case of a hovercraft, or across the bow and stern of a thin parallel side hull providing a side seal for the air cushion in the case of a surface effect vessel. The flexible seal reduces the air leakage of the air cushion, but it causes jounce and even in calm waters, it causes the boat to travel "cobblestone on water drift". As the water surface becomes unsmooth, the flexible seals can be separated from each other, which further affects ride performance. In addition, in rough waters, the flexible seal often fails to maintain the presence of the air cushion, which causes the hull to sink deeper into the water until the seal is regained and the air cushion is re-established. The loss of the air cushion increases the contact surface of the hull with the water, thereby increasing the friction between the hull and the water and significantly reducing the speed of the ship. The seal has the problem of being expensive to maintain due to frequent rupture, which results in the loss of air cushion permanently and only slow movement of the boat to the repair site. US patents US5415120, US4392445 and US4523536 to donnade.

Despite the prior art of such surface effect craft, there is clearly a need for a craft that can maintain relatively stable travel and the presence of air cushions, whether or not the surface of the water is calm, without the use of flexible seals. There is also a need to improve the stability of surface effect vessels which are known to be unstable in high sea waters.

The present invention relates to a surface effect vessel having a pair of V-shaped hulls with air cushion receiving tanks containing compressed air to produce efficient, stable, smooth high speed travel. The hull of the surface effect vessel comprises two hulls joined together by deck surfaces, each hull defining a respective longitudinal dimension. The double hulls each comprise a bottom having an outer surface; and opposed sides having first and second ends connected to and extending upwardly from the bottom of the vessel, wherein the sides are curved inwardly and connected together at the first end to form a bow, and are connected at the second end by a transversely extending transom; a step surface (a substantially flat surface) extends inwardly from the bottom of the vessel substantially perpendicular to the longitudinal dimension such that a plane formed by the step surface divides each twin hull into two parts; a bow portion extending forward of the plane and an air cushion portion extending rearward of the plane.

The bow portion of the bottom has a first surface and a second surface connected to each other to form a V-shape extending from adjacent the bow to the stepped surface. The apex of the V defines the keel of the bow portion. The first surface and the second surface each form an angle with a horizontal plane, which is defined as the ship bottom pitch angle of the ship body. A cross-section of the hull substantially perpendicular to the longitudinal dimension defines a bottom lift angle in the range of 45-65 degrees. When the bottom transverse lift angle is defined by the transition between the bottom surface of the bow portion and the stepped surface, the bottom transverse lift angle is reduced to below 25 degrees.

The cushion portion of the bottom has an cushion-receiving pocket formed therein which extends inwardly from the outer surface of the bottom intersecting the step surface on the one hand and rearwardly from the step surface to the transom on the other hand. The air cushion receiving tank forms a secondary double hull section extending from the step surface to a position adjacent the transom. A compressed air generator, as is well known in the art, is in fluid communication with the air cushion receiving tank.

Accordingly, the invention comprises an article of manufacture possessing the features, properties, and relationships of elements which will be described hereinafter by way of example, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the present invention, reference should be made to the following detailed description taken together with the accompanying figures wherein:

fig. 1 is a perspective view of the hull of a surface effect vessel of the present invention.

Fig. 2 is a bottom view of the invention shown in fig. 1.

Fig. 3 is a right side view of the hull of the surface effect vessel.

Fig. 4 is a cross-sectional view taken along line 4-4 of fig. 2.

Fig. 5 is a cross-sectional view taken along line 5-5 of fig. 2.

Fig. 6 is a cross-sectional view taken along line 6-6 of fig. 2.

Fig. 7 is a cross-sectional view taken along line 7-7 of fig. 2.

Fig. 8 is a cross-sectional view taken along line 8-8 of fig. 2.

Fig. 9 is a cross-sectional view taken along line 9-9 of fig. 2.

Fig. 10 is a cross-sectional view taken along line 10-10 of fig. 2.

Like reference numerals refer to like parts throughout the several views of the drawings.

A preferred embodiment of the surface effect vessel hull is shown in fig. 1-10, wherein the surface effect vessel hull is indicated generally at 10. Referring first to fig. 1, it can be seen that the hull 10 comprises a pair of twin hulls 12 interconnected by a deck 14.

As shown in fig. 2, each catamaran hull has a longitudinal dimension a and includes a bottom 16 having an outer surface 18, and a pair of opposed sides 20 connected to the bottom 16 and extending upwardly therefrom. To more specifically illustrate the structure of the present invention, the side 22 forms the line connecting the side 20 and the bottom 16. The first ends 24 of the sides 20 are connected to form a bow 26, and the second ends 28 are connected to one another by a transom 30 extending transversely therebetween. The stepped surface 32, as can be seen most clearly in fig. 3 and 8, extends inwardly from the bottom 12 of the vessel substantially perpendicular to the longitudinal dimension a. As shown in fig. 2, the stepped surface 32 lies in a plane B that defines a forward extending bow portion 34 including the bow 26 and an air cushion portion 36 extending rearwardly from the plane B and including the transom 30. In a preferred embodiment, the bow portion 34 comprises 50% of the total bow length from the bow 24 to the transom 30, i.e., the stepped surface 32 is generally located just midway between the bow 26 and the transom 30. In other embodiments, the stepped surface 32 may be located 42% -80% of the longitudinal length of the hull 10 from the bow 26 and still form a hull with acceptable performance. The bow portion 34 of the bottom 16 includes a first surface 38 and a second surface 40 joined along a keel 42 to form a V-shape. Each surface 38, 40 forms an angle C with a horizontal plane, which is defined as the bottom-wise rise angle of the hull. As shown in fig. 5, the angle C is preferably 55 degrees in a cross section of the bottom 16 near the bow 26. In other embodiments, however, the angle C near the bow 26 may be between 30 degrees and 65 degrees and still function satisfactorily. In a preferred embodiment, the angle C tapers to 16-20 degrees at the tailgate 30 to the angle C' shown in FIG. 8. In other embodiments, the angle C' may be between 25 degrees and 0 degrees and still function satisfactorily.

The cushion portion 36 of the bottom 16 has an cushion receiving channel 44 formed therein and extending inwardly from the outer surface 18 of the bottom 16 and rearwardly adjacent the transom 30. The air spring receiving pocket 44 is bounded by a stepped surface 32 at the forward end, a chute side wall 46 projecting rearwardly toward the tailgate 30, and a downwardly curved pocket top 48 which tapers in the illustrated embodiment as shown in fig. 9 and 10. In other embodiments, the air cushion receiving groove 44 may have many different shapes known in the art, and the illustrated shape is merely one example of a shape that may work effectively. The side walls 46 of the air cushion-receiving tank and the sides 20 of the twin hull 12 form a pair of secondary twin hull sections 50 extending from the step surface 32 to the transom 30. Each secondary double hull section 50 has a fin 52 formed thereon and extending substantially the entire length of the secondary double hull section 50. In a preferred embodiment, the length of the cushion-receiving tank 44 (the longitudinal length of the cushion-receiving tank side walls 46) is greater than the resulting transverse width of the cushion-receiving tank 44 (the dimension transverse to the hull and perpendicular to the mid-ship plane) when measured perpendicular to the longitudinal dimension a between the fins 52.

In a preferred embodiment the fins 52 extend from adjacent the transom to a position forward of the stepped surface 32 and then to the bottom surface 18 of the bow portion 34, said position forward of the stepped surface being spaced from the stepped surface by a distance equal to 2.9% to 7.1% of the overall longitudinal dimension of the hull 10. In a preferred embodiment, the fins 52 are equal to 5% of the overall longitudinal dimension of the hull 10, for example, in the case of a one hundred foot boat, the fins 52 would be five feet beyond the stepped surface 32. The fins 52 exceeding 5% cause the boat to slow down without adding protection to the air cushion accommodating tanks. The vertical dimension of the fins 52 (typically measured perpendicular to the hull) preferably extends from the bottom surface 18 a distance of 0.5% to 1% of the overall longitudinal dimension of the hull 10. For example, with a longitudinal dimension of the hull 10 of 100 feet, the vertical dimension of the fin is approximately equal to 9-12 inches.

The portion of each fin 52 that is the end of the hull 10 includes a fin keel portion 54. The fin keel portion 54 of each fin 52 lies substantially in the same plane and substantially in the same plane as the part of the keel 42 of the bow portion 34 of the hull 10 adjacent the step surface 32.

A compressed air generator, generally indicated at 58, is preferably mounted within the hull 10 and is connected by a conduit 60 to an outlet 62 formed in the top 48 of the air cushion-receiving tank 44. The generator 58 for generating compressed air is well known in the art and may be provided as a stand alone device as shown in fig. 3, or a separate device connected to each outlet 62 by an extension conduit 60 may be employed. The device may be driven by its own engine or by the power take-off of an engine in the cabin.

The surface effect vessel hull 10 may be made of fiberglass, synthetic resin, composite materials, aluminum, steel, or any other suitable material. Boats or ships built with the surface effect ship hull may employ any driving method, including standard outboard engines for small boats and larger cabin gas or diesel or turbine engines for large ships. The amount of power required to start such a boat is much less than that required by a conventional boat or boat.

Although a preferred construction of the surface effect vessel hull 10 of the present invention has been thus described, it should be kept in mind that it is merely a preferred embodiment. No attention is paid to the description of the use of the surface effect vessel hull 10. Of course, many different deck structures may be constructed on the hull 10 depending on the intended use of the ship and the passenger/cargo transportation use, including, but not limited to, racing boats, luxury yachts.

The surface effect vessel hull 10 described below is described with respect to a hull 10 having a longitudinal length of one hundred feet. However, different sized hulls 10 can be built in roughly proportional sizes, which can be adjusted by one of ordinary skill in the art depending on the particular design application of the watercraft in which the surface effect watercraft hull 10 is used. The surface effect ship hull 10 does not employ any flexible seals, thereby eliminating any problems associated with seals as well as bump travel, high maintenance costs, control problems, high peak resistance (which means that a ship with a flexible seal is difficult to float on air cushion and to negotiate peaks, which requires a lot of power, which is not required when the ship is on air cushion). The surface effect craft hull 10 is a catamaran having catamarans with compression cushions on approximately 50% of their length. Each hull 12 has a bow portion 34 which is the remaining 50% of the longitudinal dimension. The bow portion 34 of each twin hull 12 has a V-shaped bottom 16 with a sharp entrance near the bow 26 and has a bottom transverse lift angle of about 55 degrees which decreases to below 25 degrees near the step surface 32 when the uninflated boat is driven for many years, thereby easily generating a dynamic lift when the boat is accelerated so that the boat easily begins to skim the surface of the water. The pointed entry of the bow portion 34 is designed to deflect the oncoming waves gradually down and sideways over most boat lengths. Thus, even when the surface effect ship 10 runs on a wide sea surface, the water passing under the air cushion is made to flow substantially horizontally. The advantage of this design of changing the flow of an approaching wave before it reaches the air cushion portion 36 of the hull 12 is apparent. The flexible seal used in conventional surface effect boats is not required, thereby eliminating the high maintenance costs and maintenance time required to repair the flexible seal. Without the wave becoming substantially horizontal, the wave strikes the flexible seals of a conventional surface effect vessel, thereby reducing the volume of the air cushion and causing the pressure of the air cushion to vary and thus requiring additional buoyancy, and the violent impact of the wave with the bow is a major factor that can lead to bumpy driving. The sharp entrance of the bow portions 34 of the two hulls 12 greatly reduces pitching, green and sloshing compared to conventional surface effect ships.

However, once the boat is planing on the surface, a large portion of the bottom 12 remains submerged and thus creates drag. When the air cushion portion 36 of the surface effect ship hull 10 is traveling over air, drag is greatly reduced by providing a compression air cushion under this portion of the hull. Thus, the surface effect craft hull 10 combines the dynamic lift with the buoyancy achieved by the compressed air cushion, thereby allowing the craft to glide easily and significantly reduce drag on the hull 12. The bow portion 34 of the hull 12 has only a small submerged area which creates drag because the bow portion 34 creates very efficient dynamic lift. The compressed air cushion that creates the buoyancy of the air cushion platform occupies a substantial portion of the hull surface of the air cushion portion 36 of the hull 12 that is in direct contact with the water and reduces drag. This combination of buoyancy takes the most advantage of the dynamic lift and air cushion platform buoyancy, resulting in a highly efficient hull structure not previously achieved in successful boat hull designs.

The use of twin hulls 12 each having a separate compression cushion provides improved stability without significant increase in drag. The separate hull and separate air cushion create a large roll restoring force which will create a surface effect vessel that is not susceptible to gravitational forces. The stiffness and roll damping are also significantly improved because the air cushions act on the air cushion separation arms and thus ensure roll stability. The bridge span between the hulls 12 is much smaller than that of a conventional surface effect vessel of the same width. The wide spacing of conventional surface effect boats results in a heavy boat because the wide spacing between the hulls requires significant structural reinforcement. The twin hulls 12 also increase the performance efficiency at all speeds compared to a single air cushion surface effect vessel design designed only for efficient travel at one speed. The improvement in performance also benefits from having an air cushion receiving tank with a longitudinal dimension that is significantly greater than the dimension of the transverse pair of the hull orthogonal to the mid-ship plane.

Placing the air cushion-receiving channel 44 too forward reduces the dynamic lift and exposes the air cushion-receiving channel 44, which forces the use of a flexible curtain as in prior art conventional skin effect boats. Starting to form the air cushion receiving groove 44 too far from the bow 26 will significantly increase the resistance. Studies have shown that a 50% solution of the bow part 34 and the air cushion part 36 each is a preferred embodiment of the surface effect vessel hull 10.

The cushion-receiving groove 44 must be protected so that water does not enter the cushion-receiving groove or allow an unacceptable amount of gas to escape forward. The sharp entrance to the bottom transom angle decreasing below 25 degrees deflects the incoming waves downward and sideways and changes the water flow conditions as the water approaches the air cushion receiving tank 44 so that the water flows substantially horizontally. The fins 52 that extend forward of the cushion-receiving channel 44 cover the cushion-receiving channel 44, thereby preventing the escape of gas and preventing water from entering the cushion-receiving channel 44, thereby maintaining the cushion.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained. As certain changes could be made in the above embodiments without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the specific and generic features described herein, as well as all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

The present invention has now been described.

Claims (6)

1. A surface effect vessel hull comprising:

two catamaran hulls connected by a deck, wherein each catamaran hull defines a longitudinal dimension;

each twin hull including a bottom having an outer surface, opposed sides connected to and extending upwardly from the bottom, a transom connected to and connected to the bottom and extending upwardly from the bottom, a stepped surface extending inwardly from the bottom substantially perpendicular to said longitudinal dimension, said stepped surface lying in a plane passing through said hull generally transversely to said longitudinal dimension, the plane defining a bow portion extending forwardly of the plane and an air cushion portion extending rearwardly of the plane;

the bow portion of the bottom of each twin hull vessel including first and second surfaces connected to each other to form a V extending from adjacent said bow to said stepped surface, a line formed by said interface forming a keel for said bow portion, the first and second surfaces each forming an angle with a horizontal plane passing through said keel which angle is at least 45 degrees in a cross-section adjacent said bow, said angle decreasing to less than 25 degrees at said stepped surface;

the cushion portion of each catamaran hull bottom having an cushion-receiving tank formed therein, said cushion-receiving tank extending inwardly from an outer surface of said bottom and rearwardly from said step surface to adjacent said transom, said cushion-receiving tank defining a secondary catamaran section extending from said step surface to said transom;

a compressed air generator in fluid communication with the air cushion receiving tank.

2. A surface effect vessel hull according to claim 1 wherein said bow portion of each catamaran hull has a longitudinal dimension from said bow to said stepped surface equal to 35% to 80% of the longitudinal length of the catamaran hull from said bow to said transom.

3. A surface effect vessel hull according to claim 1, wherein said angle decreases from at least 55 degrees near said bow to 20 degrees or less at said stepped surface.

4. The surface effect vessel hull of claim 1 including fins extending downwardly from each secondary double hull section, said fins extending from adjacent said transom to a position forward of said step surface, said position forward of said step surface being spaced from said step surface by a distance equal to 2.9% -7.1% of the overall longitudinal dimension of said hull.

5. A surface effect vessel hull according to claim 4 wherein each of said fins includes a keel portion, the fin keel portions of each of said double hull sections lying generally in the same plane and substantially in the same plane as the keel of the bow portion of the hull adjacent the stepped surface.

6. The surface effect vessel hull of claim 1 comprising twin hulls having longitudinal axes generally parallel to each other, and said twin hulls are spaced apart from each other.