US3742888A

US3742888A - Stable multiple-chamber air cushion boat hull

Info

Publication number: US3742888A
Application number: US00213979A
Authority: US
Inventors: W Crowley
Original assignee: W Crowley
Current assignee: AQUA AIR DYNAMICS Corp
Priority date: 1971-12-30
Filing date: 1971-12-30
Publication date: 1973-07-03
Anticipated expiration: 1990-07-03

Abstract

A soft riding, stable multiple-chamber air cushion boat hull having a plurality of high pressure air chambers around the periphery automatically providing heave stability as well as roll and pitch stability. The hull may further include a vent slot providing a means for exhausting the spill out of the continuously charged high pressure chambers and further makes a sharp reduction in the bow wave pressure. In addition to providing stability the high pressure chambers lift the boat providing a low friction, soft riding air cushion support.

Description

United States Patent [191 Crowley STABLE MULTIPLE-CHAMBER AIR CUSHION BOAT HULL [76] Inventor: Walter A. Crowley, Tower 801, 801

- Pine St., Apt. 14 A, Seattle, Wash.

[22] Filed: Dec. 30, 1971 [21] Appl. No.: 213,979

[52] US. Cl. 114/67 A, 180/126 [51] Int. Cl B63b 1/38 [58] Field of Search 114/67 A; 180/116,

[56] References Cited UNITED STATES PATENTS 9/1972 Bertin 114/67 A 7/1970 Girodin 114/67 A [451 July 3,1973

FOREIGN PATENTS OR APPLICATIONS 1,001,059 8/ 1965 Great Britain 114/67 A Primary Examiner-George E. A. Halvosa Attorney-Richard W. Seed, Benjamin F. Berry et al.

[5 7] ABSTRACT A soft riding, stable multiple-chamber air cushion boat hull having a plurality of high pressure air chambers around the periphery automatically providing heave stability as well as roll and pitch stability. The hull may further include a vent slot providing a means for exhausting the spill out of the continuously charged high pressure chambers and further makes a sharp reduction in the bow wave pressure. In addition to providing stability the high pressure chambers lift the boat providing a low friction, soft riding air cushion support.

8 Claims, 11 Drawing Figures PAIENImJuLa um SHEUIBF3 INVENTOR WALTER A. CROWLEY FIG 3 ATTORNEYS PATENTEDJUL 3 I973 Q INVENTOR.

WALTE R A. CROWLEY v ATTORNEYS PAIENIEBJuLa ms 3.742.888

sum 3 or 3 INVENTOR WALTER A. CROWLEY AT TORN E YS STABLE MULTIPLE-CHAMBER AIR CUSHION BOAT nuts BACKGROUND OF THE INVENTION It has long been recognized that an excessively large amount of power generated by a moving ship is absorbed in the frictional and other resistance between the ship and the water. The large amount of resistance is caused by the fact that the conventional ship has approximately the same displacement at rest as it has in motion and consequently has a relatively large wet surface subject to the frictional resistance. The large bulk of the hull in, the water produces large head and wave resistances in addition to the frictional resistance.

Another type of boat, denoted as hydroplanes or surface boats, are distinguished by a more or less flat bottom set at an angle to the line of motion, the hull being so proportioned that with the higher speeds a lifting force is produced which tends to raise the forward part of the hull out of the water thereby reducing its resistance. However, a planing or surface boat is pitched nose-up due to the thrust line of the propeller being below the resistance of the boat hull, and only the weight of the boat forward of the center of lift holds the bow down to prevent the boat from flipping over on its back. (Of course a head wind, plus too much thrust, can still cause this to happen to light weight, overpowered, racing boats.)

The forward part of the hull is suspended in the air by the combination of forward thrust of the propeller below the boat hull, and the sum of all the wind, wave, and water friction reverse force, (drag), opposing the thrust. The pivot point about which these forces tend to produce a nose-up rotation, is the center of lift supporting the boat, usually a few square inches of hull at the aft lower surface of a high speed boat. The counterforc which tends to bring the nose of the boat down, is, of course, the weight of the boat forward of the center of lift. The heretofore described condition is frequently an unstable combination of rapidly changing forces and the bow of the boat tends to rise and fall violently during high speed over moderately rough water, even on smooth water at some speeds. The instability gives a very uncomfortable ride, and requires that passengers stand up, clinging desperately to anything handy, while fighting to keep down their lunch.

In an attempt to have a boat which has the low frictional resistance of the hydroplane and yet have a greater stability attempts have been made to provide a boat with a cushion of air beneath the hull while not greatly detracting from the stability thereof.

Examples of attempts to accomplish hull stability and low frictional resistance are illustrated by the U.S. Pat. No. 3,174,573 granted to .I. E. Chaplin on Mar. 23, 1965, wherein he has a fair amount of heave stability but very low roll and pitch stability. The use of the multiple chambers as shown in this patent or US. Pat. No. 3,332,508 to J. H. Burton et al., and the approach of compartmenting jet slots in a single annular jet air cushion vehicle with the divided plenum area such as illustrated in Australian Pat. No. 219,133 granted to C. S. Cockerell were attempts to obtain roll and pitch stability. However, the cone shaped skirts of Chaplin and Burton resulted in a great deal of lost lift area between the separate units thus requiring relatively high air pressure for a given load on the overall load supporting area. The compartmenting jet slots of Cockerell were of small effectiveness with reasonable speed and daylight clearance.

Later developments of inflated trunk skirts, bag skirts, and finger skirts further reduced the effectiveness of the compartmenting jet slots. In the meantime, work on sidewall cushioned vehicles and captured bubble air cushion vehicles as well as surface effect ships were proceeding. In each instance they failed to properly design for good roll and pitch stability, either not compartmenting the air lift chamber or by not obtaining the free peripheral air flow for each compartment that is necessary for individual compartment heave stability.

With the above noted facts in mind it is an object of the present invention to provide a boat hull which has not only good heave stability but likewise has good roll and pitch stability.

It is another object of the present invention to provide a boat hull which utilizes a multiple high pressure chamber concept including a relatively low pressure venting system whereby the stability is increased without substantially reducing the carrying capacity of the hull.

A further object of the present invention is to provide a multiple compartment high pressure air cushion boat hull wherein the hull is aquadynamically sound thereby not greatly interfering with the movement of the hull across the water.

It is still a further object of the present invention to provide a stable boat hull incorporating multiple chamber air cushions wherein the exterior side surface of the hull is formed with downwardly depending skegs or pontoons which serve to not only trap the high pressure air within the chamber but also serve as low drag, buoyant members improving overall stability and flotation.

It is still another object to provide an air cushion type boat hull wherein the multiple chambers are separated by low drag divider walls separated to form vent slots. These divider walls may well be buoyant thus serving a dual function.

Still a further object of the present invention is to provide a boat hull incorporating the multiple chamber air cushion device wherein the necessary venting is provided by the configuration of the hull thus eliminating the need for putting a separate venting slot therein.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective bottom view of a boat hull designed in accordance with the present invention illustrating the multiple chambers and venting arrangement.

FIG. 2 is a bottom plan view of the hull of FIG. I. further depicting the relationship of the side skegs and the divider walls.

FIG. 3 is a sectional view of the hull along lines 3-3 of FIG. 2.

FIG. 4 is a bottom plan view of an alternative hull design incorporating the high pressure multiple chamber concept.

FIG. 5 is a sectional view of the hull along lines 5-5 of FIG. 4.

FIG. 6 is a sectional view of the hull of FIG. d along lines 6-6 in that figure.

FIG. 7 is a bottom view of still another hull design in accordance with the present invention.

FIG. 8 is a sectional view of the hull of FIG. 7 along lines 8--8.

FIG. 9 is a perspective from the bottom of yet another hull design in accordance with the present invention.

FIG. is a bottom view of the hull design of FIG. 9.

FIG. 11 is a side elevational view of the hull design of FIG. 9.

DETAILED DESCRIPTION OF THE DRAWINGS As can be seen in FIGS. 1-3 the inventive boat hull comprises a pair of substantially vertically placed side skegs or pontoons 2 having tapered inner portions 4 leading to a generally flat depressed area 6 in the forward portion of the boat and a similar portion 8 in the aft portion of the hull. The

depressed areas

6 and 8 are separated by low drag divider wall 10 which gradually tapers to a sharp edge 11 which overlies a projecting curved surface 12. The aft portion of chambers 8 is closed by a low drag gradually tapered divider wall 13 which terminates in a vertical section forming the stern of the boat. The

sections

6 and 8 are defined by the sides 4,

divider walls

10 and 12 respectively and in the forward portion of the boat by the bow 14. The bow 14 includes a pair of downwardly and rearwardly tapered water contacting portions 15 terminating in a water parting edge 16 at the bow of the boat. The after sur face of the bow 14 is a forwardly curved hollow portion 17 similar to the surface 12 as described with respect to divider 10. The dividers, side skegs and bow and stern portions provide four discrete sections adapted to receive therein air or other gas at high pressure thus forming four legs which support the vehicle in a stable position. When the hull is in motion, the four discrete hollow portions will be continuously charged with air which will in turn escape in a generally rearward direction. The four sections serve as lifting devices, causing a major portion of the hull to ride above the water rather than through it and further, the air escaping rearwardly serves as a boundry layer between the hull and the water providing a relatively frictionless soft riding support for the hull. This embodiment of the hull design includes a centrally located longitudinal narrow vent between a pair of vertical walls 20 which extend downwardly approximately the same distance as the bow 14, the divider l0 and the stern section 19, which extends to the bow to allow some of the water contacted to pass under the hull, reducing the bow wave resistance and thus increasing the efficiency.

The four

discrete sections

6 and 8 as noted above are designed to receive air under a pressure greater than that merely required to displace water to provide buoyance. The air is provided, in the preferred embodiment, by means of a pipe or conduit 22 from a source of high pressure air, not shown, since the particular source may be a commercial item and is not considered a part of this invention, to the distribution pipe 24 located within the central channel 19 and from which distribution

pipe cross pipes

26, 28 channel air under pressure into the

chambers

6 and 8 whereat it will form a lifting bubble.

Thus in operation, the underside of the hull is pressurized by forcing the air through the conduits 18, 20, 22-and 24 into the four

chambers

6, 8 thus raising the hull to its traveling position. The orifices of the four conduits into the air chamber are restricted in size so that their resistance to flow will maintain a substantially higher upstream air pressure for effectively stabilizing the boat. These restricted orifices may be replaced by suitable flow control valves. Forward motivation is provided for the hull by any commerical means well known in the art and not considered a part of the present invention and therefore not shown. During forward motion the air under pressure is continuously supplied to the four

discrete chambers

6,8 and because of the depth of the dividers 10 and the aft portions 13 will escape as discrete bubbles rearwardly as the hull moved in a forward direction. For stability during the roll, the air trapped within the chamber on the side towards which the hull is rolling will be compressed thus providing greater lift while the side walls of the central vent 16 will be raised on the side away from the direction of roll allowing air to escape from this side decreasing the pressure and tending to right the hull. It is to be understood that the roll compensation is an automatic function of the hull configuration and the compensation will be accomplished whenever the chambers are charged. The particular dimensions of the dividers, the skegs and the central channel are not critical but the dividers, including the stern, must be such that the air may escape to the vent from the chamber which are tending to lift and be trapped within the chambers tending to be submerged. The action of the hull is similar for heave and pitch stability in the compressing and venting action thus providing automatic compensation and inherently stable structure.

It is to be understood that although the bow shape as shown and described has been found to be efficient and practical it is not of itself considered to be a part of the present invention. The requirement that the hull minimize the water resistance and not detract from the stability of the vehicle is essential and any configuration which accomplishes these ends will be satisfactory when used in conjunction with the compartmented hull as shown.

Referring to FIGS. 4-6, a second configuration employing the basic compartmented hull structure wherein the lift is provided by charged chambers and stability is provided by a differentiation in pressure, high in the portion tending to submerge and low in the portion tending to elevate, is incorporated. The hull in cludes a pair of downwardly depending side skegs or pontoons 40 which are of a low resistance design and may well be buoyant. Intermediate the skegs 40 spaced from and generally parallel thereto are a pair of downwardly depending low resistance tapered members 42. The space between the skegs 40 and the members 42 is closed at the stern by a tapered element 44, separated amid ship by a divider 46 and closed at the front by a portion of the bow 48 which extends rearwardly to overlap a portion of the high pressure chamber. In much the same fashion as described with respect to FIGS. 1-3 the bow portion 48 and the divider 46 form a cavity extending forwardly from the lowermost edge designed to be filled with air during operation. The

high pressure chambers

50, 52 adapted to be filled with air are defined by the elements as hereinabove described and are supplied air under pressure from any well known means through conduit 53 feeding a plenum 54 which has

outlets

56, 58 into the

chambers

50, 52. A means for channeling the water and thus reduce the wave head as well as providing a relatively low pressure conduit for air spilled over from the high pressure chambers is provided between the members 42. The low pressure chamber 60 is open at the rear and functions in the same fashion as the vent 19 of FIGS. l-3.

Yet another hull configuration incorporating the high pressure chambers and low pressure vent is shown in FIGS. 7 and 8. In this embodiment the

high pressure chambers

70, 72, 74 and 76 are located inboard and adjacent to the side skegs or pontoons 78. The high pressure areas are supplied by conduits 80 from a commercial source of high pressure air, not shown for clarity. The relatively low pressure area 82 gradually tapers rearwardly at 86 to the stern of the hull allowing escape of the air. The separation between the forward high pressure chambers and the low pressure chambers is provided by tapered surface 84 terminating in an edge 85 which as seen in FlG. 7 is tear drop in configuration extending to the rear of the hull.

Yet another configuration of the hull design in accordance with the present invention may be seen in FIGS. 9 through 11 wherein the hull includes

side skegs

100, 102 as described hereinabove as well as a water cutting or penetrating bow portion 104. The bottom of the hull includes four

side chambers

106, 108, 110 and 112 as well as a fifth center chamber 114. The side chambers 106 through 112 are separated from the center chamber 114 by means of

intermediate wall portions

116, 118. As described hereinabove the air under pressure is trapped within these chambers and serves to lift and reduce frictional resistance of the boat. It has been found that for maximum efficiency the central section 114 should be as flat as possible and should have an angle to the horizontal of approximately 5, said angle not being particularly critical except that it should be as flat as possible and terminating in a flat portion 120 as best seen in FIG. 11. It is to be understood at this point that not only the central portion 114 flattens out at the after end but likewise the two side

rear sections

106 and 112 likewise flatten out to reduce drag and to reduce cavitation due to entrained air in the water ahead of the thrust propeller.

Air under pressure is introduced to the chambers at the bottom of the hull via plenum 122 which is supplied from any available source via conduit 124 as described hereinabove. As best seen in FIG. the air is applied to the chambers themselves from the plenum 122 by means of downwardly extending open conduits 126 which feed to rear chambers, conduits 128 which feed the two forward side chambers and 130 which feeds the central chamber.

As noted above the central chamber should be as flat as possible and approximately 5, whereas the four side chambers as well as the hull have been found to be most efficient with an angle of about l0"; however, it is to be noted that the precise angle is not critical as long as it is sufficiently flat that it does not introduce a lot of air and turbulence into the water causing cavitation of the thrust propeller.

Thus, it can be seen that great stability is provided for a boat hull by compartmenting the bottom portion and placing a great deal of pressure upon the outside corners while providing a central relatively low pressure area allowing a rearward escape of air which leaves the high pressure area. The soft riding qualitites are obtained by absorbing most of the waves passing under the boat in the air chambers. This is further enhanced by a soft rollof foam produced at the lower edge of the divider-walk which i arm the air chambers under the boat.

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

1 A boat hull designed to suppress the pounding, rolling, and pitching normally associated with such vehicles comprising;

an elongated main body portion having an upper surface adapted to a variety of configurations and uses,

means to impart linear movement to the hull,

a pair of parallel skegs extending substantially the entire length of the hull, one along each side, said skegs being the lowermost element of the hull, said skegs continually in contact with the supporting water during operation of the hull,

a plurality of pressurized air chambers within the bottom portion of the hull between the two skegs, said skegs serving as a wall portion of the air chamber,

a central low pressure area separated from the pressurized chambers and located therebetween, said area adapted to receive air overflow under pressure from the pressurized air chambers and exhaust it to the atmosphere, and

means for supplying air under pressure to the pressurized chambers whereby when the hull is in motion, it partially rides on a bubble of air captured within the chambers, said pressure being greater along the outer edges providing a direct reactionary force to any tendency of the boat to roll or pitch since the air is captured and compressed in the area tending to dip while the air in the high portion is allowed to escape thereby generating a moment counter to the normal movement.

2. A boat hull as in claim 1 wherein the central low pressure area comprises a narrow channel having walls of less depth than the skegs extending the entire length of the boat, reducing the bow wave pressure by allowing some of the water to pass the length of the hull.

3. A boat hull as in claim 1 wherein the low pressure area comprises a generally centrally located chamber.

4. A boat hull providing a stable ride comprising;

a top surface,

a bottom surface,

bow, stern and sides joining the top and bottom and completing the hull structure,

said bottom surface comprising a plurality of high pressure chambers along the outside edge adapted to entrap air under pressure to displace water and separated from each other by divider walls, said high pressure chambers connected to a source of pressurized air, a pair of parallel sides running substantially the full length of the hull along the outside edge, said sides forming the lowest part of the bottom and continually in contact with the supporting water during operation of the hull, and a low pressure area between at least some of the high pressure chambers separated therefrom by divider walls of less depth than the sides whereby water and excess air forced out of the high pressure chambers may escape into the low pressure area, such that when the hull tends to roll or pitch, the water below the chambers in the direction of the movement is further displaced by the compressed air, thus increasing the buoyancy whereas the water below the opposing chambers is displaced less tending to resist the movement, thus producing a righting force.

5. A boat hull as in claim 4 wherein the hull is subter. stantially rectangular and the high pressure chambers 7. A boat hull as in claim 4 wherein the side skegs are are located at the four comers of the hull. buoyant members and further offer little resistance 6. A boat hull as in claim 4 wherein the divider beduring movement through the water.

tween some of the high pressure chambers are trans- 5 8. A boat hull as in claim 7 wherein the dividers are verse to the normal direction of travel and are designed buoyant. to offer little resistance when passing through the wa-

Claims

1. A boat hull designed to suppress the pounding, rolling, and pitching normally associated with such vehicles comprising; an elongated main body portion having an upper surface adapted to a variety of configurations and uses, means to impart linear movement to the hull, a pair of parallel skegs extending substantially the entire length of the hull, one along each side, said skegs being the lowermost element of the hull, said skegs continually in contact with the supporting water during operation of the hull, a plurality of pressurized air chambers within the bottom portion of the hull between the two skegs, said skegs serving as a wall portion of the air chamber, a central low pressure area separated from the pressurized chambers and located therebetween, said area adapted to receive air overflow under pressure from the pressurized air chambers and exhaust it to the atmosphere, and means for supplying air under pressure to the pressurized chambers whereby when the hull is in motion, it partially rides on a bubble of air captured within the chambers, said pressure being greater along the outer edges providing a direct reactionary force to any tendency of the boat to roll or pitch since the air is captured and compressed in the area tending to dip while the air in the high portion is allowed to escape thereby generating a moment counter to the normal movement.

4. A boat hull providing a stable ride comprising; a top surface, A bottom surface, bow, stern and sides joining the top and bottom and completing the hull structure, said bottom surface comprising a plurality of high pressure chambers along the outside edge adapted to entrap air under pressure to displace water and separated from each other by divider walls, said high pressure chambers connected to a source of pressurized air, a pair of parallel sides running substantially the full length of the hull along the outside edge, said sides forming the lowest part of the bottom and continually in contact with the supporting water during operation of the hull, and a low pressure area between at least some of the high pressure chambers separated therefrom by divider walls of less depth than the sides whereby water and excess air forced out of the high pressure chambers may escape into the low pressure area, such that when the hull tends to roll or pitch, the water below the chambers in the direction of the movement is further displaced by the compressed air, thus increasing the buoyancy whereas the water below the opposing chambers is displaced less tending to resist the movement, thus producing a righting force.

5. A boat hull as in claim 4 wherein the hull is substantially rectangular and the high pressure chambers are located at the four corners of the hull.

6. A boat hull as in claim 4 wherein the divider between some of the high pressure chambers are transverse to the normal direction of travel and are designed to offer little resistance when passing through the water.

7. A boat hull as in claim 4 wherein the side skegs are buoyant members and further offer little resistance during movement through the water.

8. A boat hull as in claim 7 wherein the dividers are buoyant.