US3481297A

US3481297A - Multi-mode variable geometry surface effect ship

Info

Publication number: US3481297A
Application number: US689743A
Authority: US
Inventors: Peter J Mantle
Original assignee: General Dynamics Corp
Current assignee: General Dynamics Corp
Priority date: 1967-11-13
Filing date: 1967-11-13
Publication date: 1969-12-02
Anticipated expiration: 1986-12-02

Description

P. J. MANTLE v 3,481,297

MULTI-MODE VARIABLE GEOMETRY SURFACE EFFECT SHIP Dec. 2, 1969 5 Sheets-Sheet 1 Filed Nov. 15, 1967 PE TER J MA/VTLE INVENTOR a/MM ATTORNEY Deg. 2, 1969 P. J. MANTLE 3,431,297

MULTI-MODE VARIABLE GEOMETRY SURFACE EFFECT SHIP Filed Nov. 13, 1967 5 Sheets-Sheet 2 PE T E H J. MAN TLE INVENTOR.

ATTORNEY Dec. 2, 1969 p. J, M N 3,481,297

MULTI-MODE VARIABLE GEOMETRY SURFACE EFFECT SHIP Filed NOV. 13, 1967 5 Sheets-Sheet 5 PETER J. MA/VTLE INVENTOR.

w/JMM ATTORNEY P. J. MANTLE 3,481,297

MULTI-MODE VARIABLE GEOMETRY SURFACE EFFECT SHIP Dec. 2, 1969 v5 Sheets-Sheet 4.

Filed Nov. 13, 1967 PETERJMA/VTLE INVENTOR.

A 7'TORNEY Dec. 2, 1969 J, MANTLE 3,481,297

MULTI-MODE VARIABLE GEOMETRY SURFACE EFFECT SHIP Filed Nov. 13,1967 5 Sheets-Sheet 5 PETE/Pi MANTLE INVENTOR.

ATTORNEY United States Patent ABSTRACT OF THE DISCLOSURE A surface effect ship is provided having a skirt at the front portion of the vehicle with side hulls on a rear portion of the vehicle extending backward from the skirt. The side hulls are rotatable from a vertical downward position, in which they hold an air cushion, to a horizontal outward position, in which they form a portionof the aerodynamic surface of a ship operating in a high speed ram wing mode.

The present invention relates to vehicles for traveling over water and for limited traveling over land, the vehicle being at least partly supported above the surface over which it operates by dynamic interaction with the surface below, such interaction being known as surface effect.

Surface effect ships operating at low speed over water rely for support of the ship upon the conventional captured air bubble or region of higher pressure entrapped under the planform of the vehicle by conventional means, such as a plenum, peripheral jets, sidewalls, or recirculation means. If it is desired to control yaw and direction, it is necessary to have at least a portion of the side hulls of the vehicle extending downward into the water surface. This construction is more fully described in application Ser. No. 611,355 of Peter I Mantle and Arnold M. Hall, entitled Multiple Hull Vehicle With Air Cushion Support filed Jan. 24, 1967. As described therein, these surface penetrations, or hulls, are shaped like boat hulls to reduce hydrodynamic drag to a minimum. Unfortunately, this design produces increasing hydrodynamic drag as the speed increases to the point where the efficiency of the vehicle, defined as weight times velocity over power, decreases to an unfeasible figure. Therefore, vehicles which are to be used at higher speeds must be designed with reduced hulls or none at all, which will make them more efficient at high speeds, but relatively less controllable at low speeds. Also, these vehicles which are designed to travel clear of the water, supported primarily by increased air pressure under the vehicle eventually reach a point in speed at which the air pocket underneath the vehicle is too quickly lost, and at this point their efliciency descends also to a non-feasible level. Above this speed the only surface effect vehicle which can operate efficiency is the ram wing vehicle, which generates by interaction with the ground an increased pressure region on its underside, but also generates a reduced pressure region on its topside by known aerodynamic principles. A vehicle designed for operation in this high speed region will, of course, possess neither a means of support nor control of direction at low speeds or intermediate speeds.

The present invention obtains the advantages of all three of these modes to provide efficient operation at low, intermediate, and high speeds. It does this by providing side hulls on the vehicle on the rear portion thereof which are rotatable to vary the geometry of the vehicle to the most efficient form in all three modes. In the low speed mode, the side hulls are rotated to point straight downward to act as displacement or planing hulls, thereby providing all of the advantages noted in the above mentioned application Ser. No. 611,355. In the intermediate mode, the side hulls are rotated outwardly at an angle so as to be clear of the water, but to point downwardly sufficiently to maintain an air cushion underneath the vehicle. In the high speed mode, the hulls rotate to a horizontal position where they form together with the rest of the vehicle an aerodynamically designed surface to provide maximum lift and efficiency as a ram wing vehicle.

Accordingly, it is an object of the invention to provide a surface effect ship which is efficient in the low, intermediate, and high speed modes.

It is further an object of the invention to provide a surface effect ship which has side hulls which are efficiently designed as displacement or planning hulls.

It is yet another object of the invention to provide a surface effect ship with hulls which rotate outwardly so as to clear the water surface, but provide means to retain a supporting air cushion.

It is still another object of the invention to provide a surface effect ship having side hulls rotatable to a horizontal position where they form a portion of an aerodynamic surface supporting the ship.

It is a further object of the invention to provide a surface effect ship with an air cushion retaining skirt which may be collapsed against the lower surface of the ship at high speeds.

Further objects of the invention will become apparent in the following description when considered in conjunction with the following figures wherein:

FIG. 1 is a side elevation of a surface effect ship according to the present invention with the rotatable side hulls extending vertically downward.

FIG. 2 is a front elevation of the surface effect ship of FIGURE 1.

FIG. 3 is a front elevation of the surface effect ship in FIGURE 1 showing the side hulls rotated outwardly at an angle so as to be clear of the water.

FIG. 4 is a top elevation of the surface effect ship in FIGURE 1.

FIG. 5 is a top elevation of the surface effect ship in FIGURE 1 with the side hulls rotated to extend horizontally outward.

FIG. 6 is a bottom elevation view of the surface effect ship according to FIGURE 1 showing the underside of the vehicle with its collapsible skirt.

FIG. 7 is a part section, part elevation view along the lines 77 in FIGURE 6 showing the construction of the collapsible skirt.

FIG. 8 is a bottom elevation view of a portion of the collapsible skirt in the open position.

FIG. 9 is a bottom elevation view of the collapsible skirt in FIGURE 8 shown in the closed position.

FIG. 10 shows a diagram of the relationship between speed and performance efiieiency of the surface effect ship according to the present invention compared with conventional craft in the low, intermediate, and high speed modes.

Referring now to FIGURE 1, there is shown a surface effect ship 20 according to the invention comprising a body portion 21, a cabin 22, and side hulls 23. Side hulls 23 are rotatable around a pivot line shown in FIGURE 1 as dotted line 24, by mechanisms controllable from cabin 22, not shown. Each of side hulls 23 is designed generally in accordance with the teachings of the above mentioned application Ser. No. 611,355. Each is provided with a chine line 25 with a chine therebelow sloping inwardly toward a keel 26. Since the side hulls 23 must fair with the body 21 when in the horizontal position, they are sloped inwardly toward the rear, as may be seen more clearly in FIGURE 4. The shape of body 21 descends toward the rear in accordance with well-known aerodynamic principles. It also has a very faint hump, so that the fairing line 28 of side hulls 23 is slightly below the top of body 21. The lower portion of cabin 22 is also shaped as a hull 27 in accordance with well-known marine hydrodynamic principles as taught in the above-mentioned application Ser. No. 611,355.

On the underside of body 21, forward of the side hulls 23, there is suspended the skirt 31, composed of flexible, but relatively stifi, panels 32 connected between themselves by elastic panels 3-3, as shown more specifically in FIGURES 7 through 9. The skirt 31 when opened in the low and intermediate speed modes, contains, together with hulls 23, the air cushion which supports the vehicle in its flight. The construction of skirt 31 will be described subsequently.

When in the low speed mode, the ship 20 is steered by movable rudders 34 attached in a rotating manner to the rear end of each of the two side hulls 23. These rudders 34 also function as elevators when the side hulls 23 are in their horizontal position in the high speed mode. The rudder elevators 34 are controlled from the cabin 22 in all speed modes by known mechanisms not shown. In the intermediate and high speed modes, the control of direction of the ship is managed by an air rudder 35, having a movable rear end section 36.

Propulsion of the ship in all modes of speed may be provided by engines 37 mounted on the rear deck of the ship 20. Engines 37 are shown as jets, but may alternately be propellers. It may also be feasible in the low speed mode to provide propulsion by a marine screw, not shown, or by the same mechanism which provides the air cushion for the underside of the vehicle, to be described subsequently.

In FIGURE 2 is shown a front view of the ship 20 with the hulls 23 extending downwardly in the low speed mode. The skirt 31 is inflated to contain at the front end of the ship the air cushion which supports the vehicle. The rear ends of the skirt 31 lie back against the inside of the hulls 23. As is seen in FIGURE 2, when the hulls 23 are penetrating the water and the ship is supported by an air cushion, the surface of the water will be depressed slightly under the ship by the increased pressure.

In FIGURE 3 is shown the ship 20' in the intermediate speed mode with the hulls 23 rotated so that the keels 26 are at approximately a 45 angle from the vertical. At this angle, they will be clear of the water, but they will still act to help contain the air cushion, which still provides a major portion of the total support of the ship. In this mode, however, a small portion of the support of the ship is provided by the aerodynamic effect of the shaping of the central body portion 21 of the ship. In this mode, little or no assistance is provided aerodynamically by the side hulls 23. As shown in FIGURE 3, in the intermediate speed mode, the skirt 31 is still extended downwardly and the rear ends of it are stretched outwardly as far as they can go to lie against the inner sides of the hulls 23.

In FIGURE 4, showing a top view of the ship 20 in the low speed mode, there can be seen an opening in the central body portion 21 containing the fan 38 which provides the air for the air cushion on the underside of the body 21. The construction and ducting of the fan 38 are not shown as they are well kown in the art of surface effect ships. In FIGURE is another top view of the ship 20, this time with the side hulls 23 rotated out horizontally. In the top views in FIGURES 4 and 5, it will be seen that the line of rotation 24 of the hulls 23 is exactly in line with the fairing lines 28 where the hulls 23 fair with the body portion 21. It will be appreciated that this is mechanically necessary to assure smooth flowing lines. Also seen in FIGURE 5 is the rear flap 39, which in the high speed mode, shown in FIGURE 5, extends horizontally outward from the rear underside of the ship .20. Rear flap 39 can be seen more completely in FIG- URE 6. It is suspended from the underside of the body portion 21 at a point a short ways forward of the rear edge of the body portion 21 and between the rear ends of the two side hulls 23. It is rotatably movable about its upper edge and is controllable from the cabin by a standard mechanism, not shown. It is used in the low speed mode and intermediate speed mode to help contain the air cushion providing all or a major portion of the support of the ship 20, and in the high speed mode is movable to help provide longitudinal control of the attitude of the ship along with the rudder elevators 34.

FIGURE 7 shows a section of one of the flexible flaps 32 which form the skirt 31. These flexible flaps 32 bend so as to lie flat or extend downwardly, as desired. They are supported in between them by elastic panels 33, as shown in FIGURE 8, from bending too far outwardly and allowing the air cushion to be dissipated. The flexible panels 32 may be made of leather or inelastic rubber or any other flexible substance which will hold up under the demands of tension placed on them. The elastic panels 33 in between the flexible members 32 are made of an elastic material, such as rubber. In operation, the skirt 31 is expanded to its open position by individual blasts of air on each of the flexible flaps 32 through passages 41. Air is supplied to each of passages 41 by the fan 38 through ducting which is in itself well known in the art and is therefore not shown. Alternatively, flaps 32 may be pushed open by small jacks operated from the cabin. It will be recognized, of course, that once the skirt is open it will stay open due to the pressure of the air cushion trapped behind it in the low and intermediate modes. In the high speed mode, flaps 32 are intended to lie fiat against the undersurface of the vehicle, and therefore no air will be supplied to passages 41. Although there are shown a large number of flaps 32, it will be understood that any number down to two flaps 32 will be elfective to contain an air cushion.

The effectiveness of the surface effect ship disclosed herein in accomplishing the objects of the invention may be seen by reference to FIGURE 10 which plots performance efiiciency, WV/P, against the Speed of the craft. Dashed lines 44 indicate typical efliciencies for a craft having side walls extending into the water. This corresponds to the low speed mode of the present invention and is shown, for example, in the above mentioned application Ser. No. 611,355. In this mode, typically, the efiiciency of the craft starts out relatively high and decreases as the craft approaches hump speed, which is the speed at which the hull or hulls switch from displacement to planing support. There is, typically, a dip in efiiciency at the hump speed, after which, since the bulls are now planing on the surface of the water rather than displacing water, there will be a rise in efiiciency for a while, As the speed gets higher, however, the efficiency of the planing hull craft inevitably decreases to the point of unfeasibility, as shown by lines 44. As FIGURE 10 indicates, this type of craft will be relatively more eflicient if the draft of the craft in the water is relatively less.

The efl'lciency of the typical air cushion vehicle in the intermediate mode is shown by dash-dotted lines 45. In the intermediate speed mode, the craft is supported by an air cushion but does not penetrate the water at any point. Due to the power necessary to maintain the air cushion, this type of craft is quite inefficient at lower speeds and rises to a maximum efliciency at a speed considerably above the most eflicient speed of the low speed mode. However, as the speed gets higher, it takes an increasing amount of power to maintain the cushion under the rapidly moving vehicle, and therefore the efiiciency begins to decrease above a certain speed in the intermediate range.

Dotted lines 46 in FIGURE 10 show the typical efiiciencies for a ram wing craft, which corresponds to the high speed mode. In this mode of travel, the vehicle relies for its support on decreased pressure on the upper surface due to aerodynamic lift and increased pressure on the lower surface due to proximity to the surface and the ram wing effect. This mode of vehicle is more efficient than the other two modes of vehicles, as indicated by the relative positions of dotted lines 46, but since it must be at relatively high speed to be supported at all, its efiiciency drops sharply below its customary ranges of operation. As shown in FIGURE. 10, vehicles in both the intermediate and high speed modes operate relatively more efficiently with decreased air gap between the vehicle and the surface over which it is traveling. This is to be expected, since it decreases the power requirements for maintenance of the relatively higher pressure region under the vehicle.

Solid line 47 indicates the typical efliciency of the variable geometry surface effect ship according to the present invention. At the lowest speed, below hump speed, the craft is supported at its rear end by displacement hulls 23 and at its front end either by hull 27 or by the air cushion inside of skirt 31. As the speed increases to bump speed, the efficiency dips at points 48 and then rises as the craft goes over hump speed and hulls 23 become planing hulls," Above hump speed, the craft would be supported at its front end by the air cushion behind skirt 31. However, as the vehicles efliciency dips toward point 49, the hulls 23 will be drawn gradually out of the water, and it will come to rely more purely on the air cushion for its support. It will then have shifted into the intermediate speed mode, and its efiiciency will then rise to a relative maximum at point 50. As the craft continues to go faster, the bulls 23 will be rotated further toward the horizontal, the skirt 31 will be pressed backwards by increasing aerodynamic pressure, and the vehicle will gradually pass into the high speed mode of travel, in which its efliciency will rise to point51.

It will be understood from the foregoing that suitable alterations in the mechanisms and substitutions of materials may be made without departing from the spirit or scope of the invention as defined by the appended claims.

What is claimed is:

1. A surface effect vehicle which depends in operation for a portion of its support on a region of superatmospheric pressure on its underside, comprising:

a body planform having an intended line of travel;

a pair of displacement hulls on said body planform, being rotatable along axes generally parallel to said line of travel from a first position extending downwardly to a second position extending horizontally outwardly from said body planform providing support for said vehicle in water in said first position, said hulls having continuous planing surfaces on their lowermost extremities providing hydrodynamic lift at low speeds above hump speed; and

a. skirt suspended from the underside of said body planform forward of said side portions containing together Witth said side portions when in said first position, a region of superatmospheric pressure on the underside of said body plan-form.

2. A surface effect vehicle as defined in claim 1, wherein said skirt is collapsible against the underside of said planform.

3. A surface effect vehicle as defined in claim 1, further comprising:

a flap rotatable about an axis perpendicular to the line of travel on the underside of said planform adjacent the rear edge thereof, said flap, together with said skirt and said side portion-s when in said first position, containing said region of superatmospheric pressure.

4. A surface eflect vehicle which depends in operation for a portion of its support on a region of superatmospheric pressure on its underside, comprising:

a body planform having an intended line of travel;

a pair of side portions on said body planform, being rotatable along axes generally parallel to said line of travel from a first position extending downwardly to a second position extending horizontally outwardly from said body planform, wherein said side portions are aerodynamically shaped on their upper surfaces in said second position to provide regions of subatmospheric pressure thereover in forward travel; and

a skirt suspended from the underside of said body planform forward of said side portions, containing, together with said side portions when in said first position, a region of superatmospheric pressure on the underside of said body planform.

5. A surface effect vehicle which depends in operation for a portion of its support on a region of superatmospheric pressure on its underside, comprising:

a body planform having an intended line of travel;

a pair of side portions on said body planform, being rotatable along axes generally parallel to said line of travel from a first position extending downwardly to a second positi n extending horizontally outwardly from said body planform, wherein said side portions have at their rear edges controllably rotatable surfaces, said surfaces acting as rudders in said first position and elevators in said second position; and

6. A surface effect vehicle which depends in operation for a portion of its support on a region of superatmospheric pressure on its underside, comprising:

a. body planform having an intended line of travel and being aerodynamically shaped to provide a region of subatmospheric pressure thereover in forward travel;

a pair of side portions on said body planform, being rotatable along axes generally parallel to said line of travel from a first position extending downwardly to a second position extending horizontally outwardly from said body planform; and

a skirt suspended from the underside of said body planform forward of said side portions, containing, together with'said side portions when in said first position, a region of superatmospheric pressure on the underside of said body planform.

7. A surface effect vehicle which depends in operation for a portion of its support on a region of superatmospheric pressure on its underside, comprising:

a body planform having an intended line of travel;

a skirt suspended from the underside of said body planform forward of said side portions, containing, together with said side portions when in said first position, a region of superatmospheric pressure on the underside of said body planform, wherein said skirt is collapsible against the underside of said planform and the rear edges of said skirt lie flat against the inside surfaces of said side portions in said first position.

8. A surface effect vehicle which depends in operation for a portion of its support on a region of superatmospheric pressure on its underside, comprising:

a body planform having an intended line of travel;

a skirt suspended from the underside of said body planform forward of said side p rtions, containing, tO- References Cited gether with said side portions when in said first posi- UNITED STATES PATENTS tion, a region of superatmospheric pressure on the underside of said body planform, and including: 112891808 12/1918 P Y et 115-4 a series of flexible flaps rotatable between a vertical 5 3,205,847 9/1965 m 114-671 position pointing generally downward and a hori- 3:389:67? 6/1968 Wmter zontal position lying flat against the underside of i la f r ANDREW H. FARRELL, Primary Examiner controllable means to force each of said flaps to said vertical position; and 10 US. Cl. X.R. an elastic surface extending between each pair of said 5