GB2075935A - Air cushion vehicle skirts - Google Patents

Abstract

The cushion (15) of a gas-cushion vehicle (10) suitable for over water use, is contained, at least in part, by a plurality of flexible wall structures or skirts (30, 31, 32) disposed one above the other and divided from each other by structural components (33, 34, 35) defining surfaces cooperating with the skirts so as to at least restrict the outward escape of cushion gas. The components (33, 34, 35) preferably comprise foil members which may be made stationary or movable. If made movable, this may be done automatically, in response to unwanted movements and attitudes (e.g. heave and pitch) of the vehicle. Applied to bow wall of a rigid sidewall craft, to allow high waves to spill between the foils, deflecting one or more of skirts 30, 31, 32. <IMAGE>

Description

SPECIFICATION Improvements in or relating to gas-cushion vehicles This invention relates to gas-cushion vehicles, that is to say, to vehicles for travelling over a surface and which, in operation, are supported above that surface, at least in part, by a cushion of pressurised gas, for example, air, formed and contained beneath the vehicle body.

The vehicle-supporting cushion may be contained, at least in part, by flexible wall structures or "skirts" attached to and depending from the vehicle body.

Gas-cushion vehicles for operation over water are naturally designed to travel over waves, the heights of which are substantially the same as the heights of the largest waves to be expected. Hitherto, such vehicles have only been called upon and consequently have only been designed for operation over waves of relatively small height, say 3 to 4 feet.

To allow gas-cushion vehicles to operate over large waves, say 10 to 16 feet, a cushion is required of substantially the same height as the waves.

However, this introduces problems in manufacturing the large flexible skirts needed to contain the vehicle-supporting cushions. Such skirts are also very expensive as they make use of substantial quantities of flexible sheet material.

The present invention is particularly, (but not exclusively), concerned with the "sidewall" type of gas-cushion vehicle, comprising a vehicle body and a laterally-spaced pair of "sidewall" structures extending longitudinally along the sides of the vehicle body and depending therefrom so as to contain the sides of the vehicle-supporting cushion. In the case of sidewall vehicles for operation over water, the sidewalls thereof are usually of rigid construction and, in operation of the vehicle, dip into the water so as to provide a cushion-gas seal.

A sidewall gas-cushion vehicle designed to operate over large waves has been disclosed by British Patent No. 1,184,062. (U.S. Patent No. 3,559,608 of Tattersall corresponds).

According to the present invention, in operation, the cushion of a gas-cushion vehicle is contained, at least in part, by a plurality of flexible wall structures or skirts disposed one above the other and divided from each other by components defining surfaces cooperating with the wall structures so as to at least restrict the outward escape of cushion gas.

The components preferably comprise foil members. The foil members may be made stationary or movable. If made movable, this may be done automatically, in response to unwanted movements and attitudes of the vehicle.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein Figure 1 is a front end view, in section, of a sidewall gas-cushion vehicle, Figure 2 is a side view, in medial section and to an enlarged scale, of the bow part of the vehicle, and Figure 3 is a view looking in the direction of arrow Ill of Figure 2.

Figure 1 shows a sidewall gas-cushion vehicle of the form disclosed by British Patent No. 1,184,062.

The vehicle 10, which is shown travelling overthe surface of water 2, comprises a pair of laterallyspaced rigid body structues (sidewalls) 11 of buoyant construction and of hollow, elongated from extending longitudinally in substantially parallel array and adapted to carry the payload of the vehicle, structural means in the form of spaced members 12 extending between the fore-and-aft ends of the body structures 11 so as to interconnect them and flexible sheeting means 13 covering the space between the structures 11 and attached thereto in a sealing manner so as to form a membraneous barrier between the space and the atmosphere above. Axial fan means 14 are disposed in horizontal ductsforforming a cushion 15 of pressured air within the space.The sheeting 13 is subjected to pure tension and can thus be made of thin, lightweight flexible material.

Access to and exit from the interiors of the body structures 11, which are of multideck construction, is by way of doorways 17 formed in the outer side surfaces of the structures. The vehicle 10 is propelled by conventional waterscrew propellers 18 driven by engines 19 disposed in the body structures 11.

As the payload of the vehicle 10 is carried within the sidewall body structures 11, the centre of gravity (c.g.) of the vehicle is disposed within the cushion 15. The design of the vehicle 10 is such that its c.g.

will also be disposed within the cushion 15 even if the vehicel is carrying little or no payload.

With reference now to Figures 2 and 3, much of the bow end of the vehicle-supporting cushion 15 is contained by a plurality of strip-like flexible wall structures or skirts 30,31,32 disposed one above the other and divided from each other by structural components in the form of foil members 33,34,35.

The upper faces of the foil members 33,34,35 define surfaces which cooperate with the lower edges of the wall structures 30,31,32 so as to at least restrict the outward escape of cushion air.

The lower edges of the wall structures 30,31,32 are flexibly restrained by tie-cords 36,37,38. Tie-cords 36 are secured to a spacing member 12, and tie-cords 37 and 38 to the trailing edges of foil members 34 and 35.

The lower part of the bow end portion of the cushion 15 is contained by a two-stage flexible skirt system comprising a wall structure 40, the upper edge of which is secured to the leading edge of foil member 35, and a row of contiguous flexible skirt members 41 attached to and depending below the lower edge of the wall structure 40. The skirt members 41 are of the form disclosed by British Patent Specification No. 1,043,351. Briefly, each skirt member 41 comprises a generally triangular sheet of flexible material folded over to give the member a "U"-like plan form, with a middle or lateral portion 41a flanked by a pair of said of tie-portions 41b. The skirt members 41 are restrained by tie-cords 42 attached to and extending between the inner corners of the side portions 41b and a support beam 43 attached to and extending laterally between the body structures 11.

The flexible components 30,31,32,40,41 are of rubberised fabric.

In operation, the flexible skirt system 40/41 deflects in the well-known manner to accommodate small waves.

If the vehicle 10 encounters large waves, one or more of the flexible wall structures 30,31,32 can deflect inwards on impact, so as to accommodate these waves.

With reference to Figure 3, if desired, the wall structures 30,31,32 can each be of multi-partform (Adjacent edges of the contiguous parts are indicated by the dotted lines 45, 46,47). This arrangement localises wall deflection. Adjacent flexible wall portions can be divided by vertical structures which may comprise supports for the foil members 33,34, 35.

The invention not only introduces a substantial saving in the cost of manufacture, it also tends to localise any damage to the flexible material, thus easing repair problems.

The foil members 33,34,35 not only provide cooperating air-seal surfaces for the flexible wall members 30,31,32, they also serve to generate vehicle-restoring forces should the vehicle 10 pitch or roll unduly in heavy seas.

These vehicle-restoring forces can be modified by giving the foil members 33,34, 35 a dihedral or anhedral shape.

The use of such shapes will, however, necessitate corresponding changes in shape of the flexible wall structures 30,31,32.

The foil members can be made to remain stationary or, alternatively, may be made movable. If made movable, movement can be automatic, to correct unwanted movements and attitudes of the vehicle.

To this end, the foil members may be moved by actuator means operable by devices (for example, accelerometers) sensitive to the unwanted changes in vehicle movements and attitudes.

The structure illustrated by Figures 2 and 3 can also be used to contain the stern end of the vehicle 10. To prevent "scooping", the flexible skirt members 41 may be replaced by "double" skirt members, as disclosed by British Patent Specificiation No.

1,109,562.

Claims (10)

1. A gas-cushion vehicle, wherein in operation, the vehicle-supporting cushion is contained, at least in part, by a plurality of flexible wall structures disposed one above the other and divided from each other by components defining surfaces cooperating with the wall structures so as to at least restrict the outward escape of cushion gas.

2. A gas-cushion vehicle as claimed in Claim 1, wherein the components comprise foil members.

3. A gas-cushion vehicle as claimed in Claim 1 or 2, wherein the foil members are made stationary.

4. A gas-cushion vehicle as claimed in Claim 1 or 2, wherein the foil members are movable.

5. A gas-cushion vehicle as claimed in Claim 4, wherein the foil members are movable automatically in response to unwanted movements of the vehicle.

6. A gas-cushion vehicle as claimed in any one of Claims 2 to 5, wherein the foil members have a dihedral shape.

7. A gas-cushion vehicle as claimed in any one of Claims 2 to 2, wherein the foil members have an anhedral shape.

8. A gas-cushion vehicle as claimed in any one of Claims 1 to 7, wherein the wall structures are of multi-part form.

9. A gas-cushion vehicle as claimed in any one of Claims 1 to 8, comprising a vehicle body and a laterally-spaced pair of wall structures extending longitudinally along the sides of the vehicle body and depending therefrom so as to contain the sides of the vehicle-supporting cushion, wherein, in operation over water, the wall structures dip into the water so as to provide a cushion-gas seal.

10. A gas-cushion vehicle substantially as hereinbefore described with reference to Figures 1,2 and 3 of the accompanying drawings.