GB2458003A

GB2458003A - Amphibious vehicle having buoyant side-hulls and an air cushion skirt

Info

Publication number: GB2458003A
Application number: GB0901011A
Authority: GB
Inventors: John Christopher Lewthwaite
Original assignee: IMAA Ltd
Current assignee: IMAA Ltd
Priority date: 2008-03-06
Filing date: 2009-01-22
Publication date: 2009-09-09
Anticipated expiration: 2029-01-22
Also published as: GB0901011D0; GB2458003B; GB0804175D0

Abstract

An amphibious vehicle 1 includes two buoyant side-hulls 2b and an air cushion skirt. The skirt includes side-hull skirt structures (20, fig 10), provided below respective side-hulls 2b. Also included is a bow skirt structure (40, fig 10) which extends across a bow of the vehicle and a stern skirt structure (30, fig 10) which extends across the stern of the vehicle. The underside of the portion of the vehicle that extends between the side-hulls may be concave (18, fig 1). Rails 10 or jacks (14, fig 6) may also be provided to support the vehicle when stationary on a hard surface.

Description

AMPHIBIOUS VEHICLE

Technical Field

The present invention relates to amphibious vehicles.

Background

Vehicles such as hovercraft, comprise a raft-like structure which supports lift machinery and payload, and around which a peripheral bag and fingered skirt is attached. Pressurised air is pumped into the peripheral bag by lift fans and is distributed into fingered segments below the bag through small feed holes. This arrangement incurs a large energy loss in the air distribution system. The roll stiffness of such craft is generated by the immersion of the fingers on the down-going side as the craft heels and the support of the inflated bag. The resultant stiffness is small compared to floating type displacement vessels. As a result of the supporting air-cushion, the resistance of such craft to forward motion is small compared to other types of vessels which rely on buoyancy for their support in water.

Sidewall hovercraft have skirts or seals only at their bow and stern. The side-hulls remain in contact with the water and although their resistance remains low they require a small depth of water in which to operate and hence are not amphibious. Such sidewall hovercraft are generally slightly more stable than the above hovercraft types.

Known catamaran vessels comprise two buoyant side hulls which support the weight of the vessel when floating in water. Such side-hulls are conventionally long and narrow, and hence require a substantial depth of water in order to float. Such vessels are therefore not amphibious.

Furthermore, because of the reduction in width of their water-planes such vessels require a greater depth of water than conventional mono-hull types.

We have realised that it would be beneficial to provide an improved vehicle.

Summary

According to one aspect of the invention there is provided an amphibious vehicle comprising two buoyant side hulls and an air cushion skirt, the skirt comprising side hull skirt structures provided below respective side hulls, a bow skirt structure extending across a bow of the vehicle and a stern skirt extending across the stern of the vehicle.

In one embodiment of the invention we provide a vessel comprising two side-hull structures, and inflatable fingered segments provided below the hull structures. Such an embodiment further comprises a flexible seal which extends across the stern and bow ends. A supply of pressurised air from fans carried by the vessel inflates a cushion region below the vessel, which cushion is retained by the peripheral skirt formed of the fingered segments and the flexible end seals, and to so enable the vessel to hover clear of the surface. in order to provide adequate roll stiffness but at the same time achieve a desired vessel width to confirm to docking facility dimensional limitations, the side-hulls preferably include sufficient buoyancy to stabilise the vessel when rolling. Preferably, the depth of the side-hulls are such that the height of the centre of gravity of the vessel is restricted, which advantageously influences the roll stability of the vessel when in a hover mode. The side-hulls are desirably of sufficient buoyancy to support the vessel when floating.

One embodiment of the invention may be viewed as a catamaran with amphibious capabilities provided with an air cushion skirt.

Preferably, the fingered segments are detachably connected to the undersides of the hull structures so that they can be removed for repair or replacement. Rail members extend longitudinally along the side-hulls, and Outwardly of the fingered segments. The rail members advantageously support the vessel resting on a hard surface and so avoiding damage to the side-hull structures. The fingered segments may be directly connected to the inner sides or surfaces of the rail members.

Connection of the fingered segments is so arranged that they cannot become trapped under the rails when the rails are in contact with the ground.

Fingered segments are preferably provided across the bow of the vessel to provide a forward seal. The supporting cross-deck structure is raised in order to provide greater structural clearance at the bow and provided with an inflatable fabric ioop above the segments. Such an arrangement provides added protection to the bow from the impact of waves and permits higher speeds to be achieved in rough seas.

The fingered segments may be continued across the stern of the vessel in order to provide a rear seal to the air cushion. Such segments are preferably cone form, of conventional hovercraft type, and such segments do not scoop or collect water when the vessel is moving forward over water. The supporting cross-deck structure is raised slightly above the cones in order to provide a passage for cushion air to inflate the cones.

A system of pressurised air is preferably generated by installed lift fans which are powered by engines fitted to the vessel. The fans are preferably installed on the cross-deck structure and eject the pressurised air directly into the cushion space below the vessel, and retained by the skirt structure. The system advantageously minimises the energy loss in delivering pressurised air to the cushion. One or more fans may be fitted.

Ducted air propellers of conventional hovercraft type, powered by engines, are fitted to the vessel to provide a means of forward propulsion. One or more propellers may be fitted. Vanes or rudders may be fitted in the slipstream of such propellers in or to provide a means of steering the craft.

Pressurised air blowers may be fitted in the bows of the vessel which, when operated, blow air through louvered ducts to the side as a means of providing side force to assist steering control. The ducts may be vertical louvered to direct air forwards or backwards.

Jacks may be fitted in the deck of the vessel, so that when deployed they provide a means of lifting the vessel for skirt maintenance. Four such jacks could be installed, each at a corner position of the vessel. The jacks may be deployed with the vessel hovering, hence without incurring significant effort and remaining locked in position when the lift fans are stopped.

The structure of the vessel may be fabricated in lightweight materials such as fibre-reinforced plastics to reduce the weight of the vessel.

Brief description of the drawings

Various embodiments of the invention will now be described, by way of example only, with reference to the following drawings in which: Figure 1 is a lateral cross-section of a hovering vehicle on section A-A, Figure 2 is a lateral cross-section of a vehicle in a heeled condition hovering over water on section A-A, Figure 3 is a lateral cross-section of a vehicle on hard standing on section A-A, Figure 4 is a longitudinal section of a bow portion of a vehicle on section B-B, Figure 5 is a longitudinal section of a stern portion of a vehicle on section B-B, Figure 6 is a lateral cross section of a vehicle on section c-c, Figure 7 is an end view of the stern of a vehicle, Figure 8 is an end view of the bow of a vehicle, Figures 9(a) and 9(b) are perspective views of inflatable skirt structures, and, Figure 10 is an underside view of a vehicle.

Detailed Description

With reference initially to Figures 1 and 10, there is shown vehicle 1 with amphibious capabilities. The vehicle 1 comprises a body which comprises two side hulls 2b and mid-section, or cross-deck structure, 2a.

The vehicle further comprises an air cushion skirt which comprises two inflatable side hull skirt structures 20, an inflatable bow skirt structure 40 and an inflatable stern skirt structure 30. Collectively, the skirt structures extend around an underside of the vehicle so as to retain an air cushion. In a hovering mode propulsion equipment (not illustrated), such as a propeller assembly, mounted on the vehicle is capable of propelling the vehicle forwards.

An underlying surface 18 of the body is of continuous curved concave form, the laterally outermost portions of which define undersides of the side-hulls 2b. The vehicle 1 further comprises longitudinal rails 10 which are located at the lowermost portion of each of the side hulls 2b.

As can be seen from Figures 4 and 5 end portions of the rails 10 are upwardly inclined in the form of skids. When the vehicle 1 is located on a hard surface 11 (as shown in Figure 3), the rails advantageously provide structural support to the side-hulls.

Reference is now made to Figure 9(a). The side hull skirt structures 20 each comprise a plurality of adjacent fingered segments 4 fitted underneath the side hulls 2b. Each fingered segment 4 is constructed of flexible rubberised fabric and is of substantially U-shape arrangement.

End portions 4a of each segment are located laterally inwardly of the vehicle, and an intermediate portion 4b is located laterally outwardly.

The intermediate portion 4b forms an outer side wall. The end portions 4a are provided with through-holes 4c and allow attachment components (not illustrated), to attach the end portions to the underlying surface 18. Tab portions 25 are provided on each of the finger segments, each tab portion being provided with through-holes 25a. The through-holes 25a are arranged to register with through-holes (unreferenced) in each of the side rail members 10. By using a suitable fastener arrangement, the tabs 25 are affixed to an inner surface of each of the rails. Advantageously, this fixing arrangement of the side hull skirt structures ensures that when the vehicle is off-cushion, on hard-standing (as shown in Figure 3), the rails 10 do not rest on or trap the segments. As can be seen from Figure 1, when inflated the fingered segments 4 are within the lateral footprint of the side-hulls 2b. In other words the fingered segments 4 do not protrude laterally outermost of the side-hulls.

The bow skirt structure 40 comprises a plurality of fingered segments 4 of essentially the same shape and form as the fingered segments of the side hull skirt structures. The fingered segments 4 of the bow skirt structure are supported by an inflatable ioop 12. The bow fingered segments are fitted below the ioop 12. As can be seen from Figures 4 and 10, the loop 12, when inflated, protrudes foremost of the vehicle and is of rounded section. The loop 12 advantageously provides added protection to the bow from the impact of waves and permits higher speeds to be achieved in rough seas. The ioop 12 is inflated by air provided through the aperture 15, and so avoiding the need for a separate, dedicated pressurised air supply. As can be seen from Figure 4, a bow portion 50 of the midsection 2a of the body is raised.

This in turn provides a convenient conduit to allow the air to inflate both the ioop 12 and the bow fingered segments 4. It is also to be noted that the depths of the side hulls at the bow end are reduced and so provide greater structural clearance. As an alternative arrangement to inclusion of loop 12, deeper fingered segments could be provided around the bow, which would be of varying height to suit the change in clearance under the bow.

With reference to Figures 5 and 9(b), the stern skirt structure 30 comprises a plurality of cone segments 13. As best seen in Figure 9(b), each cone segment 13 comprises four tapering side portions 13a, 13b, 13c and 13d. The side walls 13b and 13d are each provided with tab portions 16 and 17. Each tab portion comprises two apertures 16a and 17a respectively. The tab portions allow the cone segments 13 to be attached to laterally extending rail 60 (which is connected to the rails 10 at the sides). Tab portions 17 allow the cone segments 13 to be attached to a stern portion of the vehicle body. The cone segments in use provide a rear seal to the air cushion without the tendency to scoop water in forward motion. The stern skirt structure further comprises corner skirt portions 31, each of which comprises a plurality of fingered segments 4.

Air reaches the stern skirt structure by virtue of the concave underside 18 being above the openings of the stern skirt structure so forming an air supply conduit within the region 5 (as best seen in Figure 7).

An aperture 8 is provided in the mid-section 2a and on a longitudinal axis of the body of the vehicle. The aperture 8 is in communication with a fan assembly 7. The fan assembly 7 draws air from above or from alongside the vehicle and pumps the air through the aperture 8 into a region 5 underlying the vehicle body. The air causes the skirt structures to inflate whereby an air cushion is retained under the vehicle 1, to lift the vehicle to a hovering waterline 6 (as shown in Figure 1). Pumping the air directly into the region 5 to both inflate the skirt structures and create an air cushion advantageously results in a minimum energy loss.

It will be appreciated that when the skirt structures are inflated they are capable of deflection under the action of water loads permitting the vessel to have a low resistance to forward motion and achieve high speeds.

The centre of gravity 9 of the vehicle 1 is advantageously located within the envelope of the vehicle. This ensures the adequate roll stiffness when in a hovering mode. To that end, the width, or lateral extent, of the air cushion is preferably at least three times the height of the centre of gravity. This is at least in part achieved by arranging that the side-hulls are relatively shallow in depth. Figure 2 shows the vehicle 1 in the hovering mode on water when rolled by more than a few degrees. The fingered segments 4 on the down-side are immersed, but, a righting moment is generated by the buoyancy of the immersed side hull. This righting, or restoring, moment is sufficient to ensure adequate roll stiffness of the vehicle when operated in rough sea conditions over water.

This roll stiffness is advantageously greater than the typical roll stiffness of a hovercraft Figure 6 shows a modified embodiment comprising lifting jacks 14. The jacks 14 are normally in a raised (or stowed) position and are fitted into the vehicles side-hulls 2b, towards the corners of the vessel. The jacks permit the vessel to be raised on a hard surface 11, in order that the segmented fingers 4 or cones 13 can be readily inspected, maintained or replaced. The jacks extend within the width of a segmented finger and can be deployed with the vessel on cushion, thus minimising the force required to activate the jack. The jacks may be operated either hydraulically or screwed down mechanically.

The above embodiments of the invention are able to transport any type of cargo, including freight, vehicles and/or passengers. Advantageously, the above embodiments are capable of carrying increased weight of payload as compared to a hovercraft of the same width. In other terms, the embodiments can transport the same payload amount but have reduced width, thus allowing movement and docking in areas of restricted width. A further advantage of the above embodiments is that the curved underside of the vehicle allows clearance when the vehicle is moving across uneven terrain, and so significantly reducing the risk of damage to the vehicle, and reducing the risk of underside damage over uneven terrain when stopped and resting on the side rails. There also exists the further advantage that since the side skirt fingered segments are directly attached to the underside of the hull (as opposed to be connected indirectly, for example by way of a peripheral bag structure), they are better structurally supported than those typical of other types of air-cushion vehicles. As a result, the vehicle is able to operate at higher cushion pressures and is correspondingly capable of carrying greater payloads.

Claims

CLAIMS1. An amphibious vehicle comprising two buoyant side-hulls and an air cushion skirt, the skirt comprising side hull skirt structures provided below respective side hulls, a bow skirt structure extending across a bow of the vehicle and a stern skirt structure extending across the stern of the vehicle.
2. An amphibious vehicle as claimed in claim 1 comprising an underside portion intermediate of the side-hulls of substantially curved concave form.
3. An amphibious vehicle as claimed in claim 2 in which the underside portion of the vehicle is of continuous curved concave form, the laterally outermost portions of which define respective undersides of the side-hulls.
4. An amphibious vehicle as claimed in any preceding claim which comprises a longitudinal rail member at a lower portion of each side-hull, the rail members arranged to be capable of supporting the vehicle on hard-standing.
5. An amphibious vehicle as claimed in claim 4 in which a respective side-hull skirt structure is attached to an inboard surface of the rail member.
6. A vehicle as claimed in any preceding claim in which distal end portions of the rail members are inclined.
7. An amphibious vehicle as claimed in any preceding claim in which bow portions of side-hulls and a bow portion of a mid-section of the vessel extending between the side-hulls are inclined upwardly.
8. An amphibious vehicle as claimed in any preceding claim in which the side -hull skirt structures comprise a plurality of adjacent skirt members, a skirt member comprising a portion of flexible material of substantially U-shape arrangement, end portions of the material located laterally inwardly of the vessel, and an intermediate portion of the material located laterally outwardly providing an outer sidewall.
9. An amphibious vehicle as claimed in any preceding claim comprising an inflatable bow structure which extends around the bow of the vehicle and which, when inflated, protrudes foremost of the vehicle.
10. An amphibious vehicle as claimed in claim 9 in which the inflatable bow structure is of rounded form when inflated.
11. An amphibious vehicle as claimed in claim 9 or in claim 10 in which the inflatable bow structure is located above the bow skirt structure.
12. An amphibious vehicle as claimed in any preceding claim in which the side skirt structures are attached to the side-hulls.
13. An amphibious vehicle as claimed in any preceding claim in which inflation air reaches the stern skirt by virtue of a gap above the stern skirt structure.
14. An amphibious vehicle as claimed in any preceding claim which comprises a transverse rail located towards the stern of the vehicle which extends across the vehicle, and the stern skirt structure is attached to the transverse rail.
15. An amphibious vehicle as claimed in any preceding claim in which the side skirt structures are laterally within the lateral extent of the footprint of the side-hulls.
16. An amphibious vehicle as claimed in any preceding claim in which a portion of the body of the vehicle intermediate of side-hulls is provided with an aperture, the aperture arranged to feed cushion air into an underlying region and the vehicle is arranged such that air from the underlying region inflates the skirt structures and creates an air cushion.
17. An amphibious vehicle substantially as described herein with reference to the Figures.