Gas-cushion vehicles

Claim 1

A GAS CUSHION VEHICLE FOR TRAVELING OVER SURFACES OF LAND AND WATER HAVING A FORE-AND-AFT AXIS AND COMPRISING A BODY, A FLEXIBLE SKIRT ATTACHED TO AND DEPENDING FROM THE BODY FOR LATERALLY CONTAINING BENEATH THE BODY AT LEAST ONE VEHICLE-SUPPORTING CUSHION OF PRESSURIZED GAS, AND A KEEL STRUCTURE EXTENDING DOWNWARDLY FROM THE BODY WITH ITS LENGTH SUBSTANTIALLY PARALLEL TO THE FORE-AND-AFT AXIS, THE KEEL STRUCTURE BEING OF SUBSTANTIALLY RIGID CONSTRUCTION CAPABLE OF SUPPORTING THE VEHICLE ON A HARD LAND SURFACE AND AT LEAST PARTLY SURROUNDED BY THE FLEXIBLE SKIRT, THE WIDTH AND LENGTH OF THE KEEL STRUCTURE BEING SO RELATED THAT, WHEN IN CONTACT WITH THE SURFACE OVER WHICH THE VEHICLE IS TRAVELING, THE KEEL STRUCTURE PROVIDES A RELATIVELY SMALL RESISTANCE TO MOVEMENT OF THE VEHICLE PARALLEL TO ITS FORE-AND-AFT AXIS AND A RELATIVELY LARGE RESISTANCE TO MOVEMENT TRANSVERSELY OF SAID AXIS, AT LEAST ONE OF SAID FLEXIBLE SKIRT AND SAID KEEL STRUCTURE BEING MOVABLE VERTICALLY RELATIVE TO THE VEHICLE BODY SO AS TO VARY THE RELATIVE DOWNWARD EXTENT OF SAID SKIRT AND SAID KEEL STRUCTURE.