Air cushion vessel

A high-speed marine vessel having at least one hull wherein, the weight of the vessel is supported by at least two of planing surfaces, displacing volumes, pressurised air cushions and surfaces being affected by aerostatic and aerodynamic pressure at high-speeds and further comprising cushion chambers, each of which opens only downwardly, a step that extends inwardly from each hull bottom so that a first plane defined by the step separates at least one of the hulls into a planing and displacing portion extending forward of the first plane and a pressurized air cushion portion extending rearward, such that every point of an edge of the step in the first plane is substantially at the same vertical height relative to the undisturbed water surface when the vessel is under way, a rearward enclosure arrangement defining a second plane between longitudinal sidewalls, an air cushion chamber ceiling, and the water surface, where the lower part of said second plane has a vertical location of up to 30% of the distance from the hull bottom to the air cushion chamber ceiling, said lower part of said second plane, which may be adjustable, further defining an angle with the water plane of up to 20° when the vessel is under way, said angle being measured over a minimum horizontal length representing at least 10% of the total length of the hull for vessels with length below 30 meters and at least 4% for vessels with length above 30 meters, the length of each air cushion chamber from a transom to a middle point between a foremost point and a rearward point of the step making up between 45% and 85% of the total length of the hull between the transom and bow, and wherein in a side view, the profile of the underside of the planing and displacing surface as measured over a horizontal distance from the middle point between the foremost point and the rearward point of the step is at least 30% of the distance from said middle point up to the bow, said profile defining a boundary line forming an acute angle with the water surface at speed, said air cushion chamber having an increasing athwartships width towards the transom, the average increase in width, defined by an angle measured from the middle point between the foremost point and the rearward point of the step to the transom is less than 20°, as the angle measured between a vessel centre line and respective sides of a side hull at the water level when the vessel is under way, and wherein an arbitrary athwartships section through the lowest of the forebody hull surfaces forms an average angle with the horizontal plane of at least 25°, the vessel further comprising at least one displacing and planing multifunction propulsion body, wherein the length of each propulsion body relative to the overall length of the vessel is between 10% and 100%, such that the vessel may achieve a desired positioning of the centre of upward directed forces in relation to the centre of gravity.