Ventilated flow interrupter stepped hull

1. A watercraft hull having a pair of side walls, a bottom planing surface extending therebetween and at least one ventilation step formed in at least a part of its bottom planing surface facing the water and opened to the air through at least one of the side walls to allow air to enter the step causing water to separate from the hull, said step being located such that the water separated from the hull at the step reattaches to the bottom planing surface a distance aft of the step to produce lift on the hull; said step having a forward edge portion, and means for forming a water flow interrupter projecting downwardly from the hull forward of said forward edge of the step to change the center of pressure on the bottom planing surface of the hull from where it would have been without said means.

2. A watercraft hull as defined in claim 1 , wherein said at least one step extends from one side of the hull to the other and is open to the air at both side walls.

3. A watercraft hull as defined, in claim 1 , wherein said at least one step comprises a pair of partial steps respectively located adjacent opposite longitudinal sides of the hull.

4. A watercraft hull as defined in claim 1 , wherein said at least one step comprises a plurality of transverse ventilation steps in the hull.

5. A watercraft hull as defined in any of claims 1 to 4 , wherein said means for forming a water flow interrupter is a flat wedge shaped protrusion on said hull bottom, which extends from the surface of the bottom planing surface forward of the step downwardly towards the step.

6. A watercraft hull as defined in any of claims 1 to 4 , wherein said means is a flat interceptor plate mounted on the hull.

7. A watercraft hull as defined in claim 4 , wherein said interceptor plate is mounted on the hull for vertical movement between a first retracted position in the hull and a second fully extended position.

8. A watercraft hull as defined in any of claims 1 to 4 , wherein said means comprises a concave cambered surface area formed in said hull bottom forward of the step which is at or below the waterline during operation of the watercraft to produce separation of water at the leading edge of the camber and unwetted surface area in the camber.

9. A watercraft monohull having a pair of side walls and a bottom surface extending therebetween for planing on water, said bottom surface having at least one ventilation step formed therein, said ventilation step comprising a recessed cavity in the hull bottom opening downwardly towards the water and having a forward leading edge portion joining the hull bottom, said step being open to the air through the side walls to allow air to enter the step when the hull is planing to cause water to separate from the hull to reduce friction on the hull; said step being located such that the water separated from the hull at the step reattaches to the bottom planing surface a distance aft of the step to produce lift on the hull; and water flow interrupter means projecting downwardly from the hull forward of said forward edge of the step for increasing the separation of water from the hull at and aft of said step thereby increasing the unwetted surface area of the hull bottom during operation of the watercraft and increased lift pressure forward of the step.

10. A watercraft hull as defined in claim 9 wherein said recess has a forward wall portion at the leading edge of the step which is generally perpendicular to the hull bottom, a curved top wall and a tapered aft surface which extends from the curved to the keel line of the hull aft of the step.

11. A watercraft hull as defined in claim 9 , wherein said at least one step comprises a plurality of transverse ventilation steps in the hull.

12. A watercraft hull as defined in any of claims 9 , 10 and 11 , wherein said means is a flat wedge shaped fixed protrusion on said hull bottom which extends from a forward end thereof on the hull bottom, forward of said step, aft to a rear end at said leading edge of said step which projects down into the water further than said forward end.

13. A watercraft hull as defined in any of claims 9 , 10 11 , wherein said means comprises a flat interceptor plate mounted on said hull bottom at or immediately forward of said leading edge of the ventilation step.

14. A watercraft hull as defined in claim 13 , wherein said interceptor plate is mounted for vertical movement between a first retracted position in the hull and a second fully extended position.

15. A watercraft hull as defined in any of claims 9 , 10 11 , wherein said means comprises a concave cambered surface area formed in said hull bottom forward of said step which is at or below the waterline during operation of the watercraft to produce separation of water at the leading edge of the camber and unwetted surface area in the camber.