Surface-effect aerofoil boat

Claim 2

In a surface-effect aerofoil boat having a body, noise portion, tail portion, central axis through the length of said body, front and rear tandemly arranged aerofoils attached to said body, a vertical fin, a pivotally attached aerodynamic rudder, and a driven propeller mounted for rotation on a propeller axis which is oriented in the general direction of said central axis, the improvement comprising: means for subdividing said boat to provide hollow compartments at the stern, at least one of said compartments providing a flotation compartment for said boat; means for trimming said boat by flooding and emptying at least a portion of said compartment of said boat with ballast water from a body of water on which said boat is floatable such that pitching-under of the bow of said boat is avoided during take-off and the angle of attack and lift of at least one of said aerofoils is optimized relative to a surface of said body of water for lift-off of said boat clear of said surface; means for increasing lift and decreasing drag of said tail portion along a line of contact of an underside of said tail portion with the surface of said body of water during take-off; and a gap between said fin and said rudder, said propeller rotating through said gap, and means for reducing the noise generated by rotation of said propeller through said gap.

Claim 3

The improvement as in claim 1, wherein said noise reducing means comprises: a geometry of said gap such that said gap is narrower at said propeller axis and wider radially outward from said propeller axis.

Claim 4

The improvement as in claim 2, wherein said gap is provided by a bi-concave cut-out in said fin.

Claim 5

The improvement as in claim 1, wherein said lift increasing and drag decreasing means comprises: a geometry of said tail portion such that said rear aerofoil comprises a leading edge, a trailing edge, a length from said leading edge to said trailing edge in the direction of said central axis, central portions spaced on each side of and proximate said central axis; outer portions spaced on each side of and distal said central axis; said length diminishing from said central axis to each of said outer portions such that said trailing edge extends substantially below said water surface to increase said line of contact prior to take-off, said line of contact diminishing during said take-off to increase lift and decrease drag of said rear aerofoil.

Claim 6

The improvement as in claim 4, and further comprising at least one flotation compartment in each of said outer portions and wherein said trimming means comprises: at least one trimming compartment in said tail portion to and from which said ballast water may flow, respectively, during landing and take-off of said boat.

Claim 7

The improvement as in claim 5, wherein said trimming compartment is provided with openings spaced lengthwise along said tail portion, said openings communicable with said water to provide variable ballast such that said trimming compartment ballast decreases as said line of contact decreases and increases as said line of contact increases.

Claim 8

The improvement as in claim 1, wherein said subdividing means comprises: adjustable bulkheads for varying the sizes of said compartments.

Claim 9

The improvement as in claim 1, and further comprising: inflatable air bags within said compartments of said trimming means for varying the sizes of said compartments such that voids within said compartments are variable by inflation and deflation of said bags to vary the amount of ballast water within said voids.

Claim 10

The improvement as in claim 1, wherein said front aerofoil comprises subdivided, flotation compartments.

Claim 11

The improvement as in claim 1, and further comprising means for hinging said front and rear aerofoils upwardly such that an overall width of said boat is decreasable for storage and transport of said boat.

Claim 12

The improvement as in claim 1, wherein said noise reducing means comprises a geometry of said gap such that said gap is narrower at said propeller axis and wider radially outwardly from said propeller axis to provide a tail void and a rudder void between a generally planar locus, generated by rotation of said propeller, and said tail and rudder, respectively, at least one of said voids increasing radially outwardly from said propeller axis.

Claim 13

In a surface-effect aerofoil boat having a body, nose portion, tail portion, central axis through the length of said body, front and rear tandemly arranged aerofoils attached to said body, a vertical fin, a pivotally attached aerodynamic rudder, and a driven propeller mounted for rotation on a propeller axis which is oriented in the general direction of said central axis, the improvement comprising: means for subdividing said boat to provide hollow compartments at the stern, at least one of said compartments providing a flotation compartment for said boat; means for trimming said boat by flooding and emptying at least a portion of said compartment of said boat with ballast water from a body of water on which said boat is floatable such that pitching-under of the bow of said boat is avoided during take-off and the angle of attack and lift of at least one of said aerofoils is optimized relative to a surface of said body of water for lift-off of said boat clear of said surface; means for increasing lift and decreasing drag of said tail portion along a line of contact of an underside of said tail portion with the surface of said body of water during take-off; and a gap between said fin and said rudder, said propeller rotating through said gap, and means for reducing the noise generated by rotation of said propeller through said gap and comprising a geometry of said gap such that said gap is narrower at said propeller axis and wider radially outwardly from said propeller axis to provide a tail void and a rudder void between a generally planar locus, generated by rotation of said propeller, and said tail and rudder respectively, at least one of said voids increasing radially outwardly from said propeller axis.

Claim 14

In a surface-effect aerofoil boat having a body, nose portion, tail portion, central axis through the length of said body, front and rear tandemly arranged aerofoils attached to said body, a vertical fin, a pivotally attached aerodynamic rudder, and a driven propeller mounted for rotation on a propeller axis which is oriented in the general direction of said central axis, the improvement comprising: means for subdividing said boat to provide hollow compartments at the stern, at least one of said compartments providing a flotation compartment for said boat; means for trimming said boat by flooding and emptying at least a portion of said compartment of said boat with ballast water from a body of water on which said boat is floatable such that pitching-under of the bow of said boat is avoided during take-off and the angle of attack and lift of at least one of said aerofoils is optimized relative to a surface of said body of water for lift-off of said boat clear of said surface; means for increasing lift and decreasing drag of said tail portion along a line of contact of an underside of said tail portion with the surface of said body of water during take-off; and a gap between said fin and said rudder, said propeller rotating through said gap, and means for reducing the noise generated by rotation of said propeller through said gap and comprising a geometry of said gap such that said gap is narrower at said propeller axis and wider radially outwardly from said propeller axis to provide a tail void and a rudder void between a generally planar locus, generated by rotation of said propeller, and said tail and rudder respectively, at least one of said voids increasing radially outwardly from said propeller axis.

Claim 15

The improvement as in claim 12, wherein both of said voids increase radially outwardly from said propeller axis.