Quadfoiler
A watercraft having a hull, a mast with sail, an aft rudder and a hydrofoil projecting below the bottom of the hull. The hydrofoil is pivotly connected to the hull enabling the hydrofoil to pitch on a pivot axis which is essentially perpendicular to the longitudinal axis of the hull. The hydrofoils have a vertical part which produces lateral forces to accelerate the boat in turns and resist lateral forces from the sail, and a vertical portion which curves into the horizontal portion which produces vertical lift. The angle of incidence of the hydrofoil is controlled by a sensor arm carrying a trailing sensor.
1. A watercraft comprising
a hull having a mast with sail, an aft rudder and a hydrofoil projecting below the bottom of the hull, said watercraft further comprising
means pivotally connecting each hydrofoil to the hull enabling the said hydrofoil to pitch on a pivot axis which is essentially perpendicular to the longitudinal axis of the hull, said hydrofoils having a vertical part which produces lateral forces to accelerate the boat in turns and resist lateral forces from the sail, and a vertical portion which curves into the horizontal portion which produces vertical lift,
means controlling the angle of incidence of the hydrofoil comprising a trailing sensor arm, said sensor arm being carried on a pivot in proximity to the fore end of the hull, said sensor being dragged behind the pivot, and
means connecting said sensor arm to said hydrofoil whereby when the hull is low in the water the sensor arm is constrained to pitch down, and when the hull is too high, the sensor arm pitches up, and when the sensor arm pitches down, the hydrofoil pitches up and when the sensor arm pitches up, the hydrofoil pitches down.
2. A watercraft comprising
a hull having a mast with sail, an aft rudder and a hydrofoil projecting below the bottom of the hull, said watercraft further comprising
means pivotally connecting each hydrofoil to the hull enabling the said hydrofoil to pitch on a pivot axis which is essentially perpendicular to the longitudinal axis of the hull, said hydrofoils having a vertical part which produces lateral forces to accelerate the boat in turns and resist lateral forces from the sail, and a vertical portion which curves into the horizontal portion which produces vertical lift,
means controlling the angle of incidence of the hydrofoil comprising a trailing sensor arm, said sensor arm being carried on a pivot in proximity to the fore end of the hull, said sensor being dragged behind the pivot, and
means connecting said sensor arm to said hydrofoil whereby when the hull is low in the water the sensor arm is constrained to pitch down, and when the hull is too high, the sensor arm pitches up, and when the sensor arm pitches down, the hydrofoil pitches up and when the sehsor arm pitches up, the hydrofoil pitches down, wherein the pivot axis of each hydrofoil is very close to the lift and drag vectors acting on the hydrofoil throughout the range of pitching motion of the hydrofoil.
3. A watercraft comprising
a hull having a mast with sail, an aft rudder and a hydrofoil projecting below the bottom of the hull, said watercraft further comprising
means pivotally connecting each hydrofoil to the hull enabling the said hydrofoil to pitch on a pivot axis which is essentially perpendicular to the longitudinal axis of the hull, said hydrofoils having a vertical part which produces lateral forces to accelerate the boat in turns and resist lateral forces from the sail, and a vertical portion which curves into the horizontal portion which produces vertical lift,
means controlling the angle of incidence of the hydrofoil comprising a trailing sensor arm, said sensor arm being carried on a pivot in proximity to the fore end of the hull, said sensor being dragged behind the pivot, and
means connecting said sensor arm to said hydrofoil whereby when the hull is low in the water the sensor arm is constrained to pitch down, and when the hull is too high, the sensor arm pitches up, and when the sensor arm pitches down, the hydrofoil pitches up and when the sensor arm pitches up, the hydrofoil pitches down, wherein a tension line is attached to the top of the sensor arm and travels back aft of the hydrofoil and rounds a turning block and goes forward and terminates at the top of the hydrofoil, whereby when the sensor arm pitches down the hydrofoil pitches up and conversely when the sensor arm pitches up, the hydrofoil is allowed to pitch down and the angle of attack and the lift generated by the hydrofoil is reduced.
4. The watercraft of claim 3 wherein a spring is in series with said tension line.
5. The watercraft of claim 4 wherein a dampener is operatively connected between said hydrofoil and said hull.
6. A watercraft having a mast with sail comprising
a hull having an aft rudder and a hydrofoil projecting below the bottom of the hull, said watercraft further comprising
means pivotally connecting each hydrofoil to the hull enabling the said hydrofoil to pitch on a pivot axis which is essentially perpendicular to the longitudinal axis of the hull, said hydrofoils having a vertical part which produces lateral forces to accelerate the boat in turns and resist lateral forces from the sail, and a vertical portion which curves into the horizontal portion which produces vertical lift,
means to cause the hydrofoil to pitch up when the watercraft is closer to the water and to pitch down when the watercraft gains altitude, wherein the hydrofoil rolls on a circular track, the center of the circle defining said pivot axis, the top of the hydrofoil being connected to two wheels that roll on the track, said two wheels being spaced apart so that the track constrains the angle of incidence of the hydrofoil whereby as the wheels roll on the track the hydrofoil is constrained to pitch up or down with the curvature of the track.
7. A watercraft having a mast with sail comprising
a hull having an aft rudder and a hydrofoil projecting below the bottom of the hull, said watercraft further comprising
means pivotally connecting each hydrofoil to the hull enabling the said hydrofoil to pitch on a pivot axis which is essentially perpendicular to the longitudinal axis of the hull, said hydrofoils having a vertical part which produces lateral forces to accelerate the boat in turns and resist lateral forces from the sail, and a vertical portion which curves into the horizontal portion which produces vertical lift,
means to cause the hydrofoil to pitch up when the watercraft is closer to the water and to pitch down when the watercraft gains altitude, wherein said hydrofoil is further constrained in the lateral direction near the bottom of said hull by rollers which roll in a circular path on smooth surfaces inside said hull.
8. A catamaran having two spaced apart hulls with a deck extending therebetween, each hull having a mast with sail, an aft rudder and a hydrofoil projecting below the bottom of the hull, comprising
means pivotally connecting each hydrofoil to each hull of the catamaran enabling the said hydrofoil to pitch on a pivot axis which is perpendicular to the longitudinal axis of the hull, said hydrofoils having a vertical part which produces lateral forces to accelerate the boat in turns and resist lateral forces from the sail, and a vertical portion which curves into the horizontal portion which produces vertical lift,
means controlling the angle of incidence of the hydrofoil comprising a sensor arm carrying a trailing sensor, said sensor arm being pivotally carried in proximity to the fore end of the hull, the sensor being pinned to said sensor arm and dragged behind the pivot, whereby the sensor is constrained to stay in contact with the water surface, and
means connecting said sensor arm to said hydrofoil whereby when the hull is low in the water the sensor arm is constrained to pitch down, and when the hull is too high, the sensor arm pitches up.
9. The watercraft of claim 1 wherein the watercraft is a catamaran.
10. The watercraft of claim 1 wherein the watercraft is a trimaran.