Ships – Sailboard and rig means therefor – With rig means providing vertical lift
Reexamination Certificate
2002-08-22
2004-08-24
Wright, Andrew (Department: 3617)
Ships
Sailboard and rig means therefor
With rig means providing vertical lift
C114S102160
Reexamination Certificate
active
06779473
ABSTRACT:
TECHNICAL FIELD
This invention relates to wind propelled craft and more particularly to an arrangement of a pair of wings of variable dihedral angle in which either wing can provide propulsion from the wind whilst the other provides lift or both wings can be used to generate lift.
BACKGROUND ART
The use of counter balancing airfoil surfaces to resist overturning moments from wind propelled craft is taught in several inventions subsequently referenced. The principal weakness in most approaches lies in the inability of the sails or wings to be separately oriented to the longitudinal axis of the craft at all craft speeds and their inability to provide a means of accelerating the craft from rest. Whilst it is well known that the optimum sail orientation for propulsion is approximately vertical, the sail or wing must be able to yaw relative to the craft's direction of motion between the broad reach and close hauled positions. As craft speed increases, the apparent wind direction moves towards the front of the craft which necessitates trimming the sails inwards. Similarly, any horizontal sail or wing, which is used to develop counter balancing forces, must be able to head into the apparent wind to reduce the cross wind component acting on the airfoil. Whilst there are no known craft which currently successfully use sails to develop, in part or in full, counter balancing moments, some inventions teach various elements which are relevant to this invention.
Sailboards are fast wind propelled watercraft. They combine simplicity of sailing rig with a requirement for skill and agility from the sailor to balance the pull from the hand held sail. Whilst the sail can be tilted about the mast step to generate forward propulsion, sail area is limited by the need to balance sail power with the weight of the sailor standing on a narrow board. The sail can be held at a wide angle to the craft axis on a broad reach when the craft is heading essentially downwind or the sail can be held at a small angle to the craft axis in the close hauled mode. The craft is steered by tilting the sail back so that the center of wind effort is aft of the center-board causing the craft to round up into the wind or the craft can be made to turn away from the wind by tilting the sail forward. High speed may be achieved in strong winds when the sail is angled back towards the wind direction with the weight of the sailor underneath the sail, which then generates propulsive forces and lift. A person skilled in the art can jump the board off waves when travelling at high speed and achieve flight for short distances under the initial momentum by tilting the sail to a horizontal position. However, the non-symmetric shape of the sail above the sailor and the relatively small sail area limits the flight to short distances.
A symmetrical sail for a sailboard is taught by U.S. Pat. No. 4,682,557. This device embodies a symmetrical sail pivoted at the top of a short mast, which is attached to a sailboard. The sail can be tilted horizontally to become a lifting wing when the moving craft is headed into the wind. Their device has no means of enhancing resistance to overturning moments whilst in sailing mode, but the sail is symmetrical in flight when the board is jumped off waves. Both this device and conventional sail boards have sail areas limited to approximately 4.5 to 7 square meters in order to remain manageable in up to moderate wind speeds due to the constraints of strength and weight of a sailor standing on a sailboard. A wing area of this size cannot sustain manned flight for any considerable distance. Each wing of the present invention has an area of approximately 4.5 to 7 square meters giving a combined area in flying mode capable of lifting the weight of the craft and crew.
A craft which utilizes airfoil sections in a dual sail configuration whilst providing increased resistance to the heeling moment is taught by U.S. Pat. No. 3,800,724. This craft embodied two airfoil-cambered wings that tilted about an axis parallel to the fuselage. When the left wing is tilted upwards to develop propulsive forces on port tack, the right wing is tilted horizontally to develop lift and vice versa. A rigid link between the wings ensured mutual dependency. When the craft changes tack, the vertical wing is tilted horizontal and the other wing is tilted vertical. In each case, the lifting side of the airfoil section is favorably presented to the wind. Reference is made to an optional embodiment in which the wings may also pivot about a vertical axis to align the wings to the relative wind for optimum performance. However, this craft required a power source to drive actuators, pistons, a propeller to get up to speed, ailerons, and the like. Furthermore, the fixed link between the wings ensured that when both wings were at the same angle to the horizontal, they were relatively steeply inclined thus reducing their vertical lift component.
A similar vee winged device was described in U.S. Pat. No. 3,987,982. However, this craft had no means of varying the angle between the wings, which were rigidly fixed to the fuselage. As the fuselage consequently had to tilt from one side to the other during tacking, the hull required a special shape and the pilot presumably required a tilting seat. The craft also had no means of pivoting the wings about a vertical axis to permit the driving sail to vary between the broad reach and close haul position relative to the craft longitudinal axis. It consequently would have had difficulties in moving off from rest and getting up to speed. These latter two referenced craft required a vertical rudder and ailerons to vary the angle of attack of the wings to the wind. The craft of the present invention avoids such requirements by incorporating means of controlling a single pair of wings in the wing support spar. This spar provides for tilting of the horizontal wing and a separate capability to correct the movement of the center of effort of the vertical wing that would otherwise occur, by providing a separate sliding movement of the boom along its axis relative to the spar. The requirement in U.S. Pat. No. 3,987,982 to tilt the body from one tack to the other is avoided in the present invention by the use of a universal joint between the body of the craft and the wing support spar. The body of the present invention consequently can have a flat hull such as in a simple sailboard type planing hull with a vertical center board to provide optimal resistance to lateral drift whilst in sailing mode.
A simple approach to providing simultaneous propulsion whilst providing resistance to overturning moments is taught by U.S. Pat. No. 4,674,427. A single straight wing with floats at each end is supported laterally to one side of a narrow hull. During tacking the wing must be flipped end for end to the other side of the hull. Although this device eliminates the overturning moment on the craft body when sailing, it has no means of varying the yaw angle of the sail relative to the craft axis in order to gather speed from rest. This craft would have had difficulties in tilting the sail to the opposite side of the hull during tacking.
A mast pivoting mechanism was taught by U.S. Pat. No. 4,706,590 to reduce heeling moments of the supporting vessel. However, whilst the mechanism provided a means of altering the angle of the mast relative to the hull, the device offered no means of counter balancing the over turning moments from the sail.
Resistance to over turning moments using an adjustable hydrofoil suspension system is taught by U.S. Pat. No. 5,168,824. The system provides for the adjustment of the foil surface's angle of attack in response to the movement of a float that senses the level of the water's surface whilst filtering out high frequency undulations using a system of flexible beams. The adoption of two or more such systems of beams to a watercraft permitted control of the heeling forces. Their preferred embodiment comprised two vertically mounted sails supported on buoyant outriggers displaced laterally
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