A wind powered system utilizes a free-flying airfoil tethered to a conveyance device such as a water ski, a skegged hull slab or a wheeled land vehicle which either defines or inherently has tracking means defining a preferred traverse vector across an underlying surface. The tractive force of the airfoil is applied at the center of lateral resistance of the conveyance device such that there is no destabilizing moment caused by the airfoil, thereby removing an artificial limit on the sail area that is imposed upon fixed mast sailing craft. A control bar provides a mount for a tether reel which enables the conveyance device, when same is a kite, to be launched from the water without requiring the assistance of a boat.

BACKGROUND OF THE INVENTION 
The use of kites as a means for delivering a tractive force for a vessel is 
believed to go back at least as far as the Egyptian Pharaohs. Referring to 
such use of a kite with a watercraft such as water skis or a hull craft, 
there are advantages to a kite as opposed to a sail which is mounted on a 
fixed mast. 
The most important advantage is the elimination of the capsizing moment 
that the mast exerts on the vessel. In the design of sail boats, in the 
end the speed limiting factor is always sail area, which if pushed to the 
limits makes for really exciting sailing as the large sail means the boat 
is pushed close to a capsizing heel in strong winds. Even in an adequately 
weighted keel boat, with large sails deployed when the crew is hiked out 
over the gunwales as far as possible to counter mast moment, the sail area 
maximum has been reached or exceeded. Because the center of lateral 
resistance is near the water level, but the tractive force must be applied 
considerably above the water level, there is no way to escape this moment 
with a conventional sailing craft. 
By utilizing a kite design, the tractive force need not result in an 
overturning moment at all, but may be applied at any point on the craft, 
enabling it to be aligned accurately with the center of lateral resistance 
to eliminate or virtually eliminate any moment whatsoever. 
Other advantages of kite use are in fact that once the kite rises to a 
level above 20 to 40 feet over the water, there is a substantial increase 
in wind velocity. Additionally, the laminar fluid flow which is conducive 
to efficient sailing is disrupted near the water surface, especially if it 
is choppy. There is turbulence in both the air and the water at the 
interface. As the kite rises, twenty to forty feet above the surface the 
turbulence diminishes markedly, providing a smoother and faster passage. 
As mentioned, these facts have not escaped mankind over the centuries, and 
in recent times there has been some development of kite power. 
Particularly relating to kite skiing, there is the type involving a 
towboat in which the skier is towed high in the air behind the boat. This 
invention does not relate to that type of kite skiing. 
Kite skiing independent of a tow boat has been successfully done, as 
evidenced by the disclosure in U.S. Pat. No. 4,708,078 issued on Nov. 24, 
1987 on a PROPULSIVE WING WITH INFLATABLE ARMATURE, which illustrates an 
airfoil-towed skier. The focus of that patent is on the design of the 
inflated kite and does not go into particulars about kite skiing. The 
lune-like inflated armature is the essence of the invention. This kite 
system does not require a boat for towing power, but does rely upon an 
crash boat in the event he capsizes, to board the skier and his airfoil or 
to assist him with a re-launch. The requirement that a boat accompany the 
skier is a major limitation on kite skiing as a sport for obvious reasons. 
There is a relatively high wind requirement for practical kite surfing, 
and coupling that limitation with the necessity of interesting at least 
one other boatowner in an outing limits the number of times, as a 
practical matter, that a kite skier will be able to ski. 
There is a need for a kite skiing system which is designed to enable the 
skier to launch the kite from the water without the assistance of an 
accompanying boat. A kite skiing system such as this, incorporating other 
advantageous design characteristics for ease of handling and adequate 
speed, would represent a significant advance in the sport of kite skiing. 
SUMMARY OF THE INVENTION 
The instant invention fulfills the above stated need by providing a 
fine-tuned kite skiing system utilizing an airfoil for the tractive 
element which is connected to a bridle which is tethered to a control bar 
held by the skier. The bar also mounts a reel which actually engages the 
tether lines, the reel having special means to ensure that equal lengths 
of the lines are reeled in and paid out to prevent the kite from assuming 
an uncorrectable skewered angle. 
To enable water-borne launches, the airfoil has a flexed leading edge 
formed as an arched bow which the skier can grasp and thrust skyward to 
initiate the kite after being downed. Although this feature is helpful in 
enabling independent launches at sea, the real key to sea launching 
involves the use of a tether reel, both to retrieve the kite when the 
skier is down and to enable the tether lines to be paid out by the skier 
on launching to provide enough control of the airfoil at start-up to avoid 
re-capsizing. 
Because the forces pulling the skier are in the 200 pound range, the reel 
is heavy duty and utilizes a disc brake operated by a hand actuator 
mounted on the control bar. The hand actuator has a dog or stop to lock it 
in the locked position once the tether has reached the appropriate 
effective length. The brake is used in its non-locked mode to apply a 
graduated drag on the line as it is reeled out on launching.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Although tricky to engineer, the invention is very simple in concept. At 
its simplest, it is a skier towed by a kite. The kite is actually an 
airfoil, and these terms are used more or less interchangeably throughout 
this specification despite the technical differences and each term should 
be read to include the other for purposes of description and claim 
interpretation. The wind power system utilizes an airfoil 10 which is 
connected through a tether means 12 to a conveyance means 14, which in the 
illustrated embodiment is a pair of skis supporting a skier. However, the 
conveyance means can be anything that will traverse over a surface, such 
as a single ski, a surf board, an ice boat, roller blades, a light weight 
mini-car or even a bicycle. 
The conveyance means needs only the characteristics of being mobile over an 
underlying surface and having a tracking capability. The conveyance means 
must be able to establish a traverse vector, in the preferred line of 
travel, such as by skeg, keel, center board, or in the case of a wheeled 
vehicle, the rotational axis of the wheels which establishes orthogonally 
thereto a preferred direction of travel. Otherwise the user will aimlessly 
follow the wind and end up far downwind of the point of departure. 
Although land travel is possible using the kite system, water-borne 
activities are currently more practical due to the high speeds achievable 
with the kite. Numerous styles of single-and multi-hulled vessels could 
use the system as well. In particular, a windsurfer-style hull, with a 
solid foam slab body, footgrips and a daggerboard could be used in much 
the same manner as skis, as diagrammatically illustrated in FIG. 8. A 
slalom ski/windsurfer slab hybrid with laterally oriented, snowboard-style 
footgrips would be practical, possibly with a double-ended 
alternative-deployment skeg system to permit "ambidextrous" use, so that 
the direction the user faces is not completely dictated by course and wind 
direction and configuration. This configuration is illustrated in FIG. 8, 
the solid hull 11 being reversible, having a central footgrip 13, two 
oppositely-directed footgrip pairs 15 and the alternative daggerboards 17. 
It is intended that the claims read to cover these variations where the 
context of the claim permits. For simplicity only the waterski embodiment 
is fully discussed in detail below. 
In the embodiment shown in the figures, which is a skier being towed by the 
kite, the skier becomes part of a power chain, at least during part of the 
ride cycle. Force is delivered to the conveyance means through the skier 
by means of the control bar 16 which is attached to the waist shackle 18 
on the torso of the user by the harness 20. The user engages the skis as 
well as the control bar and harness, acting as the power link between 
them. However, by delivering the tractive force through the body at waist 
level by using the shackle, the arms are free to manipulate the bar 16 for 
control purposes. Otherwise the skier would not stay up long, as he would 
be manhandling 200 pounds of tractive force in addition to the control 
functions necessary for a successful run. 
The tether control of the airfoil is similar to kite control. Left- and 
right-, top- and bottom-corner bridle lines 19 converge to main tether 
lines 21 along with the spar-center-support lines 23 to define the entire 
line 32. The result is three-point airfoil support from each side of the 
control bar, with only a single line passing through each bar eyelet to 
the reel. This configuration, when used with a rigid bowed front spar and 
spaced battens for longitudinal stiffening, provides adequate attitude and 
directional stability and control for skiing. An alternative mode of 
control involves remote operation of air surfaces on the airfoil, through 
radio control or hard wire connection through the tether. Airfoil-mounted 
control devices with a power pack, partially automatically reacting and 
partially operator controlled, would add a dimension of finesse to the 
system, along with the design trade-offs of increased expense, complexity 
and the accompanying breakdown potential. 
The skis 22, although having characteristics that are specially 
advantageous to kite skiing such as a bottom longitudinal furrow to 
increase tracking, are essentially conventional skis with slight 
modifications being possible. 
The bar or bow 16 can be made of light weight aluminum capped at the ends 
for buoyancy, fiber glass tubes, plastic tubes, or any other material 
which offers maximum strength and rigidity at minimum weight. In all 
instances the bar would be made so that its net buoyancy is positive. 
Although subject to wide variation of design, the illustrated bar has a 
straight length 24 and a bowed length 26, with the two lengths being 
joined together such as welding in the case of aluminum at the ends as 
indicated at 28. A short brace 30 connects the bars centrally, so that the 
overall arrangement of the three bars defines a planar crescent or 
circular sector shape. This shape is close to ideal for simplicity, 
strength and ease of use. The skier has the capability of adjusting the 
effective lengths of the right and left tether lines 32 by rotating the 
bow 26 roughly about its center of curvature. The harness 20 is attached 
at the perforated flanges 34, and the bar defines tether eyelets 36 at the 
ends, through which pass one or more tether lines 32 as indicated in FIG. 
2. The wide separation of the two eyelets maximizes control over the 
airfoil. 
Centrally mounted on the cross bar is the heavy duty reel 38 which extends 
parallel to the plane defined by the control bar. The spool 40 of the reel 
has a drum 42 on which the tether lines wind, and exit on opposite sides 
of the reel to pass through the tether eyelets 36 as shown in FIG. 2. 
Because the widths of the spool must be above a certain minimum in order 
to accommodate all of the tether lines when fully wound up, it is wide 
enough to make possible the irregular winding of the lines, such that one 
line becomes much shorter than the other, making skiing difficult and 
unpleasant. 
To overcome this problem a line equalizing means is desirable. In the 
instant case, the equalizing means takes the form of a disc 44 which is 
dished and has a circumference extended over almost half of the height of 
the drum. This dished flange forces both of the lines, as they are being 
reeled in, to wind up together on substantially the same track, axially 
speaking, of the drum, and thus the same length is taken up of both lines 
for each single rotation. This simple expedient is more than enough for 
this particular application of the reel, eliminating all major off-balance 
airfoil situations caused by inequitable line winding. 
The reel is provided with a winding knob 46 and also a brake 48 which 
comprises a brake disc 50 engaged by a caliper 52 controlled by a hand 
actuator 54. The brake actually used in production, and the one shown, are 
mountain bike brakes. The hand actuator has a pin or button 56 which 
passes through an aperture in the lever mechanism to lock the brake in 
engaged position. Short of full engagement the brake applies variable drag 
to the lines which is essential to launching. The forces exerted by the 
airfoil are too great to enable a controlled launching by hand, and the 
brake must be heavy duty. Any system that does not have a reel with 
controlled braking capabilities is almost certainly not one intended for 
use without an accompanying support boat as a wet launch would be 
difficult if not impossible. 
It might appear that mastering kite skiing would be a difficult and 
athletically demanding task. It is true that it does take a certain 
endurance to ski for 20 or 30 minutes without a break, and upwind legs can 
be gruelling. However, it is estimated that the rate of mastery of kite 
skiing for one who already water skis is considerably better than the 
learning curve for a novice attempting to waterski. A novice who has had 
water skiing experience and stunt kite flying experience will pick up the 
kite skiing very quickly. 
The position of attachment of the tether to the conveyance means when the 
latter is a boat or wheeled craft on land will work out to be the 
approximate point of center of lateral resistance of the vessel or 
vehicle. Obviously if offset from this point, or actually from this axis, 
undesirable moments will be experienced by the conveyance means similar to 
the overturning force on the sailboat, causing the tether t be re-mounted. 
In the event of a water skier who acts as a human force link, the tether 
is worked back and forth a small amount across the 
center-of-lateral-resistance line as needed to maintain balance and 
steering. 
With the ability to align the tractive force with the center of lateral 
resistance, coupled with the advent of modern light-weight fabrics, a 
large sail may be maintained aloft which need only pull a single skier 
rather than an entire boat. The skier can thus go quite fast. One of the 
inventors was a participant in speed trials for competition wind surfers 
and was able to steadily pass all of them to set a new course record. He 
was moving at 40 knots or better. Speeds of 40 knots are readily achieved 
and there are firm grounds for believing that speeds substantially in 
excess of 50 knots are achievable with a kiteski. 
The chart of FIG. 7 illustrates not the overall speed of the skier, but 
rather the speed upwind at various wind levels. It may be important for a 
kite skier to know this inasmuch as he or she may be required to tack 
upwind for a considerable time to get back to the starting point. It would 
be good to know on a relative scale the difficulty of the return trip 
under given wind conditions so that the skier may guide his jubilant broad 
reach departure accordingly, as he is being rapidly propelled increasingly 
further downwind of his point of departure.