Abstract:
A wind propelled vehicle defining a center of gravity. The wind propelled vehicle has a frame. A rear axle is connected to the frame at its rear portion and two rear wheels are rotatably connected to the rear axle. The center of gravity of the wind propelled vehicle is forward of the rear axle. A front wheel is rotatably connected to the frame at its forward portion. A mast is connected to the frame and a boom is connected to the mast. A sail is connected to the mast and boom. A motor is operably connected to the boom and to the front wheel. The motor is also physically connected to the boom. The motor is remotely controlled via a remote control unit. To propel the wind propelled vehicle the position of the sail is adjusted relative to the wind. Sail position adjustment is achieved by the motor turning the front wheel and manipulating the position of the boom in response to control signals generated by the remote control unit.

Description:
TECHNICAL FIELD 
     The present invention relates generally to the field of robotic sailing devices, particularly robotic sailing devices that are useful on various surfaces including roads, parking lots, grass, dirt, ice, snow and water. 
     BACKGROUND 
     Sailing small water craft and windsurfing are popular pastimes with new individuals introduced to the sports every year. Important criteria to the newcomer of these sports are learning and understanding the intricacies of wind, sail and mobility. One method to aid in this learning process is utilization of a remote controlled, wind-propelled vehicle that simulates the physics of windsurfing where one can safely learn how to control and react to diverse wind conditions. In order to more fully simulate the sailing and windsurfing experience the vehicle must be designed to accurately mimic conditions and maneuvers associated with these sports. These include a light weight vehicle with sail and center of gravity forward of the stern or rear axle for maximum wind propulsion, simulation of the physics of lift, and the ability of the vehicle to make tight turns while avoiding the hazard of rollover or capsizing. 
     Alternatively, the remote controlled, wind-propelled vehicle can be used for entertainment and competition, including the enjoyment of maneuvering and playing with the vehicle on a flat surface and racing the remote controlled vehicles and/or display skills involved in this type of activity. Such remote-controlled vehicles can be a low cost form of learning and entertainment because the power used to propel the vehicle is provided by the wind, thereby the only non-wind power requirement is for the steering of the vehicle. 
     A wind propelled sail toy vehicle is described in U.S. Pat. No. 4,886,478. This remote controlled land vehicle has a rod-like elongated frame with a mast attachment for a sail and a raised forward portion engaged to a front wheel assembly, plus an elongated axle with wheels at each end. When the sail of the sail toy vehicle is in position, the center of gravity is over the rear axle rather than forward of this location and does not attain maximum wind propulsion. In addition, the lengthy axle assembly of this vehicle is necessary to prevent rollover during sharp turns, inhibiting maneuverability and a more accurate simulation of windsurfing. This vehicle also lacks the option of a frame support reducing the strength of the overall structure. 
     SUMMARY 
     The present invention recognizes that existing robotic sailing devices are not particularly agile in that they do not turn or corner well. Furthermore, in operation, existing robotic sailing devices do not obtain a lift vector and thus do not simulate the desirable physics of windsurfing, including speed and agility. The present invention provides a robotic sailing device that is particularly agile, having enhanced speed, turning and cornering capability. 
     One preferred aspect of the present invention is a wind propelled vehicle that includes a frame that includes a wheel, skid, ski or blade at a distal portion of the frame; an axle that includes two wheels, skids, skis or blades; and a mast. In one preferred aspect of the present invention, a proximal portion of the frame directly or indirectly operably engages the axle. Optionally, the mast directly or indirectly operably engages the frame at a distal portion of the frame. Preferably, when the wind propelled vehicle is operably engaged with a sail, the center of gravity of the wind propelled vehicle is forward of the axle. In another preferred aspect of the present invention, at least one restraining device directly or indirectly engages the mast and axle and can confine a sail within a determined area and provide a rigid mast support. 
     Another preferred aspect of the present invention is a wind propelled vehicle that includes at least one frame that includes at least one wheel, skid, ski or blade at a distal portion of the at least one frame; at least one axle that includes at least one wheel, skid, ski or blade; and at least one mast. In one preferred aspect of the present invention, a proximal portion of the at least one frame directly or indirectly operably engages the at least one axle. Optionally, the at least one mast directly or indirectly operably engages the at least one frame at a distal portion of the at least one frame. In another preferred aspect of the present invention at least one restraining device directly or indirectly engages the at least one mast and the at least one axle. Preferably, when the wind propelled vehicle is operably engaged with at least one sail, the center of gravity of the wind propelled vehicle is forward of the at least one axle. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG.  1 A and FIG. 1B depict one aspect of a robotic sailing device of the present invention viewed from an elevated position. FIG. 1A depicts a robotic sailing device of the present invention fitted with a sail, mounting plate to house motors or servos to steer the craft, and wheels. FIG. 1B depicts a robotic sailing device of the present invention with the sail, mounting plate and wheels depicted to indicate the environment of the remainder of the elements of the robotic sailing device. 
     FIG. 2 depicts a front view of one aspect of a robotic sailing device of the present invention where the front wheel assembly, axle with associated rear wheels, mast with attached sail, boom in one position, and retainer apparatus, are depicted. 
     FIG. 3 depicts an overhead view of one aspect of a robotic sailing device of the present invention showing the frame with support beams, mount plate for at least one servo, front wheel assembly, axle with associated rear wheels, mast with attached sail, boom in one position, and retainer apparatus. 
     FIG. 4 depicts a side view of a one aspect of robotic sailing device of the present invention shows frame association with front wheel assembly and right rear wheel, mast with attached sail, boom in one position, and retainer apparatus. 
     FIG. 5 depicts one aspect of tubing that can attach various elements of a robotic sailing device of the present invention, preferably such that the robotic sailing device can be readily folded for storage or transportation. Depicted are two restraining devices connected by Tygon™ tubing that can be indirectly engaged to the mast. 
     FIG. 6 depicts one aspect of a front wishbone that can directly or indirectly engage a mast to a boom of a robotic sailing device of the present invention. 
     FIG.  7 A and FIG. 7B depicts stability calculations of a robotic sailing device of the present invention. Calculation symbols are defined as: μ, static coefficient of friction; m, mass of robotic sailing device; g, acceleration of gravity; v, linear velocity to entering turn; s, time in seconds; R, turning radius; P W , wind pressure; F W , wind force; A, sail area; z cf , center of acting wind force; F fw , weight of distal wheel assembly; F rw , weight of axle wheel assembly; F sm , weight of mounting plate; F fr , weight of preferred embodiment of frame, axle and supports; F to , weight of preferred embodiment of robotic sailing device; F f , frictional force; a n , normal acceleration; a t , tangential acceleration; {overscore (ω)}, angular velocity, N, normal force. In the preferred embodiment of a robotic sailing device of the present invention the weight of robotic sailing device is given, mg=3.55 lbf; turning radius measured, R=6.5 ft; A=4.363 ft 2 ; z cf =20 in; perpendicular distance of frame to tip axis, d f =12 in; perpendicular distance for axle associated wheel, drw=42 in; perpendicular distance from mounting plate, d rw =8 in. Calculations assume robotic sailing device is traveling at a 45 degree and to the wind and therefore all the wind force is acting perpendicular to the sail. 
     FIG. 8 shows another preferred embodiment of the present invention. 
     FIG. 9 shows another preferred embodiment of the present invention. 
     FIG. 10 shows another preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Definitions 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Generally, the nomenclature used herein and the procedures described are well known and commonly employed in the art and in nautical terms. For example, when referring to a frame of a wind propelled vehicle of the present invention, “proximal” can refer to the stem and “distal” can refer to the bow of the wind propelled vehicle. Where a term is provided in the singular, the inventors also contemplate the plural of that term. As employed throughout the disclosure, the following terms, unless otherwise indicated, shall be understood to have the following meanings: 
     Introductions 
     As a non-limiting introduction to the breadth of the present invention, the present invention includes several general and useful aspects, including: 
     1) a wind propelled vehicle that includes a frame that includes a wheel, skid, ski or blade at a distal portion of the frame; an axle that includes two wheels, skids, skis or blades; and a mast. 
     2) a wind propelled vehicle that includes at least one frame that includes at least one wheel, skid, ski or blade at a distal portion of the at least one frame; at least one axle that includes at least one wheel, skid, ski or blade; and at least one mast. 
     These aspects of the invention, as well as others described herein, can be achieved by using the methods, articles of manufacture and compositions of matter described herein. To gain a full appreciation of the scope of the present invention, it will be further recognized that various aspects of the present invention can be combined to make desirable embodiments of the invention. 
     I. A Wind Propelled Vehicle 
     The present invention includes a wind propelled vehicle that includes a frame  10  that includes a wheel  11 , skid, ski or blade at a distal portion of the frame; an axle  12  comprising two wheels  13 , skids, skis or blades; and a mast. Optionally, a proximal portion of the frame directly or indirectly operably engages the axle. Optionally, the mast  14  directly or indirectly operably engages the frame at a distal portion of the frame. Optionally, the wind propelled vehicle is operably engaged with a sail  15 , resulting in the center of gravity of the wind propelled vehicle being forward of said axle. 
     In a preferred embodiment of the wind propelled vehicle of the present invention, the frame is  10  elongated. At or near the bow, or distal, end of the frame  10  can be an assembly that directly or indirectly operably engages a wheel  11 , skid, ski or blade. The rear, or stern, of the frame is engaged to the approximate center of arn axle  12 . Each of the terminal regions or ends of the axle  12  directly or indirectly operably engages a wheel  13 , skid, ski or blade. Such a preferred aspect of the present invention is depicted in FIG. 1A, FIG. 1B, FIG. 2, FIG.  3  and FIG.  4 . 
     In this preferred aspect of the present invention two support beams  16  join either side of the frame  10  to the axle  12 . One end of each support beam  16  can be joined on either side of the frame  10  with the opposite end of each support beam  16  joined to the axle  12 , between the terminal regions or ends of the axle  12  and where the frame  10  engages the axle  12 . Attachment of support beams  16  give the vehicle of this invention an overall triangle shape when viewed from overhead. Engaged to the frame  10 , at a position within the frame&#39;s  10  distal portion but aft of the wheel  11 , skid, ski or blade assembly, is a mast  14  that is preferably curved in shape that rises from the frame  10  and sweeps back toward the stem of the frame  10 . Attached to the mast  14  can be a sail  15  that can sweep back toward the stem of the vehicle resulting in a center of gravity forward of the axle  12  of the vehicle when being propelled by wind. A restraining device  17  is engaged to the mast  14  such that each end extends to, and can be joined to, the axle  12  at approximately the same position of each of the support beams  16 . Preferably, one or more booms  18 , such as in a windsurfing configuration, is operably engaged to the mast  14 . 
     Preferably, the invention includes an antenna  19  that can be attached to any portion of the remote-controlled, wind propelled vehicle such as the mast  14  or frame  10  and engages a motor  20  or servo  20  attached to a mounting plate  21 , which is in turn attached to the frame  10  or support beam  16  or beams. The motors  20  or servos  20  can be controlled by a remote control device  22  that includes controls, such as joysticks, to modulate the motor  20  or servo  20 , preferably independently. One motor  20  or servo  20  preferably is operably engaged to the front wheel  11  by a steering device  24  such as wire and can change the direction of the robotic sailing device while under way. Another motor  20  or servo  20  is preferably operably engaged to the sail  15  or boom  18  by a sail modulating device  23  such as a string, which can act as a main sheet in a sail boat. In operation, the restraining device  17  prevents the sail  15  from progressing too far to port or starboard, while the sail modulating device  23  can change the attitude of the sail  15  relative to the wind and allow for trimming of the sail  15  to provide acceleration or deceleration of the robotic sailing device while under way. 
     In a preferred aspect of the present invention two restraining devices  17  join the mast to another portion of the robotic sailing device, such as the axle  12 . One end of each restraining device  17  can be joined to either side ofa mast  14  with the opposite end of each restraining device  17  joined to the axle  12 , between the terminal regions or ends of the axle  12  and where the frame  10  engages the axle  12 . Attachment of restraining devices  17  can keep a sail  15  confined to a determined region and provide a rigid support to the mast  14  to reduce or eliminate the requirement of a forestay, such as a front wire. 
     Each of the attachments of the various elements of the present invention can be quickly engaged or disengaged from their appropriate positions of the wind propelled vehicle of the present invention without necessity of tools. The attachments are joined by clamps, wing-nuts, and flexible tubing  50  such as Tygon™, where one end of the tubing  50  fits over the end of one attachment and the second end can fit over a second attachment thus joining the two, as depicted in FIG. 5, or be joined to the second attachment by an appropriate method or device such as a pin, screw, tie down, wire, twine, snap, or clamp. Velcro™ also can be utilized to join different attachments particularly the mast  14  to the sail  15  using loops of Velcro™ material. String, twine or rope can also be used, particularly for attaching the clew of the sail  15  to the aft portion of the booms  18 . This allows for easy transportation and minimal storage requirements and for quick assembly and disassembly without the need of tools. Preferably, the folded and/or disassembled robotic sailing device of the present invention can be stored in a carrying device such as a bag or box. Elements can be directly engaged, meaning the elements physically touch one another, by permanent or semi-permanent attachments such as welds or solder or by temporary attachments such as by screws, bolts, wing-nuts, twine, tubing or the like. Elements can be indirectly engaged, meaning the elements physically do not touch one another directly, by permanent, semi-permanent, or temporary attachments. Such indirect engagement preferably utilizes an additional element, such as tubing  50 . An example of indirect engagement is provided in FIG.  5 . 
     Preferably, the mast  14 , booms  18 , axle  12 , frame  10 , supports  16  and restraining devices  17  of a wind propelled vehicle of the present invention are all made of rigid tubes and joined by flexible tubing  50 . Thus, a wind propelled vehicle of the present invention can be “totally tubular.” 
     Frame 
     A frame  10  of a wind propelled vehicle of the present invention can be of any shape including, but not limited to, an elongated pole or bar, or, as viewed from overhead a triangle, square, rectangle, oval, or circle. A pole or bar can be solid, perforated or hollow with a cross section of any geometric shape including, but not limited to, cylindrical, square, rectangular, or octagonal. The frame  10  can be, at least in part, a structure such as a platform and can be of any thickness, length and width and can be solid, perforated or hollow. Alternatively, the frame  10  can be constructed of, at least in part, tubes, poles or bars that can be, at least in part solid, perforated or hollow with a cross section of any geometric shape including, but not limited to, cylindrical, square, rectangular, or octagonal. Materials used to make up the frame  10  can be of a single or combination of materials such as, but not limited to, fiberglass, carbon, graphite, plastic, rubber, wood, and metal or metallic elements such as, but not limited to, aluminum, copper, and tin. 
     The distal region or end of the frame  10  can directly or indirectly, by way of an intermediate attachment, engage a rotatable wheel  11 , skid, ski or blade. A rotatable wheel  11  allows for rolling over a somewhat smooth and flat surface including hard composites such as pavement and asphalt, and packed earth. A skid acts as a runner to navigate over such surfaces as grass, sand and ice. Similarly a ski having a flat surface can navigate over similar surfaces and more efficiently over snow. And a blade, such as a skate, best glides over a slick, flat surface such as ice. 
     The proximal region or end of the frame  10  can directly or indirectly engage an axle  12 . The proximal region or end of the frame  10  can directly or indirectly engage an axle  12  by way of, at least in part, but not limited to, clamps, wing-nuts, tubing, plastic, Velcro™, nylon, wire, twine, or cloth. Tubing  50  can be used to engage the frame to the axle by having each attachment fastened into different ends of tubing  50 , or, the frame can be engaged to an axle  12  by being wrapped or strapped together, at least in part, with plastic, Velcro™, nylon, wire, twine, or cloth. 
     Axle 
     An axle  12  of a wind propelled vehicle of the present invention can be of any shape including, but not limited to, a tube, rod, pole or bar, and can be a single or multiple of pieces. The axle  12  can be, at least in part, solid, perforated or hollow with a cross section of any geometric shape including, but not limited to, cylindrical, square, rectangular, or octagonal. The axle  12  can be made of a single or combination of several materials such as, but not limited to, fiberglass, graphite, plastic, rubber, wood, and metal or metallic elements such as, but not limited to, aluminum, copper, and tin. The terminal regions or ends of the axle  12 , or any part of the axle, can directly or indirectly engage any combination of rotatable wheels  13 , skids, skis or blades. 
     Support 
     A support or supports  16  of a wind propelled vehicle of the present invention can be directly or indirectly engaged to, for example the frame  10  and axle  12 . The support or supports  16  can add strength to the overall structure of the invention and increase stability while turning or cornering when being propelled by wind. Each support  16  can be of any form including, but not limited to, a tube, shaft, rod, rail, wire, rope or strap and can be a single or multiple of pieces. A shaft, rod, or rail can be solid, perforated or hollow with a cross section of any geometric shape, but not limited to, cylindrical, square, rectangular, or octagonal. Each support  16  can be made of a single or combination of several materials such as, but not limited to, fiberglass, graphite, plastic, rubber, wood, and metal or metallic elements such as, but not limited to, aluminum, copper, and tin. Each support  16  can be engaged to, but not limited to, the frame  10  and axle  12  by way of, at least in part, clamps, wing-nuts, tubing  50 , plastic, Velcro™, nylon, wire, twine, or cloth. Each support  16  can be attached over, on or to, but not limited to, the top, bottom or side of a platform-like frame  10 . 
     Mast 
     A mast  14  of a wind propelled vehicle of the present invention can be of, at least in part, any form including, but not limited to, a tube, shaft, rod or bar and can be a single or multiple of pieces. The mast  14  can be, at least in part, solid, perforated or hollow with a cross section of any geometric shape including, but not limited to, cylindrical, square, rectangular, or octagonal. The mast  14  can be made of a single or combination of several materials such as, but not limited to, fiberglass, graphite, plastic, rubber, wood, and metal or metallic elements such as, but not limited to, aluminum, copper, and tin. An end or a terminal region of the mast  14 , or any part of the mast, can directly or indirectly engage, but not limited to, the frame, preferably within, the proximal half the frame  10 . The mast  14  can directly or indirectly engage a frame  10  by way of, at least in part, clamps, wing-nuts, tubing  50 , plastic, Velcro™, nylon, wire, twine, or cloth. 
     Boom 
     The wind propelled vehicle of the present invention can have at least one boom  18 . The at least one boom  18  are preferably two booms  18  in a windsurfing configuration. The at least one boom  18  is, at least in part, any form including, but not limited to, a tube, shaft, rod or bar and can be a single or multiple of pieces. The at least one boom  18  may be made of a single or combination of several materials such as, but not limited to, fiberglass, carbon, plastic, rubber, wood, and metal or metallic elements such as, but not limited to, aluminum, copper, and tin. 
     The preferably two booms  18  can be engaged at one end or terminal region of each of the preferably two booms  18  to make up the forward end of the at least one boom  18  by, but not limited to, preferably a front wishbone or tubing, plastic, Velcro™, nylon, wire, twine, or cloth. A front wishbone can encircle the mast or attach the mast by way of, for example, clamps or wing-nuts, or being wrapped or strapped together with plastic, Velcro™, nylon, wire, twine, tubing  50 , or cloth. A front wishbone can be, but is not limited to, pig tail shaped or curved and can be, at least in part, solid, perforated or hollow. A front wishbone can be made of a single or combination of several materials such as, but not limited to, fiberglass, graphite, plastic, rubber, and metal or metallic elements such as, but not limited to, steel, aluminum, copper, and tin. A front wishbone can attach the preferably two booms  18  by, for example, tubing, wrapped or strapped that can, but is not limited to, encase and join the ends of the preferably two booms  18  to form the forward section of the at least one boom  18 . Alternatively, the end or terminal regions of the preferably two booms  18  can be joined by tubing  50 , clamps or wing-nuts, or being wrapped or strapped together with plastic, Velcro™, nylon, wire, twine, or cloth. The front or forward section of the at least one boom  18  can be engaged to the mast  14  by, but not limited to, tubing  50  or wrapped or strapped with plastic, Velcro™, nylon, wire, twine, or cloth. 
     The rear end or aft of the at least one boom  18  can be formed by the preferably two booms by engaging the opposite or rear ends or terminal regions of each of the preferably two booms by, but not limited to, preferably a rear wishbone or clamps, wing-nuts, tubing, plastic Velcro™, nylon, wire, twine, tubing  50  or cloth. A rear wishbone can be, but is not limited to, curved and can be, at least in part, solid, perforated or hollow. A rear wishbone can be made of a single or combination of several materials such as, but not limited to, fiberglass, graphite, plastic, rubber, and metal or metallic elements such as, but not limited to, aluminum, copper, and tin. A rear wishbone can attach the preferably two booms by, but is not limited to, tubing, wrapped or strapped that can, but is not limited to, encase and join the rear ends of the preferably two booms to form the rear section of the at least one boom. 
     Restraining Device 
     The wind propelled vehicle of the present invention may have at least one restraining device  17  to keep the sail  15  of the vehicle confined to a determined area thereby preventing an undesirable shift in the center of gravity that can adversely affect performance of the vehicle. The at least one restraining device directly or indirectly engages the frame  10 , axle  12 , mast  14 , or boom  18 . The at least one restraining device  17  is of any form or combination thereof including, but not limited to, a tube, shaft, rod, rail, wire, rope, or strap and can be a single or multiple of pieces. A shaft, rod, or rail can be solid, perforated or hollow with a cross section of any geometric shape, but not limited to, cylindrical, square, rectangular, or octagonal. The at least one restraining device  17  can be made of a single or combination of several materials such as, but not limited to, fiberglass, graphite, nylon, plastic, rubber, wood, and metal or metallic elements such as, but not limited to, aluminum, copper, and tin. The at least one restraining device  17  can be engaged to, but not limited to, the frame  10 , axle  12  and mast  14 , by way of, at least in part, clamps, wing-nuts, tubing  50 , plastic, Velcro™, nylon, wire, twine, or cloth. 
     A preferred embodiment of the present invention can have an end of the at least one restraining device  17  engaged to the mast about, but not limited to, the midsection of the mast  14 . The opposite end of the at least one restraining device  17  can be attached to another portion of the robotic sailing device, such as the axle  12 . Dependent upon its material makeup the at least one restraining device  17  can receive pressure, such as compression, and support to the mast  14 . In one aspect of the present invention the need of a forestay, such as a wire, to support the mast  14  can be eliminated. 
     Sail 
     The wind propelled vehicle of the present invention can have a sail  15  that directly or indirectly engages one or more of, or any combination thereof, the mast  14 , frame  10 , axle  12 , at least one boom  18 , or at least one restraining device  17 . The sail  15  is of any shape including, but not limited to, a triangle, square, rectangle, oval or circle or can be a solid wing sail. The sail  15  can be a single or multiple of pieces of one or more same or different materials. The area of the sail  15  can be of any size such as between about 0.5 to about 10 square feet, preferably between about 2 to about 8 square feet, and more preferably between about 3 to about 6 square feet. Preferably, the sail  15  has the shape and is made of the same or similar material or materials as are windsurfing sails. In one preferred aspect of the present invention the sail  15  has a windsurfing configuration which in operation prevents, at least in part, a lift vector on the boom or booms  18 . In this configuration, the need for a downstay is reduced or eliminated. 
     The sail  15  consists of any one or a combination of materials such as, but not limited to, Mylar™, plastic, nylon, paper, cloth, or canvas or any combination thereof. The sail  15  can directly or indirectly engage the mast  14 , frame  10 , axle  12 , at least one boom  18 , or at least one restraining device  17  of the wind propelled vehicle, at least in part, by such means as, but not limited, to clamps, wing-nuts, tubing, Velcro™, nylon, wire, twine, cloth, and plastic. The sail  15  can utilize the wind to propel the vehicle forward as understood by those familiar with the art. The sail  15  can be confined to an area by at least one restraining device  17  while the motion and position of the sail  15  can be controlled by a sail modulating device. In one aspect of the present invention, the sail  15  can include battens to provide rigidity, shape and strength to the sail. In the alternative, the sail  15  can be provided without battens and be cut to allow a curved leading edge of the sail when underway and full of wind. 
     Steering Device 
     The wind propelled vehicle of the present invention can have at least one steering device that can modulate the direction of the robotic sailing device while underway. Preferably the steering device modulates the angle of the front wheel, ski, skid or blade to effect a change in direction. The steering device is preferably directly or indirectly engaged with the front wheel  11 , ski, skid or blade by an appropriate structure, such as a wire. The at least one steering device can include at least one motor  20  or servo  20  that can modulate the front wheel  11 , ski, skid or blade, preferably under remote control direction of a user, such as a human operator using a remote control device  22 . The motor  20  or servo  20  can be located at any appropriate location on the robotic sailing device, but is preferably located on the frame  10  and/or support  16 , and is preferably provided on a mounting structure, such as a mounting plate  21 . 
     Sail Modulating Device 
     The wind propelled vehicle of the present invention may have at least one sail modulating device. The at least one sail modulating device can include at least one motor  20  or servo  20 . The at least one sail modulating device can directly or indirectly modulate the sail  15 , preferably using configurations known the nautical arts, such as configurations of a main sheet in a sailboat. For example, a modulating device  23 , such as a string, can be modulated using a motor  20  or servo  20  under control of, for example, a remote control device  22 . The string can be attached to the sail  15  or boom  18  or booms  18  to allow the sail  15  to be sheeted in or sheeted out by an operator as appropriate or desired. A pulley, restraint or system of pulleys or restraints can be used to direct the course of the string along the robotic sailing device. For example, FIG. 1A shows modulating device (i.e., string)  23  tied to boom  18  at one end. At its other end, modulating device  23  is connected to motor  20 . Between motor  20  and boom  18 , modulating device  23  is directed through pulley  86 . 
     Embodiments Utilizing Skis, Skids and Blades 
     As stated repeatedly above, it is possible to utilize the present invention with skis, skids and blades in place of wheels. For example, FIG. 8 shows skis  87  connected to rear axle  12  and ski  88  connected to the forward portion of frame  10 . FIG. 9 shows skids  89  connected to rear axle  12  and skid  90  connected to the forward portion of frame  10 . Likewise, FIG. 10 shows blades  91  connected to rear axle  12  and blade  92  connected to the forward portion of frame  10 . 
     Dimensions 
     The ratio of axle  12  length to frame  10  length of a wind propelled vehicle is preferably between about 1:1 and about 2:1. More preferably, that ratio is about 1.2:1, about 1.4:1, about 1.6:1 or about 1.8:1. This ratio allows for the wind-propelled vehicle of the present invention to efficiently turn and comer such that maneuverability is enhanced at higher velocities than a vehicle with a longer axle  12  length in relation to it&#39;s frame  10 . 
     Lift 
     The wind propelled vehicle of the present invention is provided lift when a sail is operably engaged to the invention and wind is propelling the invention. Lift constitutes an upward force that allows for less gravitational opposition on surfaces of the robotic sail device in contact with land, water, snow or ice and thereby results in less friction and increase speed and agility of the robotic sail device while under way. The lift is generated through the forward force of the wind engaging the sail  15  that can be attached to the mast  14 . The combination of the force provided by the wind and the sweep of the mast toward the stem of the vehicle generates lift. 
     Center of Effort 
     When a sail  15  is engaged with a wind propelled vehicle of the present invention and the wind propelled vehicle is being propelled by the wind, the center of effort of the sail  15  is preferably forward of the axle  12 . The center of effort being forward of the axle  12  provides for improved speed and simulates the desired physics of windsurfing. In the preferred aspect of the present invention the center of effort of the sail  15  is established at or near the geometric center of the sail  15 . 
     Stability and Performance 
     When a sail  15  is affixed to the wind propelled vehicle of the present invention and said vehicle is under way with wind, the invention exhibits the ability to perform sharp turns with a relatively small turning radius and displays enhanced stability during operation. The physics and calculations involved in describing the stability of performance of one aspect of the wind propelled vehicle of the present invention is presented in FIG.  7 A and FIG.  7 B. 
     II A Wind Propelled Vehicle that Includes At Least One Frame 
     The present invention includes a wind propelled vehicle that includes at least one frame  10  that includes at least one wheel  11 , skid, ski or blade at a distal portion of said at least one frame  10 ; at least one axle  12  comprising at least one wheel  13 , skid, ski or blade and at least one mast  14 . 
     A wind propelled vehicle, comprising: 
     1) at least one frame comprising at least one wheel, skid, ski or blade at a distal portion of said at least one frame; 
     2) at least one axle comprising at least one wheel, skid, ski or blade; 
     3) at least one mast; 
     wherein a proximal portion of said at least one frame directly or indirectly operably engages said at least one axle; 
     wherein said at least one mast directly or indirectly operably engages said at least one frame at a distal portion of said at least one frame; 
     wherein when said wind propelled vehicle is operably engaged with at least one sail, the center of gravity of said wind propelled vehicle is forward of said at least one axle. 
     The wind propelled vehicle of the present invention can have multiples of the aforementioned elements, particularly multiple sails  15 , frames  10  and axles  12 . For example, a wind propelled vehicle of the present invention can have more than one frame  10 . The frames  10  can be arranged in tandem such as one behind the other, next to each other or any combination thereof. The frames  10  can be positioned in a variety of configurations, such as circular, square, triangular or rectangular arrangement with the distal or front portions of each positioned in relatively the same direction. Preferably, the configuration is similar to those in sailcraft, such as sailboats, with multiple sails, but that need not be the case. The frame  10  or multiple of frames  10  can engage rotatable wheels  11 , 13 , skids, skis, or blades, in any combination. Each frame  10  need not be individually engaged with such wheels  11 ,  13 , skids, skis or blades. For example, multiple frames  10  can be provided in tandem on a single axle  12  or each frame  10  can have an independent axle  12 . Preferably, each individual frame  10  includes a mast  14 , which preferably includes a sail  15 . The multiple sails  15  can be controlled by one or more sail modulating devices  23 , which can act separately or in concert. The direction of the wind propelled vehicle can be controlled by one or more steering devices  20 , 24  that can act separately or in concert. 
     All publications, including patent documents and scientific articles, referred to in this application are incorporated by reference in their entirety for all purposes to the same extent as if each individual publication were individually incorporated by reference. 
     All headings are for the convenience of the reader and should not be used to limit the meaning of the text that follows the heading, unless so specified.