US20030122350A1

US20030122350A1 - Surface traversing apparatus with stepped running surface

Info

Publication number: US20030122350A1
Application number: US10/175,590
Authority: US
Inventors: Mark Vance
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-06-15
Filing date: 2002-06-17
Publication date: 2003-07-03
Also published as: AU2002315221A1; WO2002102479A3; WO2002102479A2

Abstract

The surface traversing apparatus includes a main body having a shovel that curves upwardly at the front thereof. A rider is releasably secured to the top surface of the surface traversing apparatus by a binding that holds the rider's boots. The surface traversing apparatus further includes a diffuser, which defines a stepped running surface, positioned on the bottom rear portion of the apparatus. The diffuser operates to reduce both parasitic drag and form drag while providing increased directional stability when the surface traversing apparatus runs flat against the snow.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Serial Nos. 60/298,844, filed Jun. 15, 2001, and 60/351,188, filed Jan. 23, 2002, which are hereby incorporated by reference.[0001]

FIELD OF THE INVENTION

The present invention relates generally to surface traversing apparatuses for carrying a rider on snow, and more particularly to skis and snowboards.

BACKGROUND OF THE INVENTION

For purposes herein, the term ski shall refer to both downhill skis and snowboards. For racing as well as general ski use, it is desirable to have the ski slide as freely as possible over the snow. For practical purposes, a free sliding ski will travel further over the snow, extending the glide for the user and minimize any skating and pushing with ski poles or other methods required to traverse flat ground. A free sliding ski is easier to maneuver, requiring less physical effort by the user to initiate turns. And finally, a free sliding ski will gather greater speed for the racing enthusiast, netting a lower time through the racecourse.

Many factors contribute to the sliding performance of a ski. The general physical dimensions and shape of the ski are important, as well as the component parts. In the construction of a ski, a great deal of attention is focused in such areas as stiffness in both flex and torsion, running surface length and base material, side cut, and dampening. The ski engineer addresses these construction criteria through the utilization of various materials and methods, thereby tailoring the ski's performance envelope to meet the categorized ability levels of the skiing public. The dynamic motion of a ski over the snow is the sum of its component parts acting in concert, resulting in the skis ultimate glide and control characteristics.

Generally described, the performance of skis as they slide over the snow in flat or near flat angular relation to the snow surface is affected by several factors that contribute to the skis glide and control capabilities. First, parasitic drag is one opposing force with respect to glide. Parasitic drag is a term used to define the number of molecules of a particular medium (in this case snow) in direct physical contact with the ski. The length of the ski and side cut physically define the wetted surface of the ski in contact with the snow. The more wetted surface in contact with the snow, the greater the parasitic drag. Various base materials, waxes and base grinds have been designed to be applied to the ski base to reduce the interactional effects in the boundary layer between the wetted surface of the ski and the snow. However, drag reduction as a result of base preparation, is still dependent upon the amount of wetted area the ski applies to the snow surface.

A second contributing factor to glide performance is form drag. This type of drag is the dependent upon the shape of the ski. The physical footprint the ski applies into the snow defines it drag form. Fluid dynamics teaches that streamlining an object reduces the drag imparted upon the object (ski) as it proceeds (in this case) over, or through a medium.

The ski is limited with regard to the amount of design streamlining that can be added to the basic shape by other performance requirements, primarily turning characteristics. A ski requires a side cut in order to achieve a turn. The amount and specific shape of the curved side cut acting jointly with the designed flex, determine the skis turning capabilities and qualities. In terms of design priority, a ski is designed first and foremost to fit turning criteria for the performance application envisioned by the engineer. As the hourglass perimeter shape or side cut of a ski is essentially locked in by predetermined turning requirements, the opportunity for form drag reduction is greatly reduced.

Lastly, a third factor related to maximizing glide is tracking stability. Directional control of a ski is a function of the angle developed between the ski and the surface of the snow. That is to say, as the ski is angled to one side, the edge engages the snow and applies a force that changes the skier's direction or track. Edging and turning is the action used by the skier to control speed. Conversely, as the angle is decreased, the force applied by the edge is reduced and ultimately becomes zero, at which point the ski is flat against the snow surface. With the ski running flat, the edges are disengaged from the snow and the ski becomes directionally unstable. The ski in this condition, of its own accord, cannot track straight. As the ski glides forward and impacts various bumps and undulations in the natural terrain, angular forces are imparted to ski. These forces cause the ski to change the direction of travel. The skier in turn must continually make fine edging adjustments to control direction and maintain a straight course. These fine edging adjustments contribute to the drag coefficient of the ski when running flat.

SUMMARY OF THE INVENTION

In accordance with aspects of the present invention, a ski or snowboard is presented that addresses the performance of the ski as it slides over the snow in flat or near flat angular relation to the snow surface. As described above, the reduction of wetted area is paramount in minimizing the effects of parasitic drag. The invention reduces the wetted area of the ski in flat relation to the snow surface. Additionally, the invention effectively streamlines the base of the ski without modifying the two dimensional outline shape, thereby reducing form drag. Further, the invention enhances straight-line stability of the ski to assist the skier in minimizing directional inputs, also reducing drag.

In accordance with one embodiment of the present invention, a base of a runner for gliding over snow is provided. The base includes a front portion including a flat running surface generally defining a first surface plane, and a rear portion. The rear portion includes a central running surface and a first inner edge located along at least a portion of the perimeter of the central running surface. The base further includes a first outer portion disposed adjacent the central running surface. The first outer portion includes a first outer running surface and a first outer edge located along at least a portion of the perimeter of the first outer running surface. At least a portion of the first inner edge is at a different elevation than the first surface plane.

In accordance with another embodiment of the present invention, a snow traversing apparatus is provided that includes an elongate body having a front end, a rear end, a top surface, and a base that extends along the approximate length of the body. The base includes a front portion extending between approximately the longitudinal midpoint of the elongate body and the front end. The front portion defines a front running surface that is planar across the entire front portion in the lateral direction as the front running surface extends to the end of the body. The base also includes a rear portion extending between the end of the front portion disposed at approximately the longitudinal midpoint of the elongate body and the rear end of the elongate body. The rear portion includes a central running surface generally defining a central surface plane, two outer running surfaces, a portion of the central running surface being at a different elevation than the outer running surfaces; and first and second inner edges disposed between the central running surface and the first and second outer running surfaces, respectively. The base further includes first and second outer edges surrounding a portion of the perimeter of the first and second outer running surfaces, respectively.

In accordance with still another embodiment of the present invention, a base of a runner for gliding over snow is provided. The base includes a front portion including a flat running surface generally defining a first surface plane, and a rear portion having a removably attachable stepped portion. The stepped portion includes a central running surface and first and second inner edges located along at least a portion of the perimeter of the central running surface. The base also includes a first outer portion disposed adjacent to the stepped portion. The first outer surface includes a first outer running surface and a first outer edge located along at least a portion of the perimeter of the first outer running surface. At least a portion of the first inner edge is at a different elevation than the first surface plane. The base further includes a second outer portion disposed adjacent to the stepped portion on the side opposite of the first outer portion. The second outer portion includes a second outer running surface and a second outer edge located along at least a portion of the perimeter of the second outer running surface. At least a portion of the second inner edge is at a different elevation than the first surface plane.

Taken together, the present invention endeavors to reduce both parasitic drag and form drag of the ski while providing increased directional stability while running flat against the snow.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: [0014]
FIG. 1 illustrates a bottom perspective view of a snow ski in accordance with aspects of the present invention; [0015]
FIG. 2 illustrates a bottom view of the snow ski shown in FIG. 1; [0016]
FIG. 3 illustrates a partial rear side elevation view of the snow ski shown in FIG. 1; [0017]
FIGS. [0018] 4A-4C illustrates cross-sectional views taken along lines A-A, B-B, and C-C, respectively, in FIG. 3;
FIG. 5 illustrates a schematic cross-sectional view taken along lines A-A, section B-B, and section C-C, respectively, in FIG. 3; [0019]
FIG. 6 illustrates a bottom perspective view of a snowboard constructed in accordance with aspects of the present invention; [0020]
FIG. 7 illustrates a rear partial side elevational view of the snowboard shown in FIG. 6; [0021]
FIG. 8 illustrates a bottom perspective assembly view of a snow ski having a modular design constructed in accordance with aspects of the present invention; [0022]
FIG. 9 illustrates a bottom perspective assembly view of a snowboard having a modular design constructed in accordance with aspects of the present invention; [0023]
FIG. 10 illustrates a cross-sectional view of the ski of FIG. 8 without a step liner; [0024]
FIG. 11 illustrates a bottom perspective assembly view of another embodiment of the connection between the diffuser and the base of the ski/snowboard; [0025]
FIG. 12A illustrates a partial side elevational view of the connection between the diffuser and the base of the ski/snowboard shown in FIG. 11; [0026]
FIG. 12B illustrates a cross-sectional view of the connection between the diffuser and the base of the ski/snowboard shown in FIG. 11; [0027]
FIG. 13 illustrates a partial side elevational view of another embodiment of the connection between the diffuser and the base of the ski/snowboard; [0028]
FIG. 14 illustrates a cross-sectional view of yet another embodiment of the connection between the diffuser and the base of the ski/snowboard; [0029]
FIG. 15 illustrates a bottom view of the ski in accordance with aspects of the present invention showing the wetted area; [0030]
FIG. 16 illustrates a bottom view of the snowboard in accordance with aspects of the present invention showing the wetted area; [0031]
FIG. 17A illustrates a partial side view of the rear portion of another alternative embodiment of the ski in accordance with the present invention; [0032]
FIG. 17B illustrates a partial rear side elevation view of the snow ski shown in FIG. 1; and [0033]
FIG. 18 illustrates an alternative embodiment of a ski showing a diffuser having an inwardly tapering rear portion.[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described with reference to the accompanying drawings where like numerals correspond to like elements. FIG. 1 illustrates a bottom perspective view of one exemplary embodiment of a [0035] snow ski 10 formed in accordance with aspects of the present invention. The snow ski 10 includes a main body having a shovel 12 that curves upwardly at the front of the snow ski 10. A rider is releasably secured to the top surface 14 of the snow ski 10 by a binding (not shown) that holds the rider's boots. The snow ski further includes a diffuser 16 positioned on the bottom rear portion of the ski. The diffuser 16 operates to reduce both parasitic drag and form drag while providing increased directional stability when the ski runs flat against the snow.
Referring now to a bottom view of the [0036] ski 10 shown in FIG. 2, the body of ski 10 includes a base 18. The base 18, disposed along the bottom of ski 10, is defined by right and left outer edges 20 and 22. In the embodiment shown, the right and left outer edges 20 and 22 are curved inwardly toward the longitudinal axis of the ski from one end of the base to the other end in order to form an hourglass shape that curves outwardly towards the front and rear ends of ski. Used herein, the directions of left, right, front, and rear are in the context of the position of a rider, the part of the ski to the rider's right being the “right side” and so forth. A rider is generally oriented as having a position generally facing the shovel of the snow ski 10.
The [0037] base 18 includes a substantially flat planar front portion 18A having a front running surface and a rear portion 18B having a stepped or raised running surface formed via the diffuser 16. The front portion 18A begins at approximately the waist or longitudinal midpoint of the ski 10 and extends to the front end thereof. The rear portion 18B includes a central rear running surface 24, and longitudinal side walls. The side walls and the central rear running surface 24 converge at right and left inner edges 30 and 32. Thus, the central rear running surface 24, the inner edges 30 and 32, and the longitudinal side walls, define the diffuser 16. The rear portion 18B further includes right and left outer running surfaces 26 and 28, which are disposed adjacent to the sides of the central rear running surface 24. Preferably, the front and rear ends of the right and left inner edges 30 and 32 do not end abruptly, but rather blend to become coplanar with the outer running surfaces 26 and 28 (FIG. 3). Thus, in this manner, the central rear running surface 24 blends into the outer running surfaces 26 and 28 as well.
The [0038] diffuser 16 of the base 18 is stepped by forming the central rear running surface 24 of the diffuser 16 slightly lower in elevation than the right and left running surfaces 26 and 28 (i.e. the central rear running surface 24 is spaced a further distance apart from the top surface of the ski 10 than the right and left running surfaces 26 and 28). The right and left running surfaces 26 and 28 are preferably flat or straight across laterally, and in this embodiment, are substantially coplanar with the front running surface of the front portion 18A. In the embodiment shown, the right and left inner edges 30 and 32 are disposed parallel to the longitudinal axis of the ski 10. Alternatively, as shown in FIG. 18, the right and left inner edges may taper inwardly as they extend from the beginning of the diffuser to its end to further reduce drag. The central rear running surface 24 is preferably flat and decreases in elevation when compared to the top surface 14 as the surface 24 extends rearwardly. Thus, the diffuser 16 is wedge-shaped and increases in thickness as it extends toward the rear end of the ski 10.
Alternatively, the central [0039] rear running surface 24 of the diffuser 16 may extend rearwardly with an arcuate shape corresponding to the approximate radius of curvature of the sidecut of right and left outer edges 20 and 22. In the embodiment shown, the diffuser 16 begins just rear of the rider's boot (the oval shown in phantom in FIG. 2) and extends to the rear end of the ski. Alternatively, the diffuser may begin at approximately the waist or longitudinal mid-point of the ski, or begin at any location between the approximate midpoint of the ski 10 and rear end of the ski. In the embodiment shown, the diffuser 16 is integral with the ski 10. However, as shown in FIGS. 8-14, and described below, the diffuser 16 may be of a modular design that can be selectively attached and detached from the ski body.
It will be appreciated that the front running surface, the central [0040] rear running surface 24, and the right and left running surfaces 26 and 28 may be formed with a slight curve along their length to provide camber to the ski.
FIGS. [0041] 4A-4C illustrate cross-sectional views of the ski 10 along the lines A-A, B-B, and C-C, in FIG. 3, respectively. As best shown in FIG. 4C, a possible exemplary construction model of ski 10 will now be described. A core 38 is disposed within snow ski 10 and is generally symmetric about the longitudinal axis of snow ski 10. The core 38 is preferably constructed of wood and has steps on either side corresponding to the stepped base 18. However, a wide variety of construction materials could be used to compose the core, such as polyurethane or other structural foams. Preferably, the steps of the core 38 are inside of the right and left inner edges 30 and 32. The core 38 is surrounded by a torsion box 40 preferably constructed of a composite thermoset material such as fiberglass.
These structural configurations and materials described herein are exemplary in nature. Other structural configurations or components may also alternatively be used. For example, it is contemplated that injection-molding techniques could be used as an alternate board construction methodology. It is also contemplated that materials could possibly be utilized which would allow the entire base or even the entire ski or snowboard to be cut from a single piece of material, and thus not require multiple layers of materials. Further, in another alternate embodiment of this invention, the edges need not be formed at 90-degree angles, but rather could be beveled within a wide range of angles. [0042]
The running surfaces [0043] 24, 26, and 28 are located below the torsion box 40. The running surfaces 24, 26, and 28 are preferably made of P-Tex plastic. P-Tex is the standard material used on bases on standard downhill skis or snowboards. The central rear running surface 24 is bound on its right and left sides by the right and left inner edges 30 and 32, respectively. All of the edges 20, 22, 30, and 32 are preferably standard metal edges typically used in skis or snowboards. They include edge ears 42 that project inwardly and are held in place between the P-Tex and fiberglass layers of the running surfaces 24, 26, and 28, and torsion box 40, respectively. The right and left inner edges 30 and 32 are also locked in place by the right and left running surfaces 26 and 28 abutting against the right and left inner edges 30 and 32. The right and left running surfaces 26 and 28 are bounded on their outer sides by the right and left outer edges 20 and 22, respectively.
When the word “edge” is used within this application, it designates any type of step, (e.g. the right [0044] inner edge 30 designates the step between the central rear running surface 24 and the right outer running surface 26). The word “edge” is not meant to apply only to a traditional metal edge piece. As previously described, it is contemplated that a snowboard base could be made from a single piece of material. In this situation the inner and outer edges of the snowboard would cut into the single piece of material. The “steps” between the central running surface and the outer running surfaces in this embodiment would still be defined as “edges” for purposes of this application.
To protect the sides of the [0045] torsion box 40, right and left side walls 44 and 46, disposed above right and left outer edges 20 and 22 respectively, shield the sides of snow ski 10. A top layer 48 is disposed over the entire top surface of the snow ski 10 to protect the top of torsion box 40, and to support top graphics. The top layer 48 and side walls 44 and 46 are preferably constructed of acrylonitrile butadiene-styrene (ABS), but may be constructed of other materials. Alternatively, top layer 48 may be integral with the right and left side walls 44 and 46 and extend down the sides of snow ski 10.
Of particular note in FIG. 5 is the angle (α) that represents the edge slope of [0046] snow ski 10. Edge slope angle (α) is the angle that the slope of a line between comers of right inner edge 30 and the right outer edge 20, or between the left inner edge 32 and left outer edge 22, makes with the central rear running surface 24. The edge slope angle is determined in this embodiment at the rearward wide point of the ski. In the preferred embodiments of the invention, edge slope angle (α) is around three (3) degrees. However, angles ranging anywhere between 0.1 degree and 10 degrees are contemplated. When edge slope angle (α) lies within these ranges, snow does not accumulate in the area between the inner and outer edges. Both the height of the step and/or the lateral distance between the edges may be varied in order to change the edge slope angle (α).
While the present invention has been described above and illustrated herein with respect to skis, the diffuser may also be utilized by snowboards to achieve less drag and improved tracking stability. FIGS. 6 and 7 illustrate one suitable embodiment of a [0047] snowboard 110 formed in accordance with the present invention. The snowboard 110 includes a shovel 112 that curves upwardly at the front of the snowboard 110 and a tail 114 that curves upwardly at the rear of the snowboard 110. A rider is secured to the top of the snowboard 110 by bindings that hold the rider's boots (not shown). The snowboard further includes a diffuser 116 positioned at the bottom of the rear portion of the snowboard 10. The diffuser 116 preferably begin at approximately the waist or longitudinal mid-point of the ski, but can begin at any location between the approximate midpoint and rear end of the snowboard 110. The diffuser 116 reduces both parasitic drag and form drag while providing increased directional stability when the snowboard runs flat against the snow.
FIGS. 8 through 14 illustrate various embodiments of snow skis or snowboards formed in accordance with aspects of the present invention. The differences between the embodiments illustrated in FIGS. [0048] 8-14 and described below lie in the modular design of the diffuser and methods of selectively attaching the diffuser to the ski body. Although some embodiments are shown with either a snowboard or with a snow ski, it will be appreciated that the embodiments work equally well with both skis and snowboards and both should be considered within the scope of the present invention.
Referring now to FIGS. 8 and 9, the [0049] diffuser module 216 or 316 consists of base material, such as P-Tex, and is attached in this embodiment by an adhesive. The substructure of the body of the ski 210 or snowboard 310 is pre-molded or otherwise formed with the proper recessed diffuser elevation profile 220 or 320 integral to the body of the ski 210 or snowboard 310, respectively. In this embodiment, a step liner may or may not be used. FIG. 10 shows a cross-sectional view of the ski 210 where the step liner is not used. It will be appreciated that by having a modular design, the diffuser module 216 or 316 can be removed for repair or modification purposes, and later a new piece reapplied.
FIG. 11 illustrates another embodiment of a [0050] snowboard 410 utilizing the modular design of the diffuser 416. The diffuser 416 utilizes a detachable backbone or “shoe” structure 422 that defines the elevation profile of the diffuser 416, and provides a semi-rigid platform to which the diffuser base material 424 attaches. The structure 422 can be made from a variety of materials, however a molded durable plastic or phenolic material is preferred. As best shown in FIGS. 12A-12B, the diffuser 416 attaches to the body of the snowboard 410 via a set of tongues 430 that slide through slots 432 in the recessed cavity 434 in the snowboard body and are retained with a pin 440 or spring loaded ball bearing or other capture mechanism held within an attachment lug 442.
Alternative attachment methods, such as various threaded screw designs are possible options as well, and is shown in FIG. 13. [0051]
FIG. 14 illustrates yet another embodiment of a ski or [0052] snowboard 610 utilizing the modular design of the diffuser 616, where the diffuser “shoe” serves as the structure 622 that defines the elevation profile of the diffuser 616, and the attachment platform for the base material 624. The diffuser 616 attaches to the ski or snowboard body 613 via a keyway that is an integral part of the body 613. The diffuser 616 carries the matching shape, keyed to the ski or snowboard body 613. Attachment is accomplished by engaging the keyed faces 650 of the shoe and the ski or snowboard 610 at the tail, then sliding the diffuser 616 forward into place along the recessed receiver of the ski or snowboard 610. A removable pin or screw, or an adhesive may be used to secure the diffuser 616 in place.
FIG. 17A shows a partial side view of the rear portion of another alternate embodiment of a ski or snowboard with a diffuser in accordance with the present invention. The [0053] ski 700 is substantially identical in construction, material, and operation as ski 10 described above with respect to FIGS. 1-4C, except for the following differences which will now be described in detail. The ski 700 is constructed in a manner converse to that previously described with respect to ski 10. Whereas in FIGS. 1 through 14, and for ease of comparison FIG. 17B, the diffuser of the ski/snowboard 10 is stepped by forming the central running surface slightly lower than the right and left outer running surfaces so that the diffuser progressively descends in elevation below the elevation of the running base (RBE) in the front portion of the ski and the right and left outer running surfaces. Conversely, FIG. 17A shows the ski 700 having a ski body 713 in which the diffuser 716 is created by progressively elevating upward from the running base the left and right outer running surfaces (the central running surface of the diffuser forms the rear portion of the running base of the ski 700). The right outer running surface forms a progressively elevated outer edge 722. By constructing the ski 700 in this manner, the central running surface 724 of the diffuser 716 is at substantially the same elevation as the running base (RBE) of the front portion of the ski. Thus, the running base of the front portion, in conjunction with the central running surface of the diffuser, forms a continuous and flat running surface from the Forward Contact Point (FCP) to the Rear Contact Point (RCP) with no elevation change in the base.
Of particular note in this embodiment, a blend radius R is utilized to connect a line formed by the progressively elevated outer running surfaces (shown in FIG. 17A as outer edge [0054] 722) and the point of tangency with the central running surface. In one embodiment, the blend radius R is approximately equal to the radius of curvature of the side cut of the right and left outer edges of the ski. In other embodiments, the blend radius may be between 0 and 2 times the radius of curvature of the side cuts. It will be appreciated that other radii and shapes are contemplated to be within the scope of the present invention. While the ski 700 is described with respect to FIG. 17A with side cuts having a radius of curvature, it will be appreciated that the present invention works equally well with straight skis.
The [0055] ski 700 described above and illustrated in FIG. 17A may include a selectively detachable diffuser as previously described in FIGS. 8-10 and 12-14, and attached as previously described or in various other attachment methods. Additionally, while the embodiment of FIG. 17A depicts a ski, it will be appreciated that the new construction method may work equally well with snowboards, and thus is within the scope of the present invention.
In accordance with another aspect of the invention, the stiffness of the diffuser in the various embodiments described above with respect to FIGS. [0056] 1-18 can be selected depending on the conditions of the slope to be traversed and rider preferences. For example, in race conditions where the slope is packed with an icy running surface, the rider may select a ski with a diffuser having a high degree of stiffness or may exchange a diffuser with less stiffness for a diffuser with greater stiffness (for those embodiments having a selectively detachable diffuser), whereas in soft snow conditions, a rider may choose a ski having diffuser with a lower degree of stiffness. It will be appreciated that a set of diffusers can be constructed from known materials so that each diffuser has a slightly different stiffness, ranging from extremely stiff to extremely flexible.
The benefits of a ski or snowboard constructed in accordance with the principles of the present invention will now be described in detail with reference to FIGS. 15 and 16. FIG. 15 shows the general pressure distribution of a ski while gliding with the running surface flat against the snow utilizing aspects of the present invention. FIG. 16 shows the general pressure distribution of a snowboard while gliding with the running surface flat against the snow utilizing aspects of the present invention. The overall wetted area of a conventional ski/snowboard is the entire ski minus the shovel portion, whereas the area A shown as cross hatched in FIGS. 15 and 16 defines the wetted areas of a ski/snowboard embodied with the present invention. The areas RA and LA on the right and left side of the ski/snowboard, aft of the waist or longitudinal midpoint outside the area defined by the diffuser, define the areas of reduced direct pressure or an intermittent pressure zone facilitated by the invention. Thus, right and left outer surfaces define the areas of reduced direct pressure or an intermittent pressure zone facilitated by the invention. Since the diffuser's elevation increases in proportion to the widening side cut of the ski aft of the waist; the diffuser has a smaller wetted area than the actual outline of the ski, thereby reducing the amount of parasitic drag. [0057]
Additionally, as a conventional ski/snowboard glides over a particular area, the snow must pass under the ski/snowboard. Snow lying within the track of the ski/snowboard defined by its narrowest point or waist is pressurized by the load imparted by the ski. A given pressurized molecule in this area will pass from the forward wide point of the ski to the rear wide point, contacting the running base and scribing a hypothetical straight line along the running base defining the skis trajectory as it passes over that particular molecule of snow. [0058]
However, snow encountering the passing ski outside this central area, in the area described as the transition zone, is not continually pressurized by the passing ski. A given molecule in the transitional area will pass under the forward wide point of the ski and will be briefly pressurized. It will contact the running base and will scribe a hypothetical straight line along the running base defining the skis trajectory. As the ski passes further, the molecule will intersect the narrowing side cut curve of the perimeter of the ski, and will exit from under the outer edge and return to a depressurized state. As the ski continues to move, due to the curved side cut shape of the ski at the waist, the width of the ski begins to increase and in effect forms a wedge shape. The molecule will re-encounter the edge of the ski at a point aft of the waist. Due to the curved wedge shape created by the side cut, the molecule collides with the side of the ski and is perpendicularly displaced relative to the skis trajectory a distance D equal to the maximum width at the rearward wide point. The energy to move the molecule the required distance is deducted from the inertia of the ski and is called form drag. [0059]
The diffuser of the present invention minimizes the effects of form drag by proportionally reducing or diffusing the load carried by the outermost, rearward portions of the ski. It accomplishes this with a proportional relative elevation change between the diffuser and the remainder of the rearward base of the ski. The diffuser depressurizes the drag zones by effectively elevating the drag zone portions of the base off the snow surface. With the drag zones in a depressurized state, a portion of the molecules that previously would have collided with the side of a conventional ski and be displaced contributing to form drag, instead now pass freely under the side of the ski and are not laterally displaced. As the number of molecules perpendicularly displaced relative to the skis trajectory a distance D have been reduced, energy required to move said molecules is reduced and ski inertia is conserved. The skis momentum is better maintained resulting in a faster ski and a ski that will glide further. [0060]
The diffuser further provides improved tracking stability to a ski or snowboard constructed in accordance with aspects of the present invention. A ski gliding flat against the snow surface has minimal straight-line stability. Directional stability of a conventional ski is derived from the perpendicular opposing forces acting upon the right and left sides of the ski in the drag zones. When these forces are balanced, the ski proceeds in a straight line. However, as the ski tracks over uneven terrain, the forces become unbalanced. In the unbalanced state, the molecules colliding with the side of the ski in the drag zone are greater on one side than the other. With the perpendicular forces unbalanced, the ski pivots about its vertical axis and assumes a new track. Since the terrain is rarely flat, the ski does not inherently track straight and the skier must continually initiate small course corrections by angling the ski and marginally engaging the edges. Any engagement of the edges results in a net deduction of inertia from the ski and slows the rate of flat glide. [0061]
A ski with greater side cut (smaller turning radius) exhibits less stability as the angle formed as a function of the skis trajectory and the side cut at a given molecular point of collision is greater. Therefore, when unbalanced, more perpendicular force is applied to the side of the ski causing it to rotate about its vertical axis at a greater rate. Conversely, a ski with less side cut (larger turning radius) will exhibit better flat straight line stability as the unbalanced perpendicular forces at the collision points will be less, resulting in a slower rotation about the vertical axis. [0062]
As previously described, the diffuser depressurizes the drag zones and reduces the number of molecules perpendicularly displaced relative to the skis trajectory. Therefore, the total perpendicular force applied in the drag zone is reduced in the unbalanced state, and the ski's reaction to pivoting around its vertical axis is reduced in proportion. Straight tracking is therefore enhanced while the ski is flat against the snow. [0063]
Additionally, a second contributing factor to straight-line tracking occurs as a result of the diffuser's shape. The lines formed as a result of the elevation change between the diffuser and the remaining base of the ski, (i.e. right and left inner edges), are parallel or approximately parallel to the longitudinal axis and line of trajectory of the ski. As there is approximately no side cut in the shape of the diffuser, there can be no perpendicular forces acting upon it, therefore, the ski tends to continue tracking straight. [0064]
While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention. U.S. Pat. Nos. 6,193,244 to Vance; 5,580,078 to Vance; and 5,871,224 to Vance are hereby expressly incorporated by reference. [0065]

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A base of a runner for gliding over snow, the base comprising:

a front portion including a flat running surface generally defining a first surface plane;

a rear portion including a central running surface and a first inner edge located along at least a portion of the perimeter of said central running surface; and

a first outer portion disposed adjacent said central running surface, said first outer portion including a first outer running surface and a first outer edge located along at least a portion of the perimeter of said first outer running surface, wherein at least a portion of said first inner edge is at a different elevation than said first surface plane.

2. The base of claim 1, further comprising a second inner edge and a second outer portion, said second inner edge being located along at least a portion of the perimeter of said central running surface on the opposite side of said central running surface from said first inner edge, said second outer portion being disposed adjacent said second inner edge, said second outer portion including a second outer running surface and a second outer edge located along at least a portion of the perimeter of said second outer running surface, wherein at least a portion of said second inner edge is at a different elevation than said first surface plane.

3. The base of claim 2, wherein said central running surface is curved longitudinally and is substantially straight across in a lateral direction along substantially the entire length of said central running surface.

4. The base of claim 2, wherein said central running surface is substantially planar along substantially the entire length thereof.

5. The base of claim 2, wherein said first inner edge lies generally parallel to said second inner edge along at least a portion of the length of the base.

6. The base of claim 2, wherein said first and second outer running surfaces and said first and second inner edges, respectively, are symmetric about the longitudinal axis of the base.

7. The base of claim 1, wherein said front surface plane is substantially coplanar with said central running surface.

8. The base of claim 1, wherein the elevation of said central running surface decreases with respect to said first surface plane as said central running surface extends in the rearwardly direction.

9. The base of claim 1, wherein said first and second inner edges taper toward the longitudinal axis of said base as said inner edges extend in the rearward direction.

10. The base of claim 1, wherein said central running surface begins at a location rear of the approximate longitudinally midpoint of the base.

11. The base of claim 1, wherein an angle formed between said central running surface and a line running between said first outer edge and said first inner edge at the approximate rearward wide point lies in the range of between 0.1 and 10 degrees.

12. A snow traversing apparatus comprising:

an elongate body having a front end, rear end, a top surface and a base that extends along the approximate length of the body, said base including:

(i) a front portion extending between approximately the longitudinal midpoint of said elongate body and the front end, said front portion defining a front running surface that is planar across the entire front portion in the lateral direction as the front running surface extends to said end of said body;

(ii) a rear portion extending between the end of said front portion disposed at approximately the longitudinal midpoint of said elongate body and said rear end of said elongate body, said rear portion including:

(a) a central running surface generally defining a central surface plane; two outer running surfaces, a portion of said central running

(b) surface being at a different elevation than said outer running surfaces; and

(c) first and second inner edges disposed between said central running surface and said first and second outer running surfaces, respectively; and

(iii) first and second outer edges surrounding a portion of the perimeter of said first and second outer running surfaces, respectively.

13. The apparatus of claim 12, wherein said central running surface is curved longitudinally and is substantially straight across in a lateral direction along substantially the entire length of said central running surface.

14. The apparatus of claim 12, wherein a portion of said central running surface is at a lower elevation than said outer running surfaces.

15. The apparatus of claim 12, wherein said front running surface is substantially coplanar with said central running surface.

16. The apparatus of claim 12, wherein said central running surface begins at a location rear of the approximate midpoint of said elongate body.

17. A base of a runner for gliding over snow, the base comprising:

a rear portion having a removably attachable stepped portion, said stepped portion including a central running surface and first and second inner edges located along at least a portion of the perimeter of said central running surface; and

a first outer portion disposed adjacent to said stepped portion, said first outer surface including a first outer running surface and a first outer edge located along at least a portion of the perimeter of said first outer running surface, wherein at least a portion of said first inner edge is at a different elevation than said first surface plane; and

a second outer portion disposed adjacent to said stepped portion on the side opposite of said first outer portion, said second outer portion including a second outer running surface and a second outer edge located along at least a portion of the perimeter of said second outer running surface, wherein at least a portion of said second inner edge is at a different elevation than said first surface plane.

18. The base of claim 17, wherein a portion of said central running surface is at a lower elevation than said outer running surfaces.

19. The base of claim 17, wherein said front surface plane is substantially coplanar with said central running surface.

20. The base of claim 17, wherein said central running surface begins at a location rear of the approximate longitudinal midpoint of said base.