US3493240A - Laminated fiber glass ski and process for making the same - Google Patents

Description

H. R. JENKS LAMINATED FIBER GLASS SKI AND PROCESS FOR MAKING THE SAME Feb. 3, 1970 5 Sheets-Sheet 1 Filed June 6. 1967 N wu mm mm Nw #565527 A. LIE/V69 INVENTOR.

Filed June 6. 1967 Feb. 3, 1970 H R. JENKS 3,493,240

LAMINATED FIBER LASS SKI AND PROCESS FOR MAKING THE SAME 3 Sheets-Sheet 2 56552 5 J6 RIG-1 H 7 mv bq r o a ATTOZ/VEJ S Feb. 3, 1970 H. R. JENKS LAMINATED FIBER GLASS SKI AND PROCESS FOR.

MAKING THE SAME Filed June 6. 1967 3 Sheets-Sheet 5 INVENTOR.

United States Patent ice 3,493,240 LAMINATED FIBER GLASS SKI AND PROCESS FOR MAKING THE SAME Herbert R. Jenks, 354 Broadway, Costa Mesa, Calif. 92627 Filed June 6, 1967, Ser. No. 643,926 Int. Cl. A63c 5/00, 5/12 US. Cl. 28011.13 17 Claims ABSTRACT OF THE DISCLOSURE A laminated fiber glass ski having improved strength and flexibility characteristics, marked by enhanced ability to retain its initial shape and flexibility after prolonged use, such characteristics being obtained through selected and controlled glass fiber orientation; and a new process for producing such skis through simultaneous application of heat and internal and external pressure.

The present invention relates generally to a fiber glass ski and to the method of making the same. More specifically, this invention relates to an improved fiber glass ski having enhanced strength and flexibility characteristics as well as a pronounced ability to maintain its initial shape and flexibility after prolonged use. The present invention also relates to a new method of producing skis by applying both internal and external pressure during the heat curing period.

A good snow ski combines a rather delicate balance between rigidity and flexibility, while maintaining other important facts such as weight, camber and shape. In order to distribute the skiers weight as uniformly as possible throughout the running surface of the ski, the ski is provided with a camber which is a slight bow running from the tip to the heel, and that combined with the rigidity of the ski acts to distribute some of the skiers weight outwardly towards the tips and heels. The amount of camber and the associated rigidity of the ski should be such that the shape of the two skis will be uniform and so that when the skiers weight is applied to the ski, the ski will flatten out and place a maximum amount of running surface on the snow. A ski must also be sufliciently rigid to oppose a twisting torque so that when the skier is turning, the edges of the skis will retain their bite in the snow rather than flattening out, but of course some torsional action is desirable to assure that the ski will track properly.

On the other hand, a ski must be sufficiently flexible so that it can follow irregularities in the surface of the snow without plowing through them which would slow the speed of the ski and perhaps cause it to dig in. It should also be flexible in order to permit the skier to execute a turn, since flexibility is required to permit the ski to bend slightly during a turn. If a ski is too flexible however, it will not perform adequately on hard packed snow or ice because the skiers weight will not be adequately distributed throughout the running surface and the tips and heels of the ski will not be of any assistance. In fact, the tips of very flexible skis are sometimes known to jump or chatter while skiing over hard packed snow and this is an indication not only that the tips are not providing an effective running surface, but that little assistance will be obtained from that portion of the ski when the skier executes a turn since the edges will not dig into the snow but will continue jumping or chattering as they run. As a result, a ski which is too flexible is not easily controllable on hard packed snow conditions. By the same token, a ski which is too rigid will not perform adequately on soft snow conditions since the downward thrust of the tip will cause the tip 3,493,240 Patented Feb. 3, 1970 to dig into the snow and the downward thrust of the heels will make turning diflicult.

Another important consideration in the characteristics of a good snow ski is its ability to retain its initial shape and flexibility after prolonged use. Snow skis were first made of wood and it was found that the characteristics of hickory wood provided the best ski since hickory retains its strength and flexibility longer than any other wood. The difliculty with wood is that its resilience deteriorates when the wood becomes wet. Thus it was found that the life of a wood ski was severely limited because no amount of wax or shellac could keep all of the water out and the flexibility and the initial camber imparted to the ski would soon diminish. The first approach towards solving this particular problem was the application of various types of plastic on the running surface of the ski in which the plastic had a very dense structure to prevent the entry of moisture from the running surface into the wood. While this eliminated the necessity for constant coating of wax on the running surface, it still did not prevent the entry of moisture into the wooden part of the ski from the top or the sides. The next approach was to coat the entire ski with a layer of plastic or fiber glass which kept most of the moisture out unless the plastic was chipped or cracked.

ther types of skis were attempted using metal or various combinations of wood, metal and plastic laminated together in order to obtain the aforementioned flexibility characteristics. In such instances, the wood employed was more for the purpose of providing dimension and body to the ski rather than flexibility and the strength and flexibility was provided either by the metal strips or the fiber glass sheets. Also, some all-plastic skis have been attempted but they have not proven satisfactory because of their weight or lack of flexibility or their difficulty in manufacture. There are currently on the market a great variety of skis which almost uniformly consist of laminations of wood and fiber glass or wood, fiber glass and metal. In the skis constructed of laminations which include metal, the flexibility and rigidity characteristics are dependent upon the strength of the metal and the other laminates used do not contribute to this characteristic. In such instances, the problem of metal fatigue becomes important and after a relatively small number of flexures. the metal will cease to perform satisfactorily and will in fact crack and break rendering the ski useless. This has been a particular problem in such metal skis which have continuous metal edges where the edges are of a very hard steel. In addition, such skis having metal laminations frequently lack adequate flexibility in the tips and heels unless formed of such thin sheets that they are likely to become permanently bent. In the skis which combine a lamination of fiber glass and wood, the wood does not provide flexibility but only acts as a spacer and the top and bottom fiber glass skins are the ones which do the work. Such skis tend to be somewhat on the heavy side and in addition, should there be a break in the fiber glass skin permitting the entry of moisture into the wood, the ski will rapidly lose its flexibility. In such skis, the shear stresses are transferred through the wood fibers which break down gradually in use and the wood softens quickly when wet further deteriorating the fibers so that their ability to transfer the stress is soon lost.

Attempts have been made to produce a ski entirely of fiber glass in which the problem of excess Weight previously encountered is solved by the provision of hollow cores inside the ski. No satisfactory method has been developed for the manufacture of such skis on a production basis since the various designs so far developed have required extensive hand work because of the difliculties in assuring control of the orientation of the fibers. If the fibers should be nonlinearly distributed when the ski is finished, it will result in nonlinear flexibility distortion or warping of the skis which is difficult to correct. Another type of so-called all fiber glass ski has been made consisting of three parts, a top skin, a bottom running surface and a central epoxy core all of which are individually cut, pre-cured and then cemented together. In this particular ski, both the top and bottom skins are provided with continuous metal strips which actually take a portion of the load of the flexing encountered by the ski in use and are the first to fail after prolonged usage. In addition, the cementing of the layers does not provide a sufficiently integral structure so that internal stresses are at once set up which will unalterably influence the characteristics of the ski thereafter.

The present invention provides a solution to the various problems mentioned above by providing a ski of laminated fiber glass which includes no metal or wooden laminates but relies entirely upon the strength and elasticity of the fiber glass, and a unique method by which such a ski is formed to impart the desired strength and flexibility to the ski. In addition, the present invention provides an improved method for making such skis on a production basis. By forming an integral structure without having cemented bonds between dissimilar pre-cured layers of material, and by curing such structure in the desired shape, greater control over the desired characteristics is possible and so is the expectation that those characteristics will endure.

It is an object, therefore, of the present invention to provide a ski having improved strength, flexibility and durability characteristics.

It is a more specific object of the present invention to provide a ski which is light in weight, but is strong, and can be made to have both the longitudinal and torsional flexibility desired for various skiing requirements.

It is also an object of this invention to provide a fiber glass ski which retains its initial shape and flexibility after prolonged usage.

It is also an object of the present invention to provide an improved process for manufacturing a fiber glass ski.

More specifically, it is an object of the present invention to provide an improved method of laminating a fiber glass ski and molding it into an integral structure.

It is a further object of this invention to provide an improved process for the production of a laminated fiber glass ski employing the application of internal and external pressure.

Further objects and advantages of the invention will be readily apparent after reading the following detailed description in conjunction with the accompanying drawings in which:

FIGURE 1 is a side elevation of a ski inside the mold showing the upper and lower platens thereon but with the side rails removed;

FIGURE 2 is a plan view partly in section and somewhat foreshortened, showing some of the details of construction and molding of the ski;

FIGURE 3 is a sectional view of the ski inside the mold showing the cross-sectional configuration of the ski after cure but prior to removal of the interior molding means therefrom;

FIGURE 4 is an exploded perspective view showing the various laminates used and their relative and associated positions; and

FIGURE 5 is an exploded perspective view showing the details of lamination and construction of the tip of the ski.

The various portions of the mold include a bottom platen 12 and an upper platen 14 of a length to extend to substantially the entire length of the ski. As shown in FIGURE 1, the lower platen 12 is bowed upwardly in the center at 13 an amount sufficient to impart to the molded ski the desired amount of camber. At the heel and of the ski, t e p en 1,2 slopes upwardly at 16 to provide a slightly upwardly lifted heel. The tip of the ski is curved in a conventional manner and the lower platen 12 is curved upwardly at 18 for that purpose. The top platen 14 likewise has a heel portion which slopes upwardly at 20 and also has a curved tip portion 22. As shown in FIGURE 3, the platen 14 Consists of a top plate 24 and an integral lower boss portion 26 designed to fit within the side rails 28.

Referring to FIGURE 2, the remaining portions of the mold 10 are shown comprising four side rails 28 which are secured to the lower platen 12 by means of screws 29 or other similar means. The side rails 28 are of a length sufficient to extend for that portion of the ski wherein the sides are straight and parallel. As can be seen in FIGURE 2, the heel and the tip of the ski begin to curve inwardly as the ends are approached. Accordingly, separable heel side plates 30 are secured to the platen 12 by a plurality of screws 31. The heel side plates 30 each form one-half of the side of the heel and are separated along the longitudinal center line of the mold 10 at 32 so that after the ski has been molded, these portions can easily be broken away and the ski removed therefrom without damaging the molded ski.

At the tip of the ski, sidepieces 34 are secured to the platen 12 by the screws 35 and are also separated at 36 at the extreme tip of the ski so that they can be separated for removal of the molded ski. A perspective view of this portion of the mold can be seen to better advantage in FIGURE 5.

On each side of the mold, near the center, two pressure bag mounting blocks 38 are mounted aligned with the side rails 28. The mounting blocks 38 have a plurality of elongated pressure bags 40 secured therein which are adapted through the construction and configuration of the mounting blocks 38 to extend at an angle into the interior of the mold and curve around so that they are positioned longitudinally in the mold 10 parallel to the side rails 28.. The drawing shows two sets of four pressure bags each, however, the present invention is not intended to be limited to such a number since the number may vary depending upon the ratio between the height and the Width of the structure being laminated and therefore the number of hollow cells desired. The pressure bags 40 extend into a terminating block 42 which has a plurality of extensions 44 extending therefrom which are in turn received in a manifold 46. The manifold 46 has an intake 48 which is adapted to be connected to a pressure source such as steam or air as will be more fully described in connection with the details and steps of the manufacturing process. The pressure bags 40 and therefore the mounting blocks 38 are situated so that the bags 40 enter the interior of the mold 10 at a point near the middle portion of the ski since this is the portion of the ski which is thickest and therefore permits the addition of extra reinforcing material at this point to eliminate any structural weakness which might accrue from the nonalignment of the structural cells at this point. In addition, the center portion of the ski which is normally the position at which the ski is secured to the skiers foot, requires the least amount of flexibility and therefore undergoes the least amount of stress in that regard.

Turning now to FIGURE 4, additional features of the mold construction can be seen. The lower platen 12 is provided with a rounded longitudinal rib 50 which extends substantially the entire length thereof and forms the rounded groove along the bottom of the molded ski which is a customary feature of skis and enhances their tracking abilities. Other types of ribs could be provided to form other configurations of grooves if desired. Slots 52 are formed along the lower inside corners of the side rails 28 and are adapted to accommodate the metal edges 56 and to hold them in place during the ensuing assembly and curing procedures.

To form the lower skin, the first layer of material laced in the mold 10 is a sheet of plastic material 54 of a type having a very low porosity and a very low coefiicient of friction such as a high molecular weight polypropylene. A suitable material of this type is currently being sold under the trade names Cytex or P-Tex. Such materials have frequently been used by other ski manufacturers and have been found to be satisfactory for this purpose. The sheet 54 forms the running surface and this sheet is cut to the general outline of the ski shown in FIGURE 2. After the running surface 54 is in place, then the metal edges 56 are inserted into the slots 52. The edges 56 consist of hardened steel sections a few inches in length having an L-cut shaped cross-section whereby the long portion of the L overlaps the edge of the running surface sheet 54 and the thick part of the L forms the outwardly extending portion of the edge. By inserting the edges 56 into the slots 52, the ski will be formed with What are known as off-set edges which means that the edges extend out past the sides of the ski. The short segments of edges 56 are placed end-to-end substantially the entire length of the ski and a short distance into the tip before excessive curvature is encountered. Short segments permit the ski to flex freely as determined by the flexibility of the fiber glass materials and will not materially change the flexibility characteristics. The segments should not be greater than about six inches, and preferably are about one to three inches long. Segments of differing lengths may also be used to advantage. The short strips are more costly and take more time during assembly but the longer strips tend to make the ski more rigid. To balance these factors, shorter segments may be used near the tip and heels if greater flexibility is desired.

The next laminate is a sheet 58 which has :been previously folded into a channel so that the bottom is substantially the width of the ski and the sidewalls follow the tapering contour of the side walls of the ski as shown in FIGURE 1. The sheet 58 is a woven fiber-glass material in which the fibers are bi-directionally oriented, which means there are approximately an equal number of fibers oriented in the direction which runs longitudinally to the ski as Well as laterally. The material of laminate 58 is previously impregnated with an uncured resin and is a dry condition. Following the U-shaped laminate 58, the next laminate is a plurality of flat sheets 60 which are also cut to the outline of the ski shown in FIGURE 2. The sheets 60 are a fiber-glass material in which the fibers are uni-directionally oriented in the longitudinal direction. The fibers of the sheets 60 are just held together by occasionally spaced lateral fibers sufiicient to keep these sheets together. The sheets 60 are also previously impregnated with a dry, uncured resin. The number of the sheets 60 may be varied according to the amount of flexibility desired for the ski. The drawing, FIGURE 4, shows four (4) such sheets but the invention is not contemplated as being so limited. If some variations in flexibility are desired, such as providing a slightly less flexible heel portion than that for the tip portion, extra sheets 60 may be added at various points; or the sheets may be staggered in length to give a uniform taper out toward the tip or heel while having uniformly varying flexibility as Well.

Also, instances where additional resistance to twisting torque may be desired for certain portions of the ski uni-directional sheets such as 60 may be inserted at this point adjacent the sheets 60 but having the uni-directional fibers oriented angularly with respect to the longitudinal axis of the ski. The sheets 60 complete the assembly of the lower skin.

A central core is next formed to separate the lower and upper skins. This core comprises a plurality of longitudinal channel members previously folded into a U- shape. The channel members 62 are positioned first immediately on top of the sheets 60 with the open side of the channels facing upwardly. These channels 62 do not extend the entire length of the ski but only approximately the length of the side rails 28. Referring back to FIGURE 2, the channel members 62 are shown in dotted line following the curved contour of the pressure bags 40 and terminating near the center section of the ski where the pressure bags 40 exit from the sides of the ski. In FIG- URE l, the side of a finished ski shows where the pressure bags 40 exited from the side of the ski and the side walls of the channel members 62 and 64 can be seen therein. The top set of channel members 64 are inserted with their open sides facing downwardly so that the side walls thereof engage the side walls of the channel members 62 in a sliding relationship. Before the channel members 64 are so positioned however, the pressure bags 40 are inserted and each one is laid into one of the channel members 62. Since the thickness of the ski varies, and tapers down toward the tips and heels, it is necessary to have the side walls of the channel members 62 and 64 taper near their ends and this taper is shown at 65 in FIGURE 4. Channel members 62, 64 are bi-directional fiber glass materials impregnated with uncured resin, as is the case with the other materials used herein, are dry. The channels have been previously folded by a hot pressing device.

After the pressure bags 40 and the channel members 62 and 64 are in place, several side sheets 66 are inserted and these side sheets extend up to where the heels and tips begin and therefore the side sheets are also tapered as previously described. Since the pressure bags 40 exit near the center of the ski these side sheets 66 are of a length to extend from about the point designated at 67 in FIGURE 2, up to a point approximately that designated by the numeral 68. Thus, there will be four separate sets of these side sheets 66. The sheets 66 are inserted between the outer edges of the channel members 62, 64 and the side walls of the U-shaped sheet 58.

The upper skin is now formed in a manner similar to that for the lower skin. The first laminate is a second set of uni-directional fiber glass sheets 70 of a type and configuration substantially the same as the uni-directional sheets 60, being cut to the outer configuration of the finished ski and being previously impregnated with uncured resin. Sheets 70 may also be staggered in length or some of them placed on a bias if desired. After these sheets are in place, a second large U-shaped channel sheet 72 is placed in the mold. The sheet 72 is substantially similar to sheet 58 in that it is also a fiber glass material in which the fibers are bi-directionally oriented and is previously impregnated with uncured resin. The side walls of sheet 72 may be placed either inside or outside of the side walls of sheet 58. The final laminate is another U- shaped material inserted as an overlay 74 whereby the side walls extend outside of the side walls of the large U-shaped sheets 72 or 58. The overlay 74 is preferably a fine mesh fabric of bi-directional type such as a Dacron mat which has likewise been previously impregnated with an uncured resin. Overlay 74 is intended primarily for dress or decorative purposes and may be colored and printed as desired. The sheets 70, 72 and 74 together comprise the upper skin.

Referring now to FIGURE 5, the various laminates in the tip section of the ski are shown in exploded form. It is to be understood that the same type and sequence of laminates are used in the heel section of the ski and therefore a separate view thereof has not been included. The laminates forming the upper and lower skins, as has been previously mentioned, extend into the tip of the ski. Thus, the running surface sheet 54 is shown but the sides thereof are cut at 55 to accommodate the last portion of the edges 56. The first large U-shaped, bi-directional sheet 58 is shown extending up to the very tip of the ski and in order to permit the upward curvature of the material, the sides are cut or notched as shown at 59 to permit this curvature. The first set of uni-directional sheets 60 are likewise shown positioned immediately above the sheet 58 and extending up to the tip of the ski.

Since the U-shaped channels 62 and 64 do not extend all the way to the tips or heels of the ski, it is necessary to provide some amount of spacing between the upper and lower skins as provided by the channels in the rest of the ski. In order to accomplish this, a plurality of bi-directional fabric sheets 76 are placed between the uni-directional sheets 60 and 70. These sheets 76 are so cut as to provide a central hollow cavity section 78 which is filled with a mixture 80 which comprises an uncured resin putty which has been mixed with a filler of small hollow sphere-like elements 82. Upon curing, this material will impart substantial strength to the tip of the ski while maintaining its solid configuration but will not add ex cessive weight to the-tip.

Above the tip sheets 76 and the core material 80, the uni-directional sheets 70 extend up to the tip and above the sheets 70 is the bi-directional sheet 72 and the overlay sheet 74. As previously mentioned, to permit the upward curvature of the U-shaped sheets 72 and 74, their edges may be cut or notched as shown at 75. To further protect the tip against injury and to stiffen the curved portion thereof, a metal toe piece 84 is inserted into the mold along the sides of the tip whereby the toe piece 84 i will extend along the outer sidewalls of the overlay sheet 74 and when the resin is cured, will adhere thereto and form an integral part of the ski.

The steps taken to manufacture the ski in accordance with the present invention include first of all the assembly and positioning of the various laminates as has been previously described. When all of the laminates and the pressure bags 40 are in place, the upper platen 14 is then placed on top of the laminates and positioned so that the center section 26 fits inside the side rails 28 and bears directly downwardly on the overlay 74. The entire assembly is then placed in a press which has an upper and lower pressing surface which corresponds substantially to the upper and lower surfaces of the platens 12 and 14. The pressure inlets 48 are then connected to a source of steam or air. The outer platens of the exterior press are then actuated to place pressure upon the outside laminates at the same time, the bags 40 are pressurized and may be heated slightly if steam is used until the resin materials become soft and begin to flow slightly. The platens of the outside mold are also heated until the plastic is soft and this condition is maintained until such time as all of the uncured resin is soft and slightly runny. With pressure being applied by the outer press, the pressure on the inside bags 40 is then relaxed for a short period and then reapplied so as to permit the escape of a substantial amount of the entrapped air between the various layers. The pressure inside the bags 40 is then raised until the soft resin begins to work out of the cracks in the mold showing that it is all in a molten state. The pressure on the inside bags is then raised to approximately 125 lbs. per square inch, the temperature on the outer platens is raised to 300 to 330 F. and the entire assembly is allowed to remain at this temperature and pressure for approximately 30 minutes for curing. After the expiration of this curing period, the mold is removed from the press and the pressure sources disconnected from the inlets 48. The upper platen 14 is then removed and the side rails 28, 30 and 34 are disconnected from the lower platen 12 and the pressure bags are slid out from the interior of the channels 62, 64 so that the ski can be removed from the mold. The ski is then ready for sanding and finishing, and the edges 56 may be ground and finished as well.

During the heating and pressure cycles, after the resin has become liquid, the expansion of the tubular pressure bags 40 against the adjacent side and bottom walls of the channels 62, 64, cause the adjacent sidewalls of those channels to adhere initially to one another and upon further expansion of the pressure bags 40, the sidewalls will tend to be displaced vertically and will tend to slide in that plane. Since initial pressure against those sidewalls forces them together, and the heat applied to the uncured resin causes those sidewalls to adhere to one another, the resultant application of pressure in the bag places the fibers in the sidewalls under tension as they tend to slide apart and they are allowed to cure in that condition. Maximum structural strength is provided by fibers which are under tension since they are the first to bear any tension loads and likewise will be the first to bear compressive loads. By placing these fibers under tension, if they are to fail under a compressive load the amount of the load they can Withstand will be much greater than if those fibers were not straightened by tension but were rather kinked or folded, in which case they would fail rather easily under load.

The unidirectional sheets 60 and also undergo some changes during the pressure process. Since there are a number of gaps or spaces between the adjacent channel sections and the various other laminates inside the ski itself, the initial pressure by the pressure bags will cause the uni-directional fibers in sheets 60 and 70 to crowd over and fill in the gaps to form fillets in which the fibers will be longitudinally oriented for maximum strength. As a result of the molding process the entire inside assembly of laminates will become an integral body forming a strong and adhering structure having the desired shape without internal stresses. FIGURE 3. demonstrates this integral construction showing the condition of the interior of the mold following the curing cycle and prior to the removal of pressure inside the pressure bags 40. After the ski has been removed, a small sheet of plastic material (not shown) can be cemented over the apertures 86 which are left in the sides of the ski.

While particular embodiments of the present invention have been shown and described, it will be apparent to persons skilled in the art that changes and modifications might be made without departing from the invention in its broader aspects.

I claim:

1. A laminated fiber glass ski comprising:

a plurality of resin impregnated fiber glass sheets, said sheets laminated to form upper and lower skins;

a plurality of longitudinally extending channel members, said channel members being situated between said upper and lower skins to form a central core which extends less than the entire length of the ski, said channel members extending from the tip of the ski and terminating near the center of the ski at one side thereof, and the remainder portion of said channel members extending from the heel of the ski and terminating near the center of the ski at. the other side thereof, said channel members providing hollow cores which are closed at the tip and heel ends thereof and which provide apertures in the sides near the center of said ski, and means for closing said apertures;

said lower skin further including a plastic running surface sheet bonded thereto, metal edge strips molded between said running surface sheet and said lower skin, said edge strips having a portion thereof exposed along the lower lateral sidewalls of said ski, said edges comprising a plurality of segments having a length of less than six inches.

2. A ski as described in claim 1 wherein adjacent sidewalls of said channel members adhere to one another and the fibers thereof are in tension in the vertical plane.

3; A ski as described in claim 1, in which said upper and lower skins each comprise a plurality of fiber glass sheets wherein a portion of said sheets are of the type having substantially all of the fibers thereof oriented longitudinally with respect to said ski.

4. A ski of the type described in claim 3 wherein the remainder portion of said fiber glass sheets is of the type wherein the fibers are about evenly oriented longitudinally and laterally with respect to said ski.

5. A ski of the type described in claim 1 wherein the heel and tip portions of the ski further include a plurality of fiber glass resin impregnated sheets, said sheets being situated between said upper and lower skins and extending from the extremity of the aforesaid central core to the extremity of the ski, said sheets shaving outer configurations cut to shape of the heel and tip respectively and having a central open section forming a cavity, said cavity being filled with liquid resin combined with a filler.

6. A method of making a laminated fiber glass ski, the steps comprising:

arranging a plurality of resin-impregnated fiber glass sheets in a mold to provide an upper and a lower skin separated by a central core having a plurality of longitudinal hollow cells, inserting expansible internal pressure means in said hollow cells;

simultaneously applying heat and both internal and external pressure to said sheets whereby tension is exerted upon the glass fibers as the resin begins to cure;

curing the resin in said sheets to form an integral structure; and

then removing said expansible pressure means from said hollow cells.

7. The method described in claim 6 further including, forming a heel portion and a tip portion by inserting a further plurality of impregnated fiber glass sheets at the tip and heel ends of said ski betWeen said upper and lower skins, providing a center cavity in said sheets, and filling said cavity with a mixture of resin and a suitable filler.

8. The method described in claim 7 further including laminating a plastic running surface sheet along the bottom of said lower skin, placing a plurality of segmented edge pieces between said running surface sheet and said lower skin whereby a portion of said edges projects outwardly along the sides of said ski.

9. The method described in claim 8 further including the step of aligning substantially all of the fibers in a portion of the sheets in said upper and lower skins longitudinally with respect to said ski.

10. The method described in claim 6 further including the step of aligning substantially all the fibers in a portion of the sheets in said upper and lower skins longitudinally with respect to said ski.

11. The method described in claim 6 further including placing a plurality of resin-impregnated strips along each side of said upper and lower skins and said central core.

12. A method of making a laminated fiber glass ski, the

steps comprising:

arranging a plurality of resin-impregnated fiber glass sheets in a mold to provide a lower skin, folding some of said fiber glass sheets to provide a central core having a plurality of longitudinal hollow cells,

arranging an additional plurality of resin-impregnated fiber glass sheets to provide an upper skin, inserting internal pressure retaining means in said hollow cells, and then closing said mold;

simultaneously applying heat to said mold and internal pressure to said pressure means whereby tension is exerted upon the glass fibers as the resin begins to cure;

curing the resin in said sheets to form an integral structure;

then removing said pressure means from said hollow cells.

13. A method of making a fiber glass ski, the steps comprising:

first fabricating a mold having the configuration of the finished ski;

placing a first plurality of dry, resin-impregnated fiber glass sheets in said mold to provide a lower skin; folding a plurality of said dry, resin-impregnated fiber glass sheets into longitudinal channels, inserting said channels into said mold upon said lower skin; placing a second plurality of dry, resin-impregnated fiber glass sheets in said mold to provide an upper skin;

inserting longitudinal pressure means into said channels;

simultaneously heating said mold, applying external pressure thereto, and applying internal pressure to said longitudinal pressure means;

curing the resin to form an integral structure; and

then removing said pressure means from said channels.

14. The process described in claim 13 wherein said channels are pre-folded into substantially a rectangular cross section and whereby upper and lower channels are placed in interlocking fashion to form longitudinally extending hollow cells.

15. The process described in claim 13 wherein the step of applying internal pressure to said longitudinal pressure means is executed after applying heat and external pressure at a time when the resin has become tacky.

16. The method described in claim 13, further includmg:

providing a plurality of apertures in the sides of said mold near the center thereof, curving said channel members near the center thereof to align the cores thereof with said apertures, inserting said pressure means through the sides of said mold through said apertures whereby said channels and said pressure means are curved near the center of the mold and extend longitudinally the length of the mold from the center to the ends thereof.

17. The process described in claim 16 whereby the step of removing said pressure means from said channels is followed by the step of covering the openings left in the sides of the skis by the removal of said pressure means.

References Cited UNITED STATES PATENTS 2,695,178 11/1954 Rheinfrank 280-1113 2,971,766 2/1961 Holley 280-11.13 3,270,111 8/1966 Haldemann 156-156 XR 3,272,522 9/1966 Kennedy 280-1113 FOREIGN PATENTS 572,337 3/1959 Canada.

985,174 3/1951 France. 1,351,207 12/1963 France.

LEO FRIAGLIA, Primary Examiner MILTON L. SMITH, Assistant Examiner US. Cl. X.R.

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