SI9400092A - Process for making hollow ski and hollow ski made by this process - Google Patents

Abstract

In prior art hollow skis the raw material is arranged in a mould in such a way that it surrounds an elastic air chamber which is pressurised, whereafter the material is cured. The process of the invention is intended to provide a hollow ski of low weight and high rigidity. To this end the air chamber takes the form of two sections of a double hose (6, 7) side-by-side in the longitudinal direction of the ski. In each section of the double chamber a fibre-fabric outer hose (7) is pushed over an airtight, thin-walled and expandable plastic inner chamber (6) and, after impregnation with a synthetic resin, it is inflated through the inner hose and pressed against the running surface and against the fibre-fabric material forming the outer layer of the hollow body which is also impregnated with synthetic resin so that a vertical ridge (8) is formed along the hollow ski. The components are firmly bonded together by curing and form the ridig bond of the hollow ski.

Description

A hollow ski manufacturing process and a hollow ski manufactured by this process

The invention relates to the manufacture of a hollow ski, in particular a cross-country ski, of plastic reinforced plastic, the starting material of which comprises part of the tread as well as the material forming the outer layer of the hollow body is inserted into the mold and enclosing the air chamber , the mold being closed thereafter and the air chamber inflated under pressure, thereby resting the starting material on the inside of the mold and forming a hollow body, after which the hollow ski hardens as well as the ski thus constructed.

DE 12 04 983 already discloses a method of manufacturing a hollow ski in which the starting material of the hollow ski is arranged in a compression mold such that it surrounds an elastic pressurized air chamber and then allows the material to harden, leaving the starting material the material of the mixture of plastics and fiberglass is in a manner known per se arranged in a compression mold such that at least part of the fiberglass extends longitudinally and that a known prestress is assigned to the longitudinal fiberglass by means of an air chamber prior to curing the mixture.

The air chamber used for prestressing the longitudinal fiberglass is slightly shorter than the compression mold and very elastic. It consists of e.g. from the rubber.

For the manufacture of a hollow ski, fiberglass-shaped webbing is inserted into a two-piece mold, and the air chamber is arranged under the webs, and then the edges are wrapped around the air chamber. At the same time, a valve is inserted into the air chamber from above, through which air is pressurized into the air chamber.

Upon completion of the ski, the valve must either be cut off leaving the air chamber in the ski or the air chamber pulled upwards from the hollow ski. Therefore, a larger hole should be cut into the upper lane. The air chamber can also remain in the ski with a valve. In all cases, the hollow ski weakens from the point of view of the upper lane.

The rigid union of a hollow ski consists of a hollow body formed by strips and a sliding base formed in a press mold. The air chamber itself is only used to produce the ski by providing prestress in the longitudinal glass fibers.

It is known from patent AT 241 311 that, in the manufacture of hollow skis, preferably heat-curable and glass-fiber reinforced plastic is pressed against the wall of the mold, comprising the lower molding portion with an approximate angle by inflating the flexible tubes arranged in the mold. letter U-shaped cross-section, the mold is designed in such a way that a flexible plate is provided as the upper molding part, which deforms in the transverse plane when the hoses are inflated. The aim is to assign different hinges to the upper lane of the hollow ski, thereby altering its flexibility. At least three inflatable hoses shall be inserted. These pipes also serve solely to form a hollow ski.

With these solutions, it was not possible to produce a hollow ski with sufficient strength. Therefore, newer ski body solutions use prefabricated profiles.

WO 90/03205 discloses a ski with a portion of the tread and a hollow body whose height, measured normally on the portion of the tread, is different in length. The ski body is designed as a hollow body with parallel sideways extending in the longitudinal direction of the ski, with the width of the ski body being less than or equal to the minimum width of the tailored portion of the running surface, measured transversely with respect to the longitudinal direction of the ski. In this case, the hollow body is designed as a shell body and, on the side facing away from a portion of the tread surface, closed by the upper lug assembly. This shell body consists of extruded profiles that are made endlessly and shortened to the length of the ski. In this case, a thickness contour may be cut on each upper and / or lower shell.

With this design, it is possible to accurately define the strength, elastic and torsional properties of the ski.

However, such a manufactured ski carries a relatively high weight and is therefore not particularly suitable for a cross-country ski. In addition, despite the possible use of extruded profiles, manufacturing costs are quite high.

The PCT application WO 91/6350 further discloses the process of making a ski out of a stubby hollow body. In this case, the extruded, extruded or similarly stranded hollow body is first brought into an approximate oval shape. Thereafter, partial cuts are cut from this hollow body to the length of the ski being manufactured. These partial pieces are then subjected to pressure treatment, such as rolling, compression, compression, etc., leaving the central area of the later-wearing ski not subjected to pressure treatment or to a small extent, while the pressure treatment increases with distance from the central area. Finally, as is well known, a steel profile is attached to the edges of the lower surface, the sliding surface of the ski. The tufted hollow body that forms the ski is conveniently shaped as a flat lens.

The hollow body of this type of ski also consists of an extruded profile. Such a hollow body of a hollow body, however, is thought to be efficiently made by extrusion from a light metal profile. This published solution is hardly suitable or even unsuitable for extruded plastic profiles due to the intended pressure treatment. A ski designed in this way also has a relatively high weight.

Due to its specific material properties, a metal ski could hardly be used in the field of cross-country skiing.

DE 32 36 016 Al is known to be a hollow body ski, which comprises in the longitudinal axis of the ski a running hollow body which can also be broken down by bridges in the longitudinal and / or transverse axis. The shape of the ski has a hollow body in the transverse axis, an upward, semicircular contraction. A hollow body may suitably require a vacuum or be filled with air, gas, or other solids or liquids.

The body of the ski is only revealed as a one-piece body, on which further parts are arranged, such as. ski base. Such a bridge-equipped body can be practically manufactured only as an extruded profile, so that this hollow ski also carries a great deal of weight.

It is an object of the invention to provide a process for the manufacture of a hollow ski, in particular a cross-country ski, of plastic reinforced plastic whose starting material comprising a part of the tread as well as the material forming the outer layer of the hollow body is inserted into the mold while enclosing the air chamber, the mold being subsequently closed and the air chamber inflated under pressure, thereby resting the starting material on the inside of the mold and forming a hollow body, subsequently hardening the hollow ski as well as a low weight ski thus constructed. at high strength.

The task of the invention is solved by the fact that the air chamber is formed of two hollow ski sections in the longitudinal direction, adjacent to each other, of the double hose, whereby each air hose section is airtight, thin-walled and flexible inside the hose from it pulls the plastic outer tube from the fibrous fabric and inflates the plastic tube with the inner tube after impregnation, and compresses it to the part of the tread as well as to the material that forms the outer layer of the hollow body, which is also absorbed with the artificial resin and which it consists of a fibrous fabric and, in the central area of the hollow body, to the outer hose of the second section of the double hose, thereby forming a longitudinal vertical hollow in the longitudinal direction of the hollow ski, solidifying all the parts with one another and forming a solid connection. hollow skis.

The solution according to the invention achieves a very light, high-strength hollow ski in the compression mold by inflating the air chamber. The air chamber consists of a double flexible hose, the outer hose of which is itself a functional component of the strength of the hollow ski connection. The inner hose is only light in weight and, as presented below, can also form a functional building block. This prevents these parts from being removed, which means an additional manufacturing cost and can always lead to damage to the hollow ski produced.

Preferably, if the adjacent sections of the double flexible tubes forming the air chamber consist of one piece having approximately double the length of the hollow ski and inserted from the back end of the hollow ski one way into the mold to the area of the ski tip, there bent 180 ° and inserted parallel to the first layer on the other side of the mold to the back end of the hollow ski. This results in a further reduction in manufacturing costs.

The two open hinged open ends of the inner hose of the one-piece twin hose are conveniently connected to the common source of compressed air and inflated simultaneously and with the same pressure to form a hollow body.

This helps to reduce the production time when the hollow body is evenly designed. By connecting a compressed air source at the back end of the ski, the strength of the ski is not affected. The upper and lower bands are continuous and the sensitive area of the ski tip is not strained. The rear ends can be functionally easily closed after inflating and curing.

Preferably, the hollow body is designed as a separate segment with a portion of the tread as a tendon from the back end of the hollow ski to the area of the ski tip by inflating the double hose forming an air chamber.

In this case, a separate segment may be designed as a circular segment, wherein along the length of the hollow body, the circular segment in cross-section is designed with different dimensions.

The solution according to the invention can optimally use the process for inflating the ski and at lower weight further increase the strength of the manufactured hollow ski.

This design also makes it possible to create sliding crossings, with the use of separate and circular segments for the hollow ski. In doing so, it is always advisable to anticipate the largest cross-sections in the central region of the ski, with a back-and-forth advantage to the flat design.

In order to achieve high strength even in the area of the ski tip, the hollow ski is designed there flat and uses a ski tip in the form of a piece of plastic. The tests have shown that this way can be avoided by making a conditioned break of the ski tip. In this case, the final shape of the ski tip can be made afterwards, e.g. by milling.

Further improvement of the strength of the hollow ski can be achieved by placing reinforcing elements on the material forming the outer hollow body body, which, in the finished hollow ski, lie between the inside of the material and the outside of the outer hose.

Carbon and / or glass fibers extending in the longitudinal direction of the hollow ski can be used as reinforcing elements.

However, it may also be possible to place reinforcing elements in the rigidly laden locations of the hollow body, as in the bond region.

In order to achieve the good properties of a hollow ski, the preferred choice of materials is that a part of the tread is formed of a carbon-laminate tread and a solid base connected to the base by carbon laminate, the material that forms the outer layer of the hollow body. made of carbon and / or fiberglass cloth impregnated with artificial resin or a suitable prepreg, the outer flexible tube of the double flexible tube forms with carbon fiber cloth or fiberglass cloth or aramid cloth or mixed carbon / fiberglass cloth or suitable prepreg , the inner flexible tube is made of polyamide film.

The inner hose can be used as a functional building block in the manufacture of a hollow ski, by sealing the inner side of the hollow body with an inner hose that firmly connects with the outer hose during hardening.

In the further design of the hollow ski, the hollow body may be filled with gas or a gas / air mixture, e.g. so that helium is infused.

It is also possible for the hollow body to be filled with sliding wax and connected to the tread surface by a portion of the tread surface via sliding wax outlets.

In the further design of the invention, it also includes a hollow ski, especially a cross-country ski, made of fiber reinforced plastic with a part of the tread as well as a material forming the outer layer of the hollow body, made in the hollow manner described above. to the body surrounded by a portion of the tread and the material, two longitudinal sections of a double hinge adjacent to each other are arranged side by side, wherein an airtight, thin-walled and flexible inner flexible hose consisting of an outer flexible hose consisting of fibrous fabrics, and this outer flexible tube, after the formation of the hollow body and the hardening of the hollow ski, rests on the material forming part of the tread as well as the outer layer of the hollow body, which is also impregnated with artificial resin and consists of fibrous fabric as well as in the central the hollow body region to the outer flexible tube of the second double flexible tube, and is firmly connected therewith, with the outer portions extending to one another their flexible tubes designed as a longitudinal hollow ski stretching, vertical bridge. The sections of the double hose are preferably designed as a connected piece, comprising approximately double the length of the hollow ski, and are then arranged parallel to each other in the hollow body from the back end of the hollow ski to the region of the ski tip and bent 180 ° in this front region. .

The preferred embodiment of the hollow ski is that the hollow body in its cross section is designed as a separate segment with a portion of the tread as a tendon.

In this case, the separate segment is in a sensible way designed as a circular segment, which has different dimensions along the length of the hollow body. In this way it is possible to use the hollow ski in the desired shape in accordance with the intended purpose, such as the. cross-country ski for sports competitions, but also as a tourist ski. Of course, it is also possible to design ski or slalom skis in this way. Part of the tread can also be fitted with steel edges.

In order to allow the ski ties to be fastened to such a hollow ski, it is advantageous that the hinge body is loosely arranged to accommodate the ski ties, with the underside of this part adapted to the shape of the hollow body.

To further increase the strength of the hollow ski, reinforcement elements may be locally located in the hollow body between the inside of the material forming the outer layer and the outer side of the outer hose. These reinforcing elements may consist of longitudinal hollow-ski carbon and / or glass fibers arranged in particular in the region of the upper lane. They can also be designed as planar elements. The hollow ski may advantageously be designed such that a portion of the tread consists of a polyethylene tread and a lower lane firmly connected to the base, of carbon laminate, a material that forms the outer layer of the hollow body, consists of carbon fabric and / or fiberglass impregnated glass or a suitable prepreg, double flexible hose outer hose consists of carbon fiber or fiberglass or aramid fabric or mixed carbon / fiberglass cloth or equivalent prepreg, inner hose consists of polyamide foil.

It is further advantageous if the inside of the hollow body is sealed with an inner flexible tube that is firmly connected to the outer flexible tube. This can fill the hollow body with gas or a gas / air mixture, both of which have a lower specific density than air.

Further, a sliding wax may be present in the hollow body, this area being thereafter connected to the running base of a portion of the tread.

The invention will be further explained on the basis of an embodiment. FIG. 1 shows a portion of the tread in top view; FIG. 2 is a cross-sectional view of a material for making a hollow ski; FIG. 3 is a cross-sectional view of a mold with inserted inserts and a non-inflated double hose; FIG. 4 is a mold according to FIG. 3 with an inflated double flexible tube, in cross-section, FIG. 5 is a plan view of a hollow ski connected to a compressed air source; FIG. 6 hollow ski cross-section through the central region.

The ski manufactured according to the method according to the invention comprises as basic building blocks in FIG. 1 shows a portion 1 of the tread, material 5, which is shown in FIG. 2, and double hose 6; 7.

Part 1 consists of a running base 2 and associated lower belts 3. The base 2 consists preferably of polyethylene. Its underside may already be profiled. However, it can also be processed afterwards, e.g. by engaging climbing aids. The lower lane consists of carbon laminate.

The base 2 and lane 3 can be cut from the strip and placed in a mold 14 according to the length of the ski.

Material 5 forms the outer layer of the hollow body 4 of the hollow ski. It consists of carbon fiber and / or fiberglass fabric impregnated with resin or a suitable prepreg. In material 5, the fibers may be arranged differently. Both knitwear and fabrics can be used. An increase in strength is achieved if the carbon fibers or even the glass fibers are arranged in the longitudinal direction, especially in the region of the upper lane. This is especially preferred for cross-country skiing.

Prior to insertion into mold 14, the material 5 comprises a cut-off according to the intended hollow ski shape. In this way, hollow skis with very different bodies can be made 4. Individual cross-sections of the ski may also have different designs. This is achieved without having to file a plurality of different parts for the body 4, as in the use of extruded profiles.

In FIG. 2 is a schematic view of a possible cut of material 5. The latter, in principle, has its greatest width in the central region, since the body 4 also has its largest circumference in this section. Of course, it is also possible that the material 5 consists of several parts which are jointly inserted into the mold 14.

A further base element forms tube 6; 7. The latter is designed to attach an outer flexible tube to the inner hose 6. The hose 7 thus forms an inflatable air chamber and consists of a thin, highly flexible material such as, for example, a flexible hose. made of polyamide film. Pipe 7, one of which forms the strength of the ski link, consists of carbon fiber or fiberglass fabric or aramid fabric or mixed carbon / fiberglass fabric or an appropriate prepreg.

In FIG. 3 and 4 show how the building blocks of a hollow ski are inserted into a mold 14 and produced a hollow ski.

A part 1 is placed in the lower part 14a of the mold 14 with the base 2 down. The trimmed material 5, which forms the outer layer of the body 4, is placed in the upper part 14b of the mold 14. This consists essentially of several individual fabric strips, e.g. four strips. These are laid out one after the other and impregnated with artificial resin, for example. epoxy resin. Preferably, it already prefers to attach to the inner wall of the mold so as to avoid the formation of wrinkles leading to ejection. The pre-prepared tube 6 is then inserted into the mold 14; 7. In this case, the latter is as seen in FIG. 5, from one piece. Tube 6; 7 is laid from the back end 11 of the hollow ski on one side of the mold 14. It is guided to the area of the ski tip 9. There it is folded 180 ° and guided back parallel to the first layer on the other side of the mold 14 to the end 11 of the hollow ski. The tip 9 is only inserted in the front of the material 5 before bending the pipe 6; 7 (Fig. 5). This consists of a piece of plastic, which is only finalized after pressing the hollow ski. Experiments have shown that in such a way the fracture of tip 9 can be substantially avoided. At the end of the hollow ski 11, the two adjacent ends of the tube 6 forming the air chamber are connected to the compressed air source 13, as shown in FIG. FIG. 5. This ensures uniform inflation.

Of course, two tubes can also be inserted 6; 7. However, the insertion of one tube 6; 7 and the bend in the anterior region of the hollow ski proved to be expedient. After this preparation, the mold 14 is closed. The position of the building blocks in the mold 14 is shown schematically in FIG. 3.

After the mold 14 is closed, the tube 6 is inflated on both sides evenly. This is followed, in principle, by the re-purging of the air, which is re-discharged after completion of manufacture. By inflating the tube 6, as described above, the tubular tube 7 is pressed to the part 1, especially to the belt 3, as well as to the inside of the hollow ski material 5, which (the material) forms the outer layer of the body 4. In the central region of the resulting body 4, the two adjacent sides of the tube 7 are pressed together and form a vertical bridge 8, as shown in FIG. 4.

After the design is complete, the hollow ski hardens. It is advisable that the hollow ski solidifies at a temperature between 70 ° C and 150 ° C for a time between 20 min and 30 min. In this way, all parts, including tube 7, form a rigid connection of the hollow ski. This achieves low hollow weight and high rigidity.

After completion of the compression step, the hollow ski is removed from the mold 14 and the attachments to the source 13 are removed. The end 11 itself then closes in a known manner, and completes the hollow ski. It is no longer necessary to remove the building blocks from the inside of the hollow ski, thus shortening the processing time and preventing any possible damage to the hollow ski.

The tube 6, which consists of a flexible foil, is firmly connected to the tube 7 and seals the body 4 outwards.

In FIG. 6 is a cross-sectional view through a hollow ski according to the invention in the central region. The lower part forms part 1. The latter consists of a base 2 and a belt 3, both parts being firmly connected. The body 4 of the hollow ski is surrounded by material 5 which forms the outer layer.

This material 5 consists of several artificial resin-soaked fabric strips and fits to Part 1. In the body 4 there is a tube 6; 7, which, in the longitudinal direction of the hollow ski, comprises sections adjacent to one another. These parts are firmly pressed to one another during fabrication with an inflatable step and permanently bonded to the curing. The tubes 7 at the same time form a vertical bridge 8 extending along the body 4 in the central cross-sectional area of the hollow ski.

A preferred embodiment is that the body 4 in its cross section is designed as a separate segment with part 1 as a tendon. In this case, a separate segment may also be a circular segment, comprising different dimensions along the length of the body 4. This results in particular torsional rigidity and, in connection with the bridge 8, a rigid rigid design.

In the area of tip 9, the hollow ski is planar, the tip 9 being used in the form of a piece of plastic.

To further increase the strength, reinforcing elements are locally arranged between the inner side of the outer layer and the material 5 as well as the outer side of the tube 7. These may consist of carbon and glass fibers running along the longitudinal direction of the hollow ski, arranged in particular in the region of the upper lane.

The planar elements can be arranged in particularly loaded positions, in the region of the ligament or also in the region of the end 11 or in the area of the tip 9 of the hollow ski. These reinforcement elements 11 can be easily inserted into the mold during manufacture.

In order to correctly attach the body 4 in the form of a separate bond segment to the hollow ski properly, a panel 10 may be arranged for the bonds. This comprises, on the side facing the body 4, the same shape as its surface, the panel 10 on the side of the bond being flattened.

In a preferred embodiment, the panel 10 is loosely attached to the hollow ski. However, it may also be rigidly linked to the material 5.

As already stated, the hollow body is sealed with a tube 6. In this way, the interior can be filled with gas or a gas / air mixture, such as e.g. helium. However, it is also possible to apply a sliding wax that protrudes in the direction of the running base and improves the sliding properties of the hollow ski.

The hollow ski can, of course, also be designed in another form, e.g. perpendicular. Its design makes it possible to realize the design of the latter by means of circular or circular cross-sections and smooth transitional shapes, so that this already submitted form can only be produced in a cost effective manner.

The hollow ski according to the invention comprises high strength at low weight. This solution is therefore particularly suitable for cross-country skiing for sports and tourism purposes.

Claims (27)

Patent claims A method of manufacturing a hollow ski, in particular a cross-country ski, of plastic reinforced plastic, the starting material of which comprises part of the tread as well as the material forming the outer layer of the hollow body is inserted into the mold, enclosing the air chamber, whereby the mold is subsequently closed and the air chamber inflated under pressure, thereby resting the starting material on the inside of the mold and forming a hollow body, after which the hollow ski hardens, characterized in that the air chamber is formed of two in the longitudinal direction hollow skis, adjacent to each other, of double hose sections (6; 7), each air-tight, thin-walled and flexible inner flexible hose (6) made of fibrous fabric consisting of fibrous fabric the outer hose (7) and the latter, after impregnation with artificial resin, is inflated with the hose (6) and compresses to the part (1) of the tread as well as to the material (5) which forms the outer layer of the hollow body (4), which is also infused with artificial a resin consisting of fibrous fabric and in the central region of the body (4) to the tube (7) of the second section of the tube (6); 7), thereby forming a vertical bridge (8) in the longitudinal direction of the hollow ski, whereby all parts are firmly bonded to each other and form a solid connection of the hollow ski. A method according to claim 1, characterized in that the adjacent sections of the air chamber (6; 7) forming the air chamber consist of one piece having approximately double the length of the hollow ski and extending from the rear end (11) Insert the hollow skis on one side into the mold (14) to the area of the ski tip (9), bend there by 180 ° and insert the second layer on the other side of the mold (14) to the end (11) of the hollow ski. Method according to Claims 1 and 2, characterized in that the two open hinged open ends (1) of the one-piece pipe (6; 7) are connected to the common compressed air source (13) and inflated in the area of the hollow ski end (11). at the same time and with the same pressure, thus forming the body (4). Method according to claims 1 to 3, characterized in that from the end (11) of the hollow ski to the tip region (9), by inflating the air chamber tube (6; 7), the body (4) is in its cross section design as a separate segment with part (1) as a tendon. Method according to claim 4, characterized in that the separate segment can be designed as a circular segment, wherein along the length of the body (4) the circular segment is cross-sectioned in various dimensions. Method according to one or more of Claims 1 to 5, characterized in that the hollow ski is designed flat in the area of the tip (9) and the tip (9) is used in the form of a plastic part. Method according to claims 1 to 6, characterized in that the material (5) forming the outer layer of the body (4), when inserted into the mold (14), has reinforcing elements lying between the inner side of the finished hollow ski. material (5) and the outside of the pipe (7). A method according to claim 7, characterized in that carbon and / or glass fibers are stretched in the longitudinal direction of the hollow ski as reinforcing elements. A method according to claim 7, characterized in that the reinforcing elements are placed at the solidly loaded locations of the body (4), as in the bond area. The method according to claims 1 to 9, characterized in that a part of the tread is formed of a carbon-laminate tread and a solid base, firmly bonded to the base, the material forming the outer layer of the hollow body is formed of a fabric made of carbon and / or glass fibers impregnated with artificial resin or an appropriate prepreg, the outer flexible tube of the double flexible tube forms with carbon fiber or fiberglass fabric or aramid fabric or mixed carbon / fiberglass fabric or an appropriate prepreg, inner flexible tube formed from polyamide film. Method according to one or more of Claims 1 to 10, characterized in that the inner side of the body (4) is sealed with a tube (7) that firmly connects with the tube (6) during solidification. Method according to one or more of Claims 1 to 11, characterized in that the body (4) is filled with gas or a gas / air mixture. Method according to claim 12, characterized in that helium is blown into the body (4) as a gas. Method according to one or more of Claims 1 to 11, characterized in that the body (4) is filled with liquid sliding wax and connected to the surface of the running base (2) of the part (1) via sliding wax outlets. 15. A hollow ski, in particular a cross-country ski, of plastic reinforced plastic with a part of the tread as well as a material forming the outer layer of the hollow body, made according to the method according to claims 1 to 14, characterized in that they are in the body ( 4, surrounded by a part (1) and a material (5), two two longitudinal sections of the hollow ski, adjacent to each other, of the tube (6; 7), in which the airtight, thin-walled and flexible tube (6) extends from the air plastic tube (7) consisting of fibrous fabric, and this tube (7), after the formation of the body (4) and the curing of the hollow ski, rests on the material (5) forming the part (1) as well as the outer layer of the body (4) , which is also impregnated with artificial resin and consists of a fibrous fabric, as well as in the central region of the body (4), on the tube (7) of the other tube (6; 7), and which are firmly connected thereto, being interconnected the contact section of the tube (7) is designed as a longitudinal hollow ski stretching, vertical bridge (8). 16. A hollow ski according to claim 15, characterized in that the tube sections (6; 7) are designed as a connected piece, comprising approximately double the length of the hollow ski, both being parallel to each other in the body (4) from the end (11). ) hollow skis to the tip region (9) and in this anterior region, bend 180 ° to each other. Hollow ski according to Claims 15 and 16, characterized in that the body (4) in its cross section is designed as a separate segment with a portion (1) as a tendon. 18. A hollow ski according to claim 17, characterized in that the separate segment is designed as a circular segment that has different dimensions along the length of the body (4). Hollow ski according to claims 16 and 17, characterized in that a plate (10) for receiving ski ties is loosely arranged on the body (4), with its underside being adapted to the shape of the body (4). Hollow ski according to one or more of Claims 15 to 19, characterized in that in the area of the tip (9) the hollow ski is flat and the tip (9) is used as a plastic part. Hollow ski according to one or more of Claims 15 to 20, characterized in that locally reinforcing elements are arranged in the body (4) between the inner side of the material (5) forming the outer layer and the outer side of the tube (7). 22. A hollow ski according to claim 21, characterized in that the reinforcing elements consist of longitudinal hollow-ski carbon and / or glass fibers arranged in particular in the region of the upper lane. A hollow ski according to claim 21, characterized in that the reinforcing elements are designed as planar elements. Hollow ski according to claims 15 to 23, characterized in that the part (1) consists of a base (2) made of polyethylene and a belt (3), firmly connected to the base, of carbon laminate, the material (5) forming the outer body layer (4) consisting of carbon and / or fiberglass fabric impregnated with artificial resin or a suitable prepreg, duct (7) double flexible hose (6; 7) consists of carbon fiber or fiberglass fabric, or aramid fabrics or mixed carbon / fiberglass fabrics or suitable prepreg, tube (6) consists of polyamide film. Hollow ski according to one or more of Claims 15 to 24, characterized in that the interior of the body (4) is sealed by a tube (6) which is firmly connected to the tube (7). Hollow ski according to one or more of Claims 15 to 25, characterized in that the body (4) is filled with gas or a gas / air mixture, both having a lower specific density than air. Hollow ski according to one or more of Claims 15 to 25, characterized in that there is a sliding wax in the body (4), and this area is subsequently connected to the base (2) of the part (1).