FR2675391A1 - Winter sports' ski comprising a stiffener and a base - Google Patents

Abstract

Ski consisting of a first lower assembly or base, the front end of which is raised to form the tip; and a second upper assembly or stiffener, the two assemblies being linked to each other by linking means produced by means of a flexible and/or partially rigid link.

Description

WINTER SPORTS SKI COMPRISING A STIFFENER AND A
BASE
The present invention relates to a ski, such as an alpine ski, a cross-country ski, a monoski or a snowboard. It relates more particularly to an improvement in this type of skiing.

 We already know different types of ski and there are many variations. These consist of an elongated beam, the front end of which is curved upwards to form a spatula, the rear end also being more slightly to form the heel.

 Current skis generally have a composite structure in which different materials are combined so that each of them intervenes optimally, taking into account the distribution of mechanical stresses when using the ski. Thus, the structure generally comprises peripheral protective elements, internal resistance elements to resist the flexural and torsional stresses, and a core. These elements are assembled by gluing or by injection, the assembly generally being carried out hot in a mold having the final shape of the ski, with a front part strongly raised in a tip, a rear part slightly raised in the heel, a central arched part. .

 Despite the manufacturers' concern to manufacture good quality skis, they have not, to date found a high performance ski satisfactory in all conditions of use.

 The present invention relates to improvements made to these skis in order to facilitate their manufacture which makes it possible to obtain the desired characteristics. due to the diversity of parameters that can be chosen.

 The ski according to the invention consists of a first lower assembly or base, and a second upper assembly or stiffener, the two assemblies being linked with each other by connection means produced by a flexible connection and / or partially rigid.

 According to an additional characteristic, the stiffener has a length less than the length of the surface of the base in contact with the snow. It is advantageously between 50 and 80% of the base length.

 According to an advantageous arrangement the base and the stiffener are elongated beams whose height is variable along the ski to decrease towards the front and rear ends.

 According to one of the embodiments, the connection between the base and the stiffener is produced by a flexible interface, constituted by a sheet of elastic or viscoelastic material, and extends under the entire lower surface of the stiffener.

 According to another variant, the flexible connection is partial and extends only under part of the length of the stiffener.

 According to another variant, the connection between the base and the stiffener is a rigid connection and does not extend under the entire lower surface of the stiffener.

 Other characteristics and advantages of the invention will emerge from the description which follows with reference to the appended drawings, which are given only by way of nonlimiting examples.

 Figure 1 is a side view of a first embodiment of a ski according to the invention.

 Figure 2 is a cross section along II-II of Figure 1.

 Figure 3 is a cross section along III-III of Figure 1.

 Figure 3a is a variant.

 Figure 4 is a side view showing the various components of the ski according to the first embodiment.

 Figures 5 and 6 are schematic views showing the ski in cross section and in two variants.

 Figures 7, 8, 9 and 10 are top views showing three embodiments of the stiffener.

 Figures 11 to 16 are side views showing different variants of the connecting means.

 Figures 11 and 12 show flexible partial connections.

 Figures 13 and 14 show rigid partial connections.

 Figures 15 and 16 show mixed connections, partially flexible and partially rigid.

 Figures 17 to 21 are variants showing in cross section and schematically other embodiments.

 Figures 22 and 23 are side views showing variants.

 FIG. 24 is a diagram representing the stiffness of a ski as a function of its flexion.

 Figures 25 and 26 are views similar to Figure 1 illustrating alternative embodiments.

 FIG. 27 is a cross-sectional view along T of FIGS. 25 and 26.

 Figure 28 is a side view of the ski equipped with its support.

 Figures 29, 31, 32, 33, 34 and 37 are side views showing variants.

 FIG. 30 is a cross-sectional view along T1 of FIG. 29.

 FIG. 35a shows a detail of the embodiment of FIG. 34.

 FIG. 35b shows a detail of the embodiment of FIG. 33.

 Figures 35c and 35d are views similar to Figure 35b showing two variants.

 FIG. 36 shows in perspective a detail of the embodiment of FIG. 34.

 Figure 38 is a cross-sectional view similar to Figure 27 showing a variant.

 Figure 39 shows an alternative embodiment.

 FIG. 1 represents a ski according to a first embodiment according to the invention. it comprises a lower assembly or base (1) and an upper assembly or stiffener (2) Said stiffener (2) is disposed above the base (1) and linked to the latter by connecting means (3).

 The base (1) is the element in contact with the snow and is in the form of an elongated beam (10) having its own distribution of thickness, of width and therefore its own stiffness. This elongated beam can have a stiffness less than or equal to that of a conventional ski.

The base (1) comprises a central part (113) slightly arched, having a lower sliding surface (114) and an upper surface (115). The central part (113) occupies most of the length of the base and is extended on the one hand at the front by an anterior part (116) raised to form the spatula (117) and on the other hand, by a rear part (118) slightly raised to form the heel of the ski. The rear part (118) being relatively short and of low lift, and the front part (116) is longer and much more arched, as is known per se and shown in the figures.

 The structure of the base (1) can be of the sandwich type or of the box type or of any other type. In Figure 2, a preferred structure is shown comprising a rigid upper reinforcement (101) in the shape of a shell with a "U" section forming a top wall (102) and two side walls (103 and 104), covering a core. (105), the assembly being closed at its lower part by a lower element (106) comprising the metal edges (107,108), a sliding layer (109) generally made of polyethylene as well as lower reinforcement elements (110,111). An upper surface layer (112) covers the upper reinforcement to form the decor of the base.

 The reinforcing layers (101,110,111) can be of all types such as layers of composite materials such as fiberglass, carbon fiber with epoxy or polyester resin, or a metal alloy.

 The core (105) can be filled or unloaded foam, wood or aluminum honeycomb.

 The surface layer providing the decoration can be made of polyamide or other material, such as a thermoplastic material. It can be monolayer or made up of several layers.

 According to the invention, the upper face (115) of the central part (113) of the base (1) is covered with a stiffener (2). This element is intended to complete the distribution of the stiffnesses of the base (1) so as to obtain the desired overall distribution. Said stiffener (2) can be of any kind, any shape and any structure.

 According to an advantageous arrangement, the stiffener (2) is in the form of an elongated part (20) also having its own distribution of thickness, width and therefore stiffness.

 In the embodiment given by way of example and represented in FIG. 3, the structure of the stiffener is of the box type and is formed of a core (201) disposed between an upper reinforcement (202) and a lower reinforcement (203 ) .. The stiffener can also consist of a simple profile made of a single material.

 The upper reinforcement (202) is covered with another additional reinforcement layer (204) in the shape of an inverted "U" and forming an upper wall (205) and two side walls (206,207). A surface layer (208) covers the top and the side faces of the stiffener (2) to form the finish and the decoration thereof.

 As previously for the base, the reinforcing layers of the stiffener can be of all types such as layers of composite materials such as fiberglass, carbon fiber, with epoxy or polyester resin. The core (201) can be filled or unloaded foam, wood or aluminum honeycomb. The surface layer providing the decoration can be made of polyamide.

 According to an advantageous arrangement, (Figure 4), the stiffener (2) has a length "L2" less than the length "L1" of the base (1). Thus, the front end (209) of the stiffener is located between the point (119) of spatula contact of the base and the front end (120) of the standardized area for mounting the fasteners. Similarly, the rear end (210) of the stiffener is located between the rear contact point (121) and the rear end (122) of the standardized area for mounting the fasteners. Thus, if the base (1) has a length "L1" of contact with the snow, the stiffener (2) has a length "L2" such that "L2" is less than "L1".

 For example, the length "L2" of the stiffener is between 50% and 80% of the length "L1". In addition, the relative longitudinal position of the stiffener (2) relative to the base (1) may for example be such that the middle (211) of the stiffener (2) is at the middle (123) of the length (L1 ) contact of the base (1) with snow.

But it could be otherwise; thus the middle (211) of the stiffener (2) can be further forward (AV) or further back (AR) relative to the middle (123) of the base.

 As regards the width of the two elements, the stiffener (2) can have the same width as the width of the base (1), as shown more particularly in FIG. 3. But it can be otherwise; thus the stiffener (2) may have a width "12" less than the width "11" of the base (1) and thus be narrower than the latter, as shown diagrammatically in FIG. 5. Similarly, the stiffener (2) can be wider than the base (1), as shown in Figure 6.

 Note also that the width of the two base assemblies (1) and / or stiffener (2) can be constant or variable as shown in Figures 7, 8 and 9.

 FIG. 7 shows, in top view, an exemplary embodiment of a ski according to which the width "12" of the stiffener (2) is variable and roughly follows the variation of the width "11" of the base ( 1).

 Figure 8 is a view similar to Figure 7 showing another embodiment in which the width "11" of the base (1) is variable while the width "12" of the stiffener is constant.

 FIG. 9 is another variant according to which the variation of the width "12" of the stiffener is opposite to that of the width "11" of the base, that is to say that when the width "11" of the 'base 1 increases, the width "12" of the stiffener 2 decreases.

 According to the embodiments of FIGS. 7 to 9, the variation of the width "12" of the stiffener is continuous, but it could be otherwise, as shown in FIG. 10. According to this variant, the stiffener 2 comprises in its central zone (212) a narrowing in width to form two lateral clearances (213,214) extending over a length "L'2" less than "L2", the stiffener (2) thus comprising a central part (215) of reduced width .

 The base (1) and the stiffener (2) are elongated parts of respective height "hl" and "h2". Of course in a cross section the two heights "hl" and "h2" can have the same value, but also be different. Thus, in a cross section, "hl" can be greater or less than "h2". In addition, "hl" and / or "h2" can be constant depending on the longitudinal position where the measurement is made. However, to obtain a good distribution of the stiffness, it is advantageous to vary one or the other of the heights "hl" or "h2" and even the two "hl" and "h2". Thus the stiffener can have its height "h2" which decreases forwards or backwards, or even both forwards and backwards as shown. It is the same for the base.

 According to the invention, the stiffener (2) is linked to the base (1) by connection means (3) such that the connection between the two elements is flexible and / or partially rigid.

 The embodiment shown in Figures 1, 2 and 3 shows an example where the connection (3) between the two base assemblies (1) and stiffener (2) is completely flexible. To this end, the connecting means (3) are produced by a flexible interface (30) arranged between the two assemblies, over the entire length of the stiffener. The interface therefore has a width "12" equal to that of the stiffener (2) and a length "L2" equal to that of the latter.

 The interface (30) is produced by a layer of a flexible material of the elastic type, and in particular of the viscoelastic type, of thickness from 0.1 to 5 mm, which is glued or welded on the one hand to the upper surface. (115) of the base (1) and on the other hand under the lower surface (216) of the stiffener.

The material used can be elastic with a hardness of 10 to 85 shores A or viscoelastic material with a modulus of elasticity of 15 to 160 megapascal, a hardness of 50 to 95 shores A and a damping value of 0 , 13-0.72. Obviously, these data are only examples of implementation, and for a temperature of 20 degrees and a frequency of 15 hertz.

 The interface (30) is fixed to the base (1) and the stiffener (2) is produced either by a thermosetting resin of the polyester, vinylester or polyurethane epoxy type or a thermoplastic film, or any other means.

 The flexible connection according to the embodiment previously described is total and extends under the entire length (L2) of the stiffener (2), but it can be otherwise. Indeed, the flexible connection can only be partial and not extend under the entire length of the stiffener (2), as shown in FIGS. 11 and 12.

 FIG. 11 therefore represents a first variant according to which the connection (3) is flexible and partial, and is produced by two flexible interfaces, a first flexible front interface (31) and a second flexible rear interface (32) disposed respectively under the front end (209) and rear end (210) of the stiffener (2).

 FIG. 12 represents a second variant according to which the flexible connection (3) is produced by a flexible central interface (33) disposed between the base (1) and the stiffener (2) in the central zone of the ski and the length of which " L3 "is less than the length" L2 "of said stiffener, to constitute a partial flexible connection.

 According to other variants, the connection (3) between the base (1) and the stiffener (2) is partially rigid; that is to say that the connection, when it is rigid, does not extend under the entire surface of the stiffener (2) as shown in FIGS. 13 and 14.

 FIG. 13 shows a variant according to which the connection (3) is partial and rigid; that is to say that the stiffener (2) is rigidly connected by its central lower surface (218) to the base (1). Thus, only the central part (212) is fixed to the base (1) while the front part (219) and the rear part (220) are free.

 Figure 14 shows another arrangement where the connection (3) is rigid and partial. According to this arrangement, only the front and rear ends (209 and 210) of the stiffener (2) are fixed to the base (1) to leave the central area (212) free.

 The rigid connection (3) can be obtained by any means such as bonding, by mechanical connection such as screws or rivets or even by welding, in particular by ultrasound or by vibration.

 Of course the connection (3) between the base (1) and its stiffener (2) can be mixed, that is to say partly flexible and partly rigid as shown in FIG. 15.

 Thus, according to the variant of FIG. 15, the central zone of the ski comprises a flexible central link (33), while the front and rear ends (209 and 210) of the stiffener are fixed to the base (1) by two partial links , rigid, a first rigid link or front link (35) and a second rigid link or rear link (36).

 According to the variant of Figure 16, the arrangement is opposite. Thus, the rigid partial connection (34) is in the center as in the variant of FIG. 13, but the front (219) and rear (220) parts of the stiffener (2) are linked to the base by flexible partial connections, a first flexible front link (31) and a second flexible rear link (32). The rigid central link (34) can be obtained by a downward projection coming from the stiffener or a central intermediate wedge or central rigid interface (340).

 According to the embodiment described above, the upper surface (115) of the base is a surface whose generator is parallel to the lower sliding surface (114). But it could be conceived that the upper surface (115) is oblique and inclined as shown in FIG. 17 where the connection interface (3) is inclined either towards the inside of the ski, or towards the outside.

 Figures 18, 19 and 20 are schematic views in cross section of three other alternative forms of the interface.

 According to these different variants, the interface area is not flat but has a complex shape. According to the variant of Figure 18, the surface of the interface (3) is curved. According to the variant of FIG. 19, the base (1) comprises a longitudinal hollow profile and the lower surface (216) of the stiffener (2) comprises a corresponding projecting profile. The arrangement shown in Figure 20 is reversed. Thus the base (1) comprises on the top a projecting profile and the lower surface (216) of the stiffener comprises a corresponding hollow profile.

 According to the previous embodiment, the lower surface (216) of the stiffener (2) has a shape complementary to the upper surface (115) of the base, and this at least at the connection, but it could be otherwise. , as shown in the variant of FIG. 21 according to which it is the connection (3) which ensures the form cooperation, on the one hand with the base (1) at its lower surface, and on the other hand with the stiffener (2) on its upper surface.

 Note that the surface layer (112) of the base (1) can extend over the entire length thereof, including in the area of the connection or only in areas where there is no said connection (3).

 According to Figures 1, 2 and 3, it can be seen that the surface layer (112) is interrupted at the level of the connection. Thus the flexible connection and therefore the interface (30) is directly fixed to the upper reinforcement (101) of the base.

 FIG. 3a shows a variant according to which the surface layer (112) of the base extends even in the region of the connection. Thus the interface (30) is fixed on the surface layer (112) of said base (1).

 The stiffness of the stiffener (2) may be less than or equal to that of the base (1).

 Figures 22 and 23 show variants in which the stiffener (2) mounted on a flexible interface is retained longitudinally relative to the base (1). For this purpose the base (1) comprises two stops, a first front stop (130), and a second rear stop (131). FIG. 22 is an embodiment according to which the stiffener is somehow embedded in the base. Figure 23 is another embodiment.

 The embodiments of FIGS. 12 and 13 make it possible to obtain a ski whose stiffness varies non-linearly with the deformation of the ski. This ski reacts differently depending on the speed and the amplitude of the flexions. Indeed, at rest and during slight bending, given the presence of the front (ea) and rear (er) spaces, the base is not in contact with the ends of the stiffener. On the other hand, from a certain bending, there is contact and action of the stiffener on the base. FIG. 24 schematically represents the curve of the stiffness of the ski as a function of the bending of the latter.

 It can also be noted that the flexible connection produced with an elastic interface and produced with a sheet may be such that said sheet has a constant or variable thickness. For example, being thicker towards the front or vice versa, or even thicker both forwards and backwards. One could also conceive of the use of a layer of flexible material whose properties are such that the stiffness is not constant throughout this layer. Indeed it could be more flexible at the front or vice versa.

 Figure 25 shows a particularly suitable improvement when the stiffener (2) has a width less than the base (1).

 Thus according to this improvement, the ski comprises at least one support (4) intended to receive the binding (s) (5) for retaining the skier's boot. Said support (4) has the shape of a stirrup having the shape of an inverted "U" and comprises an upper wall (40) extended laterally and downwards by two side walls (41, 42) to constitute a housing ( 43) lower having the shape of a longitudinally extending hollow profile intended for the passage of the stiffener (2).

it should be noted that the dimensions of the housing, both horizontal "14" and vertical "h4" are greater than the horizontal dimensions "12" and vertical "h2" of the stiffener to form a space "e" necessary for the freedom of the latter.

 According to a characteristic of the invention, the stiffener does not directly receive the stresses of the skier. Also, the support or the bracket (4) is supported only on the base (1).

 To this end, the lower ends (44 and 45) of the side walls of the support are connected to the upper surface (115) of the base (1).

Advantageously, the connection between the support and the base is rigid and obtained for example by gluing, welding or any other means, such as mechanical.

 The support (4) constitutes the mechanical element for transmitting and distributing the stresses of the skier on the base.

 According to the embodiment of FIG. 25, the support (4) receives at the front the front attachment (51) and extends rearward over a length "L4" up to under the rear attachment (52). Said rear attachment (52) commonly called heel being itself fixed on the rear part of said support (4).

 FIG. 26 represents a variant according to which the ski comprises two supports (4) spaced from one another, a first front support (4a) on which the front stop (51) for retaining the boot is fixed, and a second support or rear support (4b) on which the heel piece (52) is fixed.

 The support (4, 4a, 4b) can be an injected plastic element or a metal profile, a pultruded or extruded plastic element.

 Of course, the support (4, 4a, 4b) can be in one and the same piece or be made up of different pieces, or even made up of a part of the corresponding fixing (5, 51, 52).

 Note also that the connection (6) between the support (4, 4a, 4b) and the base can be rigid but also flexible. FIG. 28 represents such a variant, and in which the connection is produced by an interface (60) made of flexible material.

 Figures 29 and 30 show another variant in which the stiffener (2) is linked to the base (1) by a transverse articulation (7).

To this end, two lateral retaining walls (70, 71) are provided which are integral with the base (1). Of course, it may be possible to provide, in addition to this variant, a support (4) for the fastenings, as shown in FIG. 31.

 In Figure 32, there is shown another variant in side view according to which the base (1) comprises in its central part (113), a projection (8) to which the stiffener (2) is connected; the connection can of course be rigid or flexible and in this case, produced by an interface as in the previous embodiments.

 Figures 33 to 36 show other embodiments in which the stiffener (2) is connected to the base by its front and rear ends (209, 210) by retaining means constituted by intermediate elements (90, 91 ) vertical and lateral restraint. According to the variant of Figure 33, the lower surface (216) of the stiffener (2) is not directly in contact with the upper surface (115) of the base (1), while in the variant of Figure 34 , there is contact. The retaining means (90, 91) each consist of at least one transverse wall (92) extending upwards and a horizontal wall (93) extending towards the center of the ski to constitute a lower housing (94) open towards the center of the ski and closed laterally by two lateral walls (95, 96) of lateral retention. The ends (209, 210) of the stiffener being engaged and retained in the lower housing (94). We could block the two ends in their corresponding housing or block only one of the ends (209 or 210) and allow the displacement of the other (210 or 209) in its corresponding housing, as shown in Figures 35c and 35d . In FIG. 35c, the clearance "el" allows displacement "d" of the corresponding end. But the relative displacement can be done against the action of an elastic system (97), as shown in Figure 35d.

 The longitudinal and vertical retaining means (90, 91) could also be constituted by articulation systems (90 ', 91') as shown in Figures 37 and 37c. Thus, the front (209) and rear (210) ends of the stiffener (2) are linked to the base (1) by a transverse articulation axis (90, 91), said articulation (90 ', 91') being retained at the base (1) by a hinge support (80) comprising two lateral retaining walls (81, 82).

 The bracket (4, 4a, 4b) shown above has the general shape of an inverted "U", but it could be otherwise, as for example that is shown in FIG. 38. According to this variant, the bracket (4) is formed by a part having the general shape of a "U" whose transverse wall (46) is disposed between the stiffener (2) and its base (1).

 Note also that in the embodiments where only the central part of the stiffener is linked to the base, the damping of the ski is achieved by the friction of the ends (209 and 210) of the stiffener on the upper surface of the base.

 FIG. 39 represents a variant of a ski in a cross section according to which it comprises an outer casing (200) under which the base (1) is located with its stiffener (2). The outer envelope (200) having for example a decorative effect.

 Of course, the invention is not limited to the embodiments described and shown by way of examples, but it also includes all the technical equivalents and their combinations, and other variants are also possible without departing from the scope. of the invention.

Claims (41)

 1. Ski formed by a first lower assembly or base (1), the front end of which is raised to form the tip (117); and a second upper assembly or stiffener (2), the two assemblies being connected to each other by connection means (3,30,31,32,33,34,35,36,340) produced by a flexible connection and / or partially rigid.  2. Ski according to claim 1, characterized in that the stiffener (2) has a length "L2" less than the length "L1" of the surface of the base (1) in contact with the snow.  3 .. Ski according to claim 2, characterized in that the length "L2" of the stiffener is between 50 and 80% of the length "L1".  4. Ski according to claim 3, characterized in that the front end (209) of the stiffener (2) is located between the tip contact area (119) of the base and the front end (120) of the area mounting fixings.  5. Ski according to claim 3, characterized in that the rear end (210) of the stiffener (2) is located between the heel contact zone (121) of the base and the rear end (122) of the zone mounting fixings.  6. Ski according to any one of the preceding claims, characterized in that the middle (211) of the stiffener (2) is located at the middle (123) of the area in contact with the snow from the base.  7. Ski according to any one of claims 1 to 5, characterized in that the middle (211) of the stiffener (2) is located in front of the middle (123) of the area in contact with the snow from the base.  8. Ski according to any one of claims 1 to 5, characterized in that the middle (211) of the stiffener (2) is located behind the middle (123) of the area in contact with the snow from the base.  9. Ski according to any one of the preceding claims, characterized in that the width "12" of the stiffener. (2) is equal to, less than or greater than the width "11" of the base (1).  10. Ski according to claim 9, characterized in that the width "12" of the stiffener (2) is constant.  11. Ski according to claim 9, characterized in that the width "12" of the stiffener (2) is variable and changes as a function of the longitudinal position.  12. Ski according to claim 11, characterized in that the variation of the width "12" of the stiffener is continuous.  13. Ski according to any one of the preceding claims, characterized in that the base (1) and / or the stiffener (2) is an elongated beam.  14. Ski according to claim 13, characterized in that the height "hl" of the base (1) and / or the height "h2" of the stiffener is constant.  15. Ski according to claim 13, characterized in that the height "hl" of the base (1) and / or the height "h2" of the stiffener is variable.  16. Ski according to claim 15, characterized in that the height "h2" of the stiffener decreases towards the front.  17. Ski according to claim 16, characterized in that the height "h2" of the stiffener decreases towards the rear.  18. Ski according to any one of the preceding claims, characterized in that the base (1) is a beam constituted by a core (105) disposed between two reinforcements, a first upper reinforcement (101) and a second lower reinforcement ( 110,111), and comprises a sliding layer (109) laterally comprising two lateral metal edges (107,108), said upper reinforcement being covered, at least in part by a surface layer (112).  19. Ski according to claim 18, characterized in that the surface layer (112) of the base (1) is interrupted at the level of the stiffener (2).  20. Ski according to any one of the preceding claims, characterized in that the stiffener (2) is a beam constituted by a core (201) disposed between two reinforcements, a first upper reinforcement (204) and a second lower reinforcement (203 ), said upper reinforcement being covered with a surface layer (208).  21. Ski according to any one of the preceding claims, characterized in that the connection (3) between the base (1) and the stiffener (2) is produced by a flexible interface (30,31,32,33).  22. Ski according to claim 21, characterized in that the interface consists of a sheet of elastic or viscoelastic material.  23. Ski according to claim 22, characterized in that the sheet of flexible material has a variable hardness.  24. Ski according to claim 22 or 23, characterized in that the sheet of flexible material has a variable thickness.  25. Ski according to any one of claims 22 to 24, characterized in that the sheet of elastic or visco material has a thickness of between 0.1 and 5 mm.  26. Ski according to any one of claims 21 to 25, characterized in that the flexible connection (30,31,32,33) extends under the entire lower surface (216) of the stiffener (2).  27. Ski according to any one of claims 21 to 25, characterized in that the flexible connection is partial and extends only under a part of the stiffener (2).  28. Ski according to any one of claims 21 to 25, characterized in that the interface (33) is disposed only under the middle zone of the stiffener over a length "L3" less than the length "L2" of the stiffener.  29. Ski according to claim 27, characterized in that the flexible connection is constituted by two interfaces, a first flexible front interface (31) disposed under the front end (209) of the stiffener (2) and a second flexible rear interface ( 32) disposed under the rear end (210) of said stiffener (2).  30. Ski according to any one of the preceding claims, characterized in that the connection (3) between the base (1) and the stiffener (2) is a rigid connection (34,35,36) and does not extend not under the entire lower surface of the stiffener.  31. Ski according to claim 30, characterized in that the stiffener (2) is rigidly fixed by its central zone (34) on the upper middle surface of the base.  32. Ski according to claim 30, characterized in that the front and rear ends (209,210) of the stiffener (2) are fixed to the base (1).  33. Ski according to any one of the preceding claims, characterized in that the upper surface (115) of the base (1) cooperates with the lower surface (216) of the stiffener (2) by complementary shapes.  34. Ski according to claim 33, characterized in that the upper surface of the base (1) comprises a longitudinal hollow profile or a longitudinal projecting profile and the lower surface of the stiffener respectively comprise a corresponding projecting profile or a profile in corresponding hollow.  35. Ski according to any one of claims 1 to 32, characterized in that the shape of the lower surface (216) of the stiffener (2) is different from the upper surface (115) of the base (1) and the connection comprises at its lower surface a shape complementary to the shape of the upper surface of the base while the upper surface has a shape complementary to the shape of the lower surface of the stiffener (2).  36. Ski according to any one of claims 1 to 30 and 33 to 35, characterized in that one of the connections connecting the ends of the stiffener (2) to the base (1) is flexible, while the other is rigid.  37. Ski according to any one of claims 1 to 20, characterized in that the stiffener (2) is linked to the base by at least one transverse articulation (7, 90 ', 91').  38. Ski according to claim 37, characterized in that the stiffener (2) is pivotally mounted on the base (1) by means of a transverse articulation (7) disposed in the central zone of the ski.  39. Ski according to claim 37, characterized in that each of the ends (209, 210) of the stiffener (2) is connected to the base (1) by a transverse articulation (90 ', 91').  40. Ski according to any one of the preceding claims, characterized in that it comprises at least one support or stirrup (4) linked to the base (1) intended to receive the bindings (5, 51, 52) for the shoe retention on the ski.  41. Ski according to any one of claims 1 to 20, characterized in that each end (209, 210) of the stiffener (2) is linked to the base (1) by an intermediate retaining element (90, 91) .