as can be seen from fig6 and 7 , the ski of the invention comprises an elastic compensation superstructure provided with a special front constraint in the form of a more complex innovative plate composed not only of the traditional base member ( connected to the centre of the ski ) but also of a front prolongation 5 which reacts against the ( aforedescribed ) counter - flexure with a downward thrust f spat on a point 6 situated around the middle of that ski portion between the front jaw p and the section 4 ( where the tip curvature commences ). the connection of the ski to the front end of said elongated plate at the point 6 must satisfy precise fundamental connection conditions , allowing freedom of rotation about a transverse - horizontal axis , and freedom of longitudinal sliding , so that no limitation is imposed on the flexibility of the shovel portion itself . this means that said connection must simultaneously act as a hinge and as a bilateral support . in this respect it must allow free rotation of the shovel portion about a transverse - horizontal axis , but must hinder movements between the plate and ski in a vertical direction but must allow relative sliding in a longitudinal direction . it must hence be a hinge ( of transverse - horizontal axis ), to allow freedom of rotation between the shovel portion and said plate end , but must be horizontally slotted to also allow its relative longitudinal sliding ; it can hence be defined as a slotted hinge . this superstructure is therefore provided with at least three separate points of application to the ski , one of which is situated in a position 6 which is significantly advanced ( with respect to the front jaw ), possibly and preferably around the middle of the portion between the front jaw p and the section 4 where the curvature of the tip commences . consequently when the ski counter - flexes , the dynamic load f exerted by the skier is divided into at least three forces : two ( f ′, f ″) or more acting on the base central region , and an additional force ( f spat ) acting on said more advanced point 6 . it should be noted that the most significant role of this superstructure is not merely to damp and absorb vibrations , although it undoubtedly and effectively performs this valuable accessory function . its main role is to exert a supplementary reactive thrust f spat on the point 6 , to induce an elastic compensation effect thereat to significantly modify its counter - flexure deformation ; it hence achieves the desired effect on the elastic deformation and on the related distribution of the reaction load ( fig4 ). it should however be noted that this effect is also substantially dependent on the elastic characteristics of the basic ski , which has to be adequately flexible particularly in the portion 7 below the arm 5 . the proposed configuration shown by way of example in fig6 and 7 can be subjected to suitable improvement . in this respect , to be applicable to any ski it cannot be prefigured in a standardized form ; it requires adaptation to the shape ( in terms of the progression of the thicknesses and curvatures ) of the ski for which it is intended . moreover , the value of the thrust f spat is strictly dependent on the flexibility of the arm and would be very difficult to regulate and preset ( in order to achieve a determined preload value and assume certain values increasing with the elastic counter - flexure deformation ). the aforesaid problem is radically simplified by using the following more evolved constructional variant ( fig8 - 11 ). the superstructure is no longer a single member but two members : a traditional base plate 10 and an independent semi - rigid front prolongation arm 11 , i . e . a sort of rocker arm ( fig8 ), as described hereinafter . the prolongation arm 11 , connected at its front to the slotted hinge 6 , is connected at its rear to the front end of the base plate 10 by a hinge 12 , it being also provided with a retro - prolongation 13 the end of which acts as a reaction element . said end is provided with an element 14 of adjustable advancement ( for example by means of a screw ), which abuts against the base plate 10 ( fig8 , 9 ) or against the basic ski ( fig1 , 11 ), according to design requirements related to its elastic characteristics , by acting preferably on an interposed elastic or semi - elastic element 15 ( for example a high resistance rubber insert ). it should be noted that in the second of the aforesaid cases , in which the design provides for the reaction element of the rocker arm to bear on the basic ski ( fig1 , 11 ), two supplementary forces act frontward through the rocker arm : in addition to the force f spat , the force f ′″ exerted by the element 14 also acts on the ski . as an alternative to the aforedescribed proposed configurations , the base plate can be split into two half - plates , i . e . the superstructure portion below the boot comprises two distinct separated parts : a rear part 9 below the heel fixing unit , and a front part 8 below the sole . this latter provides all the aforedescribed functional aspects , as illustrated in fig1 , which shows an extension of the structure already shown in fig8 , and in fig1 which shows an extension of the structure shown in fig1 . finally , the solution shown in fig8 , 9 and the solution shown in fig1 , 11 can be simultaneously adopted ( whether the base plate is whole or split ), by simultaneously applying a first counteracting element 14 acting on the base plate , and a second counteracting element 16 acting on the ski , as shown in fig1 and 15 . a further embodiment ( very particular , moreover for its simplicity ), is shown in fig1 and 17 . it concerns exclusively the solution in which the base plate is fractioned into two different and separated parts 8 and 9 . it involves only the front part 8 and it foresees the prolongation arm 5 to be integral part of it up to point 6 ( fixed to the ski in the “ slotted hinge ” way as described and considered up to now ). said front plate portion ( underneath the boot sole ) is fixed to the central region 1 of the ski through a transverse - horizontal axis solid hinge 17 , at the rear with respect to the front jaw p . in this case the action f of the skier is transmitted to the ski by three forces : the f ′ one exerted on the heel fixing unit , the fspat exerted by the end 6 of the arm and the f ″ one exerted on the aforesaid hinge . independently of the embodiment used , the ski of the invention is particularly advantageous by demonstrating an adequate flexibility combined with good distribution of the reaction load . the superstructure of the ski according to the invention can be constructed of traditional materials or , advantageously , of different materials such as composites , magnesium alloys , or monostructural hybrids which enable a specific weight reduction to be obtained for equal strength characteristics . in addition , the superstructure can be produced using economical industrial pressing , forging and moulding techniques .
a downhill ski having a thrust support acting elastically downwards on a point in that portion between the front jaw of the binding and the section where the tip curvature commences .