Jumping ski

Abstract: This invention relates to a jumping ski which is particularly adapted to the so called V-style. The ski according to the present invention has a cross-section with a flat base and longitudinal running grooves and a smooth curved upper side, which, together with the underside, forms an aerodynamic wing profile having its maximum camber nearest to the centre line (S). Additionally the cross section of the ski is twisted in towards the centre line (S), such that the angle of attack of the ski tip towards the air is reduced, in order to avoid stalling whilst in flight. The ski boots are fastened to a flat area where the cross section of the ski is rectangular and, in a plan view, makes a skew parallelogram.

Description: This invention relates to the curve of the upper side of jumping skis being formed like a wing profile. In ski jumping the V-style has found favour relative to the "classical" jumping style. An important reason for this success is that with the V-style the skis cover a larger area against the wind. This means that more air molecules must be displaced by the passage of the skis through the air, such that the potential lift can be increased. Another advantage with the V-style is that the skis are separated with a larger distance such that the moment of lateral stability increases with the larger arm. "Classical" jumping skis are still used in V-style jumping. These skis are characterised by a rectangular cross-section which is not, however, aerodynamically favourable. A German document DD-A- 270 011 discloses a jumping ski which is modified to guarantee an improved take-off and a longer jump as well as a higher stability of flight in an ordinary ski jump. This is obtained by giving an almost convex form to the lower surface beginning at the tip of the ski. This form is then continuously changed along the jumping ski into a more or less concave cross section profile at the ski contact point to the running jump track. The purpose of the invention is to give the cross-section of the jumping skis an aerodynamic shape, akin to an aeroplane wing profile, in order to reduce drag and to increase lift. The invention is set out in claim 1. Advantageous embodiments of the invention are featured in dependent claims 2 and 3. The invention is further explained by reference to figures 1 to 3. Fig 1 a) shows a cross-section through a rectangular classical jumping ski, b) shows a cross-section through a wing profile formed jumping ski, in accordance with the invention, and Fig 2 a) shows a plan view of the left ski, b) shows all the cross-sections (seen from the front) of the left ski in accordance with the invention, and Fig 3 a) shows the dihedral angle of the skis in the in-flight position, b) shows a plan view of the V-shape of the skis in the in-flight position. Fig 1a) shows a cross-section through a normal "classical" jumping ski with 6 longitudinal running grooves. Fig 1b) shows a cross-section through a wing profile formed jumping ski where the wing profile is pointing inwards towards the centre line (S). Fig 2a) shows the plan view of the left ski. The relative wind is indicated by arrows at an angle of 20° to the inside of the ski. The ski jumping boots are fastened to the ski on a flat part; in plan view, approximately a skew rectangle. Apart from this flat part (line 6 in fig 2b), the outside edge of the skis have a constant height of ca. 5mm (the trailing edge), whereas the inside has a thickness (height) which varies from ca. 5mm (line 1 in fig 2b) to ca. 12mm (line 5 in fig 2b). Fig 2b) shows all the sections (profiles) through lines 0 to 6 in fig 2a). Line 0 in fig 2b) indicates a stippled profile (wing profile) with a smaller angle of attack. This is achieved by twisting the ski tip in towards the centre line (twisted anticlockwise in the diagram). The skis still have normal "tension" where the centre part lifts itself up from the base. In fig 2b) the left ski is loaded with weight, making the centre part lie flat on the base. A symmetric (normal) ski tip can also be used, especially such ski tips which have a low height. The disadvantage that such a ski tip might create is turbulence in the air stream because of too large angle of attack. Fig 3a) shows the angle between the underside of the ski and the horizontal plane in the direction of motion. This angle increases with the increasing distance between the skis and has the dominant influence on lateral stability. Fig 3b) shows the skis in the V-style in-flight position seen in plan view. The angle of attack of a wing is the angle between the relative wind and the chord line of the profile. With normal elasticity and under stable flying conditions, the tip and the tail of the ski will bend up, due to the lift, where the optimal wing profiles are formed (with the top point at a position near 1/3 of the chord line).

Claims: A jumping ski, which has a cross-section with a flat base and longitudinal running grooves and a smooth curved upper side, wherein the curve of the upper side is formed like a wing profile, said wing profile pointing in towards a center line (S), whereby the attack of the wing is the angle between the relative wind and the chord line of the profile. The jumping ski according to claim 1, characterized in that the tip of the ski is twisted towards said center line (S), to avoid turbulence in the air stream because of too large angle of attack. The jumping ski according to claim 1, characterized in that the upper side of the ski has a flat part being in a plan view approximately a skew rectangle where the boots are to be fastened.

Inventors: KOLSET EINAR, KOLSET, EINAR
Applicants: KOLSET EINAR, KOLSET, EINAR
Application year: 1993
Main classification: A63C5
IPC codes: A63C5