Structural behaviour of slalom skis in bending and torsion

In the present work, an integrated approach to the ski structural evaluation problem is presented involving several activities and based on data of different nature. The research stages were Laboratory tests, Field tests and Analysis Software developments; these activities were synchronously carried out in order to give to engineers the information needed for a correct ski design, involving also information from the other disciplines like biomechanics and material sciences. The ski stiffness properties in bending and torsion are two fundamental design parameters and a Contact Method and an Optical Method were compared in this work, leading to equivalent results. After application of proper sensors on a pair of racing skis, the calculated deflection curves and the measured deflection curves were compared to confirm the possibility of applying the method during field tests. To achieve the in field bending and torsion diagram on the ski, two slalom racing skis were used and strain sensors were applied to the top foil of the skis at sections regularly distributed along the ski. The ski were calibrated during laboratory tests under different bending and torsion test conditions. In the field tests, three professional testers were involved, different for skill levels and anthropometrics, and special slalom courses with short poles were performed. As a results, the instantaneous bending and torsion moment curves on the ski were evaluated: the deflected shape of the ski was evaluated, projected onto the snow surface and visualized at each frame in the snow field after developing a specific LabVIEW application. Quantitative index were introduced to compare the inner and outer ski during the courses. The results of these analysis can be of interest not only to the ski-binding-boot manufacturers, but also to the whole ski community as the proper scientific knowledge of the skiing phenomena allow for virtual analysis of performance, comfort and safety improvements.