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In the continued quest to reduce friction between mobile surfaces, that between the sole of a ski and snow stands out because of its long history of debate, the joy of skiing, as well as the notion that understanding of this complex issue may have broad, more general implications. For decades, a wide spectrum of parameters involved has been studied, and different theories advanced, that resulted, however, in only modestly successful guidelines for the creation of faster skis. The work presented in this book was directed towards unvealing the influence of the surface chemistry and structure on the tribological properties of a slider gliding on snow. Using a novel experimental test method, we find that more than the chemical composition of the bottom of the slider, the surface topology of it dominates the rate of descent, with the remarkable observation that at an optimum surface roughness range (0.2 µm Ra 1µm, Ra: arithmetical mean surface roughness) yields optimum performance, essentially irrespective of the material used for the ski sole. The observed results may be explained by the interaction of the surfaces with the friction-induced water films, on which the skis glide.

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Jan Lukas Giesbrecht was born May 3, 1979 in Zurich, Switzerland.He studied Material Science at the Swiss Federal Institute ofTechnology (ETH) Zurich, which he successfully completed in 2006.Then, he joined the Polymer Technology Group of the Department ofMaterials at ETH, headed by Paul Smith for his doctoral studydescribed in this book.

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