Modelling of slalom waterskiing

Abstract

This paper proposes a study of the kinetics and dynamics of slalom waterskiing. The discipline of slalom waterskiing is first described. Then the forces applied on a “static” skier, i.e. just pulled behind a boat, are expressed as a function of water drag coefficients, speed and pitch angle. A slalom point model is finally proposed, made of three major contributions: water friction, water lift and an additional water drag contribution on the slalom skier, creating the traverse motions. Assumptions are made in order to quantify the three angles characterizing the ski position during the slalom traverses. The model is simulated on an EXCEL worksheet, for a large range of conditions (boat speed between 52 and 58 km/h, rope length between 18.25 and 13 m, and three skier masses of 60, 80 and 100 kg). The water friction coefficient was fitted to a value allowing to simulate successful slalom courses. The simulations provide a significant set of kinematics and dynamics parameters (skier velocity, acceleration, tangential force and rope tension). The model duly renders the variations of the skier velocity, and it reflects the increasing difficulty for the skier to complete the slalom at higher boat speed and shorter rope length.