OPTIMAL SAILOR POSITION ON AN OLYMPIC DINGHY

Abstract

As the Laser Olympic dinghy is one of the highest level sail racing classes in the world, there is an interest in obtaining scientific facts around the tons of experience that already exist. For this reason, a numerical investigation was carried out to find the optimum heel and trim angles for upwind sailing. Flat water was assumed. Systematic Computational Fluid Dynamics (CFD) Simulations were carried out to find the optimum trim versus heel at speeds of two, three, four and five knots. During these computations the leeway was fixed for each speed. The leeway angles were estimated using the resistance results obtained from the tank tests and foil theory. A special purpose VPP was developed accepting CFD results at the given speeds as input for the hydrodynamic forces, while the aerodynamic forces were obtained using Hazen’s empirical model. The output from the program was the true wind speed required to achieve the target speed at 45 degrees true wind angle. By systematic variation of the sailor’s position the optimum heel (and the corresponding trim) was obtained at the minimum required wind speed. The reason for developing this unconventional VPP was to avoid interpolation between the speeds computed by CFD. Since the resistance/speed relation is very non-linear interpolation would have been too approximate for finding the rather flat heel/trim optima. The computational techniques and the optimum heel and trim angles of the dinghy will be reported in this thesis. In the course of the computations several interesting flow phenomena were investigated, such as the interactions between the centreboard and the rudder, and between the hull and the appendages. These by-products will be briefly reported in the Conclusions and Future Work –chapter.