Sail optimisation for maximal speed

A variety of approaches to sail optimisation are reviewed. A mathematical model is described which allows the optimisation of the spanwise lift distribution of a high speed craft with a criterion of maximal offwind speed. The model uses a numerical lifting line approach to predict the aerodynamic forces and moments allied to an empirical model of the hydrodynamic forces. A further model is presented which yields the optimal sailplan for a yacht based on a criterion of maximal speed made good to windward; this may be calculated either for a single windspeed, or in an averaged sense for a selection of different windspeeds. The vortex lattice method is used to predict aerodynamic forces and moments, whilst the hydrodynamic forces and moments are estimated using a performance prediction approach based on data from the Delft systematic yacht hull series. Three variations in rig type are considered: a basic sloop rig, a sloop rig with a roached mainsail, and a ketch rig. In both models the optimisation is carried out using a genetic algorithm. Typical results are presented, and scope for future work is discussed.