Optimizing Spanwise Lift Distributions Yacht Sails Using Extended Lifting Line Analysis

摘要

This paper discusses how to maximize the drive force produced by an upwind sail. It aims to provide a betternunderstanding of the behavior of this force as a function of the heel angle of the yacht and the wind speed. It alsondiscusses the corresponding optimal spanwise loading distributions. An extended lifting line code, based onnWeissinger’s method, is developed to analyze the performance of an isolated mainsail in upwind conditions. It isnextended to account for the heel angle of the yacht via effective angle theory, and an image sail is used to model theninfluence of the sea surface. Profile drag is modeled using experimental data. The extended lifting line code isnvalidated against wind-tunnelmeasurements and data fromthe literature. A second code is then used to optimize thenspanwise loading on a mainsail such that the drive force is maximized. Constraints are implemented to ensurenpositive circulation over the entire span and to limit the sectional loading to realistic values. Finally, the extendednlifting line code is inverted to calculate the twist distribution necessary to produce the desired, optimized loadingndistribution for a given sail planform. The calculated twist distribution is found to be realistic and achievable.