Abstract

This study embarked on a computational exploration of the aerodynamic interactions between the mainsail and foresail (jib) in sailboat configurations, contrasting these findings with the performance of a hypothetical larger single mainsail of equivalent area. Through a set of two-dimensional simulations, the study analyzed the lift and driving force coefficients at varying angles of attack, with the sails modeled as rigid structures. These simulations revealed that a two-sail arrangement comprising a jib and mainsail significantly outperforms a single mainsail of similar combined area in lift generation, efficiency, and the ability to sail closer to the wind—key factors in competitive sailing. In the presence of the mainsail, the jib was found to produce more lift at lower angles of attack and to allow for higher pointing into the wind (lower AoA) without the risk of the sail fluttering from insufficient wind angle. While in the presence of the jib, the mainsail could sustain higher angles of attack without flow separation. These results challenge traditional theories, such as the widely discussed “slot effect”, by providing new insights into sail interactions and their implications for sail design and racing strategy. The study suggests avenues for further investigation, including models incorporating sail flexibility, three-dimensional modeling, mast geometry, and the inclusion of hull, keel, and rudder dynamics to fully capture the complex reality of sailing conditions.