This thesis investigates the yaw stability of wind-driven vessels using wingsails, addressing the urgent need for decarbonising global shipping. An analytical method is developed to assess directional stability based on aerodynamic and hydrodynamic characteristics, yielding a universal stability criterion validated with SEAMAN data. The study explores practical stability assessment approaches and evaluates the impact of varying hydrodynamic parameters, aerodynamic models, and surge coupling effects.

Results show that while stability diagnostics are invariant under different hydrodynamic models, significant variations occur in destabilised hulls. Including a boundary layer in the wind model has negligible effects on stability but increases computational effort. The closed-loop analysis assesses proportional and derivative feedback control strategies, demonstrating satisfactory stability for both human and autopilot control across all points of sail in the original hull configuration.

Time-domain responses to step rudder inputs indicate small steady errors and oscillatory components under human control, with autopilot control yielding even more robust outcomes. The study highlights the importance of surge coupling in stability analysis, often overlooked in previous models. The thesis concludes that wind-driven vessels can achieve directional stability under active control schemes, providing a foundation for future research on sustainable maritime transportation.