Performance Enhancement of Autonomous Sailboats via CFD-Optimized Wing–Tail Sail Configurations

The development of energy-efficient propulsion systems for autonomous sailboats requires innovative sail designs that balance aerodynamic performance and maritime operational reliability. This study presents a novel rigid wing sail system comprising a NACA 0020 main sail with an embedded NACA 0018 tail sail, specifically designed for uncrewed ocean navigation. Through systematic CFD analysis using ANSYS Fluent 2022R1, three configurations were compared: (1) the proposed hybrid wing–tail system, (2) a single main wing sail, and (3) traditional flap sails. The investigation focused on two key design parameters—tail sail area (25–40% of main sail area) and deflection angle (0–15°)—that were evaluated across angles of attack from 0° to 30° under typical marine wind conditions. The results reveal three critical findings: First, the hybrid system achieves a 29.5% higher peak lift coefficient than a single wing sail and an 11.6% improvement over slotted-flap sails. Second, increasing the tail sail area to 35% of the main sail optimizes both the lift coefficient (CL max = 1.16) and the lift-to-drag ratio (L/D = 7.5 at 9° angles of attack). Third, as the tail deflection angle increases, the maximum lift–drag ratio shifts forward, and at small angles of attack, the maximum lift–drag ratio increases by 40%. The hybrid wing–tail sail design proposed in this study significantly enhances the aerodynamic performance of uncrewed sailing boats, providing new insights for the sustainable development of marine renewable energy technologies and autonomous vessels.