This study investigates the hydrodynamic forces and motion characteristics of a pilot boat operating in close proximity to a large vessel during pilot transfer operations. Despite the high risk of accidents during boarding and disembarking, the complex interaction between two ships in difference length overall under forward speed and contact conditions remains insufficiently understood. In this study, first, full-scale measurements were conducted using five different target vessels to identify motion patterns such as motion, alongside position and angle. Second, captive model tests were performed to quantify the steady hydrodynamic forces acting on the pilot boat. The analysis demonstrated that the yaw moment increases when the pilot boat is positioned at the aft section of the ship’s hull (approximately 1/6 L abaft midship). This phenomenon, driven by the fluctuation of pressure distribution near the stern, explains the operational difficulty. These findings provide data for improving pilotage safety and developing operational guidelines for maneuvering in confined hydrodynamic fields.
