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Abstract A method for predicting the maneuvering motion of a planing hull is proposed based on a 4-degree-of-freedom equation of motion (surge-sway-yaw-roll) in a ship-fixed coordinate system. The hull hydrodynamic/hydrostatic forces are expressed using a derivatives form. The forces and moments required for the predictions are calculated using captive-CFD. The derivatives obtained from the calculated forces and moments are stored for several ship speeds, and the derivatives for the arbitrary ship speed are calculated by an interpolation technique. The turning for a 12.88m length planing hull called GPPH is calculated by changing the steering angle (δ) from -5° to -25°. The approach ship speed is 20.5 m/s. The simulation results are compared with the free-run-CFD results. At relatively small steering angles from -5° to -15°, the results showed good correspondence with the free-run-CFD results. At relatively large steering angles of -20° and -25°, the calculation results by the present model are consistent with the CFD results up to non-dimensional time (t*) of approximately 5. After that, the roll angle in the present calculations diverged. The CFD calculation at δ = -25° also diverged without reaching a steady turn. Further investigation is required. INTRODUCTION Maneuvering simulation models for displacement-type ships have already been established, as represented by the MMG model (Yasukawa and Yoshimura, 2015). Therefore, if the hydrodynamic force parameters related to the maneuvering motions of the target ship can be determined by conducting tank tests such as rudder force tests, oblique towing tests etc. or similar CFD calculations, it is possible to predict the maneuvering motions with reasonable accuracy in a short calculation time. On the other hand, a reliable maneuvering simulation model for high-speed planing hulls has not yet been established. One of the reasons is that there is a lack of data to construct the simulation model and to determine the hydrodynamic force coefficients to be used in the model. To obtain such data, it is desirable to conduct tank tests using ship models, but there are facility constraints and equipment restrictions due to the high-speed of the target ship. These make it difficult to obtain satisfactory data.