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It is of crucial importance to adjust the trim angle properly during the forward acceleration of a planing craft in cases such as ‎sport ‎competitions and military missions. In these applications, the goal of trim ‎adjustment is to reach the final cruising speed as soon as ‎possible. Present study tries to answer this question: How the angles of the drive ‎system and/or a control element should be changed ‎during acceleration phase in order that the craft can reach to its final speed in the minimum possible time? This is an optimal control ‎problem with the drive and control element angles as its control variables. To solve such problem, a 3-DOF dynamic model is ‎developed ‎based on the theoretical and empirical methods. Both propeller operation and the engine are ‎taken into account for the propulsion system. ‎Then, the solution algorithm of time-optimal control problem is explained ‎according to an indirect method. Results for a planing mono-hull ‎with two different weight distributions show a similarity in trend between the optimal solution for control ‎variables and the hull ‎instantaneous trim angle. As the second case study, the solution for an aerodynamically alleviated racing catamaran is presented.‎