An effective method to reduce the violent motion behaviour of fast planing vessels in waves may be found in the application of active control devices in conjunction with advanced motion control systems. This study aims to develop a computational tool for the design and optimization of these ride control systems for high speed planing monohulls. Hydrodynamic characteristics of both transom flaps and interceptors are determined by systematic series of model test experiments in the towing tank of the Laboratory of Ship Hydromechanics at the Delft University of Technology. Transom flap results at downward deflection angles are validated with formulations found in literature. In addition, experiments at up angle flap positions have been performed to increase the range of application for motion control purposes. The hydrodynamic performance of the interceptors and transom flaps are compared in order to determine their efficiency. The experimental data was implemented in a nonlinear time domain mathematical model that can predict the seakeeping behaviour of fast monohulls. Simulations demonstrate the improvement in motion behaviour of a fast planing vessel with a ride control system sailing in head waves.