Development of a Forced Roll Mechanism for Planing Hull Models

A Forced Roll Mechanism was designed and built at the Hydromechanics Laboratory at the United States Naval Academy. The FRM was designed as a dynamometer that forces a planing hull model in roll and measures the resulting roll moment as well as the heave and sway forces. The model is fully restrained in all six degrees of freedom. The dynamometer can be configured to either oscillate the model or hold the model at a fixed roll angle, and measure the forces whether dynamic or static in nature, while allowing different testing conditions in terms of speed, rise and trim. The FRM was bench tested using known forces and moments to ensure accuracy and the measured lift forces for zero roll tests were compared with analytical predictions. Initial testing results show that the added inertia hydrodynamic coefficient depends on roll oscillation frequencies for low frequencies. The rig construction and calibration as well as preliminary results are presented.