This paper outlines the requirements, concept and feasibility of a six degree-of-freedom test rig for dynamic experiments with captive models. The specifications are driven by the requirements of submarine testing, although the rig must also be fully capable of testing surface ship models. Large amplitude motions and rates are required in order to obtain the nonlinear stability derivatives.

The test rig was designed for operation on the carriage of the 200 meter towing tank at the Institute of Marine Dynamics, St. John's. It will accept submarine models up to 6 meters long, using a sting mount at the tail of the model to alleviate support interference, but modelling the propulsion system will generally require an alternative mounting arrangement. The principal actuators are hydraulically-driven ballscrew jacks, Under the control of a microcomputer. In addition to testing with harmonic motions, there is a capability for measuring forces and momenta for an arbitrary trajectory of the model, subject only to kinematic limitations.

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