Full Scale Dynamics were contacted to assist with confirming the as-built properties of a dummy rudder test rig. Various steel plates had been designed to change the moment of inertia of the rotating dummy rudder and this design parameter required experimental calculation to verify the design. As part of the testing, temporary springs were installed to create a rotating dynamic system and the properties of this system were measured using an angle potentiometer, accelerometer and an instrumented impact hammer. These tests were able to confirm the original design to the satisfaction of the client.