Smith and Cummins 



However, the towing system allowed small oscillations in surge, and it is 

 planned to undertake a three-mode analysis at a later date. 



The towing system is as shown in Figs. 1 and 2. Such an arrangement per- 

 mits the application of tow forces at the model center of gravity while permit- 

 ting responses in all six degrees of freedom. Restoring forces in the surge and 

 sway modes are provided by springs K^ and K2. External forces in the heave, 

 surge and sway modes are measured, using variable reluctance force gauges. 

 The motions in the six degrees of freedom are measured by film type potenti- 

 ometers mounted as indicated on the tow strut and excitation forces by force 

 gauges mounted in the model. 



////////// 



DRIVE 



^ PITCH 

 POTENTIOMETER 



FORCE GAGES 



Fig. 1 - Pitch and heave experiment 



442 



