TEST ARRANGEMENT AND PROCEDURES 



The experimental data were obtained during sea trials which were 

 conducted in deep water off the Bahama Islands. Figure 3 is a schematic 

 diagram of the towing arrangement. The towed body was launched from 

 the ship and cable was reeled out to a predetermined nominal scope. The 

 nominal scope is defined as the amount of cable in the water at essentially 

 zero speed. For test purposes, nominal scopes of 100, 200, and 280 feet 

 were used. 



All tests were conducted in Sea States of to 1/2 to obtain as near 

 steady-state conditions as possible. The roll and pitch of the body were 

 monitored during the tests to insure the proper orientation of the body. 

 In general, the roll angle was about zero (within ±1 degree) and the pitch 

 angle was about 6. degrees nose down. 



The body was towed at speeds from 2.5 to 10.5 knots with the cable 

 scope held fixed at each of the three nominal values. The following 

 parameters were measured and recorded: 



1 . body depth 



2. body pitch angle 



3. body roll angle 



4. cable angle at the body 



5. cable tension at the body 



6. cable angle at the ship 



7 . cable tension at the ship 



8. speed of the ship relative to the water 



PRESENTATION OF EXPERIMENTAL RESULTS 



The experimental values of tension, depth, and angle for the three 

 nominal cable scopes obtained from all of the tests are tabulated and 

 presented in Appendix A. To illustrate the quality of the measurements, 

 the data for a representative case (280-foot nominal cable scope) are 

 presented in graphical form in Figures 4, 5, and 6. Figure 4 presents the 

 measured cable tension at the ship as a function of speed. Figure 5 is the 

 measured depth of the towed body as a function of speed. Figure 6 is the 

 cable angle at the ship as a function of speed. It may be noted that at speeds 

 above 4 knots, there is very little scatter in the data on depth and cable 

 angle. As may be expected, the tension data show more scatter since the 

 cable was vibrating and the ship was pitching and heaving slightly. However, 

 the faired curve should be closely representative of the mean tension values 

 corresponding to any given steady-state condition. 



