by a factor of 0.55 to reflect DTNSRDC at-sea data, were used to calculate the 

 cable configurations. The normal drag coefficient, C , based on cable diameter, 

 also determined from at-sea data, was assumed to be 



C = 5.23 - 0.85 log,_Re (Ribbon Faired Cable) (1) 



R lU 



where Re is the Reynolds number based on diameter. 



Predicted tension in the remote sensor cable as a function of cable length is 

 shown in Figure 2. The results indicate that the length should be approximately 

 twice that of the vertical separation of the ends for minimum tension. 



TOWCABLE AND DEPRESSOR 



A readily available, stock cable manufactured by Rochester Corporation was se- 

 lected as a suitable towcable. This cable is double-armor construction utilizing 

 galvanized improved plow steel as the strength member; it has nine electrical con- 

 ductors in the core; the overall diameter is 0.343 in. (8.71 mm); and the rated 

 breaking strength is 42.3 kN. For purposes of calculation, the towcable was assumed 

 to be ribbon-faired for a length of 120 m starting from the depressor to gain the 

 maximum depth advantage provided by the reduced normal drag of fairing. The remain- 

 der of the cable was left bare to prevent excessive tension buildup along the cable. 

 Fode loading was used for the normal and tangential components of drag for bare 

 cable. The normal drag coefficient C based on cable diameter and the tangential 

 drag factor f were assumed to be 



C = 1 727 + MM 

 ^R ^''^' ^ Re 



(Bare Cable) (2) 



53.45 



f = 0.0062 + 



Re 



The above equations were determine from DTNSRDC at-sea data. 



The calculated towcable length and towing tension required to achieve a depth 

 of 200 m at a speed of 10 knots are shown in Figure 3 as functions of tension pro- 

 duced by the depressor. The resulting towcable breaking strength factor of safety 



