1. Using Figures 18 and 19, estimate the length of towcable required to obtain 

 the depth and the desired cyclic depth variation. A tension coefficient C near 1.5 

 should be selected for the deepest portion of the depth cycle for the reasons 

 discussed above. 



2. Launch the depressor and begin paying out towcable. 



CAUTION 



If the towcable is on the winch at little or 

 no tension, ship speed should be maintained 

 at 3 knots or less during launching operations 

 to prevent the outer towcable lays from burying 

 themselves under subsequent lays. 



The towcable is marked at intervals using patches of ribbon fairing to provide a 

 measure of the amount of cable payed out. The marking scheme is listed in Table 5. 

 A metering device, such as a metering streaming sheave, also can be used to determine 

 cable payout. 



3. After paying out the desired cable length, secure the towcable to the ship 

 towpoint. Always install a tension dynometer to monitor towing tension. 



4. Set desired towing depth and commerce towing at operational speed. 



CAUTION 



Do not allow the towcable tension to exceed 18 kN 

 (4000 lb) . If sea conditions or other factors 

 cause tension surges to approach this value, 

 decrease towing speed. Also, if median tension 

 vary greatly from those predicted in Figure 21 

 the depressor should be retrieved and inspected 

 for damage. 



5. Observe towing depth and fine tune the depth setting, as required, using 

 the depth readout (ideally the CTD depth readout). To change the depth, dial in a 

 new setting and allow sufficient time for depressor depth transients to settle 

 before making any further adjustments. 



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