by the addition of horizontal and vertical tip-plates, as 

 shown in Figure II-l. This configuration towed satisfac- 

 torily in basin tests and at sea. These extensions are 

 vulnerable during handling, hoviever; Figure Il-l(b) shows 

 how the starboard end plate was bent during a launching 

 mishap. The extensions also interfere with storage on deck 

 as they protrude below the rear supports. 



Observation of the towing characteristics, made 

 during the basin towing tests, give indication that the 

 deficiency can be remedied by effecting minor changes in 

 the location of the stabilizing surfaces. 



Cable 



Surges in tension of approximately double steady 

 state values were observed in the system during the sea trial 

 due to high seas. Since the system was at short scope (700 

 feet) , for which condition the cable angle at the towpoint 

 was quite steep (61 degrees) , any heaving motion of the towing 

 vessel must result in a corresponding heave of nearly equal 

 magnitude at the depressor. The small margin of static 

 stability in pitch of the depressor, and the location of 

 the towpoint well aft of the main-wing quarter chord line, 

 result in characteristics which tend to minimize response 

 in pitch for disturbance frequencies of the order encountered 

 during the trials. The depressor on short scope is thus 

 literally pulled vertically through the water when the towing 

 vessel heaves. Making allowance for human error in judging 



33 



