measurements with an overall accuracy of +13.3 N (+3 lb). Two 360-degree rotary 

 potentiometers attached to the gimbaled towpoint (Figure 8) provided measurements 

 of towline kite and cable angle. These potentiometers, in conduction with the 

 three-to-one ratio gear sets, provided angle measurements of +60 degrees with an 

 overall accuracy of +0.3 degree. Carriage speed measurements were supplied from 

 a magnetic pickup located on the towing carriage. This speed measurement tech- 

 nique has an overall accuracy of +.05 m/s (+0.1 knot). An eight-channel strip- 

 chart recorder was used for readout and recording of all measured data. 



PROCEDURES 



Towing performance was examined for wetted scopes of 3.7 m (12.3 ft) and 

 5.7 m (18.8 ft) for towline configurations A-1, B-1, C-1, C-2 and the 14 percent 

 bevel truncated NACA 0020 towline through a speed range from 1.03 m/s (2.0 knots) 

 to 9.26 m/s (18 knots). Configuration C-3 was examined through the speed range at 

 a scope of 5.7 m (18.8 ft). Depressor roll angle, towing tension, kite angle, 

 cable angle, towline wetted scope, tow speed and visual observations of the 

 general towing performance were recorded during each experimental run. 



DISCUSSION OF RESULTS 



All of the towline configurations towed in an acceptable manner (i.e., stably 

 and with small kiting angles). Figures 9 through 11 present the average corrected 

 kite angle for each towline configuration towed at the 5.7-m (18.8-ft) scope 

 length as a function of tow speed. The corrected kite angles were determined by 

 subtracting the measured depressor roll angle from the kite angle measured at the 

 gimbaled towpoint for each speed. This corrects for the component of towline kite 

 angle induced by the roll angle of the depressor. Averaged data for all measured 

 parameters recorded during the evaluation of each towline configuration are listed 

 in Table 2. 



As shown in Figures 9 through 11, all of the towline configurations 

 demonstrated increasing kite angle with increasing speed up to approximately 

 8 knots. Above this speed the kite angle generally remained at a constant value. 

 This effect is not a towline characteristic, but is a result of the depressor 

 selected for the evaluation. Since the depressor used was a negatively buoyant 

 lifting body, the in-water weight tends to dominate the hydrodynamic force at 

 speeds below approximately 4.12 m/s (8 knots). At speeds above 4.12 m/s 



16 



