shallow angles ribbons tend to lie flat along the trailing edge of the cable. This 

 may reduce the effect of percent cable coverage on the normal component of hydro- 

 dynamic force. 



In the case of Model B the derived drag coefficients C are approximately 



* R 



double the values for Model A (and C ) a trend which could be inferred from the 



K 



data in Figure A. 2. 



It may be that the thicker (stiffer) ribbon material results in a higher 

 projected frontal area to the flow and this accounts for the higher drag co- 

 efficients when based on cable diameter. Or it may be that material stiffness 

 alters the wake to the extent that a different loading function applies or some 

 combination of the two. Regardless, it is clear that the normal hydrodynamic 

 loading function and C D derived from a 15 mil (0.38 mm) ribbon data base is a 

 poor representation for a towcable with 30 mil (0.76 mm) ribbon. 



In analyzing the tangential hydrodynamic force components, estimates of 

 tangential hydrodynamic loading function values can be made from the data in 

 Figure A.l and the following relation: 



< f t>, 



(AT/AS - w simj> ) 



r 



(3A) 



Computed values of (f ), are shown in Table A. 3, 



t <p 



TABLE A. 3 - TANGENTIAL HYDRODYNAMIC LOADING VALUES 



Speed 

 (kt) 



Model A 



Model B 



*c 



AT/AS 



R 



f t 



*c 



AT/AS 



R 



f t 



6 



9 



12 



15 



15° 



10° 

 6.5° 

 4.5° 



0.9 

 1.3 

 1.9 

 2.3 



9.19 

 16.00 

 27.58 

 43.09 



0.069 

 0.070 

 0.065 

 0.052 



9° 



5.8° 

 4° 

 2.5° 



1.6 

 2.2 

 3.2 

 4.1 



18.39 

 31.83 

 49.12 

 83.49 



0.078 

 0.066 

 0.64 

 0.049 



25 



