The 



computed values of f (<\>) are also plotted in Figure A. 3. Considering the 



values of f (<{>) as derived from the three data bases, neglecting for the moment 



the C values by which they were derived and how the C_ values ultimately scale 

 R K- 



the tangential hydrodynamic force, there is a consistency to the f (<f>) values. 



First, Models A and B both representing 50% ribbon coverage have f (<j>) values 



which closely approximate a single trend line (Figure A. 3). Second, these values 



are approximately one-half those pertaining to the 100% ribbon coverage cable. 



So it appears that wetted surface (percent cable coverage) is a key parameter 



controlling tangential drag as would be expected. 



However to compute the tangential force C must be applied. If only the 



15 mil (0.38 mm) thick ribbon models are considered, the consistency is maintained 



and so is the concept of surface area as a key parameter. When the 30 mil (0.76 mm) 



case is considered with its large C values the tangential force scales up to 



K 



where the 30 mil (0.76 mm) ribbon tangential force is twice that of the 15 mil 

 (0.38 mm) ribbon although both have the same wetted surface. Now the concept of 

 wetted surface area having a linear effect on tangential force does not hold. 



It must be concluded that the characteristics of the ribbon especially 

 material stiffness and possibly method of attachment are influencing hydrodynamic 

 forces both normal and tangential in important ways that are not understood. For 

 this reason scaling this data to ribbon cables of significantly different size 

 must be done with caution. 



