17 



Prom Figure 4 it is seen that the side-force Increases linearly with 

 sin <t> V7hen Is very small and in most cases reaches a maximum value within 

 the range of <l> investigated in the experiments. In other cases there is a 

 leveling off that suggests that a maximum value is reached at larger values of 

 <t>. The initial slope of the C curves and the position of the maximum vary 

 with the size and the construction of the cable. 



The speed of towing has a marked effect upon the coefficient of the 

 tangential force, C^, and consequently the variation of C-, with 4> is difficult 

 to determine from experiments of the type reported here. Although this coef- 

 ficient is too small and too inaccurately measured to Justify a detailed analy- 

 sis, the results agree in a qualitative vray with those obtained from other ex- 

 periments. A commonly used estimate for C-, for stranded cables is C^ = 0.02 0^,. 

 The values of C^ listed in Table 2 are of the correct order of magnitude (as 

 given by this estimate). Also in agreement with other results, C- decreases 

 with increased towing speed and with increased cable diameter. 



CONCLUSIONS 



Because of the uncertainties regarding the data the conclusions 

 reached must be of a somewhat tentative nature. However it is clear that the 

 sine-squared law for the coefficient of the normal force C holds fairly well 

 for small inclinations of the cable to the stream and that there is no indi- 

 cation of a sine term in the expression for this coefficient. Interpretation 

 of the deviations from this lavf should await confirmation of the results by 

 additional experiments. At small angles the coefficient of the side force 

 C seems to vary linearly with the angle. At larger angles there is often a 

 falling off which suggests a stalling phenomenon. The coefficient of the tan- 

 gential force C„ has not been measured very accurately but the results with 

 respect to this coefficient agree at least in a qualitative way with the re- 

 sults of other experiments. 



