bending stiffness which requires storage drum and sheave diameters to be approxi- 

 mately 2.5 times larger than those required for conventional cables of the same 

 maximum thickness (diameter). 



Consequently, the NACA 0020 towline could not be wrapped around a diameter 

 smaller than 1.5 m (5 ft) without damaging the electrical conductors or exceeding 

 the allowable stresses in the fiberglass strength member. The minimum bending 

 radius governs to a large extent the size of the handling equipment, which for the 

 NACA 0020 towline design exceeds the space limitations of the MCM helicopter. 

 Therefore, to utilize the integrated towline concept for helicopter MCM 

 operations, a new towline design was required. 



DTNSRDC developed a new fairing shape, designated 8-18-F, based upon results 



2 

 of basin model evaluations , sonar system power and data transmission 



requirements, towing tension, and space limitations of the MCM helicopter. A 19- 

 foot length of experimental 8-18-F towline was obtained for basin evaluations to 

 examine its susceptibility to kiting and to obtain hydrodynamic drag and side 

 force characteristics. 



This report includes a description of the experimental integrated towline 

 configurations, outlines the experiment, instrumentation, and experimental 

 procedures used to collect data, and provides the results of the evaluation 

 including graphical presentations of the normal drag and side force coefficients 

 as a function of Reynolds number and kite angle as a function of towing speed for 

 several towline configurations. Basin and at-sea data obtained for the NACA 0020 

 integrated towline with truncation are included for comparative purposes. 



DESCRIPTION OF THE EXPERIMENTAL INTEGRATED TOWLINES 

 A cross-sectional view of the experimental 8-18-F integrated towline, 

 designated Configuration A-1 in this report, is presented in Figure 2, and general 

 physical characteristics are given in Table 1. The 8-18-F towline materials and 

 general construction are similar to those of the NACA 0020 towline, except that 

 the strength member was designed with a blunt nose (leading edge) and a recessed 

 trailing edge. This shape accommodates the required power and data transmission 

 leads, consisting of six AWG number 17 solid copper electrical conductors and four 

 50 m optic fiber cores. Each of the electrical conductors and optic fibers is 

 coated with a ruggedizing material consisting of an S-glass/epoxy resin. The 

 leads are separated into two bundles of three copper conductors and two optic 



