The C-2 configuration was produced by making chordwise cuts to within 12,7 mm 

 (1/2 in.) of the C-1 towline leading edge at 0.3-m (12-in.) spanwise intervals 

 along the towline. The C-3 configuration was produced by doubling the number of 

 the chordwise cuts from 0.3-m (12-in.) intervals to 0.15-m (6 -in.) intervals along 

 the towline length. 



For purposes of evaluation, a 5.8-m (19 -ft) length of configuration A-1 

 towline was used. The B-1, C-1, C-2 and C-3 configurations were obtained by 

 successive modifications of configuration A-1 during the basin evaluation. A 

 5.8-m (19-ft) length of NACA 0020 integrated towline (14 percent truncation with 

 45 degree alternating bevels) was also evaluated for comparison with the 8-1 8-F 

 configurations . 



EXPERIMENTAL EVALUATIONS 

 Experiments to determine the hydrodynamic characteristics of the 8-18-F 

 towline design were performed in the DTNSIIDC deep-water towing basin using the 

 general towing arrangement shown in Figure 4. The coordinate system, equipment, 

 instrumentation, and procedures used during this evaluation are described below. 



COORDINATE AND FORCE SYSTEM 



The differential equations describing the three-dimensional static 

 configuration and tension of a cable in a uniform stream are derived from the 

 equilibrium of external forces acting on an element of the cable. A free-body 

 diagram showing a segment of cable of elemental length ds acted upon by 

 hydrodynamic, hydrostatic, gravitational, and tension forces is illustrated in 

 Figure 5. The (X, Y, Z) coordinate system shown is a right-hand, orthogonal 

 system fixed in space with the X-axis positive in the direction of tow (or 

 negative in the free-stream direction) and the Z-axis positive in the direction of 

 gravity. 



The equations are conveniently derived for an orthogonal coordinate system 

 fixed to the cable. In Figure 5, the hydrodynamic force has been resolved into 

 components Fds, Gds, and Hds where F is the force component per unit length normal 

 to the cable in the plane defined by the cable element and the free-stream 

 direction, G is the force component per unit length tangential to the cable, and H 

 is the (side) force component per unit length normal to the plane defined by the 

 cable element and the free-stream direction. The cable-fixed coordinate system 



