hence, 



C.= ^-= 6secJ_^_wm ^^q^- 



2'^ 



where 5 = y- is the drag per unit length of the cable. In measuring 6, tare 

 drags and end and surface effects must be eliminated. 



Using Equations [7], [8], and [10], the hydrodynamlc force acting 

 on the cable can be calculated from measured values of w, 6 , and the direction 

 of the cable. 



EXPERIMENTAL TECHNIQUE 



To determine the direction cosines of the lines assumed by the ca- 

 bles, the cables were towed in the deep-water basin. The tow point was placed 

 one inch above the surface of the water at a forward position on the carriage. 

 The cables were free to turn about a vertical axis through the tow point but 

 could not spin about their own axis. Two optical instruments vrere used, a 

 traveling telescope and a transit, both of which were mounted towards the rear 

 of the carriage about forty feet from the tow point, see Figure 2. The tele- 

 scope travelled along a level path at a known angle to the direction of the 

 stream and was mounted so as to sight always in the direction of gravity. The 

 relative positions of the tow point and the path of the telescope were meas- 

 ured. Then the determination of the exact position of the telescope when the 

 telescope was directly above the cable enabled the calculation of the project- 

 ed angle of the cable in the x-z plane, i.e., the angle of yaw. The transit 

 was mounted in a fixed position so as to sight always in a plane perpendicular 

 to the direction of the stream. The distance of the tow point from this plane 

 and the position of the transit relative to the tow point were measured. This 

 permitted the determination of the depth of the cable at the plane of the 

 transit, by a simple triangulatlon which took into account the angle of yaw 

 and the refraction of light at the water surface. All the Information re- 

 quired to compute the direction cosines of the line of the cable was thus pro- 

 vided. In this manner, the direction of each cable at various speeds was 

 measured . 



In a separate series of runs, the cables were towed from the drag 

 dynamometer and the drag forces acting on the cables were measured by stand- 

 ard methods. 



EXPERIMENTAL RESULTS 



The pertinent facts regarding the cables that were test 1 are listed 

 in Table 1 . 



