INSTRUMENTATION 



The parameters measured In addition to the characteristics of 

 the mooring line models themselves and their catenary configura- 

 tions were: 



1. The components of force in the upper end of the line 

 in the vertical and horizontal directions, and 



2. Amplitude and frequency of the vertical motion at the 

 upper end of the line. 



The two component force dynamometer is shown in Figure 5. Each load 

 cell has a 2.2-pound capacity. A special signal control unit ener- 

 gized the force gages and the return signal was displayed on a 

 Sanborn 320 strip chart recorder and a Weston Model 1240 Digital 

 Multimeter. On the strip chart record, resolution to t 0.05 pound 

 was obtained; on the digital multimeter, to ± 0.01 pound. The 

 force measurements were complicated by interaction between the hori- 

 zontal and vertical force gages and inertia of the dynamometer. 

 These effects were accounted for by calibration as explained later. 



The input motion was measured by a linear displacement trans- 

 ducer whose signal was recorded on a Sanborn 322 strip chart recorder. 

 The vertical force signal was recorded alongside the linear displace- 

 ment signal to obtain the phase relationship between force and motion. 

 Frequency of motion input was measured to within i 0.01 hertz by a 

 tachometer attached to the motor shaft and a Weston Model 1240 Digital 

 Multimeter. 



EXPERIMENTAL PROCEDURE 



The first task in the experimental procedure was to establish the 

 pre-experimental equilibrium configuration of the model mooring line, 

 ar.d it was accomplished as follows: 



1. Anchor Configuration - The lower end of the line was 

 secured to the anchor. In cases where the mooring was 



