1s a design area which Is not well understood although the subject has 

 been under study for many years. Analytic models of the mooring line 

 dynamics problem exist, but data for model validation obtained under 

 controlled conditions are scarce. 



In various proposed data buoy system designs, synthetic lines are 

 being considered for deep moorings to reduce the weight for easier hand- 

 ling and to lower mooring line tensions. To minimize the required length 

 of mooring line, short, slack, single-point mooring concepts are being 

 considered. To evaluate and improve the hydrodynamic performance of 

 these systems under development, the David W. Taylor Naval Ship Research 

 and Development Center (DTNSRDC) was tasked by NGAA to conduct an exper- 

 imental program to provide a data base for use in mooring line dynamics 

 studies. 



The experimental program had the following three specific objectives: 



1. To provide data on dynamic loads in model mooring 

 lines as functions of frequency to the National Data 

 Buoy Program for validation of analytic methods 

 being developed to predict the dynamics of mooring 

 lines; 



2. To determine the ranges over which the dynamic responses 

 are linear; and 



3. To observe any non- linear effects, such as out-of-plane 

 motions. 



The experiments were conducted in the Circulating Water Channel at DTNSRDC. 

 Five material samples were selected to provide a broad range of mooring 

 line physical characteristics. The experimental mooring lines were varied 

 in scope and subjected to forced vertical harmonic oscillation applied at 

 the upper end to simulate the vertical motion of a buoy. Other variables 

 were current speed and frequency of oscillation. Horizontal and vertical 

 comDonents of tension were measured at the upper end of the mooring line, 

 and observations of the response motions were made. 



