DESCRIPTION OF MODEL AND PROTOTYPE 



The 1/40- scale model of the NRL Platform was constructed of wood and 

 metal in such a manner as to ensure meeting the weight and mass distri- 

 bution requirements of the full-scale structure. Table 1 presents 

 principal dimensions and dynamic properties of the prototype. The test 

 conditions for the five displacements, which include the drafts, weights, 

 and natural periods at these conditions, are listed in this table. 

 Photographs of the model are shown in Figure 1. 



TEST PROCEBUBJJS AND EQUIPMENT 



Tests were run in regular and irregular waves with the model completely 

 free in all six degrees of freedom. During the tests, the model was allowed 

 to drift in the direction of the wave train. A light nylon line was used 

 to orient the platform in yaw when the model exhibited a tendency to 

 become aligned perpendicular to the wave direction. 



Tests were conducted in regular waves (in head and beam seas) corres- 

 ponding to full-scale wave lengths, X = 200 to 2400 ft; and wave height to 

 wave length ratios h/X = 1/25 to 1/60, They were conducted for most of 

 the displacement conditions; see Table 1. 



Results obtained from tests in regular waves made it necessary to 

 conduct tests in irregular waves corresponding to States 4 and 6 seas so 

 that the motion response of the platform could be determined for a more 

 natural environment. All five displacement conditions were tested for 

 different headings relative to the seas; that is, 0, 45, and 90 deg. 



An aircraft- type gyroscope was installed in the model to measure pitch 

 and roll angles, and Donner accelerometers were used to measure heave, sway, 

 and surge motions. Data were recorded on both paper charts and magnetic 

 tape. Motion pictures were taken during the tests. This film was used in 

 the analysis of the heave data for some of the regular wave tests. 



