exists of removing an excessive amount of acrylic plastic versus having some 

 roughness around joint mismatches, it is better to leave that roughness. Also, 

 extreme care must be exercised not to exert so much pressure on the buffing 

 wheel that local heating and galling of the acrylic plastic occurs. Since this 

 care was not exercised at all times during buffing of the large-scale capsule, 

 some surface areas on the acrylic plastic hull were locally scuffed. 



Dimensional Inspection. At the completion of fabrication, each 

 individual scale model was checked for its sphericity and diameter. This 

 dimensional check together with previously conducted sphericity and thick- 

 ness measurements of individual pentagons constituted the complete record 

 for an individual NEMO model. Since the paperwork representing the 

 complete dimensional record of each model NEMO is quite voluminous, 

 only the dimensional record for one typical NEMO model has been included 

 in this report (Appendix C). This dimensional record is briefly summarized 

 here: 



NEMO Model 18 Nominal 



Hull Thickness (in.) 

 Internal Radius (in.) 

 Outside Diameter (in.) 



These deviations from the nominal can be considered representative for all 

 the other scale models with one or two exceptions. One of the models, NEMO 

 no. 1, had sphericity deviations considerably in excess of the representative 

 values enumerated above. The internal sphericity and thickness of this model 

 varied from 7.200 to 6.875 inches and from 0.495 to 0.450 inch, respectively. 

 Although those sphericity deviations were considered unacceptable ( 1 ,000% 

 larger than the permissible deviation of 0.03t) the NEMO Model no. 1 was 

 used in the test program to determine the effect of excessive sphericity devia- 

 tions on the collapse pressure of acrylic plastic hulls under long-term hydrostatic 

 loading. 



The measurement of thickness and sphericity on individual pentagons 

 was performed utilizing micrometers and a dial gage mounted in a vertical mill. 

 Upon assembly of pentagons into a sphere, the sphericity was measured with a 

 female template and feeler gage while the diameter was measured with dial- 

 indicator-equipped calipers. 



0.515-0.465 



0.500 



7.028-6.994 



7.000 



15.040-14.995 



15.000 



81 



