Figure 36. Storage of completed large pentagons between individual steps of 

 the fabrication process. 



Annealing of the large pentagons was performed in a walk-in oven. 

 Each pentagon was placed there individually for 24 hours either in a wooden 

 storage box, or in the mold, while the temperature was maintained at 160°F. 

 After the annealing period, the temperature in the oven was slowly reduced 

 to 100°F at which time the pentagon was removed from the oven. 



Quality Control. Since it was predicted prior to the machining and 

 annealing operations that some realignment of the curvature would take 

 place on the full-scale pentagons when residual stresses were relieved, a 

 dimensional check was made on all pentagons after all major steps in their 

 fabrication were completed (Appendix A). Thus, a measurement of the 

 sphericity and thickness was made on all spherical pentagons after annealing, 

 but prior to assembly and bonding into a sphere. The effects of bandsawing, 

 milling, and annealing on the sphericity of the pentagon can be seen by com- 

 paring the sphericity of the first thermoformed spherical sector (Figure 30a) 

 to the sphericity of the annealed pentagon made from that sector (Figure 37). 



62 



