Figure 40. Typical sample of a properly solvent-bonded joint on a 15-inch-diameter 

 capsule model. 



Although the procedure developed for solvent bonding model capsules 

 produced satisfactory joints, grave doubts existed whether this technique would 

 produce satisfactory results for the large-scale capsule. It appeared that in order 

 to solvent bond the large pentagons, the dimensional control of individual pen- 

 tagons would have to be so strict as to make the fabrication cost unacceptable. 

 Also, the cost of a clamping system for placing the solvent-bonded joints in a 

 large sphere under uniform compression would, in all probability, be higher 

 than the cost of fabrication up to the bonding stage. In view of these problems, 

 it was decided to find a different joint bonding technique that, although being 

 as costly as the solvent bonding technique for the models, would be distinctly 

 less for the large-scale capsule. 



The alternate bonding technique investigated was the cast-in-place 

 adhesive. The prime characteristics of this bonding technique are: (1 ) the 

 pieces to be bonded are maintained in a fixed relationship to each other by 

 spacers that do not permit the pieces to contact each other, (2) the space 

 between the acrylic plastic members is made fluid tight by placement of 

 adhesive tapes over both sides of the space, (3) the adhesive is poured into 

 the taped-over space by means of a funnel or squeeze bottle, and (4) filling 

 the joint space is done in more than one pour, with the mechanical spacer 

 being removed from the joint after the first increment of adhesive-filled joint 

 has set, but before the succeeding increment of adhesive covers it (Figure 42). 



67 



