PHASES 3 AND 4— EVALUATION OF DESIGN AND 

 FABRICATION 



Capsule Test Specimens 



The model capsule series consisted of 22 acrylic plastic hulls with 

 nominal 15-inch outside diameter and 14-inch inside diameter. All were 

 made of one-half-inch grade G Plexiglas plate stock that had been cut, 

 thermoformed, and machined into spherical pentagons that subsequently 

 were assembled and bonded with acrylic adhesives. The details of forming, 

 machining, and bonding were discussed under "Fabrication Process." It is 

 important to note here that models no. 1 through 1 1 were bonded with 

 solvent-type adhesive while those numbered 1 1 through 22 were bonded 

 with the self-polymerizing PS-18 cement. 



Three distinctly different types of metallic polar plates were 

 fabricated for the model NEMO series. 



1. Operational polar plates represented faithfully scaled-down 

 hatches and bottom plates proposed for the 120-inch capsule (Figures 19 

 and 57 through 62). All attempts were made here to reproduce all the 

 working parts and details of the end plates that would be found in the 

 120-inch NEMO. The top hatch not only had a hatch that opened, but also 

 the locking mechanism required for it. Since two different hatch designs 

 (Figures 19 and 60) were proposed for the 120-inch capsule, two faithfully 

 scaled-down hatch designs were also fabricated for the model capsules. The 

 bottom plate in the operational end plates (Figure 18) incorporated all the 

 penetrations planned for the large capsule. It was felt that if the operational 

 polar steel inserts performed successfully on models without any difficulties 

 (jamming of hatches, failure of electrical penetrators, pulling out of end 

 plates under hoisting operations, or ripping out of retention flanges under 

 hydrostatic loading), no unforeseen difficulties would be encountered 

 during the operation of the proposed 120-inch NEMO system or any scaled- 

 down version of it (for example, the 66-inch system). 



Some of the models equipped with operational end plates had also 

 internal tie rods connecting the top hatch with the bottom plate. The pur- 

 pose of these pretensioned tie rods was to subject the acrylic plastic capsule 

 to compressive preload while the capsule was out of water. Use of tie rods 

 on some of the models was considered necessary to simulate the 120-inch 

 NEMO that probably would utilize internal tie rods for reduction of tensile 

 stresses in the sphere when it floats on sea surface. For the models, each of 

 the four tie rods was preloaded 25 pounds. Together, they applied sufficient 

 force on the polar plates to counteract the forces that would be exerted 



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