WET SUITS 



285 



black concentration, temperature, extension, compression, and the Theological history of the 

 material. Flexing of such material can damage the interfacial bonding of the carbon black par- 

 ticles, resulting in irreversible resistivity changes. Decreases in resistivity with static com- 

 pressional loading would cause hot regions. The negative temperature effect on resistivity 

 would result in less power release whenever the rubber is allowed to cool. All of the afore- 

 mentioned effects could very easily cause power- release variations in excess of the 10-percent 

 maximum power variation requirement. 



Table 40 

 HEAT-RELEASE-SYSTEM REQUIREMENTS 



Electrically conducting rubber was eliminated as a candidate heat-release material be- 

 cause the resistivity cannot be controlled to the degree required in this application. 



Carbon and Graphite Yarns and Fabrics— The relatively new development of carbon and 

 graphite yarns and fabrics presents interesting possibilities for diver's suit heat- release ma- 

 terial. These materials are flexible and strong, have good dimensional stability, and allow 

 more uniform heat release compared to resistance wires. The use of such materials had to be 

 ruled out during the present program because of technological problems associated with pro- 

 viding high stretch, constant resistivity, and ease of fabrication into the insulating material. 



Carbon filaments comprising carbon yarns possess a high modulus of elasticity (about 

 6 X 10^ psi) along with a low elongation at break (about 3.5 percent) and a high tensile strength 

 (about 1.8 X 10 ' psi). Carbon yarns are available in a range of filaments per ply, plies per 

 yarn, and twists. The yarns can be woven or knitted in various configurations with or without 

 other materials such as glass. Yarn and plain woven fabrics are very flexible in bending but 

 very stiff in elongation. 



Knitted fabrics display some stretch, however isotropic, but suffer from filament fatigue 

 due to interfilament abrasion. 



Resistance Wires— Metal alloy resistance wires remained the only candidate for immediate 

 application. Despite their susceptibility to fatigue, copper alloys can be soft-soldered with rel- 

 ative ease. The criteria for selection of the alloy, wire gauge, physical configuration, and 

 electrical circuitry are described in the section of this chapter titled "Resistance Wire 

 Circuitry." 



DESIGN 



Wet Suit and Snag Suit 



The rubber wet suit design consists of a jacket with an attached hood, trousers, mitts, and 

 boots. Figures 108 and 109 show a suit on aquanaut W. Tolbert, USNMDL. General design 

 features include a jacket opening from the breastbone downward, gussets on the wrists, ankles, 



