tial (Fig. 5.19), or to be able to open the hatch 

 on the surface. 



The most used fairing material is fiber- 

 glass molded and cut to the desired shape, 

 and bolted or screwed to the exostructure. 

 An aluminum alloy, Alcad 5083, constitutes 

 ALUMINAUT's fairing, while plain sheet 

 metal serves the purpose on small, privately 

 owned submersibles of the SEA OTTER vari- 

 ety. Though fiberglass offers a wider variety 

 of advantages than metal, e.g., non-corro- 

 sive, greater formability, the process of de- 

 signing and fabricating a mold is costly, and, 

 for one-of-a-kind vehicles, may be excessively 

 expensive where sheet metal serves almost 

 as well. In vehicles where an echo sounder 

 transducer is located within the fairing, it is 

 necessary to cut out the fiberglass portion 

 the transducer will insonify and install a 

 rubber-based section to serve as an "acoustic 

 window." 



The overall design of the fairing is an 

 individual matter. Obviously it must be so 

 configured as to permit the submersible to be 



handled, especially during launch and re- 

 trieval. It should also permit easy removal 

 for access to external components. For exam- 

 ple, DEEPSTAR 4000's fairing (Fig. 5.20a) is 

 attached in sections sufficiently small to al- 

 low hand-removal and access to any compo- 

 nent. On the other hand, the fairing on the 

 Navy's DSRV (Fig. 5.20b) may be removed, 

 but requires a lifting device which may be 

 quite difficult to manage in high seas. 



PRESSURE TESTING 



When the pressure hull is completed, and 

 thru-hull penetrators are in place or 

 blanked, it is customary to subject the struc- 

 ture to pressure tests. For submersibles of 

 the BEN FRANKLIN variety, there are no 

 options on the choice of test tanks; only the 

 ocean is sufficiently large. Hence, pressure 

 testing of the hull must be deferred until the 

 vehicle is in actual service. For smaller vehi- 

 cles, e.g., up to ALVIN-size, there are several 

 test facilities throughout the country where 



Fig. 5.19 STAR III approaching an undereiraler structure off Nassau, Bahamas. (Gen. Dyn. Corp.) 



266 



