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Re: [PSUBS-MAILIST] In my search for a simple, cheap pressure hull ...

Hey Guys,
   I worked in the fiberglass industry for some time
as a plant foreman in a storm shelter manufacturing
facility. As a general rule, one can expect the tinsel
strength of standard composites to be 15 times that of
concrete, and 3 times that of mild steel. In
compression, the advantage is less. About 1:1 with
mild steel, and 4-5:1 over concrete. This is by
WEIGHT, not by thickness. The chance of making a
mistake in fabricating here, for anyone not VERY good
with these materials, is quite high. It is a hard
media to work with even if you are experienced with
it. Steel is SO much more forgiving. Also, composites
that are damaged, even minor amounts, are virtually
impossible to repair without leaving an uneven flex
and compression area in the structure. The problem
with that, I hope, is obvious. I for one think metals,
at least for p-subs, is the cheapest and easiest way
to go. Maintenance and monitoring are also much
simpler. One needs ultrasound or MRI types of NDT rigs
to inspect composites for integrity. 

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