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Re: PVC

A little observation about PVC.  It has a compressive strength of about
10,000psi.  This is about 1/10th that of the steel I understand is commmonly
used in subs.  It is maybe half as expensive as steel on a volume basis! and it
is about 1/7th as heavy.  So to make a pressure hull it would cost maybe 5 times
as much as the same steel hull and weigh at least 43% more (and this doesn't
even account for the increased diameter)!  Also, have you ever tried to
precisely machine large plastic parts (for those perfect tongue and groove
joints)?  It is a very tricky task at best, steel is much easier to work with
(and repair).  I am working on some 10" PVC pipe for the main hull of a diver
propulsion unit and it is bad enough.  I can't even imagine how difficult a 7'
diameter part would be.
So let me know how it works out, eh!
Dick


F Phillips wrote:

> Hi Vance and group,  Regarding PVC crushing at 400 ft, I wonder what company
> draws huge PVC pipes in an extrusion method could just set their tooling for
> a 6", 9" 12" wall thickness and run a length of 20 ft or so at a 7 ft inside
> diameter.  Then chem weld twin conical or hemispherical end caps at the same
> 12" thinkness that fit it perfect compression tongue and grove joints and
> also chem welded view ports.  Seems as though the crush depth would be good,
> hull never rusts, easy to drill thru hull holes with extra PVC backing at
> those thru hulls.
>
> Then just use a very thick clear lexan viewing port(s) attached on the
> outside of the PVC hull with a 2 in overlap on the outside and sealed via a
> little o-ring groove and some mere location stainless small dia bolts.  The
> same end cap design could be used for a short tower with huge oversized PVC
> hinges and stainless locks for a nice pilot access hatch also with viewing
> ports.
>
> Internal PVC bulkheads and stringers could also be chem welded as required
> to give you a 100% margin over your reqired crush depth.  All equipment,
> ballast, motors, air and communications can be in smaller twin isolated
> exterior pods that have the diving planes, propellers, etc.  Does this make
> any sense.  Have at me men.
> I'm not thinned skinned.  F. Phillips
>
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