PVC, PLASTIC COKE BOTTELS & RUBBER SUBS???

[Phil Nuytten <72020.572@compuserve.com>]

Hi, Jon:
        With regard to the external stiffening 'bangles' . . I believe the
failure mode of a typical metal hull is quite different from the ulta-thin
wall failure of a vacuum-cleaner hose  or like; it's understandable that a
person would assume that a cylindrical hull would act kind of like a bent
soda-straw - flat at the 'bend' and wide at the flattened part . .and
sometimes they do. Sometimes, though, they fold in on themselves like the
pleated rubber bags found on the backs of bathroom doors ( Rubber again!
what's with this Newtoid??) . .naw, that's not a good analogy . .looks more
like a cornish pasty ( maybe they only have these in the UK??). Anyhow, the
'pleat' or rupture point is not across the hull, but longways, and folds in
towards the interior. If the material is relatively rigid, like heat
treated 6061-T aluminum, the failure mode is, sometimes, to blow a whole
segment into the cabin without the hull changing shape at all!! On the
NEWTSUIT  torso for example, we ran it up to 5 times it's working depth and
a piece the size of the palm of your hand blew in ( in the high stress area
where the head joins the body - similiar to the transition from vertical
trunk to hull on a sub, but not as bad!) and I mean blew in  . .it was no
longer attached to the rest of the torso! This is an unusual failure - but
how do you know precisely how your hull will act in a full blown, all-out,
failure!!
        With regard to the ' rubber subs' . . quick history lesson:  latex
or 'gum rubber' is found in the sap of many plants besides the well-know
'rubber trees'  (Hevea brasiliensis - originally from South America but
extensively cultivated in India) the milkweed plant , - wide-spread in
North America - for instance. It's use as a waterproofing agent was
historic, but the material became, well, 'gummy' from heat, ulta-violet
rays, age,petroleum products, etc. In 1839, Charles Goodyear found that
kneading a small quantity of sulpher into the natural gum, and heating it,
produced greatly improved characteristics . .vulcanizing . .this much you
probably already knew or had been taught and filed it in the
to-be-forgotten file, along with Eli Whitney, Fulton, and the other guys!! 
But listen up . .here's new stuff: at relatively modest sulpher levels,
(but much higher than 'soft' rubber) the product was called 'Vulcanite' a
hard rubber used for knife handles, combs, canes ( yeah, CANES! - so much
for the rubber crutch jokes!) etc. Goodyear's premier hard rubber product
was called 'Ebonite'  and contained up to 50% sulpher - at that
concentration, it was a rubber so rigid, so hard, it could shatter like
glass! Like glass, it was extremely strong in compression- but unlike
glass, it did not require very high temperatures to form . .in other words,
at the proper supher concentration, a very interesting candidate  for
submarine hulls!! That's the kind of thing I meant when I urged the
psubbers to at least consider other designs, other materials, other worlds.

        And that's exactly what you were doing, Jon, considering something
different than the usual, the conventional, the 'stale' . .and here I am
acting like a Dork, saying 'Jeez! don't eat that, Aylmer, that aint soup .
.. excuse me, please. Lateral thinking is critical for technological
progress - 'Banglegate' is valid until shown to be otherwise. ( I'm
starting to sound like Ric . .the 'zen of the sliding stiffener' - ) Fun
stuff, though!!

Regards
Phil Nuytten