RE: [PSUBS-MAILIST] Cement and propane tanks ?

["Gregory B. Snyder" <snyder@mnrad.com>]

Thanks Ian -
I take it from Mike's response that he isn't impressed with the idea...
Greg

-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Ian
Roxborough
Sent: Tuesday, August 17, 2004 9:00 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Cement and propane tanks ?



Hi,

from very basic research I've done on this (not with propane tanks) a
potentionally big issue would be shrinkage as the cement sets and what
would it mean for the out hull (an air gap?) and inner hull (would it
get crushed, or an air gap, or nothing?).  Could any gaps be back
filled, and how much would it cost to make sure it's got no gaps left?

In the end I drew the conclusion that it's probably better to build a
mold for the cement and build a cement only hull rather than attempting
a multi-material hull.  Although I'd be interested in hearing about any
tests if somebody was to persue that method.

Also, cement isn't that much heavier than water, so it won't add a lot
weight itself, that would have to come from lead.

On the subject of multi-material hulls, I do think about steel and
GRP/fiberglass might be worth following up on.  If I ever live by some
deep water and own a boat I would probably try some small tests samples
of GRP steel combo pressure hulls.

Ian.

On Tue, 17 Aug 2004 20:33:02 -0500
"Gregory B. Snyder" <snyder@mnrad.com> wrote:

> Hi guys -
> I do not recall if this has been discussed before, although I know
that
> both of these items have been discussed individually.
> Would it be reasonable to take a large propane tank (outer hull), cut
> off the one end at the curve - insert another propane tank (inner
Hull)
> and create a steel/rebar structure to keep it centered in the first
> tank.  Cut the holes and weld in the view ports, conning tower - etc,
> place the through hull connector pipes, then reweld the outer hull cap
> (sealing the outer hull), stand the whole thing on end and fill the
gap
> between the two hulls with cement?
> Cement would add the weight, and should be crush resistant.
> Propane tank lovers would get the benefit of saying that they used a
> propane tank, 
> and it might be ultimately cheaper than the other solutions.
> Thoughts on this?
> THanks-
> Greg
>  
> 


-- 



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