From: "Rick and Marcia" <empiricus@telus.net>
Reply-To:
personal_submersibles@psubs.org
To:
<personal_submersibles@psubs.org>
CC:
"\"Rick & Marcia\"" <empiricus@telus.net>
Subject:
Re: [PSUBS-MAILIST] Hull material
Date: Thu, 29 Dec 2005
01:50:35 -0800
Hi, Robert - I don't think we've "met".
Welcome :-)
I get the impression, and please correct me if
I'm off the mark, that you'd like to maintain the freedom of designing a sub
with compound curvature, possibly avoiding the "tin can" look (no offense
to the tin can guys!!!).
One option, and this is in support of the steel
crowd, is to build your pressure hull using the basic engineered-to-death
shapes another member suggested. Cylinders, end caps, plate,
etc. Use the composite to form an ambient pressure fairwater
around your "tin can" in any shape you want that's hopefully
hydrodynamic. You maintain the safety factor of proven engineering AND
pull off the artsy side.
Second option would be to, as Carsten suggests,
use ferrocement. It too is proven. Concrete is easy to work with
and very tough. With a tiny cockpit as you mentioned I'm not sure your
hull thickness would compensate for the buoyancy inherent due to the
cockpit's volume. You may be a little on the heavy side for a hull
going to 300 feet. You do not want this unless you are prepared to
design in permanently sealed hard tanks as extra buoyancy or to use
syntactic foam (expensive). A way around it would be to
simply design a more voluminous cabin (to a point).
Personally I love concrete but I'd test a full
sized hull to crush depth. Too many unknowns. Try to find the
paper written by David A. Smith called "Feasibility Study for Concrete
Submarine". The research was carried out at UC Berkeley (contract
number N66001-74-C-0408, Naval Undersea Center).
The nice thing about concrete is the potential
for compound-curved pressure hulls. One hull period.
Third option would be to design a composite
ambient pressure hull but that doesn't address your wish for a deeper diving
sub. Strictly scuba and you need to have your C-card for that whether
you're wet or dry. I wouldn't even begin to consider depths beyond
no-decompression scuba limits because of the gases involved in the
breathing mixes. An emergency ascent will kill or
maim you.
Fourth option is to build the bottom or base of
your sub in steel (no flat plates here) and use a plexiglass bubble for the
top half of your pressure hull, vis-a-vis, . You can't beat the
visibility and even a large half dome isn't, um, too expensive (see below).
Consider, as well, reducing your depth needs
to, say, less than 150 feet. That gives you a LOT more room to mess
around with plexi domes, costs, etc.
Warm regards,
Rick Lucertini
Vancouver