Alan,
I really hate to throw
cold water on someone's dream boat, but please reconsider this path. There
is room for lots of innovation yet in sub design, but there are a few
fundamentals that one really cannot escape with any confidence. What
worries me is not so much the calculated strength of the hull, but the degree of
confidence in that number. Use of non-standard geometries or materials
introduces uncertainty in both calculations and fabrication. Consider just the
fabrication aspect. In a conventional cylinder, if the roundness is off by just
a tiny percentage the depth rating falls off out of all proportion to the
fabrication variance. Greg recently mentioned something very similar having
to do with acrylic windows that were not correctly annealed -- their
performance went from many hundreds of feet to 50 feet. Composites can be
strong, for sure, but my understanding is that their strength varies
tremendously with the skill of the person using them. There have been composite
hulls, such as those made by Hawkes, but they were not hand laid.
Composites are wonderful
for things that want to fly through the air or float on the surface, but a sub
is the only type of vehicle I can think of where weight is actually an
advantage. You'll still have plenty of opportunity to use them on non-structural
components like fairings and soft tanks. But if you make a light pressure
hull, you'll end up with lots of lead on board to make it
sink.
Thanks,
Alec
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Hi, Frank , Glenn & Vance.
My sub will be about 25" in diameter in a semi spherical shape around my
upper body
& transitions down to about 14" around my legs. The
hulls about 6 ft long with external battery
pods out the back. So it's not much more than a kayak. My program
shows that the shell
only needs to be .5" thick at the most on the 25" dimension to get a crush
depth of over 1000ft.
Some reinforcement will need to be 2" thick. I only need to go to 250 ft to
match my dome.
So for my design in epoxy & fiberglass ( not wound carbon fiber) it
doesn't seem too prohibitively expensive.
I agree it would be stupid to use it for a big sub, but how many kayaks are
made out of steel?
Alan
----- Original Message -----
Sent: Wednesday, June 02, 2010 4:50
AM
Subject: Re: [PSUBS-MAILIST] Fiberglass
hulls
I like some of the benefits of a fiberglass hull like no rust and the
ability to make complex shapes. As for the cost though, It's not cheap. The
fiberglass fairings and dive planes I made cost almost a thousand dollars
just in material. They are a minimum of 3/8 inch thick with some small areas
up to 1-1/2 inch. If a guy was to be making a 5 inch thick pressure hull from
fiberglass, I can't imagine what the cost will be. ( LOTS $$$ )
Now I know there are places to get FRP materials cheaper than where I
went but the cost savings isn't all that much. It's not only the resin and
cloth. There's all kinds of stuff needed. It's the little things that add up.
Brushes, buckets, acetone, tools, tape, glue, paints, mold materials, dyes,
mold release, sand paper, rasps, and that list just goes on and on. And
another note.....Fiberglass dust will EAT an electric motor like a grinder,
sander, saw, or whatever tool you've got. Keep the dust out of the motor with
masking tape and be careful not to overheat the tool.
Frank D.