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Thanks Jay
I was playing round last week with the idea of roto
casting a dome by joining two thin
blown domes at the flanges, squirting acrylic resin
in through a hole in the flange & rotating it
on the horizontal & vertical axis
similtaneously. This would invlove stopping when the resin had set,
squirting in more resin & starting & slowly building up to the desired
thickness.
Its a lot easier setting a thin section than a
thick. I rotated vynil ester in a hemisphere attached to a
drill
& found it removed the bubbles caused by
mixing, wich is a plus. Didn't need much speed either.
I wasn't going to persue this till after I had
built my sub, but while we're on the subject, has anyone got knowlege
/ thoughts on this that will save me the
bother.
Alan
----- Original Message -----
Sent: Tuesday, September 01, 2009 10:39
AM
Subject: RE: [PSUBS-MAILIST] cast dome
cost
Alan
& Brian,
Our
resident expert, Greg Cottrell gave an excellent presentation on this subject
at the Raystown PSUB Conference a few years ago. He has accomplished
some remarkable things with acrylics and noted that casting a dome was not a
simple matter, fraught with opportunities for failure. He described
three methods if my memory serves me right. From his presentations it
was the audience’s opinion that it should be left to professionals when it
comes to casting a dome. Depending on the casting, the heat generated if
not compensated for, could result in an intense fire in the
mold.
R/Jay
Resepectfully,
Jay K.
Jeffries
Andros
Is., Bahamas
Save the
whales, collect the whole set.
From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Alan
James
Sent: Monday, August 31, 2009 6:10 PM
To:
personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] cast
dome cost
Brent & I have
been looking at this off site recently.
I spent a lot of
time looking for an unpolemerized methyl methacrylate with a
catalyst.
wich is the raw
materials they start with to make the sheets. Eventually I found some
with a
plastics guy who has blown domes for me.
He bought a drum of
it & said it was very hard to work with. With the domes there is a very
controlled heating process
in pressurized
ovens. Out gassing in the setting process forms bubbles that attach to the
sides of the molds
and are hard
to remove. Hugh went over to Stanley plastics & saw the process. He
said they over compensate
the dimentions to
allow for the outer faces to be taken back beyond the " bubble layer
".
I've mucked around
with polyester casting resin for a while & large castings are a bit of an
art. They can take days to set,
& there is a
relationship between temperature & amount of catalyst. If you get it wrong
the mold cracks or the materials too soft.
Hope someone else
comments, it would be interesting to learn more.
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