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Re: [PSUBS-MAILIST] cast dome cost




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

 

Hi Brian,

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.

Alan