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IanM[_2_]

wrote:
I am to the stage of casting the keel for my project. Please comment
on my proposed method of making the mold:

--make a male plug out of styrofoam with a thin coat of bondo for
fairing and smoothing.

--coat the plug with half a dozen thin coats of no texture drywall
mud.
Better do some tests on what happens to the set plaster mix when you
heat it to casting temperatures. Its not a refractory and will probably
crumble.

--suspend the coated plug in the mold box and surround with cement.
Sounds like a recipe for either a *large* steam explosion or a bad
casting. Ordinary cement retains too much moisture and will spall
violently in contact with molten metal. If you heat it enough to make
it safe to cast into it will probably crumble.

--burn out the styrofoam and bondo, leaving a smooth female mold for
pouring the lead into.
Doesn't Bondo contain talc as a filler? that *wont* burn out cleanly!
Try wax for fairing.

note: I have never cast with sand and have no desire to learn
another new skill.
Have you *ever* done a large metal casting? If not, stick to a tried and
tested method of keel casting and find some help that knows what they
are doing.

TIA mm

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
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