On Thu, 12 Jul 2007 03:13:56 GMT, Paul Oman
wrote:


Boy this thread is getting a bit nasty. Calm down guys!

One more point I want to make that might help cool things down a bit.....

wood expands and contracts with moisture

things like epoxy, fiberglass, paint, and just about all other things,
expand and contract with temperature.
So - wood and the epoxy on it don't expand and contract together...
This can cause some of the issues brought up here. Always best to
complete seal the wood with epoxy, not just one side. Also, plywood,
because of the way it is made etc. expands and contracts very little (at
least compared to 'regular' wood).


Also epoxies stick really well to most materials and is often considered
sort of a universal primer.

polyester resin (fiberglass resin) doesn't bond well (or long) to
anything but itself (I and my customers report polyester resin to wood
bond failures after a few years maybe 10 years at best). This is why
fiberglass boats are generally 100% fiberglass and not half fiberglass
and half wood (as might/could be the case with epoxy resin). So.... you
can repair fiberglass with epoxy but fixing epoxy with fiberglass resin
in not recommend (but many folks do and they get away with it).

Epoxy resins just have all around better physical properties than
polyester resin, but usually cost more.

I vaguely recall seeing water absorption numbers for epoxy at something
like 1/10 of a percent. Don't ask me where or how I got that number,
just something that is floating adrift in my head.


cheers everyone

paul oman
progressive epoxy polymers


Ha! Maybe a chance to get me some free information here =;-}

If you were planning on building a composite potable water tank what
would you use to line/paint the inside?

I have had several boats that had integral tanks. In one case the tank
appeared to have been painted inside with polyester resin and a second
boat that appeared to have gel coat on the inside.

I am considering building a spare water tank out of plywood, lined and
taped with glass, and do not have a big selection of epoxy available
here. My thoughts were to go ahead and paint it inside with several
coats of epoxy, let it cure for several weeks and then flush it with
several/many changes of water.

If some form of special, "This stuff is for lining water tanks" resin
was available I'd use it but as far as I can discover there is
nothing like that available in the country.

Thanks for any information you can give me.





Bruce in Bangkok
(brucepaigeatgmaildotcom)

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