micro-balloons etc

[patterndude at attbi.com]

Verne is probably right.  Microballoons will make the epoxy lighter and more 
sandable, but when mixed enough to make a paste, weaker.  Before you get too 
worried, the weakness is relative.  if the epoxy is 10x stronger than you 
need, than an little weakness is a good tradeoff for lightness and sandability.

If it's strength you need, then use cabosil.  It is not easy to sand because 
it is precipitated silica (rocks), it is not lighter.  It's good property is 
to increast the thixotropic index (turn it into a less runny liquid) with 
minimal damage to the strength.  Not a good idea for fillets, in my opinion.

--Lance
> Tom,
> Sounds like cabosil. If you touch it dry, it'll have a very weird feeling to
> it. Can't describe it but it'll be kind of a dry feeling you've never felt
> before. As far as mixing it, thin finishing resin works much better than the
> thicker construction stuff. Cabosil and finishing resin is the industry
> standard for putting fillets in the corners of a layup so the cloth will
> handle the radius. The common term for a mixture of resin and cabosil is
> paste. When mixing it, test it by scooping up a glob of the stuff on a
> popsicle stick. If it doesn't flow with gravity, you're just about right.
> Fillets made with paste that's too thick almost always have air trapped
> underneath that will be a crater to fill in the finished product. Hope this
> helps. BTW, cabosil is GREAT stuff. I haven't bothered with microballoons
> since I found out about it. It IS a monster to sand, though.
> 
> Verne
> 
> 
> ----- Original Message -----
> From: "Koenig, Tom" <Tom.Koenig at actewagl.com.au>
> To: "'Discussion'" <discussion at nsrca.org>
> Sent: Sunday, May 18, 2003 8:40 PM
> Subject: micro-balloons etc
> 
> 
> >
> > Help.....please
> >
> > Gray, Matt, Lance.... anyone.
> >
> > I have a huge tub at home that is a white fluffy powder, which weighs
> > nothing...( Nooooo....not that sort of powder<VBG>) I dont know wether it
> is
> > micro balloons or cabosil, or whatever.
> > When I mix it with epoxy it sort of forms the white stuff which you
> commonly
> > see in the corners of layups ( to help lay the glass), but it isnt quite
> the
> > same, it seems to be more translucent.
> > Am I not mixing properly? It seems that when I keep adding more powder it
> > becomes too dry and unworkable. It also doesn't seem that light which
> makes
> > me think it isnt micro balloons. Is it the resin I'm using ( LC 3600)?
> >
> > Sorry for the moronic question...but how can I tell what I've got? Also
> what
> > exactly is used as the fillers in the ZN kits, Bollys etc ? Do they use a
> > thixotropic additive in the resin when they form the fillets etc.
> >
> > Thanks guys
> >
> > Tom
> >
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