[NSRCA-discussion] Epoxy Question

[Martin X. Moleski, SJ]

vicenterc at comcast.net wrote:

 >     From: John Gayer <jgghome at comcast.net>

 >     Sounds as if there is enough data already to stop thinning your
 >     epoxy with alcohol. Just heat it gently with a heat gun and brush it
 >     on. Just as easy to brush on a thin coat, no loss of strength,
 >     faster cure....where's the downside?

> Well, I think we got the same conclusion long time ago.  I don't think 
> there is a downside.  It requires that you move faster or have a pair of 
> additional hands.  Can you put it in a bath of hot water?

I think that the epoxy can't tell where the heat is coming
from (hot water bath; hot air gun; microwave [?!]; the
pieces to be joined or coated; a curing oven).  Gray has
taught us that epoxy cures through a chemical reaction.
Each kind of epoxy will have its own characteristic
response to being heated while being mixed, while
being applied, or while curing.  Our job is to learn
what works in our own workshop.

I have some stuff from a bagging company that is
intrinsically thinner than epoxy that is meant for
making joints.  I know I can get a longer pot life with
it by mixing it in a larger, flatter pot that lets the
heat from the reaction warm more air and keep the mix
itself a little cooler.  I still need to mix the right
amount that I know I can get through before it becomes
impossible to spread evenly and thinly.

Every gluing system has tradeoffs.  I'd like to try
polyurethane on wing skins some day, but I know from
experience that it's hard to keep PU glues from setting
in the bottle once it is opened.  The beauty of epoxy
systems is that they have a long shelf life between
projects.

So you pays your money and you makes your choices.

				Marty