Model Forum / Radio Controlled / Air Models / March 2009

Ted shuffled out of his cave and grunted these great (and sometimes not
so great) words of knowledge:

I have done glassing with water base polyurethane and I also paint quite
a bit using latex paint.

1st, if you want the paint job to last more than 1 - 2 years before it
starts "cracking" the paint needs a stable surface.  Plain wood, or even
wood "sealed/filled" with a talc/dope mix, is not a stable surface.  The
wood will move depending on temperature, humidity, etc.

For a light weight finish I suggest the following:

Apply a thin coat of sanding sealer (I use the commercial stuff - Minwax
is what I have at the present).  When dry, sand off the "fuzzies".  This
prevents the balsa from soaking up too much of the poly and/or water.  I
have had no warping problems on 1/16" contest grade balsa and the one
bird I did that was sheeted with 1/32" balsa had no warping either.

Next, using a water base polyurethane, apply some japanese tissue.  Use
just enough poly to make sure it adheres.  When dry, DO NOT SAND.  Give
it a 2nd coat, but make it a medium coat.

When dry, CAREFULLY sand just to smooth out and bumps/bubbles that may
have formed or been picked up from the air.  It is VERY, VERY easy to
sand right through the poly.

After cleaning the surface with some rubbing alcohol and clean cloths
you are ready to prime and paint.

I have only used Nelson's paints once.  Latex will adhere quite well to
just about any surface I have tried it on.  You can even apply it
without a primer with almost 0 chance of it lifting.

Latex will never achieve a Monokote shine, however it provides a shine
that is slightly better than a pre-painted fabric.

Unless you are running a gasser, you will need to clear coat it.  I have
no idea if the crosslinker Nelson sells will work with regular latex
paint.  It would seem to me that it SHOULD WORK, but a test panel would
be the way to find out.

Hope this helps.

In an effort to get my nephew interested in modeling, we have built several
models similar to yours.  As for finishing, I begin with a coat of shellac
to prevent the balsa from absorbing moisture.  This, I follow with a coat of
"bin" or "KILZ" primer as a grain filler, sanding well.  I"m not familiar
with Nelson's paints, but I use Krylon brand spray paints for the color
coats.  My final coat is of oil base polyurethane varnish, which serves as a
fuel proof coating (the water based version was not fuel proof).  One of my
creations had a foam wing, which worked well.  Here, I started the finishing
with tissue paper glued on with thinned down Elmer's glue and followed with
the finish process, above.  All models have flown well and the foam wing
worked so well that my next airplane will also have a foam wing. Hope this
helps.
Randy Maheux