On 24 Jan 2004 09:45:22 -0800, (Doug)
wrote:

OK. So I put a rock through the bottom of my horizontal stabilizer
landing my Husky up in Wyoming (hunting gophers). I repaired it with
duct tape which got me home, and I patched it with fabric and painted
it. It is about a 12" x 12" repair. My mechanic signed off on the
annual with the repair so it is airworthy. But...it's not cosmetically
so good. Now I think I can buy the fabric, fabric "tape", and manage
to take the piece off and re-fabric it. The part I am not sure of is
the painting. All I know is the final coats of paint will be what is
on the rest of the plane which is a polyurethane (the two part stuff),
PPG Insignia White. But what do I put on top of the fabric and before
the paint (silver etc)?

Has anyone ever painted fabric with a polyurethane? What are the steps
or where do I find out?

Thanks

Yes, I have. It's a bitch.

Put on your new patch. Glue it down good, let it set up overnight and
then heat shrink it. Shoot on enough clear to wet the weave real good
and let it dry. If you shoot too much, it will drip on you and you'll
have to sand it down after it sets up. Shoot one light coat just
enough to fill the weave. Let it set up for an hour or so. Then
shoot on silver to fill the weave as much as you like. I normally
only use about 2 cross coats on the bottom of the surfaces since the
sun never shines on them. The silver coats on the bottom side is more
for filling the weave. On the top surfaces I use at least 3 good
heavy cross coats because it is the silver coat that actually reflects
the ultraviolet that penetrates through the finish coats and destroys
the polyester fabric.

Anyway, after you get through with the silver coat, you paint the
final finish coat. Two-part polyurethane is a bitch because it won't
'tack' like other paint. You spray on a light fog coat and just let
it sit for 45 minutes. If you come back any sooner than that, it will
run on you, especially on a curved surface like a leading edge. Do it
when the wind isn't blowing or you'll have dust in it. Ideally, do it
in a paint booth, but a garage will work. Take a hose and hose out
the floor before you paint to get all the dirt out of there.
Otherwise you'll scuff it up and into your surface.

Don't get in a hurry to fill the fog coat too soon or it will run all
over the damn place. The two part stuff won't set up for a long time
(45 minutes to tack). It doesn't tack real quick and if it's cold,
forget it. Shoot in the first fill coat very thin. Wait another 45
minutes for it to kick off, then hit it again. Get about three cross
coats on it and you are done. Be sure the last coat flows out nicely
or it will look like **** when it cures. Pot life will be fine and is
a couple hours, maybe three. But, I mix up what I need at each shot.

A couple days later you can buff it out with some 1000 grit then some
buffing compound. It will look like glass. I finished my
scrach-built Minimax-1500 with it from Stitts. I hated working with
it but the finish was superb. However, I will never use it again.

I just shot my towncar with base coat-clear coat. Even a moron could
shoot that stuff and make it work out right. You might look into that
process before you take on two part poly-U. Don't they have a base
coat-clear coat process for airplanes? I think they do because a
buddy of mine was shooting that a couple years ago on Comanches he was
rebuilding. I think they have some stuff that Dupont makes that
rivals the flexibility of Emeron (which is not too flexible and cracks
in a few years).

Good luck. I just bought a new paint gun at Harbor Freight from China
that rivals the new $400 guns at the Dupont store. The damn thing
cost me $49 bucks. I shot my Lincoln Towncar with it and it did the
best job I've ever seen with any gun. It's the new high flow, low
pressure type. Nowadays, painting is so easy with all the nice new
materials they have and the new guns. Why would you ever want to
shoot 2-part polyurethane? I would rethink that myself.

Here is a shot of my Minimax in the driveway. Notice how shinny the
finish is.

BWB