Re: No More Sun Bumps ( or finding the neutral zone )


aerofxinc <aerofxinc@...>
 

hello guys,
I haven't read the messages in quite a while and have just caught
myself up on the paint issues. I am a professional aircraft painter
(20 years) and have had my own shop in Fl for seven years; Aero FX. I
have painted my share of composite aircraft and I would be happy to
help anyone with any questions. From what I've read there seems to be
a question about "the black". I'm guessing this is a UV barrier
applied at construction. Depending on the type of paint you are
using, many newer generation (last 10 years) paints have incredible
UV protectors built in. Paint, like the fiberglass on your planes is
a resin. Resins are UV sensitive meaning they can be cured by UV
rays. Many paints become faded and brittle over time due to the
continual curing effect of the sun. Any paint that
says "photochemically sensitive" on the can will require a UV base
under it. If you have paint already and can't tell, place some
uncatalyzed paint on a stirstick and put it in the sun. Most will
cure over time but some designed for aircraft use will not cure until
catalyzed. These are generally polyurethanes like Jet Glo.

It was also mentioned that "gassing" and moisture might be culprits
and both are true. Any materials with a poly base are moisture
magnets. Make sure to keep your booth, hangar, etc. warm and dry. For
gassing, let the product cure out before covering it with something
else. Many hi-build primers are poly based and take a long time to
cure out completely. (30 days @ 70 degrees) Shrinking is also limited
by curing time. That's when you don't see the glass weave after
priming and sanding and then it pops up after you've painted and
flown for a month! Patience is the only answer.

I'm sorry for such a long post but paint is a laboriuos and very
meticulous process if you are to expect good results. I am available
to answer what I can via this discussion.

Mike Gifford

--- In Q-LIST@yahoogroups.com, "Steve" <sham@...> wrote:

The better the prep the better the finish. I am using PPG. Whatever
you use make sure it is all the same product after the two part
primer/sealer.
There are a lot of guys on the list with good tips. Some have used
a paint booth and some have painted outside. I am using my hanger and
building a tent out of visqueen, Go to a auto paint shop and ask for
some advice. There are also some good dvd's and several books on "How
to. "



Good luck Steve Ham



----- Original Message -----
From: Joseph M Snow
To: Q-LIST@yahoogroups.com
Sent: Sunday, February 25, 2007 11:20 PM
Subject: Re: [Q-LIST] No More Sun Bumps ( or finding the neutral
zone )


I hope be painting early April. Would you care to share some
insights?

Joseph

Steve <sham@...> wrote:
You guys need to be careful about "picking at your bumps". I
started doing this 14 months ago and I have been in the process of
COMPLETLY stripping and refinishing my plane. I thought I did a good
job of finishing the first time....but the second time you really
learn how to get the find the PERFECT finish. 40 hours the first time
and 200 the second time. Obsessive compulsive behavior...

Steve Ham

----- Original Message -----
From: Allan Farr
To: Q-LIST@yahoogroups.com
Sent: Sunday, February 25, 2007 5:33 PM
Subject: Re: [Q-LIST] No More Sun Bumps ( or finding the neutral
zone )

Hi. It's funny how these subjects come up. I was picking at some
cracked paint on the coaming of my a/c last night and it just started
flaking off right down to the fibreglass. I am carefully using a
blunt chisel and it's easily coming off. Hope it's not all like that.
Allan F

----- Original Message -----
From: viggenbuilder2
To: Q-LIST@yahoogroups.com
Sent: Monday, 26 February 2007 09:11
Subject: [Q-LIST] No More Sun Bumps ( or finding the neutral
zone )

Hi All,
I had dealt with all the bumps that had been there on the tail
cone
before Xmas, so after the cold spell began to lift back in mid
Jan, I
looked to get things ready to start priming.
I started sanding back, and noticed some more bumps had appeared.
So I
picked at these and bingo, before I knew it I had stripped about
2 sq
feet of paint without any adhesion at all.
So with Mike D's advice ringing in my head, I decided enough was
enough
and set to work to strip it all off the tail cone. This is now
done,
and I have started to refill with epoxy filler and things are at
last
seemingly better. At least I can now see the substrate and know
that
the filler will be good.
Now the interesting part is that all the paint seemed to strip
from a
neutral zone (To pinch a term from Star Trek), which as it came
off in
sheets or strips, the paint was black on the back, but the black
layer
was still on the surface it had come off of. So the black layer
had
separated causing the lack of adherance. Looking at the paint
strips,
the black on the back was firmly adhered to the paint. The black
layer
on the tail cone was also firmly attached. So it was the black
layer
that had "split"! Has anybody else had this happen ? Is this
relate to
damp conditions?
This has caused me to wonder what to do with regard to the
refinishing.
I am using epoxy primer, and two pack poly top coat, which is an
effective UV barrier, so do I need to reapply the black layer
with the
possible further problem of lack of adhesion ? Do you guys still
use
the black UV layer, or have you all moved on from it now ?

Richard Thomson
Tri Q G-BMFN 368 hours old.
richard@...

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