So
you spent months, even years researching the perfect plane for your
“mission”. You looked at fast glass (yuck epoxy fumes), you looked at
“classic fabric” (yuck MEK fumes), you finally picked “traditional
aluminum” (Look it’s non toxic, low up keep, and easy to work with…).
Then
the other shoe dropped and you found out that while yes you could just build it
bare, that’s not really recommended for the northwest climate conditions. So
you were introduced to the great Primer debate!
What
primer to use, how to apply it, terms like mixing, reducing, shooting (who
get’s shot here?), film thickness, solvent tolerance, and a host of other
technical details. Welcome to homebuilding education 101 is the name of the
game.
Most
builders are a very traditional bunch and the products in use to prime aluminum
have been around for a long time. The main problem with them is they all are
based upon toxic solvents. This means they try and kill you, while you are
trying to keep the elements from killing your airplane. What’s a poor
homebuilder to do?
Enter
Aircraft Finishing Systems of Ennis Montana. They recognized that due to
government regulation, personal health and other issues, there was an up and
coming market for environmentally friendly, user friendly paint products. They
have developed a complete line of water bourn paint systems for wood, metal,
fabric, & fiberglass. Originally the primary consumer of these new products
was the large commercial jet painters & manufacturers as they needed a
product that would work great in harsh environment that jet’s live in, but
free them from the large hazmat fees that they had to pay to dispose of the
amount of solvents it takes to paint a large jet. The same chemist that
developed the certified paint system “JetGlow” developed the top coats for
AFS.
Ok,
all that’s neat, but all I need to do is prime the insides of my RV. So on we
go. There are 2 primer products that AFS offers. The first is a 2 part epoxy
primer which sticks very well and works great as a primer, however for this
purpose we don’t specifically want a “primer”. It turns out that the
reason you want a primer is to give a good sticky base to a finish coat and hold
it onto the base material. To do that well a primer has to be porous so the
paint can grip into it nicely and not flake off. In our case we want something
to protect the aluminum from the elements so they have another product. It’s a
1 part primer sealer which adds just a bit of a gloss top coat to it, so you get
both the base primer and a sealed surface the resists corrosion for the life of
the part.
This
1 part primer / sealer is great to use. It goes on easy, cleans up with water,
dries quickly, and provides the corrosion resistance that we need. So, what’s
the steps to put this stuff on you ask? Here you go:
Clean parts with lacquer thinner (removes blue ink, sharpie,
etc) (use MASK)
Wash with dawn dishwashing soap to remove oils etc.
Etch aluminum with AFS Cleaner / Etch (phosphoric acid) (use
MASK)
wash with clean water, Let dry.
Mix up the primer by taking the 1 part primer and diluting
with distilled water until you get 20 seconds in a Dupont M50 viscosity cup.
Pour it through a medium paint filter (from Lowes) into the gun.
Paint with primer sealer. 2 coats is about right for interior
work. It’s a light finish, but enough to protect the surface.
Cleanup with warm water. After you are done with cleanup put
just an ounce of lacquer thinner in the gun and spray it, then leave the
rest in the gun until the next priming session.
So,
you caught me, what’s this aluminum etch you ask? Well the owner of AFS, Paul,
has painted many airplanes over the years and he has had the opportunity to
strip planes for repair and repaint that were painted with most of the “self
etching” primers on the market. What he has found is that in general you never
get a complete even etch of the base metal with a self etching primer. There are
areas that don’t etch for some reason or another and the adhesion of the
primer is weakened. By doing a separate etch step you can ensure a good etch
that will hold the primer on there for good.
What
gun do I use? The basic $40 top load HVLP conversion gun from Harbor Freight.
It’s bone simple, works great and cheap. The great part is that you can use
the cheaper models with the water based products since they don’t tend to gunk
up the insides of the equipment and are easy to clean out.
Shop
temps? I paint everything outside. If the temp is 60deg or higher the paint
flashes off quickly and dries between your 2 coats. Under these conditions you
get a nice smooth application of the primer and everything works great. I have
sprayed in temps as low as 40deg and it works, however the paint won’t flash
dry, so when I take it inside to the heat it does run a bit while the water
evaporates. I put up with it for the few times I need to paint during the winter
since it’s on the inside anyways. It dries to touch in about 5 min. However it takes about 24
hours to harden. If you start handling it before then the primer will scratch
easily. After a few days it’s very hard and won’t come off.
Why
did I choose this product you ask? I am building in an attached garage, and my
family can’t put up with the constant smell of solvents coming from the
airplane factory. I investigated the AFS products while building my wood &
fabric MiniMax as I needed an alternative to the MEK based Stits process. I
found AFS and have been spreading the word ever since.
One
last question always asked… Does MEK wipe it off after curing? With the 1 part
primer / sealer yes MEK will remove it. The 2 part Epoxy won’t come off with
MEK or other solvents once cured. My basic answer is, when was the last time you
flew through a MEK rain shower? This stuff is good for hundreds of hours in a
salt spray bath; I think it will keep my hanger queen RV looking nice for years
to come.
Cost
is $76 per gallon or $20 per quart. You can buy it from a number of dealers. I
got mine from Starduster (the biplane guys) in California.
http://www.starduster.com/netcat/subcat48.htm
(to buy it from starduster)
http://www.aircraftfinishing.com
(for more info direct from the manufacturer)
Aircraft
Finishing Systems
PO
Box 16418
Missoula, MT 59804
1-800-653-7200
Ph: 406-251-1373 or 1374
Fax: 406-251-1375
afs@aircraftfinishing