Refinishing questions

Just to be technically accurate - Simtec or Prestec are not gel
coats... they are polyester topcoats. Gel coat is formulated as an in-
mold coating, but can be used as a post-mold coating with the addition
of a "air-dry" additive. Linear polyurethane (i.e., two-part mixture)
is a coating formulated for finished spray application. Simtec is
essentially a polyester-based finish coating designed for application
similar to a polyurethane paint, except using polyester chemistry.

So we have:

Gel Coat - Designed as an in-mold coating, but can be modified for
application as a spray finish. Requires significant finish sanding and
polishing.
Topcoats - Designed as a finish coating - Can be urethane or polyester
chemistry. Depending on quality of spray application, finishing can
range from no sanding/polishing to minimal post-finishing required.

Hope this helps.

Bob

I finished a Silent 2 Targa kit this past fall and used the Loehle
Aero Coatings which is a two-part poly formulated for aircraft. To be
sure, there is a tremendous amount of work involved in achieving a
good finish, but the Loehle covering process worked as advertised. I
did use a pricey HVLP spray system that pumped fresh air along with
air for the gun, in deference to the toxicity of this type of
covering. The point of my response here is to say that I did both
sand and polish the two-part poly, to an excellent shine. It was hard
work, but the results are quite satisfying. I'm happy to send a photo
and correspond with anyone who is contemplating using this product.
(I'm not on commission!)

Mike Hostage
Norfolk, VA

I would like to second the comments below.
Having experience with 3 projects, the last one I did in PU. The
results were out standing, even though the spraying was done in a home
made spray both , 11ft x 34ft with a 1HP exhaust fan and fresh
filtered air coming into the spray both. The unsanded final finished
would have been ok too. But the miniscule orange peel effect is just
not exceptable to glider pilot, hence it was sanded and polished too
a nice finished.

The PU I used is the same that is used an all Bombardier Jets.
The sanding primer that goes along with it allow for very easy and
controlled sanding without plugging the sanding pad. I also used the
primer in a squeegee process on the wing. Only when I was happy with
the accuracy of the surface did I spray on the first primer coat,
sanded it and spray a second one and sanded it as well with dye, to
control the sanding process. I also sanded the finished product with a
dye as a guide.

I also had good experience with the Polyester Product.
If you go that route, use a very good tooling gel and mix it with
20%-25% Dura Tech, it transforms the gel coat into a paint like
product.
Most importantly it prevent cracking and protects it from the sun.
I finished 2 gliders like that, they are still flying with all there
glory after 15 years, one was a St.Cirrus. The second one, only has
about 12 years on it. The gel coat is heavier, it needs to be, as it
does not hide as well.
Udo


On Jan 8, 2:11*pm, wrote:
I finished a Silent 2 Targa kit this past fall and used the Loehle
Aero Coatings which is a two-part poly formulated for aircraft. *To be
sure, there is a tremendous amount of work involved in achieving a
good finish, but the Loehle covering process worked as advertised. *I
did use a pricey HVLP spray system that pumped fresh air along with
air for the gun, in deference to the toxicity of this type of
covering. *The point of my response here is to say that I did both
sand and polish the two-part poly, to an excellent shine. *It was hard
work, but the results are quite satisfying. *I'm happy to send a photo
and correspond with anyone who is contemplating using this product.
(I'm not on commission!)

Mike Hostage
Norfolk, VA

On Jan 8, 11:11*am, wrote:
I finished a Silent 2 Targa kit this past fall and used the Loehle
Aero Coatings which is a two-part poly formulated for aircraft. *To be
sure, there is a tremendous amount of work involved in achieving a
good finish, but the Loehle covering process worked as advertised. *I
did use a pricey HVLP spray system that pumped fresh air along with
air for the gun, in deference to the toxicity of this type of
covering. *The point of my response here is to say that I did both
sand and polish the two-part poly, to an excellent shine. *It was hard
work, but the results are quite satisfying. *I'm happy to send a photo
and correspond with anyone who is contemplating using this product.
(I'm not on commission!)

Mike Hostage
Norfolk, VA

Good point, Mike........one can sand and polish PU and AU as long as
enough paint is applied. The auto painters spray on one medium coat
and one flow coat and never want to touch it again. Glider shops spray
on four flow coats and sand off some of the last coat with 600W and
800W (even finer if your a fanatic) then buff it out with liquid
rubbing compound. The PIK came with sanded PU and the Genesis came
with sanded AU. One doesn't need to worry about over-spray or keeping
a the wet-edge, if your going to sand it later. I often spray one side
of a wing, let it dry, turn it over and spray the other side after
touching the blend area with 220D. I also have found a good PE "white"
primer that goes on smooth and doesn't ball up like that damned Simtec
2081.
JJ

Good point, Mike........one can sand and polish PU
and AU as long as
enough paint is applied. The auto painters spray on
one medium coat
and one flow coat and never want to touch it again.
Glider shops spray
on four flow coats and sand off some of the last coat
with 600W and
800W (even finer if your a fanatic) then buff it out
with liquid
rubbing compound. The PIK came with sanded PU and the
Genesis came
with sanded AU. One doesn't need to worry about over-spray
or keeping
a the wet-edge, if your going to sand it later. I often
spray one side
of a wing, let it dry, turn it over and spray the other
side after
touching the blend area with 220D. I also have found
a good PE 'white'
primer that goes on smooth and doesn't ball up like
that damned Simtec
2081.
JJ

When I repainted my ship in PU, I found a product at
the paint store from 3M called 'Guide Coat'. It is
a black powder that comes with a foam pad applicator.
You smear this on the painted surface, wet it down
with water and go at it with 600 - 800 sand paper on
a sanding pad. The Guide Coat shows the valleys between
the orange peel. When it is gone, the surface is smooth.
This stuff works so well and is so easy to apply that
I can highly recommend it to anyone who is trying to
finish sand their ship. I went back and reapplied the
guide coat between the 600 and 800 and it showed the
scratches, so it was also a good indicator of when
to stop with the 800 grit.
I was told to put extra paint on all the edges, which
I did. I still sanded through in spots. You really
have to hit any sharp contour with a LOT of paint,
as it is so easy to sand through. Then treat those
edges like a virgin when you sand. I'm very pleased
with the finished product, and would not hesitate to
do it again.
Brian Bange

There is a phenomenal amount of "reiniventing the wheel" by the glider
community in regards to this subject, and especially in regards to
painting with PU or AU. There is a tremendous amount of information
on a web site called Autobodystore.com. They sell excellent
instructional videos in addition to hosting a great Forum. As you can
see on the forum, all of these paint systems are sanded on a regular
basis by auto refinishers.

As JJ pointed out, keeping a wet edge and overspray are No Big Deal if
you plan on scuffing up the paint edge and knocking the oversray prior
to painting the rest. Alas, not everyone is aware of this -
inlcuding the high quality body shop who shot the K21 wing I spoke
of.

Refinishing a kilo-dollar glider by yourself using techniques and
materials you evolved from trial and error is not where I would get my
first experience in this type of work. Additionally, buying a
refinished glider is a bit of a leap of faith if the finish is less
than 5-ish years old. It is difficult to know how well all of the
prep and reacoating was done in less time.

The web site above is a great resource. Check it out!

Just bought 2 gal of PPG Concept AU (over 3 gal when mixed) Toyota
Super White 90288 and 2 gal of PCL Polyprimer
(white)...........................$1032.00 The control surfaces on the
DG-300 I'm rebuilding have been stripped, filled, sanded with 80g
followed be 220 dry and look good to go for painting. I use a 4 power
magnifying glass with a drop lite to spot anything I missed (old
eyes). The 80 grit scratches will disappear on the second coat and
will insure a good "tooth" is given to the paint which is important
anywhere you will be taping (wing roots).

One thing that hasen't been mentioned is a good water trap. All
compressors produce water and it must be trapped or your paint job
will be pock-marked with thousands of little craters caused when water
droplets form on the spray nozzle. I use a toilet-paper water trap and
it does the job, just replace the roll before each new
job...........................you can even dry out the old filter and
use it for its origional purpose!
Cheep-o, JJ

How about some details about the toilet paper dryer, JJ.



Cheap-o, II.



Larry





"JJ Sinclair" wrote in message
:

Just bought 2 gal of PPG Concept AU (over 3 gal when mixed) Toyota
Super White 90288 and 2 gal of PCL Polyprimer
(white)...........................$1032.00 The control surfaces on the
DG-300 I'm rebuilding have been stripped, filled, sanded with 80g
followed be 220 dry and look good to go for painting. I use a 4 power
magnifying glass with a drop lite to spot anything I missed (old
eyes). The 80 grit scratches will disappear on the second coat and
will insure a good "tooth" is given to the paint which is important
anywhere you will be taping (wing roots).

One thing that hasen't been mentioned is a good water trap. All
compressors produce water and it must be trapped or your paint job
will be pock-marked with thousands of little craters caused when water
droplets form on the spray nozzle. I use a toilet-paper water trap and
it does the job, just replace the roll before each new
job...........................you can even dry out the old filter and
use it for its origional purpose!
Cheep-o, JJ

On Jan 10, 7:32 am, JJ Sinclair wrote:
Just bought 2 gal of PPG Concept AU (over 3 gal when mixed) Toyota
Super White 90288 and 2 gal of PCL Polyprimer
(white)...........................$1032.00 The control surfaces on the
DG-300 I'm rebuilding have been stripped, filled, sanded with 80g
followed be 220 dry and look good to go for painting. I use a 4 power
magnifying glass with a drop lite to spot anything I missed (old
eyes). The 80 grit scratches will disappear on the second coat and
will insure a good "tooth" is given to the paint which is important
anywhere you will be taping (wing roots).

One thing that hasen't been mentioned is a good water trap. All
compressors produce water and it must be trapped or your paint job
will be pock-marked with thousands of little craters caused when water
droplets form on the spray nozzle. I use a toilet-paper water trap and
it does the job, just replace the roll before each new
job...........................you can even dry out the old filter and
use it for its origional purpose!
Cheep-o, JJ

JJ,

What do you use to build up after removing the old gelcoat?

Why AU versus PU?

Phud

On Jan 10, 8:54*am, "01-- Zero One" wrote:
How about some details about the toilet paper dryer, JJ.

Cheap-o, II.

Larry

I've had mine for some time, but I believe I paid $50 bucks for it at
the local automotive paint store. Just roll off a few sheets and it
fits in nice and snug. A compressor working hard will send moist air
right to the spray gun without a chance for it to condense and form as
water inside the holding tank, which one always drains before every
painting episode.
JJ