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Paint damage - help needed (Glider not an RV)

jantar

Member
I need some real help from some knowledge experts in the area of painting. I know we have a few of them here. In addition to building RV-7 (very slow process) I fly a lot including gliders. I just bought one from England and I had it shipped to U.S.

It looks like customs oversees opened the trailer and they did not closed it properly. As a result the top of the vertical stabilizer got scratched. I need to repair it, but I have no idea how to start. I attached a couple of pictures of the damage.


http://img511.imageshack.us/my.php?image=dsc03354gu2.jpg


http://img511.imageshack.us/my.php?image=dsc03354gu2.jpg

The finish on the glider is 2K acrylic paint (German Lesonal). I have the paint and hardener but not the thinner. The manufacturer says the ratios are 5-2-0.5. I hope I can somehow do it without the thinner since they ask to add very little of it. I will also try to match a US thinner (using MSDS data).

Now I do not know what is under the paint. It looks like some kind of base and then there is something behind the base (I think it is polyester). The area in question is about 4-5 inches wide and about ? of an inch high (all scratches). I would like to bring this area to perfect condition.

I am looking for some instructions on how to fix this area.

What materials to use under the new paint so I can even the surface first and create a good base for the 2K acrylic paint? I do not have access to European suppliers so I may have to work with US products.

Then should I mask everything and shoot the area with Sata minijet gun (I have access to this car detailing gun) or should I use fine brash to apply the paint and very fine sand paper to blend it in with undamaged area?

If someone could outline all the steps to take I would appreciate very much.

Thanks a lot.

Andrzej
 
I've owned three gliders. I found good information on the soaring discussion group on Yahoo and the newsgroup "rec.aviation.soaring"

Also, the classifieds section on www.ssa.org has several glider repair people listed.
 
Brush, sand, polish?

Andrzej,
The pictures are not in good focus, but I think the dark portion is the base epoxy fibreglass. Over this is probably a polyester based (maybe urethane) whitish layer that is a sand-able primer, and then the white paint.

Practise on some scrap material, but if you mix up the paint and hardener, let it thicken a little in the jar, and then brush it on... you should be able to sand (400, 600, 1000 grit) the new paint flat before it fully hardens (say within 24 hours). Once it is flat, then high end car paint detailing polishes should get it to shine like the rest of the tail.

For such a small area, this method may be the easiest, and not even need any filler...

gil in Tucson - refinished a 1977 German sailplane - but it was painted with a lacquer (as translated)
 
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Hi Andrzej,

is it a new glider or a used one? I?m asking because the use of acrylic paint on gliders is not too common so far, it?s just coming up slowly for the last few years. Traditionally gliders are finished with "schwabbellack" (german word) which is some kind of white coloured poyester resin. The advantage of the polyester is, that you can paint it directly on the fiberglass, when using acrylic paint you usually have a layer of some kind of filler.

I can?t recognize to much on your picture, it seems like there?s a thick layer of old polyester paint, a thin layer of filler and then the acrylic paint. (Like I said, it?s just a vague guess looking at the pic)

About your question:
with polyester paint the usual reparing procedure is as follows:
1. roughen the area with 320 grit or so
2. spray the polyester resign on
3a. grind the area in practible steps, up to 1000 or 1200 grit
3b. pray that you don?t break through the paint with your grinding (or you have to start over again, you can do that for weeks)
4. polish the area
5. be proud ;-)

As far as I know the procedure with acrylic paint is quite the same, you just have to be more careful because the laquer-layer is much thinner. I?m not too sure about the right grit to roughen before painting, maybe 600 is good enough. If you peel the paint off with the sealing tape you know you?d better chosen a rougher grit :-(

If your area is the top of the stabilizer the main function of the repair is to guard the fiberglass (the dark area in the middle is the fiberglass without protective cover) against moisture and UV-rays. Since the sun doesn?t shine too often through the horizontal stablilizer in your case it?s just about the moisture. Aerodynamics are a bit strange in this area anyway, so you?d have to do a pretty desastrous job to have a negative effect on the performance.

Kind regards,

Mario (thinking about visiting Van?s mid-october to order emphenage and wings)
 
Paint vs. Polyester

Interesting discussion here on paint vs. polyester on DG sailplanes... nicely translated into English...:)

http://www.dg-flugzeugbau.de/pur-lack-e.html

Interesting that the paint option costs around $2500 extra...

gil A.

PS In the US, the yellowing of the polyester mentioned above is virtually non-existent due to the use of Prestec paint from Simtec in CA

PPS DG sailplanes do not seem to be too fussy on brand of urethane paint used....

http://www.dg-flugzeugbau.de/pu-lack-rep-e.rtf
 
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First of all, man, whyd'ya buy a Jantar? Aside from that, I used to work at a glider repairer. If you don't have good spray equipment with the correct nozzle, you may get away with brushing such a small area and a lot of rubbing.

To start with rub down the area ending up with 600 grade, used wet. You must fair all the old paint when rubbing, the new paint is just a covering, any deep scratches need filling. If only a little filling is required a light skim of car filler is OK. When rubbing wet tape on a sheet of paper across the whole width of the VS with maksing tape, all the run off water will the drip off the paper and won't streak down the fin and will be easier to clean up.

Once you have rubbed to 600 grade, then paint. You should also expect to have to rub down once you have painted to get a good finish all the way down to about 1800. Then polish with a hard wax and a 12" dia mop.

The alternative is to send it to your local glider repairer, will probably be a better finish, much less hassle and shouldn't cost that much.

I have seen some people make an awful mess - nothing that affects the airworthiness of the glider, but its easy to screw up.

Pete
 
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