Guy Prevost
Well Known Member
Well, the painting is progressing and thanks to support and advice from Cytoxin (William) (see this RivetBangers thread http://www.rivetbangers.com/forums/viewtopic.php?t=2566&start=60 ) I no longer feel like I?ve ruined my airplane. First of all, the sanding and buffing advice given by William in the post linked above works well. I?ve saved parts I thought I was going to have to repaint for the 4th time. I?m also learning to spray. I thought I already knew how, but the parts below are much better than the early stuff, and they haven?t been buffed either!
At this point I have 46 of the 51 painted parts on my airplane done. The remaining parts are big?the fuse, wings, and wingtips. 10 of my parts have a 3 color design. The fuse is the only one of those remaining.
Here?s my process. For equipment, I?m using a DevillBiss HVLP Finish Line II (my old woodworking gun) to spray DX1791. I?m using a Harbor Freight HVLP gun to spray K36 and DPLF epoxy primers. I?m using a DevillBiss Millennium gun to spray the topcoats. All products are PPG, with the topcoat being their DCC Concept single stage paint.
For aluminum I sand with 220 grit and a DA sander. I then wash with soap and water and dry, using clean, new rags. I then flood with DX330 cleaner (again using new rags), and dry with a separate rag. After any remaining solvent flashes off, I do one more wipe with a clean rag dampened with DX330 cleaner. I then don the respirator and mix some DX1791 self etching primer. Immediately prior to spraying I give the parts a gentle wipe with a tack rag. I fog the DX1791 on lightly, clean the gun and mix up some epoxy primer (DPLF). After waiting a few minutes for the self etching primer to flash off, I spray the epoxy. The epoxy can be recoated anytime within 1 week without any additional steps. If I?m satisfied with the parts after spraying the epoxy, I?ll spray my two topcoats immediately after the 20 minute flash time (note: flash time is longer with DPLF if you use the 401 catalyst instead of the 402). If I see a problem, I?ll let the epoxy primer dry overnight and then address the issues.
For fiberglass, I did 3 initial passes with very runny micro squeegeed into the weave. I sanded between each coat with a DA sander. I then shot some K36 mixed as a primer surfacer. I fixed any flaws, sanded, fixed more flaws, etc. Eventually I mixed some K36 as a sealer (I prefer K36 to K38 due to its versatility) and shot 1 coat to even out all of the different spots from fixing flaws. 2 topcoats of DCC were applied immediately.
Lots of people skip the epoxy primer or sealer steps with good success. They also usually wind up shooting 3 topcoats to get the look they want. I figured I might as well make one of those layers a primer and help adhesion out a bit. Although people do it all of the time, PPG specifically says not to spray CONCEPT directly over the DX1791 self etching primer.
Things I?ve learned:
1. Don?t wet the floor when working with Urethane paints. I?ve always done this with lacquer in order to keep dust down. Urethane paints however, are precipitation cured. The increased humidity causes the paint to skin over more quickly, causing orange peel and solvent pop. Most of my (numerous) problems went away once I figured this out. According to DevillBiss, the most common cause of paint problems with modern paints is people wetting down the floors prior to spraying. Guilty.
2. You really do need a good filter in your air lines (like motorguard M60) even if you live in the desert and have a water filter in your lines already.
3. Cleanliness is more important than everything else combined.
4. Most problems can be fixed. I almost repainted my elevators and HS for a 4th time before conversations with those that have been there before convinced me to sand with 2000 grit and buff. Wow! That really works! Thanks again to William for that advice in the thread listed above.
5. You can never have enough light. I?ve got 5ea 4ft double fluorescent fixtures and 3600Watts of Halogen lights in my 1 car garage sized booth. They?re not really enough. Incidentally the white paint is very hard to shoot because it doesn?t show texture well in the booth. The red paint has been easy; I can see the texture of the paint I?m shooting immediately.
Anyway?I?ve still got lots of paint to shoot, but it?s going better. Colors are some shade of white, Red Mixing Base, and Dark Charcoal Metallic.
At this point I have 46 of the 51 painted parts on my airplane done. The remaining parts are big?the fuse, wings, and wingtips. 10 of my parts have a 3 color design. The fuse is the only one of those remaining.
Here?s my process. For equipment, I?m using a DevillBiss HVLP Finish Line II (my old woodworking gun) to spray DX1791. I?m using a Harbor Freight HVLP gun to spray K36 and DPLF epoxy primers. I?m using a DevillBiss Millennium gun to spray the topcoats. All products are PPG, with the topcoat being their DCC Concept single stage paint.
For aluminum I sand with 220 grit and a DA sander. I then wash with soap and water and dry, using clean, new rags. I then flood with DX330 cleaner (again using new rags), and dry with a separate rag. After any remaining solvent flashes off, I do one more wipe with a clean rag dampened with DX330 cleaner. I then don the respirator and mix some DX1791 self etching primer. Immediately prior to spraying I give the parts a gentle wipe with a tack rag. I fog the DX1791 on lightly, clean the gun and mix up some epoxy primer (DPLF). After waiting a few minutes for the self etching primer to flash off, I spray the epoxy. The epoxy can be recoated anytime within 1 week without any additional steps. If I?m satisfied with the parts after spraying the epoxy, I?ll spray my two topcoats immediately after the 20 minute flash time (note: flash time is longer with DPLF if you use the 401 catalyst instead of the 402). If I see a problem, I?ll let the epoxy primer dry overnight and then address the issues.
For fiberglass, I did 3 initial passes with very runny micro squeegeed into the weave. I sanded between each coat with a DA sander. I then shot some K36 mixed as a primer surfacer. I fixed any flaws, sanded, fixed more flaws, etc. Eventually I mixed some K36 as a sealer (I prefer K36 to K38 due to its versatility) and shot 1 coat to even out all of the different spots from fixing flaws. 2 topcoats of DCC were applied immediately.
Lots of people skip the epoxy primer or sealer steps with good success. They also usually wind up shooting 3 topcoats to get the look they want. I figured I might as well make one of those layers a primer and help adhesion out a bit. Although people do it all of the time, PPG specifically says not to spray CONCEPT directly over the DX1791 self etching primer.
Things I?ve learned:
1. Don?t wet the floor when working with Urethane paints. I?ve always done this with lacquer in order to keep dust down. Urethane paints however, are precipitation cured. The increased humidity causes the paint to skin over more quickly, causing orange peel and solvent pop. Most of my (numerous) problems went away once I figured this out. According to DevillBiss, the most common cause of paint problems with modern paints is people wetting down the floors prior to spraying. Guilty.
2. You really do need a good filter in your air lines (like motorguard M60) even if you live in the desert and have a water filter in your lines already.
3. Cleanliness is more important than everything else combined.
4. Most problems can be fixed. I almost repainted my elevators and HS for a 4th time before conversations with those that have been there before convinced me to sand with 2000 grit and buff. Wow! That really works! Thanks again to William for that advice in the thread listed above.
5. You can never have enough light. I?ve got 5ea 4ft double fluorescent fixtures and 3600Watts of Halogen lights in my 1 car garage sized booth. They?re not really enough. Incidentally the white paint is very hard to shoot because it doesn?t show texture well in the booth. The red paint has been easy; I can see the texture of the paint I?m shooting immediately.
Anyway?I?ve still got lots of paint to shoot, but it?s going better. Colors are some shade of white, Red Mixing Base, and Dark Charcoal Metallic.
. 
