Painting over gelcoat

Getting ready to paint with ppg epoxy primer / single stage paint anyway what’s proper prep for wing tip with gelcoat on them they look perfectly smooth scuff then epoxy prime over it or what is prep for these parts thanks any input is needed.

Yes

Yes, a light scuffing 180 220 grit, epoxy primer, topcoat. Enjoy

180 and 220 are way you course. I use a scotchbrite pad to give it all a dull appearance, then prime and paint. I've done it that way for years.

First thing to do is use something to remove the anti- bonding agent used to prevent the part from sticking to the mold during the manufacturing process. I.e. if wax was used a wax remover should be used. By sanding first you are just pushing the wax around and into the scratches.

Ron B. said:

First thing to do is use something to remove the anti- bonding agent used to prevent the part from sticking to the mold during the manufacturing process. I.e. if wax was used a wax remover should be used. By sanding first you are just pushing the wax around and into the scratches.

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Most mold release film is PVA (polyvynil alcohol). The wax is placed on the mold itself, then the release agent is sprayed over the wax. What comes with the part made in the mold when it is taken out of the mold is just the PVA.

Give all fiberglass (or carbon fiber) parts a good wash with soap and water, rinse very well and proceed with the above advice to scuff then prime.

Anti wax/oil/silicone wipe

Jeff, do you only rely on soap & water for composites?

Every surface i prime or paint gets a final “wash” with a prep solvent specifically targeting wax, oil, & silicone. Cheap insurance.

I happen to have Matrix MX9000 on hand. I’m sure every paint system has an equivalent product.

BP

Pounder said:

Jeff, do you only rely on soap & water for composites?

Every surface i prime or paint gets a final “wash” with a prep solvent specifically targeting wax, oil, & silicone. Cheap insurance.

I happen to have Matrix MX9000 on hand. I’m sure every paint system has an equivalent product.

BP

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Well, it’s what I did with my boot cowl I made from my own mold for my Hatz project. I guess since I know what was used to make it, I know what to wash off. Using a surface cleaner like poly fiber C 2210 wouldn’t hurt with a production part.

For the wingtips I sand them with 180 grit. Sand them enough so that the shine is gone. Have a good look at the outside edge. Oftentimes you will find some little pinholes. Fill them with glaze coat then sand smooth. If you put in a close out panel on the inside by the aileron with rivets, put a little glaze coat over the rivet head then sand smooth. When that is all done I like to prime with two coats PPG K36 primer. When that is dry sand with 320 grit on a DA sander. Give a good going over with the air blower, wipe with wax and grease remover, then paint.