insalacosm

My Feedback: (1)

Hello - I am starting to finish a few pieces of a model that are sheeted with very thin birch plywood. These pieces will be painted and I want a very smooth finish. I applied three coats of sanding sealer, sanding in between each coat, and now have applied my first coat of primer. I'm surprised by how much grain I still see. The grain isn't very deep, but it isn't the smooth finish I'm looking for. This will be an electric airplane so I'm using Model Master enamels in rattle cans. The primer I used is their Grey Primer. I'll sand this coat, should I then keep priming and sanding until I don't see any more grain? Is there a better primer to use for filling grain, maybe Krylon?
Thanks
Steve

jaka

Hi!
Automotive 2-part acryl paint (Has to be sprayed on)

Ed Smith

Sanding sealer is too soft and will not dry smooth. Us an epoxy finishing resin. It will cure very hard and sand to a smooth finish. Always use a sanding block.

Epoxy is not a lightweight filler, but then nor are three coats of sanding sealer.

Ed S

insalacosm

My Feedback: (1)

Thanks for the tips. I've never actually used finishing resin and unfortunatly don't have any on hand. Would 2 hr epoxy mixed with micro balloons work as a filler too or is this too thick?.

Dzlstunter

Caveat: I've not done this over sanding sealer, so you may have to do some experimenting if you want to try it.

What I have used to get a smooth finish is plain old spackling compound mixed with water until a brushable slurry is created. Brush that on, covering everything you will want to paint. Wait for it to dry, then start sanding it all off. What will remain is the mixture which is down in the grain. This will create a LOT of dust, by the way, so you may wish to do it over a sanding box or shopvac which is running. Wear a mask. If you can go outdoors, that's even better. Once you have the job done, hit it with a light coat of primer, being careful not to wash the filler away in the process. If you still have some areas needing attention, repeat the process in those areas. This will work on raw balsa, though you have to be careful not to get the slurry too watery and warp things. Good luck, Dzl

sensei

No matter what you do, the grain will come back in a couple of out door outings if you do not use a 1/2 oz. - 3/4 oz. glass cloth on the wood first.

Bob

Top_Gunn

My Feedback: (6)

Sanding sealer isn't a sealer, despite its name; it's a filler. You should start by sealing the wood with a couple of coats of clear nitrate dope. After that, you can fiberglass it or, sacrificing some ding resistance for less weight, apply silkspan with nitrate dope. Fill with a mixture of dope and talcum powder. (Some people use things other than talcum powder, like calcium stearate; haven't tried that myself yet.)

insalacosm

My Feedback: (1)

Sounds like the solution is to sand down the primer and then glass it. I can see the grain coming back over time if I don't glass it. I've heard of people using micro balloons to fill the weave as well. Thanks for the input!
Steve