coopwyo
Active Member
Has anyone ever used K36 primer from PPG to seal and get rid of wood grain on balsa fins? Would it add too much weight to the fins/rocket?
Automotive primer to seal fins
- Thread starter coopwyo
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Never used it but most of the time you sand any primer back down to the wood, that will loose a lot of the weight.
I've used it to paint RC airplanes. It's expensive and hazardous to work with, you'll need a respirator. I wouldn't recommend using it because it is hazardous.
If you really want to fill balsa grain I recommend using Elmers wood filler. I drip a tiny bit of water in the container and mix it in with a small brush so the top layer is about like melted milkshake. I brush it on the surface of the fin and let it dry then sand it off with 220 sandpaper. It comes out relatively smooth and doesn't take long to sand. It is a bit quicker if you paint on the filler and then squeegee off some of it with an old credit card. My best finishes for painting on top of balsa were done this way but these days I paper most of my fins and don't worry too much about the grain. The paper covers most of the grain but not all of it. On my most recent set of fins I actually put the wood filler on, sanded it smooth, then papered over it with thin cardstock. I think the surface will come out very smooth. This is not my main focus, I do it for strength.
From one of the car forums:
"
As a PPG user for many years in a collision shop, K36 sucks IMO. K38 is a better product and doesn't have the shrinkage issues that K36 has.
K36 shot through a 1.8 and mixed with a full part reducer, can hear the sand scratches starting already.
If you insist on using K36 I would only mix up enough for 1 coat and use 1/2 part or less of reducer. Once you are ready for the 2nd coat mix up some more. Adding reducer extends the pot life but increases the possibilities of shrinkage.
I've learned the hard way with K36 and now would only use K38...Eric"
"
As a PPG user for many years in a collision shop, K36 sucks IMO. K38 is a better product and doesn't have the shrinkage issues that K36 has.
K36 shot through a 1.8 and mixed with a full part reducer, can hear the sand scratches starting already.
If you insist on using K36 I would only mix up enough for 1 coat and use 1/2 part or less of reducer. Once you are ready for the 2nd coat mix up some more. Adding reducer extends the pot life but increases the possibilities of shrinkage.
I've learned the hard way with K36 and now would only use K38...Eric"
Short answer: I've never used it and have no real idea. So why am I responding? Because I have an alternative to offer*.
See post #14 in your tube spiral thread. I use the same stuff for balsa grain. Rub it in with fingers then squeegee it off with an old credit card, hotel room key card, or the like; try to hold the card such that it can simultaneously squeegee off the stuff from the high areas and "squeegee in" the stuff in the low areas. Then give a light sanding. (This particular product will be sandable in an hour or less.) The process is the same for balsa grain and tube spirals, because the challenge is the same: filling little narrow depressions in a nominally smooth surface.
See post #14 in your tube spiral thread. I use the same stuff for balsa grain. Rub it in with fingers then squeegee it off with an old credit card, hotel room key card, or the like; try to hold the card such that it can simultaneously squeegee off the stuff from the high areas and "squeegee in" the stuff in the low areas. Then give a light sanding. (This particular product will be sandable in an hour or less.) The process is the same for balsa grain and tube spirals, because the challenge is the same: filling little narrow depressions in a nominally smooth surface.
