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Building Tips and technical articles. => Paint and finishing => Topic started by: steven yampolsky on May 09, 2012, 12:23:36 AM
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I have applied the first coat of white on my old/new Stilleto and the dreaded bubbles started poping up. It seems that every day a new bubble develops. What are my options? How do I fix it?
Here's what I've done finish wise:
1) 3 coats of SIG Nitrate
2) Silkspan applied with Brodak buterate + a few more coats on top with some sanding to knock down some "fuzz"
3) Brodak silver as blocking coats
4) Two rounds of fix defects, sand silver down, spray silver again
5) 2 coats of SIG white
6) I'm painting trim colors but am avoiding fillet areas, preferring to put as little paint on there as possible
I would hate to see the poor Stiletto 35(entire fuselage and portion of the wing had suffered at the hands of a 5 year old and had to be re-built) make its debut with bubbles.
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Steve-
I don't know what fillet material you used, but here's what I do. My fillets are either balsa or epoxy with microballoons. They are applied over the silkspan or other covering. I sand them to the desired radius with medium abrasive (< 300) to remove residue and so that they are smooth, but rough enough for give added surface area for adhesion. Then I paint the butyrate on with a brush, first at both edges, but not along the center. When that is dry, I run some down the center. I do this in thin coats until time to spray silver. The spray is thin. That doesnt take much time, but I've never had any bubble or otherwise lift. If you sand or use solvent to remove whatever has bubbled, you might try this technique that doesn't allow much shrinkage area at any one time across the fillet's width. The photo is of a tail fillet, but the larger (R=1/4") wing filets on two planes look about the same.
SK
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I have fixed some fillet bubbles in the past by making a series of holes with pin and then use same pin dipped in CA to get the CA under the surface of the bubble. Depending on size of bubble and how far its lifted the pin pricking may not work. In that case you can use sharp new razor to slit bubble down the middle which may allow it to be pulled back down. Use wax paper to push bubble down with finger.
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Steve-
I don't know what fillet material you used, but here's what I do. My fillets are either balsa or epoxy with microballoons. They are applied over the silkspan or other covering. I sand them to the desired radius with medium abrasive (< 300) to remove residue and so that they are smooth, but rough enough for give added surface area for adhesion. Then I paint the butyrate on with a brush, first at both edges, but not along the center. When that is dry, I run some down the center. I do this in thin coats until time to spray silver. The spray is thin. That doesnt take much time, but I've never had any bubble or otherwise lift. If you sand or use solvent to remove whatever has bubbled, you might try this technique that doesn't allow much shrinkage area at any one time across the fillet's width. The photo is of a tail fillet, but the larger (R=1/4") wing filets on two planes look about the same.
SK
Serge,
What Epoxy are you using?
Charles
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I use SuperFil - then dope carbon veil to it.
Perfect fillets all day everyday.