Finish Problems

Well...... I did my Vulcan from bare wood up like I have all the others for the past 10 or more years. This time I got the "pull ups" all over the wing. It happened over the silkspan mostly. I use auto lacquer with plastisier, and added some retarder because of the humidity. It occured mainly where I used the 1/8th blue 3M tape. It has never happened to this degree before. It also occured over the fillets under the 1/8th tape.
It pulled all the way to the bare silkspan in many places.
I got a bunch of "repair" work to do.
Any ideas???
TIA
Bill <><

What did you use beneath the top coat? Is it lacquer all the way or dope under? One of the problems with retarder is it can lead to melt down, where the solvent eats into all of the underlayers. Lacquer can tend to skim over quicker than the underlayers. If this is what happened, it may have eaten into the underlayers, the top layer skimmed over, and then the underlayers "gass off" which causes separation. If you used all dope or all lacquer, you might get away with the use of retarder, but only if you used small quantities.

The thinner you used could also be a factor. What was your finishing procedure from bare wood up?

Hi Len,
Thanks, I believe you hit the nail on the head. I used retarder in the lacquer, more than before. I believe the retarder caused the separation. It occured mostly on the open bay area where the surface is flexible, and on the fillets where I could see the paint lift as I pulled off the tape. No amount of babying the tape made a difference.
I did the tape on the shirt, and all the "tricks", but the 1/8th blue tape just lifted the paint to the bare silkspan where ever it pulled up paint.
My process, which has been fine in this regard for over 10 years, is this:
All bare wood is filled and the silkspan is applied with Sig Nitrate.
Nitrate goes on the solid areas until a good fill is achieved. Nitrate filler (ZS) is applied to the soild areas.
2-3 coats of Sig Supercoat is brush applied to all open areas.
Lite Coat is brush applied, 3 coats or how ever many as necessary, to the whole plane.
A coat of ZS in Lite Coat is sprayed over the whole plane, and final sanded.
Lacquer light gray blocking coat, very thin. Repair as necessary.
Lacquer colors.
Dupont 3608S is used in all dope and lacquer. Never been a problem.
Then clear coat which can be Sig Lite Coat, or one of the two part auto clears if it is a foam wing plane.
Just have NEVER experienced this amount of lifting, and it is in a 1/8th wide strip, and only over the red lacquer which had the extra retarder added. The white and yellow didn't do it.
Thanks!
Bill <><

Well... Here comes the sandpaper.

What a drag!

Yeah
Bill <><

>>Nitrate goes on the solid areas until a good fill is
>achieved. Nitrate filler (ZS) is applied to the soild
>areas.
>2-3 coats of Sig Supercoat is brush applied to all open
>areas.
>Lite Coat is brush applied, 3 coats or how ever many as
>necessary, to the whole plane.
>A coat of ZS in Lite Coat is sprayed over the whole plane,
>and final sanded.

Hi, Bill

Help an oldtimer who is trying to catch up? Is ZS zinc sterate? Where do you get it in reasonable quantities (5# or less )? I understand it can be used as a sanding sealer? Does it work with butyrate?

Thanks

Another Bill

You can purchase USP grade Zinc Stearate from Sciencelab.com, the cost is $36.12 for 17.63 oz. You can also get it from Randy Smith but I don't know the quantity/cost.