More Frustration

[Chuck Feldman]

    Frustration 1 was about buterate clear dope turning milky after a drop of fuel gets on it. This "more Frustration" is about what I am going through with the same Smoothie that I had refinished in Buterate dope and discovered the damage from the fuel. So I did the refinishing as a repair again using buterate dope, for compatibility. But now I had to fine a way to protect the finish from being fuel damaged again. I have no one to spray two part automotive clear which is the obvious choice. I went to an auto paint shop and found a rattle can product that is a clear coat. This stuff is expensive $17.00 per can. So I applied it to the model and it shinned and was nice. After several flights I noticed it was getting sticky on the muffler side of the model. Damn! I tried to cure it but too no avail. I called the company they said put a heat gun to it. I did that. It remained sticky! Flew it a few more times and it got worse. Clearly this model was not going to work out. I elected to strip the model. Never did that before but I know acetone is a great solvent.  So using folded up paper towels wetted with the acetone I rubbed off the model down to the finishing resin. On the wings the polyspan released as the nitrate dope gave up its hold on the poly. This where I am right now. Bare model! I am going to sand it all down and proceed with recovering. But with what? Ultracoat? polyspan? I need advice. I hope this help some one else from getting into this mess. CF

[Balsa Butcher]

What type of buterate dope? I have found Brodak to turn milky when exposed to any fuel with over 5% nitro. The Smoothie in the pic as an example of that but since it is old, I choose to ignore it. If your's is now down to wood I would recover it with either silkspan or polyspan, whichever you are most comfortable with. Prepare as usual.  Paint with either Sig or Brodak color. Now, use Sig Lite-coat for the clear, 3-4 coats minimum. Others may recommend 2 part automotive clear and that's good too but if you want to stay with dope I have found Sig Lite-coat to hold up to as much as 15% nitro. I have not had compatability issues putting Sig clear over Brodak color, other opinions may differ.

[Tim Wescott]

If it's just a matter of a clear coat, consider getting an automotive paint shop to squirt it for you.  Show them the finished model, explain what's underneath, get a price.  They'll be all set up to do it, and may even be able to do it as part of another job.

Prices will vary wildly by how cool they think the project is -- I wouldn't be surprised at anything from a flat "no" to "wow that's cool I'll do it for free".

I'd make sure to take it to a good paint shop, though -- some cheap guys know how to do good work, but lots of them just know how to squirt paint.  You don't want to get it back with runs, bugs, dust and scratches in or underneath the clear coat.

My understanding of Sig Lite Coat is that it holds up to 15% nitro, and the longer you give it to set the better it does.  I have a recently-resurrected plane with a 10 year old lite-coat finish that stands up to 20%.  The advise that I've seen is to let it cure for a couple of weeks.

[George]

Not all butyrate dope is the same. Neither are the thinners. Unless you know a lot about dope and thinners, you are better off staying with ONE product through the entire finish process.

Some earlier threads revealed that Brodak butyrate gasses off faster than SIG. That would mean that you can paint SIG over Brodak butyrate but not the other way around...otherwise gas will be trapped between the products and possibly cause the top layer to peel off.

Some guys on these forums know LOTS about mixing products so if you ask before you mix, you may get lots of help.

Good luck.

George