Author Topic: repainting an old stuntship....and having problems... (Read 1231 times)

Scott Richlen · « **on:** April 21, 2019, 03:42:40 PM »

I am refinishing an old stuntship originally painted with Sig dope. I've sanded it down and repaired spots as needed. Now I am trying to repaint (spraying) with more Sig and having all kinds of problems - particularly at any edges where I sanded through the old finish. So, I sanded it down again and added fish-eye killer to the dope thinking that that would solve the problem. Nope! Same thing. I'm going to sand it down again and use something other than Sig, at least until I get some isolation from the original surface. But not sure what to use.

Anyone else have this experience. What did you do to fix it?

Carl Cisneros · « **Reply #1 on:** April 21, 2019, 05:18:14 PM »

Scott

wonder if it might be from oil slowly soaking in to the dope over the years.

If tht is the case, get out the paper and sand till you cant sands no more.

Carl

p.s. got the Mrs home from Walter Reed late this afternoon. she is pretty rough right now but glad to be home.

wwwarbird · « **Reply #2 on:** April 21, 2019, 08:52:04 PM »

What kind of problems are you having? Got any photos of what's going on?

Scott Richlen · « **Reply #3 on:** April 22, 2019, 06:29:45 AM »

Carl:

Considering how many flights on it, it probably is oil soak. However, some of this is on the nose which was originally glassed (cloth and epoxy). I was careful to clean it well and sand it. So, not sure.

Wayne:

Here are some pictures. What is happening is that the paint is pulling away and exposing the original surface. Other areas just end up having a rough-textured surface, but photos of that just can't pick it up well enough to see the problem.

Ken Culbertson · « **Reply #4 on:** April 22, 2019, 07:51:46 AM »

Quote from: Scott Richlen on April 21, 2019, 03:42:40 PM

I am refinishing an old stuntship originally painted with Sig dope. I've sanded it down and repaired spots as needed. Now I am trying to repaint (spraying) with more Sig and having all kinds of problems - particularly at any edges where I sanded through the old finish. So, I sanded it down again and added fish-eye killer to the dope thinking that that would solve the problem. Nope! Same thing. I'm going to sand it down again and use something other than Sig, at least until I get some isolation from the original surface. But not sure what to use.

Anyone else have this experience. What did you do to fix it?

I have but it was a long time ago before all of these wonder products. It was from oil from a leaking tank and I was not able to "fix" it. What I did was sand it down to the wood, soak it in multiple coats of thinned clear (Aerogloss if anybody remembers it) let it dry a bit then covered it with Jap Tissue. Don't know if it lasted since the plane did not survive much longer due to sudden deceleration.

Ken

Brad Smith · « **Reply #5 on:** April 22, 2019, 08:04:32 AM »

Why couldn’t you cover these areas with small piece
Of silkspan clear it and feather the edges

Ken Culbertson · « **Reply #6 on:** April 22, 2019, 09:17:48 AM »

Quote from: Brad Smith on April 22, 2019, 08:04:32 AM

Why couldn’t you cover these areas with small piece
Of silkspan clear it and feather the edges

Silkspan may be too porous. What prompted me to use Jap Tissue was from my free flight experience. It is very non-porous if you don't shrink it. and it seals easily. As an undercoat followed by silkspan - why not.

What he has is an issue that cannot be corrected, it must be contained. Something needs to seal the surface that will dry before that nasty stuff seeps through it.

Ken

Carl Cisneros · « **Reply #7 on:** April 22, 2019, 01:59:01 PM »

Scott

I got this week off due to teh Mrs.

mind if I have a first hand look at it?

Carl

wwwarbird · « **Reply #8 on:** April 22, 2019, 09:09:23 PM »

Quote from: Scott Richlen on April 22, 2019, 06:29:45 AM

Wayne:

Here are some pictures. What is happening is that the paint is pulling away and exposing the original surface. Other areas just end up having a rough-textured surface, but photos of that just can't pick it up well enough to see the problem.

Yeah, just looking at the photos it's really tough to tell what might be going on. Does it seem like a shrinkage problem or is the paint "retracting" itself from those areas similar to a fish eye problem? Either way, my initial thought is to very lightly sand the problem areas again, with something like 600 or 800, just enough to scuff the areas well and then go back and try to build it up with multiple "dry" coats.

Scott Richlen · « **Reply #9 on:** April 23, 2019, 06:08:44 AM »

Initially those areas were covered with paint (I tried to spray it dry as I was trying to build it up - similar to your thoughts), but as it built up it just shrunk away. I'm going to buy some Z-poxy today and see if I can't lay down a barrier coat and then try again with the dope.

George Waters · « **Reply #10 on:** April 23, 2019, 05:36:35 PM »

Scott Try using thin ca to hardshell these spots. I have done this a couple of times and it worked. George

Ken Culbertson · « **Reply #11 on:** April 23, 2019, 05:56:10 PM »

I don't know if it is ever possible to get all of the oil out of balsa or get anything to really stick to it again. It guess it depends on how bad it is. I have used heat (monokote gun) to draw out the heavy stuff then soaked the wood with super thinned dope. I would think that Epoxy and alcohol would work better but I have never tried it. I only do this to stop the rot. The z-poxy barrier should work to seal the mess in. I have had some luck with lifting in fillets and the like by flooding the crack with JB Weld CA and forcing it in before it sets. Not the easiest substance to feather. I also recently had some success by thinning out some blue stuff with alcohol and rubbing it in. That was really easy to feather.

Still the best cure for oil soaked noses is an electric motor!

ken

Dave_Trible · « **Reply #12 on:** April 23, 2019, 06:11:23 PM »

I don't think the new dope is etching into the old harder finish and adhering. Also I know Sig has changed dope suppliers a time or two over the years and could be slightly different formulas. I'd try partially thinning the first coat or two of new dope with some acetone. This should soften the older dope a little and promote it sticking. It might blush a little but further coats with a little retarder will make that vanish. I used Acetone for years as my ONLY thinner in dope and never had much trouble other than blush on humid days and the dope getting brittle in out years. Using just a little to get some adhesion wouldn't hurt anything.

Dave

Randy Powell · « **Reply #13 on:** April 30, 2019, 03:12:41 PM »

Yea, certainly seems to be an adhesion issue. You are getting no chemical bonding, possible due to differences in materials or oil soaking. You are also getting no mechanical bonding, probably due to the underlying paint being old and hard.

I'd say, wipe the area with Prep-Sol or equivalent, use extra thinner in the dope, maybe 40-60 to see if you can get some softening of the underlying paint. If not, you may have to sand it back to the paper finish or strip it entirely.

Peter in Fairfax, VA · « **Reply #14 on:** May 02, 2019, 03:21:56 AM »

Scott,

Did you go with Z-Poxy? I have a box of Z-Poxy products, btw. How would you thin Z-Poxy for spraying?

Peter

Scott Richlen · « **Reply #15 on:** May 02, 2019, 08:30:08 PM »

[quoteDid you go with Z-Poxy? I have a box of Z-Poxy products, btw. How would you thin Z-Poxy for spraying?][/quote]

Planning to, but got off onto other subjects. I usually use alcohol for thinning epoxy. Hopefully that works for spraying it....

Author Topic: repainting an old stuntship....and having problems... (Read 1231 times)

Scott Richlen

repainting an old stuntship....and having problems...

Carl Cisneros

Re: repainting an old stuntship....and having problems...

wwwarbird

Re: repainting an old stuntship....and having problems...

Scott Richlen

Re: repainting an old stuntship....and having problems...

Ken Culbertson

Re: repainting an old stuntship....and having problems...

Brad Smith

Re: repainting an old stuntship....and having problems...

Ken Culbertson

Re: repainting an old stuntship....and having problems...

Carl Cisneros

Re: repainting an old stuntship....and having problems...

wwwarbird

Re: repainting an old stuntship....and having problems...

Scott Richlen

Re: repainting an old stuntship....and having problems...

George Waters

Re: repainting an old stuntship....and having problems...

Ken Culbertson

Re: repainting an old stuntship....and having problems...

Dave_Trible

Re: repainting an old stuntship....and having problems...

Randy Powell

Re: repainting an old stuntship....and having problems...

Peter in Fairfax, VA

Re: repainting an old stuntship....and having problems...

Scott Richlen

Re: repainting an old stuntship....and having problems...