Dealing with cracking wing paint.

[blimpy]

My plane has had problems with the wing paint cracking for some time.

I did some investigating, wanting to make sure it wasn't some kind of structural problem.

0 My logs indicate the wings were painted in 1965 with a black non-bleeding primer and Dupont Dulux over the original
red dope and cotton covering.

0 Lifting up the "material" at the crack reveals intact dope and fabric underneath, but very heavy layer(s) of
Dulux paint ( like a rigid plastic) which have cracked.

Under the influence of "dope" and particularly the Randolf Ceconite Manual... I sanded out and "filled" these cracks
with butyrate silver... on the theory that is it both an adhesive and a filler.

Sorta worked. But, since there have been previous attempts to fill or hide these cracks with a variety of paints,
the results were mixed.

0 Any cheap spray can paint bubbles up in contact with the hot solvents ( MEK) and thinners in Butyrate Dope.

0. Silver is really soft, and doesn't build enough to fill well.

After some more sober consideration, I realized that I was mixing chemistry when I was trying to avoid it.

Next Try:

I am using a "flexible" west system epoxy with micro balloons for the following reasons:

1. compatible with dope ( per randolf manual)
2. excellent adhesion, and sandability, with filling accomplished by addition of micro balloons.
3. Should be compatible with most any paint used to blend in with the existing paint ( lipstick on pig).

I will go tomorrow to sand out the test areas I filled last week, and post some pictures of that.

-- A visit to the DuPont auto paint store got me a laughed at when I showed up with old Dulux color codes.--

Knowing that there is no "right or permanent" fix for this problem ( inflexible paint over a wooden structure that does what wood does during excursions of temp and humidity)... I think I'm gonna just use a non-catylized enamel ( centauri) to
spot paint the repairs. They will make custom spray cans for me.. or I can try to set up a compressor and use my touch up gun ( no electricity no experience ! )

Good till next time.. and the next batch of cracks appears.

All I am trying to accomplish is having a tight paint surface to keep water and dirt out, and of course eliminate the appearance that my wings are 'falling apart'. Which they 'aint. 8)

 

[ronm]

Hi Larry,

I have Dulux over vinyl dope (Stits). So I know some, but not everything about your paint and dope dilemma. In my case, all was not well. I went whole hog and stripped the tops of the wings to wood, then microbaloon/epoxy, light polyester fabric and vinyl dope. The topcoat awaits.

From your pictures, it looks like there is separation of layers some distance from the paint cracks. It is quite feasible to get the enamel off and preserve the dope and fabric underneath with some methylene chloride based paint removers. It's a fair amount of work though. Using thin drop-cloth plastic film over the applied paint remover will reduce the amount of remover you need to buy.

For a temporary solution, supergluing the cracks and sanding and painting might be worth a try . Hobby shops have it in larger poly bottles. I am thinking of the low vis watery variety. The main thing is to get the layers tied together. Then just block sand and fill. You will be limited to paint material that won't crinkle the Dulux.

BTW, my wing was sound, but the surface was quite wavy. Since there was also some paint probs similar to yours from not being hangared for a couple of years, I went the microbaloon route. The brown microbaloon/epoxy concoction I made to surface my wing is great to work with. It is like balsa wood with no grain. I used a jack plane with a very well sharpened blade.(test by shaving hair off your arm) I could cut long curly chips that were almost transparent.

However, your wing looked OK in general. I don't thing any microbaloon is needed just to fix the paint cracks. I would first try wicking some superglue under the paint cracks, block sanding, filling and painting. Did I say BLOCK sanding? Yes. Don't finger sand. Anyway, I would try this first.
ron

 

[blimpy]

THANKS RON.

you have a similar problem.

I will post my "repair" results shortly.

You were right, balloons were not needed, and I will have to sand them down where I used them.

squeegee'd west 650 flexible epoxy alone over well sanded surfaces seems to have worked well.
I will get to see it cured tomorrow.

no stripper for me... not ever again.

new owner will want to strip down to wood, but I am too broke to think about it.

 

[blimpy]

the epoxy sealer stood up fine to 3 hours of flying at 140 mph..and just sitting there smiling after a week in santa paula hanger where fog comes in every night.

the cold nights at cloverdale made the west 650 rather slow to harden totally, but some sunlight helped that..after a couple of days.

this is going to require only the most minimal sanding before it gets sprayed..and my gut feeling is that will be both a long term and invisible fix.

So: simple (squeegee application), cheap, relatively non-toxic, and nice result.

looks like this is the way to fix cracking dulux applied over dope and wood.
Time will tell if it's more flexible nature is the "real deal".

previous efforts with dope, spray cans etc, sure weren't.