Paint cracking

Hi All,
On my son's new plane, we are experiencing some cracks in the finish. He used the proper flexative, and it is only in a couple small areas.
The plane has Acrylic auto lacquer and Sig lite coat as a clear top coat. Never had this happen before. Plane is covered with Tom M.'s polyspan, which has a smooth application.
Any ideas? Paint job is only a few months old.
TIA,
Bill <><

Gotta be the Lite Cote.

In addition to adhering well, covering well, leveling well, auto lacquer shrinks very little.

Perhaps the problem is that the dope shrinks and the auto lacquer does not. To be fair, Lite Cote typically does not check, and is "low shrink", dope-wise.

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"Every formula which expresses a law of nature is a hymn of praise to God." -Maria Mitchell

Hey Bill, you don't suppose it was from the intense sun or heat at the contest, do you? or was it cracking before Marietta?

Bill,
Several of my planes that were covered with
polyspan and painted with Sig supercoat from
the wood up have experienced the same thing.
Namely ,a ding will cause the paint to chip
and delaminate from the Polyspan. I was told
by Tom to build up my finish starting with
nitrate but I balk at that.
Someone out there smarter than this old man
please respond and let us know where we may be messing up
Thanks Busby

Steve,
It did show up at Marietta under the sun. Only on the polyspan areas of the wing.

Buzz,
I always do the Nitrate thing up to attaching paper/polyspan. But it does seem that the crack/delamination IS what's occuring. Funny thing is that the ill fated RD-1 didn't experience this. It was clear coated with auto clear coat.

Bill <><

Bill,
Tom told me to put several coats of nitrate
on the polyspan prior to starting the butyrate
build up and it would bond much better.
Thanks Busby

>Steve,
>It did show up at Marietta under the sun. Only on the
>polyspan areas of the wing.
>
>
>Buzz,
>I always do the Nitrate thing up to attaching
>paper/polyspan. But it does seem that the
>crack/delamination IS what's occuring. Funny thing is that
>the ill fated RD-1 didn't experience this. It was clear
>coated with auto clear coat.

Bill;

Did you do the RD-1 with a built up wing or foam?

Bob,
Built the RD-1 with a built up wing. Barker TT36, 10 1/2 - 4 1/2 APC.
Bill <><

>Bob,
>Built the RD-1 with a built up wing. Barker TT36, 10 1/2 -
>4 1/2 APC.
>Bill <><
>

Well, there goes my theory that it was an issue of the covering flexing and the lacquer and/or dope losing adhesion.

Just curious, but how did you do the RD-1 wing? C-Tube, D-Tube, Millenium, LL?

I always thought it interesting that the RD-1 wing was a spot on match for the Sig Twister wing in terms of airfoil and area ....

V/r

>Just curious, but how did you do the RD-1 wing? C-Tube,
>D-Tube, Millenium, LL?
>
>I always thought it interesting that the RD-1 wing was a
>spot on match for the Sig Twister wing in terms of airfoil
>and area ....

built it as D-Tube on rods.

Robby told me they used the Twister wing template that Bob had from his foam wing cutting service to cut the first rd-1 wing, that is why it is so close!

this rd-1 that we had down there did not fly so good, dad ummm re-designed it and it got worse...

live and learn

Bill,

Aaron's plane has so much black or dark green on it, it probably really heats up from the sun. The RD-1 had much lighter paint colours on it, plus it was out mostly in the evening and early morning, due to the fact it got dinged up before afternoon. So I'm not sure its an apples to apples comparison studying the paint cracking issues on either. I guess the best thing is hope aaron's finish does not crack through the substrate and ignore it for the time being.

Some of this goes back to the issue of using one type of finishing material from start to finish. These days, the chemistry of non-dope finishing materials changes so often that I would suspect any automotive finishes would be at risk of chemical change by the manufacturer getting you sooner or later. Dope may be antiquated, but probably the most reliable.