Dimpled core after bagging - possible causes? - Page 2 - RC Groups
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May 02, 2012, 08:33 PM
Entropy is happening!
Jim.Thompson's Avatar
Originally Posted by wyowindworks
I really need to see videos of people who have mylars that fall off and parts that fall out of mold.
Me too Adam!

I am using a blue foam that is also used by a proffessional bloke in town who makes epoxy composite boats and other things like panels for caravans etc.
Anyway, he reports the same phenomenon as I do, depressions forming in random spots on the foam. They rectified it somehow, but he (and I) are not sure what causes it. It does seem to be a peculiarity or irregularity of this particular source of foam. It's as if the foam is reactive in spots to the epoxy and partially dissolves or something.


p.s. I have not read every post on this thread thoroughly yet!
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May 02, 2012, 09:03 PM
Just fly it!
wyowindworks's Avatar
I like Meguiar's Mold Release #8 wax.

I usually let the bagged mylar wings cure for 12 hours at room temp under vacuum. I don't like to heat the mylars when they are under vacuum. The mylars become more pliable which reduces the finish quality. Once the resin has set it's no longer necessary to hold the vacuum.

I then cure them without vacuum for at least 12 hours at 125*F with the mylars still on. I often go for 24 to 36 hours if time allows. Then I peel the mylars. Peeling the mylars too soon will almost always cause more fabric print-thru....even with light fabrics. The longer the mylars are on, within reason, the better the surface will be.

A fun experiment is to peel the mylars part way after the 12 hour room temp cure. Then peel it off the rest of the way after it has cured for a few days or at elevated temps. You will notice a very distinct surface finish difference between the two.

May 05, 2012, 08:54 PM
Registered User

steam and boiling water worked great!

Just to put closure on this, here's the wing, just about done. Just needs reinforcement at the dbreaks, and maybe I'll round the TE at the tips. I used boiling water as suggested and most dents disappeared. Then steamed the rest out with the iron and wet paper towel. Works great. I'm glad I asked because when I first saw those dents I had pretty much written off this wing

Thanks again to everyone for your help.


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