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Foam wing bagging - warping wingtip edges

Old 05-28-2020, 03:33 AM
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michajas
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Default Foam wing bagging - warping wingtip edges

Hi,
I've started to experiment with vacuum bagging wings and it works great. One issue that I have is that when tip of the wing is rounded and tapered to the tip, the mylar that is covering the top and bottom starts to wrinkle on the rounded part of leading edge
This leaves me with uneven surface (very uneven) on the wing tips. I'm trying with to overcome this issue but maybe some of you more experienced people can give me some hint?
I'm using 0.25mm thick mylar sheet (maybe to thick?).
I'm bagging the wing (for now only the part of it for testing) without any surrounding molds (as I'm sanding foam, not wire cutting).
Thanks a lot for any advice!

ps. Sorry for the repost from sailplanes but I think that this forum will be better for this question.
Old 05-29-2020, 04:42 AM
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speedracerntrixie
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Some guys scrape the Mylar with a razor blade to thin it out so it will take the compound curves better. Although I've never bagged a wing with Mylar, I have bagged with peel ply many times. What I would do is end the Mylar short of the tip and run peel ply at the tip. After bagging I would sand and prep the tip for paint and either blend in the same color as the rest of the wing or come up with a color scheme that has the tips painted a different color.
Old 05-29-2020, 05:27 AM
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michajas
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Thanks, I've heard about thinning the edges of mylar from other source already. I'll try this approach and see if it's giving good results.
As for the peel ply, that's a good idea. So basically I'll have the mylar on places that have almost straight lines and for the tip peel ply. I don't think that painting would be an issue here Although looking on DLG wings prepared by others with mylar it would be like a cheating But at least it will be backup plan if I still won't be able to do it properly with mylar!
Old 05-31-2020, 11:18 PM
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michajas
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Well I gave it a shot and I've sanded leading edge of mylar. Now it's better but still some small warps. I've also decreased vacuum pressure to -0.6 BAR (from -0.68) but I think that there is not that good adhesion of epoxy.
I'll try moving mylars from leading edge a little bit (now they almost touch each other on LE) and maybe this will help further.
Thanks!

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