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Old 03-05-2012, 02:39 PM   #15 (permalink)
Ken Fry
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Quote:
Originally Posted by turbothrush View Post
By the way I think the best book I found on Fiberglass/foam is "Advanced Composite Techniques" by Zeke Smith
Rutan's Moldless Composite Construction is another pretty good one. The Gudgeon brothers have put out a magazine for years with interesting tips, too... can't think of the name, but the WEST system epoxy site would have links.

Another issue with poly film it that is is rarely smooth in the way that mylar is. Even stretched tight, its surface has little bumps and waves (near microscopic) that show up on a glossy surface.

For those interested in very lightweight with foam-cored composites, standard vacuum bagging has the disadvantage of leaving a lot of resin in the foam surface pores. If the thing you are making permits using panels as you would use thin plywood, then you can squeegee fiberglass cloth in epoxy onto a large piece of plate glass (treated with a good mold release). Then, prime one foam side with microbubbles in epoxy, which can be about half the weight of epoxy alone. Flip this onto the table over the fiberglass. Vacuum bag and cure. Peel the panel off the table. Make the second skin the same way.

The resulting panel is perfectly flat and shiny on both sides, and can be single curvature bent into place (the curvature depending upon skin thickness vs core thickness, core stiffness, etc etc.) onto a structure, such as an airplane wing (albeit not around the leading edge) maybe about from 15% on back.

A little extreme in terms of labor to save some epoxy weight.
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