Bagging Compound Wingtips
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Home > Articles & Tips Index > Foam Cutting and Vacuum Bagging > Bagging Compound Wingtips

[Courtesy of Oliver Wilson ocwilson "at", December 1999]

The mylar won't conform to the compound curve at the tips so it has to be cut back. Neither will the mylar go around the sharp curve of the leading edge. The tips, just like the leading edge, will be left with flash that needs to be cleaned up after bagging. The only difference is that at the tips, the flash is a little wider. If this is kept in mind when shaping the core's tips the flash will usually be less than 1/2 inch wide. No joint of any kind need be involved. The whole wing is bagged as a complete unit only once (upper and lower surfaces at the same time).

The proceedure is to hold the cores in the beds with the leading edge and tips protruding about 2 inches. One or more strips of cloth, cut on the bias, are epoxied along the leading edge and around the tip of the core, each piece in one long continuous length. Then, before the epoxy starts to harden, the main layup is done over the mylars which are tape hinged at the trailing edge. The core is removed from the beds and laid on one side of the mylar. The core is carefully aligned with mylar at the root and along the trailing edge with the trailing edge of the core about 1/4 inch in front of the mylar hinge line. Care must be taken not to disturb the strip around the leading edge and tip which has not started to harden yet. Then the other side of the mylar is folded loosely over the core. As the mylar is folded, wrinkles tend to form at the hinge line and they need to be stippled out as the fold progresses. The loose sandwich of mylar-layup-core-layup-mylar is placed in the bag and aligned to the beds top and bottom and weighted down to a flat surface to hold everything in alignment for the vacuum.

If you use brown paper towels as air bleeder in the vacuum bag, top and bottom, it will be incorporated into the flash along the leading edge and tips. When removing the flash it is easy to go through the thin skin into the core. The brown paper helps to avoid this by providing a visual indication of when to stop removing flash!

Regards, Ollie

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