Thread: Cool Concept Xtreme 2
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Old Oct 10, 2012, 03:05 AM
cptsnoopy is offline
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Where is the lift?
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USA, AZ, Phoenix
Joined Nov 2005
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Quote:
Originally Posted by leipold View Post
My CX2 had a midair (thanks, Reto!) in the flyoffs at Wilson last weekend. I took a quick look, didn't see any damage, and threw it again. And again. (Dumb move.) After the round, I noticed the damage.

There's a 6-cm-long split in the leading edge about halfway out the right wing. In that region, from the leading edge back to the spar, the top skin depresses and makes 'crunchy' noises when pressed. There are some wrinkles and delams in the top skin from the spar back to the hingeline. A 'bubble' of delam is centered over the spar.

When I flex the wingtip upward, the wing actually bends (a little), and the top skin over the spar visibly moves as it does When I try to flex the wing downward (putting the top skin in tension), it doesn't bend. If I grab the wing at the spar on either side of the damaged area and try to bend it, it doesn't feel like the spar itself has any flexibility, so I don't *think* I broke it.

What's the best way to repair my baby? Am I going to have to cut the wing open?

-- Walt
Hi Walt,
Sorry about the damage to your Concept. (I'm sure Reto feels bad about it too...)
I have repaired two wings that had the top skin delam from the spar cap. Both times I cut the approximately 1" square of spread tow on the bottom of the wing ahead of the spar where the delam has occurred. Once the square piece of skin is removed you can inspect the damage. If the spar appears to be intact and the Carbon spar caps are ok then you can puncture little holes in the upper skin foam working through the access hole. The idea is to allow thin epoxy to soak a bit into the foam to help stiffen it up. Then I carefully flex the wing to slightly open up the space between the upper skin and the spar where it has separated. I use 400 grit to rough up the surface of the skin and the spar so the epoxy will have something to grip when it dries. Then I set up a bed of magazines or something similar that will conform to the curve of the top of the wing. then I have large books or for this last repair I did, reams of printer paper that were fairly heavy to press the wing down into magazines while the epoxy setup. I used Carbon cloth to reinforce the first repair I did and lightweight fiberglass for the second repair. The fiberglass was much easier to work with. I cut a small patch that I could lay up against the top skin and the spar covering the area of delam. Once everything is ready I mix up some super thin epoxy and apply it carefully between the spar and the top skin plus the adjacent skin that I poked little holes into. Then the fiberglass goes in over the wet epoxy and a little more epoxy is used to ensure a thorough wetting of the glass. Once you are satisfied that everything is done inside the wing, then lay it on the magazines (or whatever sort of "bed" you have come up with) and stack books or the like on top of the wing to keep pressure on the upper skin so it will lay back down flat and contact the spar. After the epoxy has thoroughly dried you can pull the wing out of the "bed" and inspect the repairs. If all looks ok, you can glue little strips along the edges of the access hole that provided a "shelf" for the approx 1" square to sit on. I glued them back on the wings and then used taped to cover the small gaps. My repairs do not look new again but they are strong and they seem to be working out ok.

Good Luck,
Charlie
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