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Old Oct 13, 2013, 06:51 PM
Foam flogger
Roseville, CA
Joined Apr 2009
1,135 Posts
Help!
wing repair

So I cratered my topsky a few weeks back. Elevator failed on launch and went right in. Fixing up pod and tails but not sure what i need to do to the wing. Its creased on the bottom and looks like a bit of delam on the top. Spar looks fine. Boiling water? Patch? Epoxy? Give me some advice on my first wing repair
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Old Oct 13, 2013, 07:52 PM
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It looks like you'd be better of just getting a new fuselage, from the picture (that's what I'd do anyway).

As for the wing, if it's creased, it's most likely bent also. If a crease happens because it is physically hit there, that's one thing, but if it's creased because of stress (which yours likely is), I'd use a straight edge to make sure it's still straight (if your aileron moves freely by hand it's probably o.k.)

Before filing the crease, wet a paper towel (double it twice: 4 ply thick), or wet a thin washcloth and lay it over the crease, then place a HOT iron (modelers, or house iron) on the wetted cloth for about 3 second and check, then 3 or 4 second more, until the crease had smoothed all it will. It's a balance when using heat on these things, you have to have enough heat to produce stream (some guys just use boiling water), because it acts as a regulator, no higher than 212. ANY direct (extreme) heat will instantly melt your wing!

Add for the pod, I haven't had to go there yet (knock on wood), but there are "sock" methods, balloon methods, etc. explained in great detail in their own threads here on RCG.

Hope I helped a little, keep us posted.
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Old Oct 13, 2013, 07:58 PM
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Oh, as for the fill in after you stream it out as much as possible, I'll get back to you if nobody else does. I remember reading the method, but don't recall the specifics (I'm pretty sure you don't want to fill the whole thing with heavy epoxy).
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Old Oct 13, 2013, 09:30 PM
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Canada, ON, Puslinch
Joined Apr 2010
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Not sure what the exact foam is on the topsky but I use highload 60 and its rated to take 250 f before any melting will occur. I skip the papertowels and just pour boiling water straight out of the kettle on my wings, Never a problem yet.
Another trick I do is heat MGS laminating resin in a glass hypodermic needle to thin it and I inject it right under the unicarbon spar or any delams. You basically want to expand the foam and reset the bond to the foam. In your case it is so close to the root of the gliders wing I would be tempted to glass a extra wide patch about a inch beyond that crease line.

Bagged wings are called stressed skin wings. If a force is placed on the underside of the wing [for example] the skin directs stress in the form of compression on the foam core and a buckling force on the top skin. Buckling is what lifts the skin from the core and often breaks the fibers in the unicarbon spar. The skin must be able to apply loads onto the foam and the foam must be stiff enough to handle the compression. If you can achieve that anything else is just cosmetic.
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Old Oct 13, 2013, 11:05 PM
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United States, UT, Sandy
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I have only done hollow wing repairs so though I do have massive damage on a taboo to fix. But I know you can fix the fuse. Since both repairs center about the cg you should be good. Use carbon tow and epoxy. Wrap with vcr tape for best finish.
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Old Oct 15, 2013, 01:30 PM
Foam flogger
Roseville, CA
Joined Apr 2009
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Thanks all. I treated the wing with boiling water last night. Seemed to pop out a bit, but you can still see the crease. I'm going to put some glass over them next.
As for the delam on the top. I don't have a syringe. I thought I had read on here somewhere that the glass is porous enough that if I rubbed epoxy on the delam it would soak through. Is this not accurate?
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Old Oct 15, 2013, 01:49 PM
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Canada, ON, Puslinch
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Quote:
Originally Posted by Belem View Post
Thanks all. I treated the wing with boiling water last night. Seemed to pop out a bit, but you can still see the crease. I'm going to put some glass over them next.
As for the delam on the top. I don't have a syringe. I thought I had read on here somewhere that the glass is porous enough that if I rubbed epoxy on the delam it would soak through. Is this not accurate?
Correct . Its just that the spar will not be porous if you need to get resin under there.

I just find the needles handy. I have a few hundred of them if you need one drop me a PM BTW NEVER inject CA into a confined area even if it is foam safe CA.

I use MGS resin which is thin enough I can push them through a needle.[made easier with a bit of heat] YMMV with other resins.
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Old Oct 17, 2013, 01:03 AM
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Quote:
Originally Posted by DLGjunkyard View Post
BTW NEVER inject CA into a confined area even if it is foam safe CA.
May I know why?

Sherwin
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Old Oct 17, 2013, 07:33 AM
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DLGjunkyard's Avatar
Canada, ON, Puslinch
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Originally Posted by Sherchoo View Post
May I know why?

Sherwin
Its more about the heat generated during the cure melting the foam rather than a chemical eating the foam. Foam insulates that heat therefor making it worse. Also, not all foam safe CA is foam safe. Some of it seems to age and worsen with age.
I have used brand new bottles on thin foam trailing edges and watched the foam melt. Be careful how you apply it . Its not all equal.
BTW I have used regular CA very very sparingly on foam without trouble. I suspect the difference in the two is just the cure rate.
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Old Oct 17, 2013, 07:57 AM
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Quote:
Originally Posted by DLGjunkyard View Post
Its more about the heat generated during the cure melting the foam rather than a chemical eating the foam. Foam insulates that heat therefor making it worse. Also, not all foam safe CA is foam safe. Some of it seems to age and worsen with age.
I have used brand new bottles on thin foam trailing edges and watched the foam melt. Be careful how you apply it . Its not all equal.
BTW I have used regular CA very very sparingly on foam without trouble. I suspect the difference in the two is just the cure rate.
Make sense... thanks. I've myself seen the foam safe CA melt off foam, not when I applied the CA but when I gave it kick. Realised later it was the heat was the culprit.

I've treated delam many times with thin foam safe CA. A layer of CA is spread on top of the glass. Using something smooth e.g. wax paper, I would press the CA in. The glass will bond to the foam as the CA seeps thru the porous material. No shringe nor needles required. Quick and dirty but works everytime.

Sherwin
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Old Oct 17, 2013, 08:22 AM
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Yep, You can use it . Just be cautious . Another way to slow the cure rate is to drop the temperature. Moisture is what cures CA and the cooler the air the less moisture it can hold slowing the cure rate.
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Old Oct 17, 2013, 09:00 PM
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Singapore, Singapore
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Originally Posted by DLGjunkyard View Post
Yep, You can use it . Just be cautious . Another way to slow the cure rate is to drop the temperature. Moisture is what cures CA and the cooler the air the less moisture it can hold slowing the cure rate.
Humidity is pretty high here in our part of the world (today is 84%) but curing rate seems to be 'ok' as very little heat is generated. Love these BSI Gold CAs. Anyway, now since I know that even foam safe CA can melt foam, I'll take extra caution.

Sherwin
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Old Oct 17, 2013, 09:10 PM
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For pod repair, see here. Can't really help with the wing.
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Old Oct 17, 2013, 09:48 PM
Foam flogger
Roseville, CA
Joined Apr 2009
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I replaced the pod, it was broken clean thru in two places, cracked in three more - including around the wing bolts, and small pieces were missing.
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Old Oct 18, 2013, 07:55 PM
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Good choice.
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