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Jul 06, 2003, 07:48 PM
TheTick's Avatar

How to repair hollow molded wing???

My Nemesis had a mid-air today. The leading edge got crunched in about 2" deep and 5" wide. I figured I would just cut out the damaged section, glue in a balsa block, sand to shape then fiberglass over it. No damage was done to the carbon fiber spar and is still very strong.

Is there a better way? Thanks!
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Jul 06, 2003, 08:36 PM
I'm All Thumbs
AirBornOne's Avatar

Hollow wing repair...

Bummer about your plane Tick,
My 2m moldy ASW-28 wing is only cracked, nowhere near your level of damage but my plan might work for you also.
I'll first restore, as much as possible, the original wing shape using CA to hold the glass together. Sounds like your probably missing some skin so you'll need to replace what's missing. A balloon run inside from the root end and inflated slightly can give you something to work against/to. Sort of an inside out bagging operation. You can add glass (or carbon) patches from inside this way too.
My ASW is so light,I'll finish by filling the D-box (both wings) with expanding foam. Probably the two part liquid kind. It's more predictable.
Good luck with your repairs.
Jul 06, 2003, 09:23 PM
TheTick's Avatar
Hi Jay,
What's a balloon run? The damage isn't as bad as it sounds. The top portion of the wing was dagamed pretty bad so I just cut out a 2x3" square just behind the leading edge. This gives me space to work on the bottom wing from both sides. The bottom still has all the skin and looks restorable so I'm gonna work it instead of cutting it out. I'm thinking about taping a thin plywood sheet over the bottom for support, then using epoxy and another thin plywood sheet inside to push up against the bottom support. Does this make sense?
Jul 06, 2003, 10:58 PM
Registered User
mattg's Avatar
I haven't yet had to attempt one of these jobs but have seen a very good one on a tragi wing tip.

A mold was taken of a good wingtip and a patch made of carbon cloth and epoxy. This was then let into the wing in such a way that it was a very good imitation of the original.

I'd be a bit careful about using CA as I don't think it can compete with laminating epoxy for strength over time or for being easy to sand which will be important in achieving a top class finish.
Jul 06, 2003, 11:03 PM
Registered User
I'd epoxy some 1/64 or 1/32 plywood on the inside of one skin (top or bottom). This will add some integrity and strength to the skin. Then use some blue/pink foam to build the airfoil shape for the other skin.

You might want to epoxy in a new leading edge (a hardwood dowel or the like) to bind everything together.

Jul 06, 2003, 11:27 PM
Vitruvian JART
Reed's Avatar
Listen to hkrussell - you won't be sorry.

Also - very important - you'll want to redo the lateral balance of the plane once you're done with the repair. Drill a little hole in the opposite wingtip and carefully epoxy in some leadshot or BBs. Close up with microballoons and sand with 320 or 400 grit.
Jul 07, 2003, 12:19 AM
TheTick's Avatar
Thank you soo much guys! I was gonna use light weight spackle until you recommended the foam stuff.

My main concern now is how to make the bottom look nice since I am not cutting it out. I can press it as flat as I can, but I'm sure it will still look wrinkly with the hairline tears in the skin between the wrinkles.

I'll use the foam/fiberglass method for the top then paint. It should come out nice.

Should i just cut out the bottom and do the same?

Funny thing is that it survived DS'ing all day and even crashed into some tall brush during a 50mph ds groove with no damage. Then at the end of the day, I get taken by a foamie cruising the front side.

Thanks again, I'm actually looking forward to working on it. You guys almost made it worth the crash.
Jul 07, 2003, 12:53 AM
Registered User
mattg's Avatar
You could cut out the bottom if it's bad enough. I always tend to err on the side of fixing what's there when possible.

If you do decide to leave them bottom skin in place you could use the 1/64 ply suggested by hkrussell. To get the finish smooth on the outside of the skin , first mask the area to be sanded, sand all outstanding rubbish away, use either car body filler or plastibond (or laminating epoxy and microballons if the wrinkles aren't too deep) to fill the cracks and then carefully sand back to section.

You may need some paint (I think battle scars are cool left as they are so everyone can see your job) if you want things to look schmick again.
Jul 07, 2003, 11:19 AM
TheTick's Avatar
Thanks mattg, I'm gonna leave the bottom and show off the battle scars. Didn't think about the cool factor of battle scars nicely repaired.

You guys have mentioned micro balloons. What are they?
Jul 07, 2003, 01:20 PM
Vitruvian JART
Reed's Avatar
Microballoons are a kind of powder that thickens epoxy. After you mix your epoxy and hardener, mix in some microballoons to thicken it. Many useful applications - fills more area and sands easier than epoxy alone. Microballoons also make the epoxy more brittle so be mindful of this.

You should be able to get microballoons anywhere they sell fiberglass and composites.

Cabosil is a thixotropic agent that tends to make the epoxy a bit tougher. Doesn't sand as easily as microballoons. Sometimes a mix of balloons and cabosil works well. My crystal ball says you will soon be very, very glad you heard about these substances.

This story reminds me of a JW that took out my Mach 1. He was a good guy, realized his mistake, and offered to pay me for the plane, but that's rarely the case. The problem isn't with the foam, it's with the fact that foam can lead pilots to be irresponsible and careless. It lends a sense of false security to the pilot and they sometimes never learn to be pilots who can read air, anticipate and communicate while flying, and land the plane in a controlled manner - they just become stick-twiddlers and air hooligans. Not all foam flyers are like this, but enough that it is a concern. Wait till they come down before throwing out your lovely euro-moldy, or wait till there's only one or two and always let them know where you are in the sky. And before the Foam Police jump on me about this, let me just say - "Some of my best friends fly foam."
Last edited by Reed; Jul 07, 2003 at 01:37 PM.
Jul 07, 2003, 02:42 PM
Piscine Promulgator
surfimp's Avatar
Agreed Reed, I'm extremely conscientious of non-foamie planes when I'm flying my EPP stuff. I can think of nothing that would depress me more (at least in terms of R/C soaring) than damaging a beautiful molded plane with my flying packing material Of course this sort of awareness is, to my mind, to be expected whenever people are sharing the air, regardless of what they're flying. Obviously if two Zagis collide it's no big deal in terms of repairs, but if the collision wasn't intentional and the captain had not lit the "Combat Light", so to speak, then it's a midair all the same.

To me, learning to actually pay attention to what others are doing while you're flying--even if you're all flying foam--is an essential part of becoming a better pilot (at least, it's part of my regimen). Suprisingly enough it seems combat is actually a pretty good way to learn this skill--you learn to fly your plane while watching the other guys--but regardless I think we owe it to each other to keep an eye out, especially when there's beautiful and often quite expensive planes in the air. After all, a foamie pilot can easily ditch his plane to avoid colliding with a nice moldie, and really has little excuse not to at least try to make an evasive manuver!
Jul 07, 2003, 02:46 PM
TheTick's Avatar
Thanks for the info Reed. I'm already past the point of using micro balloons, but I'll keep it in mind next time.

The other guy with the foamie was a good friend of mine. He felt worse than I did and offered to split the cost. I took all the blame because I wasn't paying attention and entered his airspace.

What kind of paint should I use for the wing once it's glassed?
Jul 07, 2003, 07:29 PM
Vitruvian JART
Reed's Avatar
The microballoons I was suggesting had to do with lateral balancing the plane. Your repaired wing will now be much heavier than the other and this will screw up the plane's performance in oh so many ways. You'll be much happier if you don't miss out this important step.

As for paint, just about anything will do. A good automotive primer, sanded to 400 or 600 and some Krylon (misted in several coats) will probably be fine - do not use Rustoleum! Or, like someone said, just leave it all funky to show the scars. It's a real plane now.

Hey Surfimp, whassup!? Glad you're not taking me the wrong way here. We could do with a few more conscentious pilots like you up here in the Bay Area.
Last edited by Reed; Jul 07, 2003 at 07:33 PM.
Jul 07, 2003, 07:51 PM
Registered User
You guys that are concerned about battle damage to the moldies caused by impacts with foamies missed the time one of my DS planes center punched a Zagi that was 'loitering' in the lift band.

The impact reduced the Zagi to it's elemental basics and left a paint/color smear on the leading edge of my wing.

It was not intentional, nor did I enjoy hitting the Zagi, but it was better his plane than mine. He's a friend of mine and I just cut him some new cores and we called it even.

Jul 07, 2003, 07:51 PM
Piscine Promulgator
surfimp's Avatar
Originally posted by Reed
Hey Surfimp, whassup!? Glad you're not taking me the wrong way here.
Heheh, let's just say I'm "multifaceted" I saw your post on ISR and realized that I want no part of being identified as a member of the "foam police" I don't like to see people knock a building material out-of-hand, but the observations that you & others have made about the consequences of "foam courage" are indeed accurate.

We foamie pilots do need to remember that while our planes are virtually indestructible, the planes of others are not necessarily so--i.e. the entire motivation for TheTick posting this thread. Hence we just really need to watch out for each other, and to avoid unintended collisions whenever possible. Get everyone going the same way in the pumps, and whatnot.

Things were more like that when I started slope soaring about 15 years ago--when all the planes were easily wrecked! Things are different now, but it's potentially a good thing in many ways. Of course the downside is the "foam courage" phenomenon. But the slope soaring community at any given site is so small, there's really no excuse not to strive to accomodate one another whenever possible. After all, we're all on the same team, no matter what we fly!