Hey guys, I got a question about my top wing trainer which still has rubber bands that hold the wing down. After several flights I can tell the top LE balsa sheeting where the rubber bands go across the top isn't going to last much longer. I tried to repair one small crack awhile back but I don't think there's any support under there like on the trailing edge. What's the best way to do this repair/reinforcement so I don't add a lot of extra weight?

Just sent you a PM.

I'm assuming this is still the same the Alpha 40 you had last year, and your right on the lack of support - just the LE, then the sheeting to the spar. The sheeting is a bit thin on the leading edge, and once it gets a crack it usually needs to be reinforced underneath. I found out how thin this sheeting is on the one I rebuilt.

I've just picked up a new Alpha 60 RTF which will need rib repair, and some sheeting repair on the wing top near the center section. I'll try to do a repair thread on this one since I didn't get to doing one on the Alpha 40 I rebuilt this spring.

Hogflyer

While I haven't used this yet (but will) I saw another post on here where someone recommend using this aluminum sheet available at your LHS, and wrap it around the LE & TE of the wing where the rubber bands go. A little epoxy and some covering over the area, you'd never be able to tell.

A buddy also has a trainer that was built up with plywood in this area. It worked, but looked pretty bad.

when i build a airplane with rubber band hold down wings i reinforce that section with fiberglass tape and either epoxy or fiberglass.a few of the them i have added 1/16 plywood to the top wing section.

For aluminum sheeting, you can cut open a soft drink can

Minnflyer, I like the idea of the aluminum sheet which I have plenty handy. Can you give me more details on that fix? What do you do about the covering since it won't stick to it, I would think it would tear easier from the rubber bands if it's loose.

Repair the wood on the leading edge of your wing. Then leave the area you are going to put the aluminum on uncovered. Cut the metal to size for the area you are going to cover. Then spread 30-minute epoxy on the metal and secure it in place with tape while the epoxy dries. Just leave the aluminum uncovered. As long as the edges of the metal aren't sticking up it won't cut your rubber bands.

Ken

why not take a file and some sand paper and chamfer or round the edges of the aluminum... no sharp edges, no cuts. if you clean it up nice and then epoxy it down to the sheeting, you can run a fillet of epoxy (the squeezeout from the application of your alum. should be enough) around the edge with your finger or a popsicle stick. it should be almost unnoticeable that it is there. I would be willing to bet that if you scuffed the surface of the aluminum with some 80 grit and then wiped it clean with alcohol, the covering would stick to it as well.

troposcuba, I like that idea...I'll try an experiment with the aluminum and see what happens.

Carbon fiber tape. I have an old Pica Rapier, 40 size, that had a crack in the leading edge balsa. Got out my iron and heat gun, lifted the covering material and pulled it back far enough to access the crack. I then ca'ed a piece of carbon fiber tape about 2" by 4" right down on top of the leading edge sheeting. Then I ironed the covering back down. I don't think it took me all of 20 minutes. Because the carbon fiber is only .007" of an inch thick it's hardly noticeable. Use thin ca and sort of roll the cf tape onto the balsa while applying the ca. I would wear a glove because the ca gets a little warm when it kicks and a plastic baggy too to prevent it from sticking to your hand. When you are done it will be as smooth as the wood and extremely strong.

the Alluminum can is a good idea, but as an alternative: mix up some 30 min - 1 hour epoxy, spread it over the affected area, lay a strip of fibreglass cloth over the epoxy and press it in, lay a layer of epoxy over the cloth and let it dry, sand the epoxy enough to get it smooth again and re-cover the wing section, worked when my dads Kadet wing snapped in half

I have to ammend my suggestion. i do believe the fiberglass or cf application would be cleaner, stronger, lighter and easier to do correctly. go figure, i am a structural guy on fullsize, so i think in terms of aluminum scab patches as a first resort. I do composites as well, but you said aluminum, so that is where my mind went.