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Old Oct 22, 2012, 02:42 PM
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United States, GA, Cornelia
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Question
Joining small balsa wings with carbon tissue?

I'm building a bug DLG, it has a 29.5" wingspan, and i was wondering if it would be suitable to join the wing halves with carbon tissue and CA or epoxy.

This is the stuff. http://www.rcfoam.com/product_info.p...f37022e986cdfe

If so, whats the best way to go about it?

Let me know what y'all think.

Thanks,
Seth
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Old Oct 22, 2012, 10:16 PM
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If this stuff is anything like the carbon "tissue" that I've played with, there is so much space in it that it's inferior to fiberglass cloth. You end up with a whole lot of epoxy and not much carbon.

If you are a truly excellent craftsman, so that you can get a REALLY good fit, you could double glue using Titebond and it would be strong enough. I wouldn't believe it either except that I saw a snapped wing of this type. It was broken very near the center, but not quite at the joint! Apparently, one applies the glue thinned 50 percent with water, waits several minutes, then joins with full strength glue.

I think I'd use a very narrow strip of light fiberglass cloth, maybe half an inch wide. But I bet even kraft paper would work. If you could get unidirectional fiberglass or carbon cloth that was very light, it would be even better, but I haven't seen anything that light.

My preference would be for slow setting epoxy, but you could probably get away with CA. You can put a piece of polyethylene, stretched tight, over either kind to give a smoother result. With the CA, you could squegee the top of the plastic to spread the glue around if it didn't seem to go where you wanted it. The plastic also seems to help it set up. An alternative is baking parchment, which seems to come off easily.

From what I've seen of the Bug, you'd be better off making the airfoil thinner. If you can get really light balsa, I advocate a wing like that of the original Apogee:
http://charlesriverrc.org/articles/a...gee36_wood.pdf
Notice that the airfoil is only a bit over 6 percent thick!

BTW, I have been fortunate enough to get a few minutes of stick time with Apogees of various sizes. The 40 inch span is far superior to the 30 inch span, and I suspect a larger Bug would fly better too. Or it could be that the 30 inch span just needed an even thinner airfoil.
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Old Oct 22, 2012, 10:36 PM
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Quote:
Originally Posted by lincoln View Post
If this stuff is anything like the carbon "tissue" that I've played with, there is so much space in it that it's inferior to fiberglass cloth. You end up with a whole lot of epoxy and not much carbon.

If you are a truly excellent craftsman, so that you can get a REALLY good fit, you could double glue using Titebond and it would be strong enough. I wouldn't believe it either except that I saw a snapped wing of this type. It was broken very near the center, but not quite at the joint! Apparently, one applies the glue thinned 50 percent with water, waits several minutes, then joins with full strength glue.

I think I'd use a very narrow strip of light fiberglass cloth, maybe half an inch wide. But I bet even kraft paper would work. If you could get unidirectional fiberglass or carbon cloth that was very light, it would be even better, but I haven't seen anything that light.

My preference would be for slow setting epoxy, but you could probably get away with CA. You can put a piece of polyethylene, stretched tight, over either kind to give a smoother result. With the CA, you could squegee the top of the plastic to spread the glue around if it didn't seem to go where you wanted it. The plastic also seems to help it set up. An alternative is baking parchment, which seems to come off easily.

From what I've seen of the Bug, you'd be better off making the airfoil thinner. If you can get really light balsa, I advocate a wing like that of the original Apogee:
http://charlesriverrc.org/articles/a...gee36_wood.pdf
Notice that the airfoil is only a bit over 6 percent thick!

BTW, I have been fortunate enough to get a few minutes of stick time with Apogees of various sizes. The 40 inch span is far superior to the 30 inch span, and I suspect a larger Bug would fly better too. Or it could be that the 30 inch span just needed an even thinner airfoil.
Thank you for the response! And i've been coming to the same assumption about this tissue.

As far as the plane goes, i'm having a guy laser cut me a short kit, this will be my first glider (other than a foam wing that i made and it worked okay). And It seemed like a pretty easy build, cheap too. So this will be my learning platform. But i will definitely look into the Apogee next, a lot of people recommend it.
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Old Oct 23, 2012, 11:20 PM
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Don't give up on gliders if it doesn't work out. The smaller they are, the harder they are to fly and the poorer their performance, even with proper design.
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Old Oct 24, 2012, 05:55 AM
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Don't give up on gliders if it doesn't work out. The smaller they are, the harder they are to fly and the poorer their performance, even with proper design.
Thank you for the words of wisdom! I am also currently building a gentle lady.
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Old Oct 24, 2012, 06:17 PM
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Thank you for the words of wisdom! I am also currently building a gentle lady.
Sounds like you didn't especially need that advice. The GL is a good way to start.
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