[quote author=Avaiojet ..
Question.
R/C guys use a single tube for attaching wings. I've had a few models like this and still have a few.
We snap roll these models and some are large. They stay together. My old Staudacher was 80.5" in span. Not large but..
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Of course there is the issue with control system, but also structurally, a single thick tube is never ideal. It's used in RC models only because it's easy to make.
The problem with a tube is that there is the smallest amount of material where you need it the most (in top & bottom to handle the tension and compression), and unnecessarily much material the closer you get to the center line.
It's kind of a mirror image of a good I-beam. But it seems to work with RC people, they are not so anal about weight and intelligent use of construction materials. L
Ps. I must add that in my free flight gliders, the wing joiners are 2x 1/4" dia. solid spring steel bars and they bend far too easily. Now we're looking for a replacement in carbon, perhaps with a square section.