Journal einhverfr's Journal: Paper airplanes (yep) 9
Ever since I was in grade school, I have had an unnatural love of paper airplanes, and ever since I was in 7th grade, I have designed my own models.
More recently, though, I have turned my attention to the most complex and challenging area: aerodynamically correct paper airplanes, which fly on lift generated by the Bernouli's Prnciple. While this is quite difficult, the planes fly in ways which are unusual in terms of paper airplanes, and can be extremely rewarding. This is a post to help show some elements of this discipline for others. If there is interest, I will add some photographs of some of my airplanes.
The first point I would make is that lifting bodies are the easiest aerodynamically correct paper airplanes to make when trying to build monocoque airplanes. This is because the simplest lifting bodies can be made out of differentially folded cones, are reasonably simple to make out of a single piece of paper, and don't require the more complex solutions to things like attaching wings.
The simplest lifting bodies however, pose a different challenge. While the center of gravity is reasonably far forward, the center of pressure is fairly far back, making the planes quite spin prone. I have found two solutions to this problem: either enhance wingtip vortices to create drag on the swept wingtips or fold the tips into non-lifting stabilizers. Non-lifting stabilizers have the advantage of causing less drag, but both types work (and fly remarkably differently). Both have the effect of robbing the wingtip of lifting action and thus move the center of pressure forward.
If trying to build fixed-wing aircraft out of paper, this gets to be a lot more complicated. My first few models flew reasonably well, but not great. Stiffness of paper, monoquoque construction, etc. are rather problematic when building larger airplanes with paper and there are other challenges as well.
The biggest challenge is how to attach the wings. Here is where I will let you figure it out
Yes please (Score:2)
If there is interest, I will add some photographs of some of my airplanes.
Chris, please post a couple of pictures! But do put a pencil or something besides it, I'm having trouble understanding scaling here.
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Pics are now up on Flickr:
http://www.flickr.com/photos/39568260@N07/ [flickr.com]
In addition to the use of a screwdriver for scale, dimensions are supplied:
The small delta-shaped lifting body is 5in wide at the tail and 11in long. The large fixed-wing aircraft is 17in long and has a 20 inch wingspan.
Also I used the heaviest general-purpose paper I had available.
Pics (Score:1)
Pics please
Re: (Score:2)
Pics are now up on Flickr:
http://www.flickr.com/photos/39568260@N07/ [flickr.com]
The small delta-shaped lifting body is 5in wide at the tail and 11in long. The large fixed-wing aircraft is 17in long and has a 20 inch wingspan.
I am planning to make a low-wing fixed-wing model soon. All aircraft are monocoque construction (meaning that the skin is weightbearing), except in the case of the fixed-wing craft, in the case of where the wings are attached where one has two separate monocoque constructed pieces fastened togeth
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I can't find any online resources on this. Did you actually figure out how to fold them yourself?
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Yes. I started these designs from scratch with no guidance on how to fold them.
In the case of the lifting body, the primary factor is tension in the paper. I.e. the stress of the paper actualy holds it in shape. The same is true of the airfoil in the other one, but paper rigidity is a major limiting factor there.
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Very cool that you created these yourself. How do they hold up against traditionally folded paper airplanes? Do they stay in the air long enough etc?
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They are very different from traditional paper airplanes in the air.
The lifting body is remarkably fast, but a little unstable. Depending on how I stop the wings from producing lift, one can get some interesting aerodynamic effects. One of the most interesting is what I call "ceiling float" where wingtip arresters stop functioning when the plane is near a ceiling, but the increased pressure (wing on ground effect) prevents spin. The plane will float across the ceiling before suddenly stalling. Note the
Thanks for the pics (Score:1)
Awesome - don't think I could fold that without cutting myself, no matter what paper I tried.