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Old Aug 08, 2012, 06:24 PM
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Actually, birds do have a vertical rudder-like surface, as and when needed. Birds are relaxed stability variable geometry platforms, with an extremely fast and complex flight control system. they can alter the drag and pitch of every flight surface in fractions of a second, and change their tail's surface area, pitch and tilt angle to maintain control. And they can even manage without a tail, though their maneuverability is limited, by altering the CG position relative to the wings and the drag from the wingtips. one of the main reasons why it took so long for humanity to create viable aircrafts is because we lost too much time trying to imitate birds, which are way too complex. By comparison, it took only 50 years to get from the Wright Flyer to the X15, and a few years more to get to the moon.
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Old Aug 09, 2012, 01:30 AM
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Originally Posted by x-surfer View Post
Yes, tumblewings are like training wheels for walkalong glider pilots. then they move on to more advanced designs like flying wings. What do you think is giving you the most yaw stability, the weight up front or the sweep back of the wings? Do you also have a twist to the wings (washout) so the stall happens first along the center line? I guess we are both talking about flying wing designs. And why not? Can you think of a flying animal with a vertical rudder-like surface?
Yes we are talking about flying wings. Yaw stability- definitely sweepback is responsible. You can reduce it and watch the dutch roll come in. The CG is where it is for pitch stability. Yes there is washout- the designs automatically build that in, and can be adjusted in the build and trim process. There's also a pretty good airfoil- a definite curve to the top surface.

I can't think of any flying animals with a vertical rudder. It's probably because yaw is so easy to control. Fish have lots of vertical surfaces because of their side to side propulsion- these go vestigial in rays which use vertical motion for propulsion. The outliers here are the dolphins and whales which have vertical fins. It's not really clear what they're for. Male killer whales and sperm whales swim much the same way, but have wildly different dorsals.
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Old Aug 09, 2012, 01:37 AM
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Originally Posted by Brandano View Post
Actually, birds do have a vertical rudder-like surface, as and when needed. Birds are relaxed stability variable geometry platforms, with an extremely fast and complex flight control system. they can alter the drag and pitch of every flight surface in fractions of a second, and change their tail's surface area, pitch and tilt angle to maintain control. And they can even manage without a tail, though their maneuverability is limited, by altering the CG position relative to the wings and the drag from the wingtips. one of the main reasons why it took so long for humanity to create viable aircrafts is because we lost too much time trying to imitate birds, which are way too complex. By comparison, it took only 50 years to get from the Wright Flyer to the X15, and a few years more to get to the moon.
Yes, you're right- I've often watch raptors as they twist their tails to at least 45 degrees to balance turns. But they have no rudders when in stable flight. They are relaxed stability, but they do have fully stable configurations. It is pretty easy for a soaring bird to glide in a rigidly stable configuration if it wanted to. They just tend to maximise everything dynamically because they can. But if you watch a seagull in strong lift, it assumes a relatively inefficient but stable configuration that is easy for humans to model. I don't think the problem was the configuration. It was the appreciation of the importance of stability as the primary design consideration- for human flight, model flight, and my particular interest, paper airplanes. The dart configuration is over-stable (as well as crude in many other ways).
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Old Aug 09, 2012, 04:56 PM
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Originally Posted by Brandano View Post
Actually, birds do have a vertical rudder-like surface, as and when needed. Birds are relaxed stability variable geometry platforms, with an extremely fast and complex flight control system. they can alter the drag and pitch of every flight surface in fractions of a second, and change their tail's surface area, pitch and tilt angle to maintain control. And they can even manage without a tail, though their maneuverability is limited, by altering the CG position relative to the wings and the drag from the wingtips. one of the main reasons why it took so long for humanity to create viable aircrafts is because we lost too much time trying to imitate birds, which are way too complex. By comparison, it took only 50 years to get from the Wright Flyer to the X15, and a few years more to get to the moon.
I have seen birds tilt and angle the tail so as to produce a force about the yaw axis so, yes they would be able to use their tail feathers like a rudder if needed. I just saw a bird without tail feathers and wondered if he could fly at all. Then he jumped and, a little labored, but he flew away.
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Old Aug 09, 2012, 06:11 PM
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Originally Posted by Edmond Hui View Post
I think trimming and trimmability (and the ability to stay trimmed) is the biggest design obstacle in free flight paper airplanes. I think tumbling types are avoiding the question, and frankly, avoiding the fun...
To me, the grace of something flying steadily into the distance is much of the fascination of the whole activity.
Wow, Ed, so you have a book out on paper airplanes. It must be a treasure trove of aeronautical information about how to really get a paper airplane trim and ready for flight. I'll bet it has great info because having a well trimmed plane is essential to getting it to soar as a walkalong glider. Have you tried the paperang in waxed tissue paper with a tape ballast to get it to fly slow enough for walkalong gliding? There is a new book on walkalong gliding which includes two paper airplanes designs (the tumblewing and a traditional design with wing washout added).
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Old Aug 10, 2012, 01:27 AM
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Wow, Ed, so you have a book out on paper airplanes. It must be a treasure trove of aeronautical information about how to really get a paper airplane trim and ready for flight. I'll bet it has great info because having a well trimmed plane is essential to getting it to soar as a walkalong glider. Have you tried the paperang in waxed tissue paper with a tape ballast to get it to fly slow enough for walkalong gliding? There is a new book on walkalong gliding which includes two paper airplanes designs (the tumblewing and a traditional design with wing washout added).
Thanks for that link- I was unaware of it. Yes, I do have a book, but that was a very long time ago, and the format of it was dictated by the publisher- (give us 16 designs and we'll publish your crazy idea...). I was motivated by the wish to get my Paperang design into print for copyright reasons, and even that (1987) was ten years after I had invented it. No, I haven't explored exotic papers, but my guess is that it won't need ballast as Paperangs tend to come out with the CG in the same place. I have to admit I haven't done much walkalong stuff as I am fascinated by letting go and watching the things fly. I spent enough hours hanging above hills in Wales in my youth to have internalised slope soaring. What I will do in the future is to add RC. I'm sure on calm days outdoor RC gliding will be possible with paper airplanes, and it would be fantastic to create a module that could be taped onto a paper airplane to allow the creation of a fully controllable paper airplane in minutes. The problem is whether to use weight shift (use two servos to move the battery fore and aft and left and right), or figure out how to wing warp...
My TED talk (apart from being an attempt to get to the TED conference) was partly just to get people to see what is possible with a well made flying wing, and partly to explore this idea of an illogical paradigm- following the rules of origami even when they don't add anything to enjoyment; or making things in a dart shape when they clearly don't fly very well. It's like designing cars that have to have brakes working all the time, for a hundred years.
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Old Aug 10, 2012, 02:34 AM
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In sixth grade one of my classes (15-20 people) had a competition to see who could make a paper airplane to go the furthest. I don't recall for sure but I imagine most of the kids made a dart plane that probably didn't go very far. What I do remember is the fact that my design completely crushed the competition. I wrapped two Pink Pearl erasers (the paralellogram-shaped ones) in a piece of paper and attached a tiny little plane to it (I'm sure it was a dart shape). I easily threw mine far down the hall while most would just drift to one side, hit the wall, and then fall. I was not awarded the prize.
I must have decided that initial kinetic energy was more important than glide angle.

http://en.wikipedia.org/wiki/File:Of...nk-erasers.jpg
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Old Aug 11, 2012, 01:09 AM
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continuously propelled paper airplanes

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Originally Posted by Edmond Hui View Post
Thanks for that link- I was unaware of it. Yes, I do have a book, but that was a very long time ago, and the format of it was dictated by the publisher- (give us 16 designs and we'll publish your crazy idea...). I was motivated by the wish to get my Paperang design into print for copyright reasons, and even that (1987) was ten years after I had invented it. No, I haven't explored exotic papers, but my guess is that it won't need ballast as Paperangs tend to come out with the CG in the same place. I have to admit I haven't done much walkalong stuff as I am fascinated by letting go and watching the things fly. I spent enough hours hanging above hills in Wales in my youth to have internalised slope soaring. What I will do in the future is to add RC. I'm sure on calm days outdoor RC gliding will be possible with paper airplanes, and it would be fantastic to create a module that could be taped onto a paper airplane to allow the creation of a fully controllable paper airplane in minutes. The problem is whether to use weight shift (use two servos to move the battery fore and aft and left and right), or figure out how to wing warp...
My TED talk (apart from being an attempt to get to the TED conference) was partly just to get people to see what is possible with a well made flying wing, and partly to explore this idea of an illogical paradigm- following the rules of origami even when they don't add anything to enjoyment; or making things in a dart shape when they clearly don't fly very well. It's like designing cars that have to have brakes working all the time, for a hundred years.
No matter what your method of continuous propulsion and control of paper airplanes (RC or walkalong gliding) you'd need to trim. There would be a split in the culture of paper planes, one remaining with "the more designs the better" and trimming a given design for best glide speed and with minimal right or left turning tendency in preparation for RC etc. I wouldn't be surprised if RC modules were getting so small to fit on a paper airplane. Here's a video, but the design is a traditional dart! With a strong enough engine, anything can fly:
LARGE FLYING RC PAPER AIRPLANE (3 min 13 sec)
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Old Aug 11, 2012, 02:50 AM
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Originally Posted by x-surfer View Post
No matter what your method of continuous propulsion and control of paper airplanes (RC or walkalong gliding) you'd need to trim. There would be a split in the culture of paper planes, one remaining with "the more designs the better" and trimming a given design for best glide speed and with minimal right or left turning tendency in preparation for RC etc. I wouldn't be surprised if RC modules were getting so small to fit on a paper airplane. Here's a video, but the design is a traditional dart! With a strong enough engine, anything can fly:
You're right. Isn't it interesting that there is a 'traditional dart' at all? What an abomination of things that fly- there is nothing in nature or a design of man that looks remotely like it. Anyone who says 'space shuttle' hasn't really looked beyond a very superficial resemblance of delta wings, which in full sized aircraft are only there to solve supersonic problems.

On trim, in case any reader is interested, paperangs are made so the CG comes out right and washout takes care of pitch stability. Roll is trimmed by easing the wing surface sideways under the central staple to make the 'billow' in the wing precisely symmetrical. The paperang is positively stable, but only gently, so that if you launch it flat, it goes straight, but if you launch it banked, it will fly in circles but slowly straighten. Yaw is taken care of by the wing sweepback.

This does create interesting problems for RC control, which is why the traditional hang gliding method of weight shift becomes interesting.
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Old Aug 11, 2012, 11:01 AM
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Ah, just listen to all that power produce......all that slowness. That much inefficiency makes me really sad.
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Old Aug 12, 2012, 02:23 AM
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Ah, just listen to all that power produce......all that slowness. That much inefficiency makes me really sad.
Exactly! That shape produces all that inefficiency silently, probably hundreds of times a day, all round the world as people fly their paper darts.
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Old Aug 13, 2012, 03:52 PM
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To get back to Ed's point that the rules should be stretched and broken to explore wider ranges for paper airplanes, lighter materials lead to slower flight and walkalong gliding. The book describes mounting a dried butterfly to fly as a walkalong glider, essentially using the butterfly airframe, evolved over millions of years, to produce a light flying model. Ed's perfectly trimmed paper airplane is where walkalong gliding begins. Chase after that glider, sculpting the air it flies through, and you have sustained and controlled flight of a paper airplane.
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Old Aug 15, 2012, 03:10 AM
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To get back to Ed's point that the rules should be stretched and broken to explore wider ranges for paper airplanes, lighter materials lead to slower flight and walkalong gliding. The book describes mounting a dried butterfly to fly as a walkalong glider, essentially using the butterfly airframe, evolved over millions of years, to produce a light flying model. Ed's perfectly trimmed paper airplane is where walkalong gliding begins. Chase after that glider, sculpting the air it flies through, and you have sustained and controlled flight of a paper airplane.
Can't argue with that! If I have an overall point really, it's that the vast majority of paper airplane makers (and that's a much larger number of people than those that make RC aircraft of any sort) are missing out on a huge part of the easily available flight envelope because they are binding themselves to rules that make no sense. Would you, as a RC modeller, obey a rule to use balsa only, with no glue? Would you obey a rule to make only aircraft with delta wings and a V section fuselage? Would you launch in a way that guarantees a stall? That's the sort of nonsense that paper airplane makers are limiting themselves to. Walkalong glider flyers are way, way ahead of what the average paper airplane maker does.
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Old Aug 15, 2012, 03:58 PM
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Personally I never stuck by these "rules" but it might just be me. Sometimes I give myself constraints, because I like a challenge. I have a nice Hoerten style flying wing that is only folded, out of a single piece of A4 paper, and will fly fine but flies better if you seal the folds with glue or with a couple of staples. The largest paper airplane I ever built had a 2 meter wingspan, built with a diamond planform, using a plastic straw for part of the fuselage and a paperclip to get the CG in the right position. the wing chord was less than 3 cm near the wingtips, and the structure was such that with no lift they would just collapse downwards, the curve of the paper could only support upwards loads. I have a very nice small aspect ratio flying plank that is essentially a piece of A4 paper with several folds on the leading edge, with the extremities cut so that the leading edge portion is bent slightly upward to provide dihedral and its trailing edge cut in an elliptical shape, while the trailing edge portion is folded and glued for strength and to add sweep, bent downward and the trailing edge again trimmed to add to the sweep. Very stable and with tabs cut in it can be made to fly many types of patterns.
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Old Aug 15, 2012, 10:14 PM
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Can't argue with that! If I have an overall point really, it's that the vast majority of paper airplane makers (and that's a much larger number of people than those that make RC aircraft of any sort) are missing out on a huge part of the easily available flight envelope because they are binding themselves to rules that make no sense. Would you, as a RC modeller, obey a rule to use balsa only, with no glue? Would you obey a rule to make only aircraft with delta wings and a V section fuselage? Would you launch in a way that guarantees a stall? That's the sort of nonsense that paper airplane makers are limiting themselves to. Walkalong glider flyers are way, way ahead of what the average paper airplane maker does.
It is instructive to look at nature for lousy aerodynamics and what survival value it has. It appears much easier for an animal to evolve gliding flight as evidenced by the wide variety of animals just looking to move about the canopy without touching the ground. They are able to climb trees and glide to a somewhat soft landing on another tree. I'm sure this gliding snake doesn't have much better aerodynamics than a paper airplane dart:
Flying Snakes... and Leaping Lizards (1 min 48 sec)

Maybe the lizard who leaps to get away from the gliding snake has a better glide ratio than the snake!
Seems like this rain forest in Borneo has tree spacing which favors gliding species:
http://ngm.nationalgeographic.com/ng...e4/media2.html
But for sustained flight, even soaring flight, these animals have a long way to go.
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