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Frisbees and Boomerangs are heavier-than-air, unpowered, and fly through the air. So are they technically gliders?

They also rotate, so I wonder if these are actually some kind of rotorcraft-type gliders. I looked up all types of rotorcraft on wikipedia, which listed 4 things: helicopters, auto-gyros, gyrodynes, and cyclocopters. All of them were powered, so none of them were rotor-gliders. But then, auto-rotation in a helicopter might be considered gliding (with a pretty bad glide ratio).

One reason I ask is because I want to try to figure out the glide ratio or lift-to-drag ratio of these weird things. Not so easy to do empirically for a boomerang since it takes a weird ascending and descending path. How would you calculate that for a rotating assymetric airfoil?

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    $\begingroup$ Autogyro gliders are not unknown. For example, the Focke-Achgelis Fa 330 en.wikipedia.org/wiki/Focke-Achgelis_Fa_330 $\endgroup$ – xxavier Apr 27 '18 at 10:38
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    $\begingroup$ What is your definition of "glider"? $\endgroup$ – Pondlife Apr 27 '18 at 14:26
  • $\begingroup$ @Pondlife I've always heard it as heavier-than-air, unpowered flight, but never heard anything about rotation one way or the other. $\endgroup$ – DrZ214 Apr 27 '18 at 19:25
  • $\begingroup$ @xxavier That's pretty weird. Surely a simple towed parasail is much more simple to deploy and pack up. $\endgroup$ – DrZ214 Apr 27 '18 at 21:35
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    $\begingroup$ @DrZ214 Paragliders, which enabled fine control, weren't invented until 1952, and parasails, for ascending, first showed up in 1962. $\endgroup$ – user71659 Apr 27 '18 at 22:24
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No, they are airfoils. Airfoils are the contoured shape of the wings that give a boomerang the proper amount of lift as it's launched and spinning through the air. They operate on the same principle as the wings and propellers of airplanes and helicopters. You might even say that a boomerang is a combination of a wing and propeller. Frisbees operate under two main physical concepts, aerodynamic lift and gyroscopic stability. When flying through the air, a Frisbee can be viewed as a wing, with Bernoulli’s Principle governing the magnitude of the lift force which keeps it aloft.

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  • $\begingroup$ If you have a source with this exclusion in the definition, please share it. Otherwise I'm inclined to disagree. A flying wing is basically just a giant airfoil, but it's also a glider, isn't it? And yes there are some flying wings that don't have any active stability, e.g., Horton III: en.wikipedia.org/wiki/Horten_H.III $\endgroup$ – DrZ214 Apr 27 '18 at 21:41
  • $\begingroup$ Not sure what you are asking. The early flying wings had a stability problem as their computers were not capable of correcting the in- flight osculations that occurred. This was overcome in the later aircraft like the F-114 with more advanced computers. Any powered aircraft can be a flying wing once the power is retarded and some glide better that others. Without power they are all flying wings, at least until they run out of altitude. $\endgroup$ – Loren Apr 28 '18 at 2:56
  • $\begingroup$ I was pointing out an example of an aircraft that is both a flying wing and a glider. (And I qualified it by saying it has no dynamic stability, so it is totally unpowered). The point was that flying wings can be considered "just an airfoil" too, but they are gliders (some of them). Therefore calling something just an airfoil is not enough to discredit it as a glider. $\endgroup$ – DrZ214 Apr 28 '18 at 4:22
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It sure seems like it, based on FAA definitions. "The Federal Aviation Administration (FAA) defines a glider as a heavier-than-air aircraft that is supported in flight by the dynamic reaction of the air against its lifting surfaces, and whose free flight does not depend principally on an engine. "

The FAA has also designated a paper airplane as a UAV ("drone"). And they do define a UAV as an aircraft It might also be a rotorcraft depending on whether a whole vehicle can also be a rotor.

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No. A glider is defined as an aircraft that is designed to fly long periods without an engine. The word that eliminates boomerangs and frisbees from this definition is ‘aircraft’ as an aircraft is defined as a machine capable of flight. Likewise, the phrase ‘for long periods’ also eliminates boomerangs and frisbees from the category ‘glider’ for obvious reasons. Both a frisbee and a boomerang can be more closely defined as a wing (or airfoil). When you look at the wing of an airplane or blade of a helicopter, those are what we call ‘airfoils’. An airfoil is a design that’s shape gives an object a positive lift to drag ratio. In the simplistic terms, the top of an airfoil is curved while the bottom is flat. Using Bernoulli’s equation, this shape results in pressure differences over the top and bottom portion of the airfoil as air flows over it. This is how a frisbee and a boomerang work. If you look at each of them from the side, you will notice a flat bottom and a curved upper side which, as previously mentioned, is what causes lift as they move through the air.

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  • $\begingroup$ Any source for the "long periods" part? It's rather ambiguous anyway. A manned glider, if launched from the typical height of a paper airplane, will not glide for long periods. Conversely, a paper airplane launched from a high altitude will glide for long periods. $\endgroup$ – DrZ214 Apr 27 '18 at 23:05

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