So, how does a frisbee fly?

Just got our dog a new frisbee (he goes thru 'em pretty fast if we're
careless and leave them within reach after a session).

This one has a large outer wire rim, small inner ring, and stretched
radially between these 8 or 10 tapered spandex wedges (i.e., these
wedges get wider as they go radially outward). There are gaps of
comparable width between each of these blades, and each wedge is twisted
by 180 degrees between inner and outer rings with most of the twist
occurring close to the inner ring, so that these wedges give a
reasonably convincing imitation of a multi-bladed propellor.

This thing seems to fly just about as well, however, whether you fly it
right side up or upside down, and whether you flip it to spin CW or CCW.
(Hurts my left arm when I try to spin it CCW, however.) In other words,
if there's any helicopter effect here, it's pretty weak.

So, how does a frisbee fly, anyway? Another of his favorites is just a
10" diameter weighted outer rim filled in with a slightly saggy "cloth
drumhead", which visibly bulges upward 1" or so at the center into a
fair imitation of an airfoil when you throw it. I've always figured the
heavy rim kept the thing spinning and thus semi-rigid, and the forward
motion of the airfoil shape gave the lift.

"AES" wrote in message
...

some text deleted

So, how does a frisbee fly, anyway? Another of his favorites is just a
10" diameter weighted outer rim filled in with a slightly saggy "cloth
drumhead", which visibly bulges upward 1" or so at the center into a
fair imitation of an airfoil when you throw it. I've always figured the
heavy rim kept the thing spinning and thus semi-rigid, and the forward
motion of the airfoil shape gave the lift.

I'm a proponent of the Bernoulli theory (Stand by with flame deflectors). I
agree with the metal mass providing fly wheel effect and the airfoil for
lift. I'll add to that my theory that gyroscopic precession makes it tilt so
the lift vector turns it. Try changing from backhand to forehand to change
the direction of rotation.

One small quibble with your post. Frisbee is a brand name and deserves
trademark recognition. That is to say, while Frisbee makes a flying disc,
not all flying discs are Frisbees. If it don't say Frisbee on the gizzie, it
ain't.

AES wrote:

So, how does a frisbee fly, anyway? Another of his favorites is just a
10" diameter weighted outer rim filled in with a slightly saggy "cloth
drumhead", which visibly bulges upward 1" or so at the center into a
fair imitation of an airfoil when you throw it. I've always figured the
heavy rim kept the thing spinning and thus semi-rigid, and the forward
motion of the airfoil shape gave the lift.

That, and a positive angle of attack. The spin keeps it gyroscopically
stable. As the forward motion decreases the Frisbee begins to settle,
increasing the angle of attack until becomes a kind of parachute. But
not always. Throwing the Frisbee up will give it a positive angle of
attack as it climbs. Once the forward motion stops the angle of attack
can become negative, generating downward lift and causing the Frisbee
to accelerate downward and back toward you like a boomerang. It comes
down faster than it would simply fall and it accelerates the whole way.

AES wrote:
Just got our dog a new frisbee (he goes thru 'em pretty fast if we're
careless and leave them within reach after a session).

This one has a large outer wire rim, small inner ring, and stretched
radially between these 8 or 10 tapered spandex wedges (i.e., these
wedges get wider as they go radially outward). There are gaps of
comparable width between each of these blades, and each wedge is twisted
by 180 degrees between inner and outer rings with most of the twist
occurring close to the inner ring, so that these wedges give a
reasonably convincing imitation of a multi-bladed propellor.

This thing seems to fly just about as well, however, whether you fly it
right side up or upside down, and whether you flip it to spin CW or CCW.
(Hurts my left arm when I try to spin it CCW, however.) In other words,
if there's any helicopter effect here, it's pretty weak.

So, how does a frisbee fly, anyway? Another of his favorites is just a
10" diameter weighted outer rim filled in with a slightly saggy "cloth
drumhead", which visibly bulges upward 1" or so at the center into a
fair imitation of an airfoil when you throw it. I've always figured the
heavy rim kept the thing spinning and thus semi-rigid, and the forward
motion of the airfoil shape gave the lift.

I'm not 100% sure and I'm not aerodynamicist, but I think two things
help a frisbee fly, or any disk even one lacking an airfoil shape.

1. The gyroscopic stabilization provided by the spinning imparted when
thrown. Just try to throw a frisbee or any disk without spinning it.
It won't go anywhere.

2. A small AOA imparted also when thrown. This is the essential part
and (1) above is really only important to the extent that it allows the
angle of attack to be maintained during flight.

Almost any object will create lift if it has some AOA. You can verify
this by extending your hand out of the car window when driving, which
most of us did as kids. If you rotate your hand from horizontal to say
30 degrees relative to the wind, you can create a fair bit of lift. And
most of our hands aren't exactly an ideal airfoil.


Matt

Casey Wilson wrote:

"AES" wrote in message
...

some text deleted

So, how does a frisbee fly, anyway? Another of his favorites is just a
10" diameter weighted outer rim filled in with a slightly saggy "cloth
drumhead", which visibly bulges upward 1" or so at the center into a
fair imitation of an airfoil when you throw it. I've always figured the
heavy rim kept the thing spinning and thus semi-rigid, and the forward
motion of the airfoil shape gave the lift.


I'm a proponent of the Bernoulli theory (Stand by with flame deflectors). I
agree with the metal mass providing fly wheel effect and the airfoil for
lift. I'll add to that my theory that gyroscopic precession makes it tilt so
the lift vector turns it. Try changing from backhand to forehand to change
the direction of rotation.

Then how do you explain how well a simple flat disk such as a CD will
fly? It certainly has no airfoil shape.


Matt

Matt Whiting wrote:
Almost any object will create lift if it has some AOA. You can verify
this by extending your hand out of the car window when driving, which
most of us did as kids. If you rotate your hand from horizontal to say
30 degrees relative to the wind, you can create a fair bit of lift. And
most of our hands aren't exactly an ideal airfoil.

The magic question though is that B or N? I found as a kid (I guess I
was bored) that curving my hand resulting in better "lift", which would
seem to implicate B.

-Robert

Robert M. Gary wrote:

Matt Whiting wrote:

Almost any object will create lift if it has some AOA. You can verify
this by extending your hand out of the car window when driving, which
most of us did as kids. If you rotate your hand from horizontal to say
30 degrees relative to the wind, you can create a fair bit of lift. And
most of our hands aren't exactly an ideal airfoil.


The magic question though is that B or N? I found as a kid (I guess I
was bored) that curving my hand resulting in better "lift", which would
seem to implicate B.

Neither, it is C.

Matt

Matt Whiting wrote in news:Fj%ng.29$Pa.4943
@news1.epix.net:

Snipola
Then how do you explain how well a simple flat disk such as a CD will
fly? It certainly has no airfoil shape.

They don't. At least none of the CD's that I've ever thrown went
very far. They all roll immediately and change direction.

I used to work at a CD plant, so I had a few to throw around.

Brian
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AES wrote:
So, how does a frisbee fly, anyway?
Its all done with invisable strings!
Rocky

"Casey Wilson" N2310D @ gmail.com wrote:


"AES" wrote in message
...

some text deleted

So, how does a frisbee fly, anyway? Another of his favorites is just a
10" diameter weighted outer rim filled in with a slightly saggy "cloth
drumhead", which visibly bulges upward 1" or so at the center into a
fair imitation of an airfoil when you throw it. I've always figured the
heavy rim kept the thing spinning and thus semi-rigid, and the forward
motion of the airfoil shape gave the lift.

more snippage
I
agree with the metal mass providing fly wheel effect

There you have it. It's the fly wheel effect. Everyone knows that a
rapidly spinning massive disk is referred to as a fly wheel.
Obviously, our predecessors didn't give them that name just on a shim.
Obviously someone must have observed that they fly. Which is probably
why they make cars so heavy, so that their rather large fly wheels
won't lift them off of the ground.

Glad we got that one figured out.
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