So, how does a frisbee fly?

"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.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

alexy wrote:

"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.
^^^^
If I'm gonna be a smarta$$, I should at least type more carefully! g

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.

--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

It's more of a cheer, isn't it?

Fly wheel, fly wheel, go on, now, fly wheel!

"alexy" wrote in message ...
alexy wrote:

"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.
^^^^
If I'm gonna be a smarta$$, I should at least type more carefully! g

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.

--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

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.

"cjcampbell" wrote in message
oups.com...
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.

True, but the increase in angle of attack is strictly a result of the change
in relative wind. The frisbee remains in basically the same attitude
throughout. It has no means of trimming for constant lift or anything like
that.

But
not always. Throwing the Frisbee up will give it a positive angle of
attack as it climbs.

The vertical path is primarily a result of one throwing the frisbee in that
direction. The path would curve down ballistically except for the basic 1G
of lift that the relatively modest angle of attack, basically identical to
the AOA in straight and level flight, provides.

Once the forward motion stops the angle of attack
can become negative,

Negative. As in, not true. The frisbee still has positive angle of attack,
and descends back along roughly the same path it took upward. It's a bit
lazy-eight-ish and, as you know, you don't need negative lift to do those.

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.

No, it doesn't come down faster that it would simply fall. It does
accelerate, just as any falling body accelerates, and just as the rising
body of the frisbee decelerated on its way up.

If the frisbee had positive lift going up and negative lift coming down, it
would never return to the person who threw it, or even come close. It would
have the same horizontal speed in each direction (reversed when plotted
against time), but significantly different vertical speeds (ie, not simply
reversed), resulting in significantly different flight paths.

Pete

"Peter Duniho" wrote in message ...
"cjcampbell" wrote in message
oups.com...
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.

True, but the increase in angle of attack is strictly a result of the change in relative wind. The frisbee remains
in basically the same attitude throughout. It has no means of trimming for constant lift or anything like that.

But
not always. Throwing the Frisbee up will give it a positive angle of
attack as it climbs.

The vertical path is primarily a result of one throwing the frisbee in that direction. The path would curve down
ballistically except for the basic 1G of lift that the relatively modest angle of attack, basically identical to
the AOA in straight and level flight, provides.

Once the forward motion stops the angle of attack
can become negative,

Negative. As in, not true. The frisbee still has positive angle of attack, and descends back along roughly the
same path it took upward. It's a bit lazy-eight-ish and, as you know, you don't need negative lift to do those.

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.

No, it doesn't come down faster that it would simply fall. It does accelerate, just as any falling body
accelerates, and just as the rising body of the frisbee decelerated on its way up.

If the frisbee had positive lift going up and negative lift coming down, it would never return to the person who
threw it, or even come close. It would have the same horizontal speed in each direction (reversed when plotted
against time), but significantly different vertical speeds (ie, not simply reversed), resulting in significantly
different flight paths.

Pete

So, tying this into a couple of recent threads... can a frisbee stall?
What would happen if it had dimples on it?
How about vortex generators? : ' )

Joe Schneider
N8437R



----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

But wait a minute. A good frisbee thrower can make a frisbee rise
straight up (like a golf ball does). The frisbee may take one path for
awhile but then starts heading up, just like a properly hit golf ball
(although not mine golf balls ). The golf ball is well understood to
rise as a result of its backward spin and low pressure on top (B).
Anyone who claims that a golf ball just follows its original path has
certainly never seen one properly hit.

-Robert

"Robert M. Gary" wrote in message
ups.com...
But wait a minute. A good frisbee thrower can make a frisbee rise
straight up (like a golf ball does). The frisbee may take one path for
awhile but then starts heading up, just like a properly hit golf ball

Yes. As I said in a different post, there are subtle aerodynamic effects
that can be used to affect the exact flight path of the frisbee. Release
attitude (pitch and roll), initial flight path, rotation speed, even impact
(intentional or otherwise ) with some object or surface mid-flight, these
all have small-but-interesting-and-useful effects on the exact course the
frisbee follows.

But those are very minor, the frisbee at all times is following basic rules
of inertia and lift (without the radical changes in configuration that CJ's
post suggests), and the original question was simply how does the frisbee
*fly*. That is, why is it possible to throw a frisbee and have it maintain
any stable path, and remain aloft longer than a thrown rock would.

Pete

"Peter Duniho" wrote

Yes. As I said in a different post, there are subtle aerodynamic effects
that can be used to affect the exact flight path of the frisbee. Release
attitude (pitch and roll), initial flight path, rotation speed, even
impact (intentional or otherwise ) with some object or surface
mid-flight, these all have small-but-interesting-and-useful effects on the
exact course the frisbee follows.

A large factor is also the gyroscopic affects (effects?) resulting from the
change in plane of rotation, like the spinning bicycle wheel being held by
the person on the turntable.

That is why (for a right handed person, throwing with the standard clockwise
rotation) the release position for a straight throw, is with the side
opposite from the hand to be held lower than the side the hand is holding.
--
Jim in NC

Robert M. Gary wrote:
But wait a minute. A good frisbee thrower can make a frisbee rise
straight up (like a golf ball does). The frisbee may take one path for
awhile but then starts heading up, just like a properly hit golf ball
(although not mine golf balls ). The golf ball is well understood to
rise as a result of its backward spin and low pressure on top (B).
Anyone who claims that a golf ball just follows its original path has
certainly never seen one properly hit.

I haven't seen an analysis of a golf ball, but I saw an analysis a while
ago on a baseball. I think it may have been in Popular Mechanics, but
I'm not sure of that. The claim was that a baseball could be thrown so
as to rise (I forgot which type of pitch it is called) on its way to the
plate. The article pretty clearly debunked this myth. The spin
imparted to the ball can make it sink a little less slowly than a strict
ballistic trajectory, but the RPM required to actually make the ball
rise was something simply unattainable by a human.

I suspect the same is true of a golf ball (I'm a golfer, but not a
terribly good one). I've watched a number of balls hit by amatuers and
pros and I've never seen one rise above the launch trajectory. The
backspin will certainly make the trajectory much flatter than a
ballistic trajectory, but I don't think the ball will rise above a
tangent line to the path leaving the club face.


Matt