So, how does a frisbee fly?

"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

Matt Whiting wrote in news:wN7og.35$Pa.5633
@news1.epix.net:

Skywise wrote:
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.

You need better technique. I can get 50' out of a CD. A larger and
heavier thin disk will go a lot farther even.

Well, the clean room was only so big.....

My take on it is that a CD simply has insufficient mass to
maintain gyroscopic stability. If you spin it fast enough,
yes, but by hand it's not easy. If it were metal I'd expect
it to fly just fine.

BTW, the CD's came out of the pressing machine with a small
plug in the center hole that had what amounted to a small
axle through it. This was punched out automatically by the
machinery. But, I had a few sample discs with it still in
place and you could actually make it spin like a top if
you could get it spinning fast enough. I usually used a
blast of compressed air, since it was handy. I mean FAST
fast. Twirling it by hand was not fast enough.

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
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Skywise wrote:
Matt Whiting wrote in news:wN7og.35$Pa.5633
@news1.epix.net:


Skywise wrote:

Matt Whiting wrote in news:Fj%ng.29$Pa.4943
:

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.

You need better technique. I can get 50' out of a CD. A larger and
heavier thin disk will go a lot farther even.


Well, the clean room was only so big.....

Yes, and it wouldn't be clean long if you were breaking CDs.


My take on it is that a CD simply has insufficient mass to
maintain gyroscopic stability. If you spin it fast enough,
yes, but by hand it's not easy. If it were metal I'd expect
it to fly just fine.

Yes, I also suspect that low mass is the limiting factor.

Matt

Matt Whiting wrote:
Robert M. Gary wrote:
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.

Golf balls clearly have lift and Cl is one of the criteria used when
evaluating ball standards. Here is a pdf describing some of the
formuals used and how the coefficient of lift for different balls
effects flight.
http://www.usga.org/equipment/techni...ublication.pdf

"It has been shown (Bearman, Harvey, 1976) that the two aerodynamic
coefficients, CD
and CL, are related to the dimensionless Reynolds number (Re) and spin
ratio (W)."

Spin is one component that determins the lift produced by the ball.

Here is an article from Cislunar Aerospace, Inc
http://wings.avkids.com/Book/Sports/...d/golf-01.html

"How a Golf Ball produces Lift

Lift is another aerodynamic force which affects the flight of a golf
ball. This idea might sound a little odd, but given the proper spin a
golf ball can produce lift. At first, golfers thought all spin was
detrimental (not good). However, in 1877, British scientist P.G. Tait
learned that a ball, driven with a "backspin" (the top of the ball
turning back toward the golfer) actually produces lift.

The dimples also increase lift. Remember, dimples help keep the flow
attached to the sphere. The dimples also cause the flow to be "focused"
into the flow of the wake. In this figure, the smoke shows the flow
pattern around a spinning golf ball. The flow is moving from left to
right and the ball is spinning in a counter-clockwise direction. The
wake is being forced downwards. This downward movement of the wake
means that a lifting force is being applied to the golf ball.
"

-Robert

Looks like someone figured it out. A frisbee produces lift by traveling
through the air just like an airplane wing. The spinning of the frisbee
does nothing to increase the lift but it does produce the stability to
keep it properly oriented to produce lift.

http://www.physlink.com/Education/AskExperts/ae16.cfm

"A frisbee has the same shape, in side view, as an airplane wing: the
curved uppper surface causes the air to move faster accross the top
frisbee than it does across the 'flat' bottom, when the frisbee is
thrown. The 'lift' is then produced by the pressure difference between
the bottom and top sides of the frisbee - the lower pressure is on top
and the higher on the bottom - therefore the net force on the frisbee
will be up - producing the needed lift.

The turning of the frisbee mostly produces 'stability', that is the
spinning keeps the frisbee level in flight due to the 'gyroscopic'
effect, i.e. any spinning disc likes to stay spinning at the same
angle.

You can see for yourself that the spinning has nothing to do with the
actual 'flying' of the frisbee by noting that you can spin a frisbee in
place, on a stick or whatever, and it will not 'lift up'. You also can
see that the frisbee is still spinning at nearly 'full speed' when it
finally hits the ground, so you have another piece of evidence that
shows that the spinning doesn't lift the frisbee."

Robert M. Gary wrote:
Matt Whiting wrote:

Robert M. Gary wrote:
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.


Golf balls clearly have lift and Cl is one of the criteria used when
evaluating ball standards. Here is a pdf describing some of the
formuals used and how the coefficient of lift for different balls
effects flight.
http://www.usga.org/equipment/techni...ublication.pdf

I never disputed that golf balls have lift. I simply said I don't think
they will rise above the launch line as was suggested.

The lift will cause them to descend more slowly that they would due to
ballistics alone, but that is far different than saying they will rise
upwards above the launch path.


Matt

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 in message ...
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).

....
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.

It is magic! Just like flying an airplane...

These folks are trying to explain away the magic he http://mae.ucdavis.edu/~biosport/frisbee/frisbee.html

Really, it's just magic...