So, how does a frisbee fly?

Matt Whiting wrote:
:
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.

That is not what I've observed. When watching professional golfers hit
balls they appear to travel a traditional trajectory (often call the
"cannon" route) for the first couple hundred feet and then take a
noticable up path when they should start to sink. That up path seems
quite dramatic to me. Its often called the "second wind". That's just
my observation.

-Robert

In article .com,
"Robert M. Gary" wrote:


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."

And, the "soft frisbees" that are sold in pet stores, and that fly quite
well, consist of a thick and quite heavy but soft tubular ring around
the outer perimeter (it's the size of your thumb or larger, and almost
feels as if it had sand in it), and then just a thin piece of plastic-y
cloth like a saggy drumhead across it.

Because of the weight of the outer ring, you can put a good spin on it
when you launch it, at which point the "drumhead" takes up an upward
dome shape, and it maintains that shape and spin throughout its entire
flight.

As another data point, a sudden gust of wind coming head-on at it can
make it suddenly "jump" vertically upward by a sizable amount -- and a
gust from behind can make it suddenly drop, even "crash-land".

So, the physics of this seems to hold up . . .

Robert M. Gary wrote:
Matt Whiting wrote:
:

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.


That is not what I've observed. When watching professional golfers hit
balls they appear to travel a traditional trajectory (often call the
"cannon" route) for the first couple hundred feet and then take a
noticable up path when they should start to sink. That up path seems
quite dramatic to me. Its often called the "second wind". That's just
my observation.

That is the same thing people claimed about baseballs, but it turned out
to be a combination of an optical illusion (the mound being higher than
the plate) and people's mind expecting the ball to drop more quickly
than it did and then perceiving this as the ball rising, when it fact it
was simply dropping at a slower rate.

I was watching golf this past weekend and they had several side aerial
shots of the drives. It was pretty easy to see the trajectory of the
ball from the lift or whatever they were filming from as the height was
about the same level as the apex of the drive. The ball was clearly
dropping away from the path of launch when viewed from the side at an
elevated position.

If you get a chance to see these sorts of shots on TV in the future,
look closely and I think you'll see the same thing.


Matt

Matt Whiting wrote in news:4chog.41$Pa.6285
@news1.epix.net:

Skywise wrote:
Snipola

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

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

True, that!


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.

Hmmm...I was just thinking...I bet the 12 inch glass masters
1/4 inch think would have gone pretty far too.

Brian
--
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Sed quis custodiet ipsos Custodes?

Matt Whiting wrote:
That is the same thing people claimed about baseballs, but it turned out
to be a combination of an optical illusion (the mound being higher than
the plate) and people's mind expecting the ball to drop more quickly
than it did and then perceiving this as the ball rising, when it fact it
was simply dropping at a slower rate.

It may not be humanly attainable to make a baseball or golfball "rise",
but it's theoretically possible, right? I think wiffle balls can rise.

Bucky wrote:

Matt Whiting wrote:

That is the same thing people claimed about baseballs, but it turned out
to be a combination of an optical illusion (the mound being higher than
the plate) and people's mind expecting the ball to drop more quickly
than it did and then perceiving this as the ball rising, when it fact it
was simply dropping at a slower rate.


It may not be humanly attainable to make a baseball or golfball "rise",
but it's theoretically possible, right? I think wiffle balls can rise.

I suspect it is theoretically possible if you can put enough energy into it.


Matt

Peter Duniho wrote:
"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.

I don't quite fully understand what you are stating. Probably my English is
not good enough. Do you think the lift (created by AOA and possibly
bernulli-shaped foil) does create a significant amount of lift or not? You
say that the (vertical) path is primarily a result of throwing, hence
determined by ballistic effects. Yet you state 1G of lift. If the lift is in
the order of magnitude of 1G, then it's certainly significant. Most
airplanes create lift in that range.. That holds also with my experience,
you don't need to give a frisbee much initial rate of climb (or any at all)
to make it go a long way without loosing much altitude. Although I have
never measured this :-) I even believe you can make it climb after releasing
it with a horizontal trajectory.

I think I have an explanation, why it doesn't work so well when throwing
CDs: As has been stated, CDs will quickly turn sideways when released in an
horizontal attitude. But a frisbee will do just the same, only slower! If we
look at the frisbee (or CD) as an airfoil creating lift (whether newtonian
or benoullian is not really important), the center of the aerodynamic force
will alwas be forward of the middle line of the plane (as with all aircraft
wings). With the cg in the middle of the disk, the aerodynamic force
supporting it, will at the same time try to pitch it up! The gyroscopic
force from the rotation translates this torque round the horizontal axis
into one round the longitudinal axis, thus a rolling torque. In fact, when
throwing a frisbee, at the point of release the disk should be slightly
rolling in the opposite direction (and/or in a rolled attitude), to keep it
roughly horizontal as long as possible.

Only due to the much lower inertia this doesn't work as well with CDs, as
the roll is so much faster!

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.

As to the mechanics of making a frisbee return to the thrower, I don't
understand the explanation given by CJ, especially the assumption of
negative lift. However, it can not be explained purely by ballistics, unless
it's thrown vertical. There needs to be some aerodynamic force towards the
thrower beyond drag, drag stops the moment the forward motion stops.

If, at the point of zero horizontal movement, the disk maintains it's
attitude towards the horizon (that is, slightly pitched up in the direction
of the original movement) it is now also pitched down in the direction
towards the thrower. While moving towards terra firma, it will gain speed
towards him, just like an aircraft will gain speed at the expense of
altitude when pitched down.

regards,
Friedrich

"Friedrich Ostertag" wrote in message
...
I don't quite fully understand what you are stating. Probably my English
is not good enough.

Probably. Nothing in my post states that the primary determinant for the
path the frisbee takes is ballistics, and in fact I specifically point out
that aerodynamic lift is what prevents a ballistic flight path.

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


Spin is one component that is totally ignored when determining the lift
produced by the ball. Calling it lift is based not only on the false
premise that the ball is not spinning but on the intentional ignorance
of the the fact that it is.

wrote

Spin is one component that is totally ignored when determining the lift
produced by the ball. Calling it lift is based not only on the false
premise that the ball is not spinning but on the intentional ignorance
of the the fact that it is.

???????????????????????????

What turnip truck did you just fall off of, and in what reality?
--
Jim in NC