"OAT"

[ejvogie]

The last name of an idiot villain from a kid's cartoon? Yep, perfect name for a troll account.




<----leaves now while this invaluable information sinks in

I mean, really, any guy that is foiled every episode by a platypus...

 

[DG Don]

I first heard the term OAT on DG review when I was lurking over there. I always understood the axis in discussion was not the axis of the disc, but rather the axis of rotation of your body as you were pulling through. You reduced OAT by keeping all forces on the same plane (ie, shoulders, elbow, wrist). Doing this led to a smoother throw and less wobble as described in Doofensmirtz's ultimate link.

Maybe this discussion is focusing too much on the axis of rotation of the disc and not enough on the axis of rotation of the throw.

Regardless of whether it's the best term to describe the cause of disc wobble, reading the information helped me throw more smoothly. Now, if I could only figure out "the Hit"...

 

[garublador]

As to what a sensor would show, why don't you put it on a disc and tell us.

I'm asking you. Assume the z axis in the output is the axis perpendicular to the flight plate. If the axis of rotation can only have components in one axis, which axis will it show as having torque applied on a wobbly throw, x, y or z?

Here's a hint, it's a trick. If you say that it's only about the z axis then you're saying the axis of rotation is straight through the flight plate and the disc won't be wobbling. The link you gave shows that when the disc wobbles the axis of rotation is not straight through the flight plate. If you say that there will be components in multiple axes then you're admitting that my explanation is also correct.

The point is to illustrate the difference between the Cartesian axes and the axis of rotation.

 

[PMantle]

Are you now still insisting that you can exert rotational inertia on the roll axis that causes the disc to roll right after release while it is simultaneously spinning on the yaw axis?

I don't know about that guy, but I've seen you do this at least 20 times.

 

[Doofenshmirtz]

I don't know about that guy, but I've seen you do this at least 20 times.

You need no help in begging the question I see.

 

[Doofenshmirtz]

The point is to illustrate the difference between the Cartesian axes and the axis of rotation.

The point is that the Cartesian axes are whatever you want them to be, "imaginary" is the word that you used. The single, post-release spin axis is determinable. You can, pre-release, exert torque on as many axes as you want, but, once released, the disc will have only one spin axis.

Let me pose my question again: are you still insisting that, after release, the disc can both spin around the yaw axis and rotate around the roll axis with the latter being caused by "torque momentum"?

BTW, i'm still awaiting that video.

 

[garublador]

The point is that the Cartesian axes are whatever you want them to be, "imaginary" is the word that you used. The single, post-release spin axis is determinable. You can, pre-release, exert torque on as many axes as you want, but, once released, the disc will have only one spin axis.

They can be whatever we want, and we want to throw about an axis that doesn't cause wobble. That's why I'm defining the "on" axis that way. We're talking about up to and at release. It's obvious you (as in the thrower) can't apply torque after release. The torque we're talking about applying at release will be about some combination of those Cartesian axes. Applying torque about an axis that isn't straight through the center of the disc, the "on" axis, will be "off" axis. So if you can apply torque about an axis other than the one through the flight plate and we call that axis the "on" axis, what's wrong with calling torque applied about some other axis, "off axis torque?" You can apply off axis torque that makes the disc either act more or less stable (see what I did there?) which will cause the disc to "roll." Now I know that it's not strictly rolling, it's actually "wobbling" real slowly so the nose angle is changing as well, but that's not important when talking about how to throw cleanly. It is important when talking about line shaping, though. Again, context is important.

I say stuff like "about the roll axis" because it's easier to visualize and explain than "with a component in the x direction assuming the z axis is perpendicular to the flight plate." People know roll, pitch and yaw. Planes do barrel rolls so it's easy to visualize. "Torque with a component in the x direction assuming the z axis is perpendicular to the flight plate" usually requires more explanation that inevitably ends with "imagine a plane doing a barrel roll." After trying to explain the same thing over and over again for a few years you figure out what works and use that rather than what's technically correct language. Anyone who really cares will look into it further. Everyone else will just have to live with more control on their drives.

 

[garublador]

BTW, i'm still awaiting that video.

One with an object that has torque components in more than one Cartesian direction? Every video of something spinning is like that if you define your axes right. Take your pick.

Now where's my answer to the sensor question?

 

[Deebo4Discs]

I'm no physics teacher but isn't it more than the axis is moving than the disc moving around different ones? The cleaner the throw, there is less movement OF the axis, not the disc AROUND the axis.

 

[Doofenshmirtz]

One with an object that has torque components in more than one Cartesian direction? Every video of something spinning is like that if you define your axes right. Take your pick.

Now where's my answer to the sensor question?

I've always been impressed with the lyrics to the Clem Snide song, "Fill Me With Your Light." My favorite line is, "I'm not convinced of anything I say." Having said that, it struck me this afternoon that it would be pretty easy to demonstrate what I believe to be the early turnover on throws that you believe are affected by "OAT" if what I think is true. This, by itself, of course, would not logically exclude your explanation. But I think it would be convincing. So I tried this:

Take an slightly overstable disc, a slightly understable disc and a stable disc. Throw them forehand with exaggerated nose down angle-of-attack and see what happens. As it turned out, for me at least, I was able to make all of them turnover and go to the ground immediately on not so hard throws. I tried my best to throw them without wobble while keeping the nose down about 10 degrees or so. Immediate turnover. The discs I threw were a Groove (it was laying around because I can't get anyone to lake it), an M4 (same) and a Proton Volt (delivered today). I threw them all forehand because I find it easier to get a really nose down angle that way. Even when they wobbled, they were still nose down and turned over fast.

I tried it with backhand throws as well, trying to get that exaggerated, nose-down angle with a clean release, it was difficult. But I was able to get the M4 to actually act as understable as it is supposed to be and the Groove to fly straight on a fairly easy throw by getting them much more nose down than I usually throw. I tried throwing hard, but just could not get a clean release while trying to throw with that much nose-down AOA.

Its testable. Give it a try and report.

 

[Smigles]

OAT is simply when you turn the inside of your hand up during the backhand throw. The thumb dragging over the disc gives it wobble.

It's your wrist that is off axis, and the wobble makes the disc take more of an anhyzer angle than intended.

That's all. Thank me later

 

[Olorin]

Does this picture help you guys? The forces on a flying golf disc

The thread on the Physics of flying discs also has lots of helpful information (and some not so helpful) about aerodynamics. For those so inclined, if you dig around, I posted links to some solid scholarly research studies of the aerodynamics of frisbee flight (eg- Hummel's Masters thesis, and Potts PhD research).

 

[Olorin]

I also compiled a list of research on the aerodynamics of flying discs that I keep at DG Resources.

 

[rocthecourse]

OAT is simply when you turn the inside of your hand up during the backhand throw. The thumb dragging over the disc gives it wobble.

It's your wrist that is off axis, and the wobble makes the disc take more of an anhyzer angle than intended.

That's all. Thank me later

OAT goes both ways... Look up under roll.