OAT Vs. turn over

[tom8658]

Your explanation was incorrect in that the airspeed over the disc does not vary from side to side, only from front to back. A disc correctly called an axi-symmetric spin-stabilized wing.

I should explain - what you wrote about air movement is correct for a certain definition of "sides", it's just that that definition is not the most useful way to understand disc flight.

is it? i dont understand a lot of these physics terms. my teaching method is all based on experience. it seems to me that if you instruct to aim with the leading edge (read: left side (rhbh)) of the disc, they can aim (and miss) a lot smaller.

It's like swinging the opposite end of a baseball bat or a hammer - it's a method to create leverage, not a physically useful definition of the disc as a wing. If you defined some point on the disc rim and called it the nose, you could, in fact, describe the flight of the disc in terms of the "nose", but it wouldn't be the same as the aeronautical definition of the leading edge of a wing, because sometimes the nose is the leading edge, but most of the time it isn't. The physics are all the same, but they will look drastically different and be horribly complex.

 

[tom8658]

I did? :-/ I'm pretty sure I meant to say it DOES vary from side to side.

That's what I was trying to correct you on. It's not actually wrong though, see above.

 

[CwAlbino]

I should explain - what you wrote about air movement is correct for a certain definition of "sides", it's just that that definition is not the most useful way to understand disc flight.



It's like swinging the opposite end of a baseball bat or a hammer - it's a method to create leverage, not a physically useful definition of the disc as a wing. If you defined some point on the disc rim and called it the nose, you could, in fact, describe the flight of the disc in terms of the "nose", but it wouldn't be the same as the aeronautical definition of the leading edge of a wing, because sometimes the nose is the leading edge, but most of the time it isn't. The physics are all the same, but they will look drastically different and be horribly complex.

Okay so it's right, but it's not the best way to explain it? gotcha

 

[tom8658]

I also read your gyroscopics wiki (not thoroughly) and I believe Torque-Induced Precession is what would explain the flutter

http://en.wikipedia.org/wiki/Precession

I think that would make sense. It would explain why flutter causes turn, I think, because the disc will roll due to the interaction of the precession with its directional velocity.

 

[Apothecary]

 

[tom8658]

Okay so it's right, but it's not the best way to explain it? gotcha

Yep. The language that you use to try to understand something is extremely important. You want to describe rotating discs, for example, in a cylindrical or spherical coordinate system to take advantage of axial symmetry. If you try to do it in Cartesian coordinates, you end up with an unholy mess.

Read that paper, if you've had some basic physics (and, more importantly, you have the patience to learn the aeronautics jargon), it's quite informative.

 

[CwAlbino]

I think that would make sense. It would explain why flutter causes turn, I think, because the disc will roll due to the interaction of the precession with its directional velocity.

So basically, flutter = Precession = OAT. What some would call OAT like garub is saying, is likely still fluttering, but I'll get to my explanation or idea about it in a second. Maybe we can come up with a detailed and correct physics explanation of OAT.

Precession = torque about an axis that is not the spinning motion torque.

-The disc spins circular like a top for an oat-free throw

-Oat is imparted on the disc, and causes it to flutter or rock back and forth. It may not look like it, but think of the top of this spinning top to be the circular disc.

Now lessen the depth of the "flutter" and here's a gif.

The thing about precession and with a disc, is that it will correct itself, because the torque is not constant. Gravity's torque is always there, but the initial torque is not. Garub's man might not be throwing OAT at all, or he may be throwing with enough snap vs slow velocity that the wobble is so low and quickly corrected. The flight is already changed though and will continue to go right.

 

[CwAlbino]

K, I g2g to work, I'll check back at the thread later.

 

[Apothecary]

So basically, flutter = Precession = OAT. What some would call OAT like garub is saying, is likely still fluttering, but I'll get to my explanation or idea about it in a second. Maybe we can come up with a detailed and correct physics explanation of OAT.

Precession = torque about an axis that is not the spinning motion torque.

-The disc spins circular like a top for an oat-free throw

-Oat is imparted on the disc, and causes it to flutter or rock back and forth. It may not look like it, but think of the top of this spinning top to be the circular disc.

Now lessen the depth of the "flutter" and here's a gif.

The thing about precession and with a disc, is that it will correct itself, because the torque is not constant. Gravity's torque is always there, but the initial torque is not. Garub's man might not be throwing OAT at all, or he may be throwing with enough snap vs slow velocity that the wobble is so low and quickly corrected. The flight is already changed though and will continue to go right.

i contend that his example is thrower oat. that is the angle of the stroke of the thrower is, in essence, a wobble.

 

[tom8658]

The thing about precession and with a disc, is that it will correct itself, because the torque is not constant. Gravity's torque is always there, but the initial torque is not.

Gravity is applying a force, not a torque, because it is applied at the center of mass. Lift is also a force. The fact that the center of mass and the center of lift are not always the same is what gives rise to a torque (called the pitching moment). That is picking nits, though.

What you said is conceptually correct - the disc will eventually stop precessing because precession is due to a finite input of energy.

Garub's man might not be throwing OAT at all, or he may be throwing with enough snap vs slow velocity that the wobble is so low and quickly corrected. The flight is already changed though and will continue to go right.

I'm pretty sure most throws have OAT to some degree, except maybe good clean putts. The trick, I think, is to have enough spin, and little enough OAT, that the disc is essentially unaffected - i.e. precession stops quickly.

What I want is a physical explanation of why precession would cause the disc to roll. I suspect that the precession of the disc somehow lessens it's effective angular momentum, causing directional velocity effects to become dominant, but I can't come up with a model.

 

[Pwingles]

i <3 this thread

 

[dodgeball]

For me, OAT is most clearly seen when u throw a basically flat shot that quickly turns into a roller. Of course the disc can turn over just by the motion of the air/wind over the disc, but it can be accentuated by the thrower. In that case the thrower is basically giving a very slight twist to the 'wings' of the disc. If the disc spins around one axis which goes through the middle of the disc and goes up and down, then this other axis would be perpendicular to this and go through the front and back of the disc, with the front of the disc being oriented with the velocity of the disc. Wobble is a kind of OAT, but this other kind has a greater impact of the flight of the disc to go left or right. Wobble robs the disc of speed and looks really ugly, but it's the other kind u really have to watch out for!

 

[CwAlbino]

Gravity is applying a force, not a torque, because it is applied at the center of mass. Lift is also a force. The fact that the center of mass and the center of lift are not always the same is what gives rise to a torque (called the pitching moment). That is picking nits, though.

What you said is conceptually correct - the disc will eventually stop precessing because precession is due to a finite input of energy.



I'm pretty sure most throws have OAT to some degree, except maybe good clean putts. The trick, I think, is to have enough spin, and little enough OAT, that the disc is essentially unaffected - i.e. precession stops quickly.

What I want is a physical explanation of why precession would cause the disc to roll. I suspect that the precession of the disc somehow lessens it's effective angular momentum, causing directional velocity effects to become dominant, but I can't come up with a model.

Sorry I was in a rush and mis-worded it. Barely made it to work on time. You're right gravity =/= torque, it's a force. Says it right in the wiki but, again, typing too quickly. I was mainly trying to get the pictures and .gif done before I had to go. The idea is that most of us see it as wobble, left to right pitch, when really it's a circular movement. Being behind the disc we only notice the left to right movement, but if we were to have multiple angles, we could see the forward to backward movement.

It's best seen in this guy's slo-mo's


What I was thinking about with gravity's torque at the time was the top. With a large circle like the top shows, there is quite a bit of force pulling the top down because the center of gravity is so far out. Causing a torque?

 

[dodgeball]

What is

Sorry I was in a rush and mis-worded it. Barely made it to work on time. You're right gravity =/= torque, it's a force. Says it right in the wiki but, again, typing too quickly. I was mainly trying to get the pictures and .gif done before I had to go. The idea is that most of us see it as wobble, left to right pitch, when really it's a circular movement. Being behind the disc we only notice the left to right movement, but if we were to have multiple angles, we could see the forward to backward movement.

It's best seen in this guy's slo-mo's


What I was thinking about with gravity's torque at the time was the top. With a large circle like the top shows, there is quite a bit of force pulling the top down because the center of gravity is so far out. Causing a torque?

Hey, it's the snap guy! I love his videos and how he explains the concept of 'snap.' I've been thinking about this lately and what is the main physical concept behind it. My thinking is that 'snap' is nothing more than a preference for rotational as opposed to linear motion during the final part of the throw and that this is a more efficient type of movement and thus creates greater disc speed. If u watch the first two 'snap' videos, it really seems that that is what he's getting at. I have more thoughts on this, but I don't want to hijack the thread here. Should I start a new thread?

 

[CwAlbino]

Hey, it's the snap guy! I love his videos and how he explains the concept of 'snap.' I've been thinking about this lately and what is the main physical concept behind it. My thinking is that 'snap' is nothing more than a preference for rotational as opposed to linear motion during the final part of the throw and that this is a more efficient type of movement and thus creates greater disc speed. If u watch the first two 'snap' videos, it really seems that that is what he's getting at. I have more thoughts on this, but I don't want to hijack the thread here. Should I start a new thread?

We've already hijacked the thread. I'll think about that while I do laundry.

 

[dodgeball]

We've already hijacked the thread. I'll think about that while I do laundry.

lol, yes, I suppose we have. It's just that you hear so much about snap and I think I've started to incorporate it into my swing. But I just want to understand a little about what's really going there...

 

[ArcheType]

Oat vs turn over works like this

When someone else does it, if it goes badly, its OAT. If it goes well, they got lucky, and its still OAT.

When you do it, its a turn over.

 

[nbiebel]

OAT = Off-Axis Torque... not whatever it means in your opinion
It is adding spin to the disc other than the flat spin around the center of the disc. You can hyzer or anny it without OAT, you can throw it flat with OAT.

OAT can be caused by every part of a throw, and the goal is to eliminate all but the OAT you wish to use to shape the flightpath.

Google OAT + Garublador to find some valuable threads if you want to get in deeper.

To also elaborate, flutter is always OAT since the disc has movement other than a flat spin around its center axis. Flutter on a highspeed disc is uncommonly severe OAT since the weight balance paired with a discs rotational inertia usually smooths out the flutter. I'd also bet that the vast majority of fluttering incidents are caused by only bad releases where the disc is being released at different times - ex. releasing fingers from the bottom of the disc before thumb on top, which adds very undesirable directional forces from the top or bottom of the disc.

I sense an incoming craving for oatmeal tomorrow.

You seem right about everything when I think about it, including the oatmeal.
Just to add, flutter is often a grip issue, which causes the disc to not come out of your hand cleanly. Which, fundamentally, does imply OAT. You can OAT discs without flutter too.

Brilliant.

 

[CwAlbino]

I just realized I did this post backwards :/ The speed is faster over the top, slower at the bottom. Slower = more pressure up, creating lift

In layman's terms.

Think of the slow vs fast discs. You need to really get a boss up to speed for it to turn, but a slower disc turns easily. It's caused by air pressure and not OAT (but it can be caused by OAT).....

lol, yes, I suppose we have. It's just that you hear so much about snap and I think I've started to incorporate it into my swing. But I just want to understand a little about what's really going there...

I'm trying to figure out how to put into words, what I'm thinking. Basically though:

Backhand has more spin than a forehand, but a slower velocity. The spin allows for more distance due to the speed being maintained longer. Forehand has more velocity, but has less spin, so it will turn harder, and fade quicker.

 

[Pwingles]

I just realized I did this post backwards :/ The speed is faster over the top, slower at the bottom. Slower = more pressure up, creating lift








I'm trying to figure out how to put into words, what I'm thinking. Basically though:

Backhand has more spin than a forehand, but a slower velocity. The spin allows for more distance due to the speed being maintained longer. Forehand has more velocity, but has less spin, so it will turn harder, and fade quicker.

This seems backwards to me. There is no way on a true sidearm throw (not a 3/4 throw like a baseball) that you are getting more velocity and less snap then a backhand throw. You are almost certainly getting more velocity and less spin backhand at least this is true if we are talking about 2 very identical throws in distance. Someone help me say this in sciency terms.