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Old 09-18-2017, 11:32 AM
MTEXX MTEXX is offline
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Default Why do overhand throws turn backwards?

A right hand back hand (RHBH) throw spins the disc clockwise. An overstable disc will turn and fade left (hyzer).
A right hand thumber (RHT) throw spins the disc clockwise. An overstable disc will turn quickly right (anhyzer)- so much that it often goes inverted and comes back around to make a 360 degree barrel roll.
Likewise, the anti-clockwise tomahawk turns left.
What is going on here?

Here is my theory
Thinking about how rollers prefer to land upside down. I'm GUESSING the CG of the disc is higher in z coordinate (e.g. closer to the top of the flight plate) than the CP. In a vertical orientation, gravity will pull on down on the CG while air holds it up at the CP. This puts a torque on the disc- attempting to roll it right/anhyzer. Precession translates part of the gravitational torque into a pitch up torque. And further, the gravitational roll must be more significant than the assymetric lift and AOA lift forces.
Unfortunately, this theory does not explain why the overhand shot CONTINUES to roll when it assumes a level flight path!!! I don't think that gravitational torque could impart a roll axis momentum- not on a spinning body...

Anyone???
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  #2  
Old 09-18-2017, 11:51 AM
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Quote:
Originally Posted by MTEXX View Post
A right hand back hand (RHBH) throw spins the disc clockwise. An overstable disc will turn and fade left (hyzer).
A right hand thumber (RHT) throw spins the disc clockwise. An overstable disc will turn quickly right (anhyzer)- so much that it often goes inverted and comes back around to make a 360 degree barrel roll.
Likewise, the anti-clockwise tomahawk turns left.
What is going on here?

Here is my theory
Thinking about how rollers prefer to land upside down. I'm GUESSING the CG of the disc is higher in z coordinate (e.g. closer to the top of the flight plate) than the CP. In a vertical orientation, gravity will pull on down on the CG while air holds it up at the CP. This puts a torque on the disc- attempting to roll it right/anhyzer. Precession translates part of the gravitational torque into a pitch up torque. And further, the gravitational roll must be more significant than the assymetric lift and AOA lift forces.
Unfortunately, this theory does not explain why the overhand shot CONTINUES to roll when it assumes a level flight path!!! I don't think that gravitational torque could impart a roll axis momentum- not on a spinning body...

Anyone???
Since the RH Thumber is released upside down, it is spinning clockwise upside down (Which means it would be spinning counter clockwise for the flight plate).
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Old 09-18-2017, 12:57 PM
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lyleoross lyleoross is offline
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I must be doing it wrong. My thumbers come out approximately perpendicular to the ground, then roll clockwise such that the flight plate is upside down from normal flight. The disc works it's way right to left but then finishes right. The disc for me does roll back counter clockwise late in its flight, as it's traveling left to right. Note, I'm not talking disc spin but flight pattern here.

If the disc followed its normal flight pattern, in theory, no gravity involved, it should curve upwards and stall, if no flip happens. I'm guessing that the Thumber, like the forehand, allows the thrower to put more spin on the disc than it can handle so it's flipping understable - so to speak. On the forehand, RHFH, an overthrown disc flips right to left and the left edge of the disc dives towards the deck. The Thumber does the same, only the disc is spinning the opposite way so it flips the other way. At that angle, with the upper flight deck coming around, aerodynamics cause the disc to flip farther.

Last edited by lyleoross; 09-18-2017 at 01:02 PM.
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Old 09-18-2017, 01:00 PM
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lyleoross lyleoross is offline
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Quote:
Originally Posted by Discette View Post
Since the RH Thumber is released upside down, it is spinning clockwise upside down (Which means it would be spinning counter clockwise for the flight plate).
I hate to be dumber than I usually am, but I'm not seeing this. My eye makes it just the opposite? What am I missing?
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Old 09-18-2017, 01:02 PM
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Quote:
Originally Posted by Discette View Post
Since the RH Thumber is released upside down, it is spinning clockwise upside down (Which means it would be spinning counter clockwise for the flight plate).
But in relation to the top of the disc, it's still spinning clockwise.

Also MTEXX, I don't know if you've played around with different stability discs overhand, but understable discs will barrel roll much faster than overstable ones.

My understanding is, since a traditional RHBH throw is being pushed upward by lift, the high speed turn is pushing down against that lift. In an overhand throw, the lift isn't much of an issue, which is why the disc is able to go into a barrel roll so easy. Then by the time it's done almost a 180 degrees rotation, it's fighting against gravity, so it stops rolling and just drops. For example, a RH grenade is thrown in the exact same position as a RH thumber, except it's spin is reversed. With the counterclockwise spin of the grenade, the turn is fighting against gravity, so it just goes straight up and back down.

Now if really want to boggle your mind, throw an Aerobie Epic overhand and try and figure that one out.

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Last edited by knettles; 09-18-2017 at 01:04 PM.
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Old 09-18-2017, 02:05 PM
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Originally Posted by knettles View Post
Now if really want to boggle your mind, throw an Aerobie Epic overhand and try and figure that one out.
I threw an Epic overhand once. It was simple to figure out. It came out of my hand and went perfectly straight.....into the garbage.

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Old 09-18-2017, 04:27 PM
MTEXX MTEXX is offline
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Thanks for the input guys.

Here is a video clip where Big John throws an overstable Discraft Flick (9 4 1 4) RHT. You can see he releases a bit flatter than vertical, but the disc is clearly rolling right (anhyzer).
https://youtu.be/d3nlgbjH6K4?t=1m20s

Last edited by MTEXX; 09-18-2017 at 04:30 PM.
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Old 09-18-2017, 05:52 PM
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fwiw, the same phenomena happens when you throw the disc with the other hand and or spin

im not a physicist but i did sleep at a holiday inn last night

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Old 09-18-2017, 06:27 PM
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lyleoross lyleoross is offline
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Quote:
Originally Posted by MTEXX View Post
Thanks for the input guys.

Here is a video clip where Big John throws an overstable Discraft Flick (9 4 1 4) RHT. You can see he releases a bit flatter than vertical, but the disc is clearly rolling right (anhyzer).
https://youtu.be/d3nlgbjH6K4?t=1m20s
I think you and are using different terminology. To me, the disc rolls clockwise but travels left out of his hand. Then late in its flight, it rolls counterclockwise and travels right.
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  #10  
Old 09-18-2017, 06:28 PM
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lyleoross lyleoross is offline
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Originally Posted by Pwingles View Post
fwiw, the same phenomena happens when you throw the disc with the other hand and or spin

im not a physicist but i did sleep at a holiday inn last night
Ha, only physicists are allowed to sleep at holiday inn.
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