Why do overhand throws turn backwards?

[MTEXX]

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???

 

[Discette]

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).

 

[lyleoross]

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.

 

[lyleoross]

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?

 

[knettles]

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.

 

[roggenb3]

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.

 

[MTEXX]

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

 

[Pwingles]

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

 

[lyleoross]

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.

 

[lyleoross]

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.

 

[armiller]

Physics nerd here, though not an expert by any means. All discs bank/roll/etc. due to moments on the disc causing a change in angular momentum.

Say I'm a right handed player and throw a thumber that is released perfectly vertical. Initial angular momentum, using right hand rule, is pointed to the left (because disc is spinning like a wheel rolling forward). Whatever is causing the disc to go a certain way from this point is a torque not in the same direction (or exactly opposite) as current angular momentum.

So we go through the forces. 1) gravity - produces no torque because through center of mass; 2) lift - this is where we get our torque, since this acts through an aerodynamic center, NOT the disc's center.

In a RH thumber, the lift is toward the right if thrown vertically (top of disc toward right). The question is where that lift center is. This depends on several things, I think, but includes the disc geometry and angle of attack (i.e. how the nose is angled with respect to the disc's trajectory). Based on how thumbers fly, I'm guessing the center of lift is behind the disc's center (toward the thrower). This would provide an upward torque (again, using right hand rule).

That upward torque, on angular momentum initially to the left, would make the angular momentum start to slant upward, which I think matches how thumbers act. All of this is basically switched for tomahawks.

This makes some sense to me, but I'd still love to see people do more work on all this. All the angles in overhand throws seem more complicated to me with overhand than with forehand/backhand throws.

 

[thirtydirtybirds]

Beat hatchet thinners will go a full barrel roll for me sometimes, with enough height. Don't know why, but it's cool.

 

[DG_player]

If you think about a thumber, it's basically a forehand with an upside down disc, albeit released at a very steep anhyzer angle. The difference is that a disc flying upside down is super over stable, so as soon as it leaves your hand it starts rolling right hard.

If you want to test it, throw a forehand, but instead of using a standard grip, throw the disc upside down with a thumber grip.

 

[Dan Ensor]

Lift dynamics and spin direction.

Throw a Skomohawk. Same flight as a thumber.

Think about a sky anny roller. Every once in a while, you'll put too much anny on it and it'll flip upside down. If the ground hadn't been there, it would continue to flip after that and act like a thumber.

Forehands to Tomahawk are a little easier to think about, because you don't have to be a contortionist to get the anhyzer angle on a disc that you would to release a backhand at the same angle as a thumber.

 

[sidewinder22]

If you think about a thumber, it's basically a forehand with an upside down disc, albeit released at a very steep anhyzer angle. The difference is that a disc flying upside down is super under stable, so as soon as it leaves your hand it starts rolling right hard.

If you want to test it, throw a forehand, but instead of using a standard grip, throw the disc upside down with a thumber grip.

FTFY The spin is reversed on a FH and thumber relative to the disc-wing aerodynamic center orientation. So after a thumper flips over right side up horizontally it is actually spinning opposite of a FH like a BH. BH and FH would also do the same relative barrel rolls like overhands if the ground didn't get in the way.

The disc flies super understable upside down because the right side up nose has to be down initially to generate lift opposite gravity from the wing being upside down. If it were initially flying right side up(FH/BH) with the nose this far down, it would be in negative lift and turn over(understable). So the upside down wing is nose up in order to generate lift, while the right side up wing is nose down so lift from the aerodynamic center is not driving it down into the ground while upside down.

Distance overhands get the disc to fly right side up with the nose still down enough for the remaining speed to maximize the glide out. Understable discs have to be thrown higher and do a complete 360 barrel roll for distance.

 

[DG_player]

FTFY The spin is reversed on a FH and thumber relative to the disc-wing aerodynamic center orientation.

I don't quite follow what you mean. Relative to the ground a thumber is spinning in the same direction as a forehand.

 

[sidewinder22]

I don't quite follow what you mean. Relative to the ground a thumber is spinning in the same direction as a forehand.

But the disc and its aerodynamic center is oriented opposite/upside down to the ground on a thumber. Take your disc in your normal thumber grip with disc upside down and spin it like a thumber(FH/"counterclockwise"), now barrel roll the disc over maintaining the disc's relative spin direction and the spin direction will appear inverted as it rolls over to the same wing orientation of a normal FH or BH and be spinning "clockwise" opposite of a FH now.

It's like looking at a clock or watch with the numbers/hands up vs numbers/hands down from a bird eye view, clockwise direction to the clock(disc) is always clockwise, but appears inverted to us with the clock inverting its orientation.

 

[DG_player]

But the disc and its aerodynamic center is oriented opposite/upside down to the ground on a thumber. Take your disc in your normal thumber grip with disc upside down and spin it like a thumber(FH/"counterclockwise"), now barrel roll the disc over maintaining the disc's relative spin direction and the spin direction will appear inverted as it rolls over to the same wing orientation of a normal FH or BH and be spinning "clockwise" opposite of a FH now.

It's like looking at a clock or watch with the numbers/hands up vs numbers/hands down from a bird eye view, clockwise direction to the clock(disc) is always clockwise, but appears inverted to us with the clock inverting its orientation.

I follow what you are saying now. We essentially said the same thing, just different frame of reference. I was referring to the orientation to the ground, hence super over stable, and spinning the same direction as a FH, while you were referring to the top of the disc, so you used opposite terminology.

 

[DG_player]

If it were initially flying right side up(FH/BH) with the nose this far down, it would be in negative lift and turn over(understable).

This is the most pertinent take away from the discussion. Anytime a cambered wing (which essentially all discs are) experiences negative lift, it always experiences a pitch down moment. Due to precession this is going to result in turnover, or under stabliness.

This describes the motion of all upside shots. It also explains certain release errors such as OAT. If you turn your wrist over enough on release that the disc is experiencing negative lift, it's going to initially turn over, even if you're a noodle arm throwing an over stable disc.

 

[curmudgeonDwindle]

Aren't there 2 sorts of thumber grips?

1. Hook thumb (most common in today's game)
and
2. Overhand wrist flip grip turned upside-down