Spin rate measurements?

[cjman]

That seems bassackward. If you do the same throw headwind vs tailwind it seems that lower spin:speed ratio makes the disc more understable, which is opposite of what you want.

Well I'm not sure exactly what your saying, so I'll state that - lowering the RPM of the disc causes it to flip less. It flies more stable to OS. The headwind has the opposite effect, causing the disc to fly more understable due to the increased air speed (disc v + wind v).
Think of this as a finesse throw where you want to maintain a straight to turning flight with a controlled finish in a headwind. Not for a wide open headwind shot where you'd be silly not to throw something OS.
'Remove some spin to counter the wind'
Tailwind has the opposite effect. More rpm is needed to maintain a straight flight.

Is that backwards? Are you in NZ, maybe?

 

[wims]

Spin increases the stability of the disc and makes turning slower. When the disc slows down its rotation it will fade

 

[R-Ogre]

Spin increases the stability of the disc and makes turning slower. When the disc slows down its rotation it will fade

If this is true, why does throwing into a headwind make a disc turn more, and a tailwind make it fade?

Think about it, by throwing with a headwind you're artificially decreasing the spin:speed ratio and by throwing with a tailwind you're increasing it. This tells me that more spin makes the disc fade, less spin makes it turn.

 

[R-Ogre]

Well I'm not sure exactly what your saying, so I'll state that - lowering the RPM of the disc causes it to flip less. It flies more stable to OS. The headwind has the opposite effect, causing the disc to fly more understable due to the increased air speed (disc v + wind v).
Think of this as a finesse throw where you want to maintain a straight to turning flight with a controlled finish in a headwind. Not for a wide open headwind shot where you'd be silly not to throw something OS.
'Remove some spin to counter the wind'
Tailwind has the opposite effect. More rpm is needed to maintain a straight flight.

Is that backwards? Are you in NZ, maybe?

This is false. Throw the same disc the same way in a headwind and a tailwind. Let's say you have a 10 mph wind and your throw generates 30 mph speed and 1500 rpm spin. The headwind throw is going 40 mph airspeed with 1500 rpm. This gives a spin:speed ratio of 37.5, and we know from experience that the disc will turn (go right on an RHBH throw) in this situation. The tailwind throw has an airspeed of 20 mph, which gives a spin:speed ratio of 75 and we again know from experience that unless we put a LOOOT of anny on it that throw is going to fade (turn left on an RHBH throw) out early.

This simple thought experiment suggests to me that more spin gives a disc high speed stability, so for a headwind shot you would want to give more spin, not less. Or, you could forget about trying to change the spin and pull out your OS disc like the rest of us. Do you disagree with that logic?

 

[Casey 1988]

Is there any existing data on spin rate in disc golf?

Are there any big tournaments, like NTs, where someone has a radar gun that can measure spin rate?

I would love to see some data, particularly how controllable it is.

E.G.
Can pros throw 30 mph shots with vastly different spin rates?
What about a full 65+mph drive?

At what speed does control over spin rate become so small it is negligible?

Uh I have seen a Pro player Ken (the Tank) Franks in 2008 who muscled discs out to 500 feet without using much spin ever, even his putt was a 0% spin slamming push putt. That was at the 2008 South Dakota State Disc Golf Championships, he was then from Nebraska. He was very acurate as he was forcing discs mostly his driving putter to 500 feet, he told me he never uses a midrange until past 600 feet to 800 feet, then 800-1000 feet he uses a fairway and control drivers depending on situation and only on holes 1020 feet+ he uses a speed 12+ driver. He was sponsoredwith Innova for 3 years since late 2006 or early 2007 and got dropped for being on lead card after the first day then dropping back after that.

 

[Casey 1988]

^ to above post

I found that Ken even did a 0% spin Push putt that he slammed the disc into the basket so hard it almost bounced out. Ken a big guy must have burned out from playing disc golf and mashing the disc all the time, he could not throw slow and on some shots that needed a slower shot to have "contol" for some shots he was using a max weight Birdie as his disc or a Sonic mold being the lightweight Hero Disc Premium Candy/Champion versions made by Innova. That was his idea of control at the time just using a slow putter and not stopping his speed.

 

[cjman]

This is false. Throw the same disc the same way in a headwind and a tailwind. Let's say you have a 10 mph wind and your throw generates 30 mph speed and 1500 rpm spin. The headwind throw is going 40 mph airspeed with 1500 rpm. This gives a spin:speed ratio of 37.5, and we know from experience that the disc will turn (go right on an RHBH throw) in this situation. The tailwind throw has an airspeed of 20 mph, which gives a spin:speed ratio of 75 and we again know from experience that unless we put a LOOOT of anny on it that throw is going to fade (turn left on an RHBH throw) out early.

This simple thought experiment suggests to me that more spin gives a disc high speed stability, so for a headwind shot you would want to give more spin, not less. Or, you could forget about trying to change the spin and pull out your OS disc like the rest of us. Do you disagree with that logic?

https://www.dgcoursereview.com/forums/showthread.php?t=6378

Check out post 7.

RPM produces lift on the left side of the disc for a RHBH throw.

In case 1, if the spin speed is reduced from 10 to 9, the ratio drops to 49/31=1.58 from 1.6. Less high speed turn.

https://www.dgcoursereview.com/forums/showthread.php?t=2250

"Turn: When a disc is fired off, it carries a lot of speed in its initial path. This causes the disc to act like it ignores the friction of air for a short period of time. Because we can count air friction as having a negligible effect during this period, all that factors into the tendency of the disc is torque. The direction of torque on a RHBH throw is clockwise (if seen from above). This means that the disc has a speed about its center of gravity which is different from its speed at its port and starboard wing.

Because the velocity on the port (left) wing of the disc is higher, the air must flow faster over its dorsal surface on that side, causing its pressure to decrease. On the flipside, air is traveling much slower over the dorsal side of the starboard (right) wing, meaning the pressure is much higher. This pressure gradient causes the disc to tilt to the right, which is what we know as turn. Because turn is velocity-based, it is easy to see why it is dominant only during the initial part of a disc's flight."

 

[R-Ogre]

https://www.dgcoursereview.com/forums/showthread.php?t=6378

Check out post 7.

RPM produces lift on the left side of the disc for a RHBH throw.

In case 1, if the spin speed is reduced from 10 to 9, the ratio drops to 49/31=1.58 from 1.6. Less high speed turn.

https://www.dgcoursereview.com/forums/showthread.php?t=2250

"Turn: When a disc is fired off, it carries a lot of speed in its initial path. This causes the disc to act like it ignores the friction of air for a short period of time. Because we can count air friction as having a negligible effect during this period, all that factors into the tendency of the disc is torque. The direction of torque on a RHBH throw is clockwise (if seen from above). This means that the disc has a speed about its center of gravity which is different from its speed at its port and starboard wing.

Because the velocity on the port (left) wing of the disc is higher, the air must flow faster over its dorsal surface on that side, causing its pressure to decrease. On the flipside, air is traveling much slower over the dorsal side of the starboard (right) wing, meaning the pressure is much higher. This pressure gradient causes the disc to tilt to the right, which is what we know as turn. Because turn is velocity-based, it is easy to see why it is dominant only during the initial part of a disc's flight."

So why does a disc turn more when thrown in a headwind? That's the easiest way to simulate a throw with reduced spin. And if more spin causes turn, why does a disc fade when it loses forward speed but still has spin?

 

[cjman]

So why does a disc turn more when thrown in a headwind? That's the easiest way to simulate a throw with reduced spin. And if more spin causes turn, why does a disc fade when it loses forward speed but still has spin?

The threads posted above have loads of info and speculation to ponder. Especially the second.

A disc will fade left when the lift created by the spin + the lift produced by the shape of the disc as it passes through the air is less than the force of gravity. These are independent forces that change and move throughout flight.

There are discs that will 'fade' to the right or straight RHBH, highlighting the importance of disc shape (comet, proxy, rocs). The shape (disc profile + weight distribution) alters the location and amplitude of the lifting forces.

 

[cjman]

Why do RHBH discs turn right?
Factors that increase the right turn of a RHBH disc:

1.Higher spin rate

2.Narrower rim

3.Nose down. Below 9 degrees Angle of Attack (AoA) contributes to a right turn by precession

4. Being beat in

5. Headwind

6. Lighter weight of the same mold, same disc

7. Lower density plastic

8. Higher dome

9. Air temperature.

https://sites.google.com/site/dgresources2/Home/aerodynamics/turnright

 

[armiller]

The main effect that spin has on a disc's flight is to increase its angular momentum and thus to cause it to resist both turn and fade.

There are quite a few interesting papers out there, both Masters and PhD theses, reporting on disc flight, some using wind tunnels and disc golf discs. If I recall correctly, they report that the Magnus effect is negligible in disc flight. The effect of aerodynamic moments caused by lift/drag is much more important than the Magnus effect, if those MS/PhDs are to be trusted.

As for headwinds, it is quite simple. Headwinds increase the velocity of air flowing over the disc, and this directly increases the magnitude of the lift force. This higher magnitude makes the disc turn more, regardless of spin. That's because it increases the moment (torque) causes about the disc's center of mass, which moment is perpendicular to its current angular momentum. As a matter of fact, a disc with higher spin will resist the turn more (i.e. turn less), but that's beside the point.

As for spin, I've said all this before somewhere. I think it's like throwing a football or baseball. Throwing it properly and efficiently (far and accurately) will naturally impart spin onto the ball. There are plenty of great NFL throws made which gain yards and score touchdowns without being perfect spirals. Likewise, I think you could gain something in disc golf by learning to control spin, but it's far more important to generate velocity while controlling trajectory, nose angle, and hyzer angle. If you do that, I bet you have also generated a the perfect amount of spin.

 

[Putt for D'oh]

A disc will fade left when the lift created by the spin +

This fallacy is pretty important to a lot of the thoughts you are posting.

A disc is a single wing not a helicopter. The spin does not create lift.

 

[sidewinder22]

There are quite a few interesting papers out there, both Masters and PhD theses, reporting on disc flight, some using wind tunnels and disc golf discs. If I recall correctly, they report that the Magnus effect is negligible in disc flight.

As for headwinds, it is quite simple. Headwinds increase the velocity of air flowing over the disc, and this directly increases the magnitude of the lift force. This higher magnitude makes the disc turn more, regardless of spin. That's because it increases the moment (torque) causes about the disc's center of mass, which moment is perpendicular to its current angular momentum. As a matter of fact, a disc with higher spin will resist the turn more (i.e. turn less), but that's beside the point.

They actually recorded a Reverse Magnus Effect although not in those words. They stated the disc rolled slightly in the opposite direction of what Magnus Effect should be. Smooth objects with laminar flow reverse Magnus. IMO why discs start out of the box so overstable is because of the laminar flow, compared to just a couple throws in adding some surface roughness to make the boundary layer airflow turbulent/energetic.

Headwinds along with increasing lift magnitude as the relative airspeed increases, will also move the Center of Pressure further back on the disc which causes the disc to behave less stable. When you get the nose down into a headwind it typically exaggerates the turning effect, although not always depending on the disc and airspeed. When you get the nose up into a headwind it typically exaggerates the fade because the CoP will never get behind the CoM.

Often considerable influence on the aerodynamics of the Frisbee has been mistakenly attributed to the effect of the spin about the axis of symmetry. Consider the motion of the left and right sides of a Frisbee due to spin in a right hand backhand throw rotating clockwise viewed from above. The motion of the left side of the Frisbee (viewed from behind) is in the direction of the velocity while that of the right side opposes velocity. Consequently the total velocity on the left (due to spin and linear velocity of the COM) will be greater than that on the right. Since lift is quadratic in velocity (eq. 2.6), the distribution of the lift might consequently be thought to be greater on the left side than the right side. The COP would be expected to shift left of the midline of the disc to the side with the higher velocity. Such a shift would cause a positive roll moment.

However, data collected from Potts and Crowther (2002) shows the roll moment to be negative, not positive. Thus the mistaken rationale presented above does not even calculate the sign of the rolling moment, much less its magnitude, illustrating the complex nature of the flow around the Frisbee. Also, it is important to understand that in the lift calculation (eq. 2.6), CL applies only to the Frisbee as a whole and the relative velocity must be the velocity of the COM, not a left or right side velocity. In any case, the roll moment is very small and does not play a large role in the flight dynamics.

 

[dorseymatt]

I bet Albert Tamm has the most spin relative to speed of any forehand on the planet.