Explanation of the physics of flying discs (FIXED)

[Marv Vega]

whip(spin) is control the more whip the longer you control the disc before old newton takes over and to answer the height question longer arms just like a longer whip makes more snap(pop) watch that slo mo show on tv the episode with that long drive champ on it i think that will explain whip dynamics. also being taller allows more time for the disc to go down before its lift brings it back up so yes being taller is better, try to think of it like being up on a hill, taller players need more strength though to compete with the spped of the smaller players snap ,so start hittin them weights because you already have a natural advantage look up the heights of some of the top pros i mean climo looks just like icabod crain . if your throwin your disc nose up instead of down you might be losing some d on your long drives

Exactly, you have greater power potential with a longer arm vs. a shorter one. Another way to look at it would be that the longer the length of the arm, the greater the distance that the force of your muscles can be applied to it and the disc. Kind of like a long reach back, the farther you can reach back the more force you can potentially generate.

 

[garublador]

This is a highly interesting thread and really crystallized somethings for me. Thank you rameka. Can you perhaps explain this to me....Whip and snap the effect on flight. I am 6'3" and over 250 lbs but can't come close to what the wirey kids I see out there can throw...I have seen old men with short little alligator arm releases throw over 350..WTF! Seems they generate a quick release like a softball pitcher perhaps and perhaps the less motion allows for more control as opposed to a big long wind up. What is more important control or whip as it relates to distance?

Making big jumps in distance is more about fixing mechanics and timing and less about physical makeup. It doesn't matter how hard you can throw if you aren't doing it right. The guys who are really chucking it have all that stuff figured out and are gaining power from places you are not and are transferring more of that power to the disc.

 

[valkyriefb11]

Making big jumps in distance is more about fixing mechanics and timing and less about physical makeup. It doesn't matter how hard you can throw if you aren't doing it right. The guys who are really chucking it have all that stuff figured out and are gaining power from places you are not and are transferring more of that power to the disc.

very very true ... but being 6'1" saves me from only throwing 150 ft

 

[Rameka]

hard to grasp, not really dude its p.f.s. and thanks for dumbing it down on that last one

I believe I was speaking relatively, with regards to the explanations of industry leaders. You came into this thread complaining that I hadn't dumbed it down enough, and so my hint was to stick with the easy explanations already given you by the people who make the discs. Now you are getting unnecessarily indignant.

commen sense cant be compensated with dictionaries

p.s. the only people who are gonna understand all your hot air(the english language can be remarkabley brisk try to take more advantage of that) and graphs should be smart enough to figure disc dynamics on their own but dont let me interupt you the choir needs its preachin

Do I sense hostility? I really don't want to have an argument with you. Why do you insist on making fun of my vocabulary?

I consider whip to be the arm and body action and spin to be the motion produced by the wrist.......maybe we are just arguing semantics here..they are different components of a throw

Ah, my mistake! I completely misunderstood how you were intending those terms to be used. I see what you mean now. What I was saying before actually does tie into this, and I'll try to add on to what Supersloth was saying. Since the hand and wrist together make up a much shorter component to the whole arm, they can generate a lot more speed with less force. This rotating force is known as torque, as you might know, and you can think of it in terms of gears on a bike. The smaller gear is easier to ride with because an imagined point on the gear goes all the way around and back in a smaller turn (less circumference to travel). Less torque is required to keep it moving. Since this "gear" (your hand and wrist) is so small, it actually accounts for most of the spin imparted on a throw. Just take a look at your wrist, angle it down like you're holding a disc, and flick it as far back the other way as it'll go. The angle is close to 180 degrees (I exaggerate a bit), if you twist your whole forearm over a little. The larger components in your arm (forarm, upper arm) don't generate as much torque, just directional velocity (vector speed). They're your "cannons", they are responsible more for the ballistic flight of the disc. Both components are essential to distance. (probably not what you wanted to hear, right? )

The directional force imparted on the disc is important, but the spin is even more important, as it's the entire reason why a disc works. In my experience, reaching back really far or trying strange run-up steps to improve my velocity has resulted in less controlled spin and release. One thing to note is that release velocity and spin have analogous effects on a disc's flight; they both make it turn more initially if they're increased.

I'd recommend a strategy to work on your throw, but as I said before, I'm not a very strong player. I'd feel bad if I gave out the wrong tips.

 

[BrotherDave]

Oh boy, time to reload, *puts gun to head, fires a second time*

 

[BENFTS]

honestly i cant thank rameka enough. i love to know the absolute most i can about something and his post was very insightful.

 

[Dave242]

Fade: Fade is not as easy to explain. Fade happens because of a phenomenon called precession. Did any of you play with gyroscope toys when you were kids? Or even things like tops? Precession is the change in the direction of the axis in rotating objects. Precession is not off-axis torque, or in any way associated with it. Precession happens because of a pressure gradient, just like turn. You see, pressure that builds up in the underside of the disc due to slower air flow isn't radially symmetric. There's a point (which differs for different discs, obviously) called the center of lift. To reiterate, the center of lift is generally in a different spot from the center of gravity. This creates an unbalance on the horizontal plane of a disc as seen from behind, just like turn.

Love your analysis and thoughts! As a EE, I have studied a bunch of physics (never aerodynamics though) and loved that part of my education. It has been over half my life ago now, so I am loving the refresher course.

One thing I would add that I think you are missing, is in the area of fade. I think another key contributing force causing fade is the extra friction on the left side of the RHBH thrown disc. This frictional force is significantly larger on the left half than on the right due to the higher effective airspeed due to the rotational speed on the left adding to the effective speed and the rotational speed on the right subtracting from the effective speed. This extra force causes something kinda like a pivot point somewhere near the left edge of the disc and pulls the disc left.

I think what happens is that in the high speed portion of the flight, the dynamics that cause the anhyzer turnover compensate for this pivot effect. As the disc slows its forward speed, this rotational friction becomes proportionally more significant. You've probably noticed a disc landing on snow, ice or even wet grass is still spinning pretty fast even after the forward speed has slowed way down. Obviously, the air friction effects forward speed more dramatically than rotational speed.

Oh.......and don't be flustered by those that are intimidated by you being articulate and thoughtful. It is not your fault that they feel this way and doubly not your fault that they put you down....thereby showing their butts to the world.

 

[Olorin]

I love this stuff! Sure it's easy to know what happens to a disc under various conditions and most people are content with that. But some of us want to know why it happens like that too. Sometimes knowing the "why" also allows us to do the "what" better as well. For me personally, I find it amazing that such a simple toy as a frisbee can be so incredibly complex! The science is actually very complex and that evokes in me a response of praise to the awesome Creator who invented all laws and the science in the first place. To realize that to truly understand the flight of a simple disc golf disc takes an understanding of aerodynamics, fluid mechanics, physics, and differential equations makes me smile. Even Sarah Hummel wasn't totally able to describe it all with her engineering Masters' thesis!

OK, I'm trying to understand two concepts that may be related. 1) What makes a disc turn right?, 2) Why does a disc thrown into a headwind turn right (or left into a tailwind)?

In trying to better understand the forces on the disc especially lift I just made a surprising discovery. This is that the typical explanation of the Bernoulli effect in the cause of lift is only partially correct. Popular treatments are often somewhat erroneous.

Here's info from a NASA website written for high schoolers:
http://www.grc.nasa.gov/WWW/K-12/airplane/wrong1.html

"The theory can be labeled the "Longer Path" theory, or the "Equal Transit Time" theory. The theory states that airfoils are shaped with the upper surface longer than the bottom. The air molecules (the little colored balls on the figure) have farther to travel over the top of the airfoil than along the bottom. In order to meet up at the trailing edge, the molecules going over the top of the wing must travel faster than the molecules moving under the wing. Because the upper flow is faster, then, from Bernoulli's equation, the pressure is lower. The difference in pressure across the airfoil produces the lift."

Another discovery was that to truly understand lift one needs to understand the Euler equations. That would require dusting off the partial differential equations that I haven't touched in 28 years, so a complete understanding is a little beyond me right now. I think I've got enough of the general idea anyway, though.

To understand lift you need both Newton and Bernoulli.
Again, from NASA:
"The real details of how an object generates lift are very complex and do not lend themselves to simplification. For a gas, we have to simultaneously conserve the mass, momentum, and energy in the flow. Newton's laws of motion are statements concerning the conservation of momentum. Bernoulli's equation is derived by considering conservation of energy. So both of these equations are satisfied in the generation of lift; both are correct. "

NASA: "To truly understand the details of the generation of lift, one has to have a good working knowledge of the Euler Equations."

This is all just preliminary to getting into the details of the 2 questions I'm exploring, but I'll stop here for now. Rameka, I'm hoping that you might find this interesting. Thanks for all the work you've done on this and for introducing this fascinating subject for enquiring minds to chew on.

P.S.- Dave, good to read your contribution. You should check out the link to Hummel's thesis. Fascinating! BTW, you look great in you avatar!

 

[Rameka]

I think another key contributing force causing fade is the extra friction on the left side of the RHBH thrown disc.

1. This frictional force is significantly larger on the left half than on the right
2. This extra force causes something kinda like a pivot point somewhere near the left edge of the disc and pulls the disc left.
3. I think what happens is that in the high speed portion of the flight, the dynamics that cause the anhyzer turnover compensate for this pivot effect.
4. As the disc slows its forward speed, this rotational friction becomes proportionally more significant.
5. You've probably noticed a disc landing on snow, ice or even wet grass is still spinning pretty fast even after the forward speed has slowed way down. Obviously, the air friction effects forward speed more dramatically than rotational speed.

1. The frictional forces in opposition to the spin imparted by torque are, from my understanding, nearly negligible. If they were significant, this would cause the disc to stop spinning in its flight.

2. I don't think that's true. The force that pulls the left wing of the disc down is the direct consequence of a precession. Precession happens because radially asymmetric pressure in the nose of the disc is converted to angular momentum and guided to the right (the disc spins clockwise, so angular momentum maintains around the front of the disc to the right).

3. I think you are confused. The dynamics that cause the disc to turn are precisely those which you are trying to explain fade in terms of. You're saying that, as the disc goes faster, there is a bigger friction gradient across the wings. As I said in 1, this torque-friction is nearly negligible. This friction has no observable effect on the flight of the disc.
As speed goes up, the pressure gradient across the wings goes up, and this generates turn. If, as you say, the increased friction gradient caused fade, then turn wouldn't ever happen.
4. (continuing from 3) These things happen simultaneously and from the same effect. To say that they are inversely proportionate from each other is to state a direct contradiction.

5. Forward speed and spin speed are exclusive phenomena. Air friction retards forward speed. Spin doesn't have anything to do with forward speed. Spin is just responsible for lift, fade, and turn.

In conclusion, I don't think such a friction force comes into effect at all. I'll gladly discuss it more, as I could be wrong...but your addition directly contradicts my explanation, so you may want to reconsider what position you have with regards to whether you agree or disagree with my original model. One of us is right

By the way, thanks for your encouragement.

 

[Olorin]

One thing I would add that I think you are missing, is in the area of fade. I think another key contributing force causing fade is the extra friction on the left side of the RHBH thrown disc. This frictional force is significantly larger on the left half than on the right due to the higher effective airspeed due to the rotational speed on the left adding to the effective speed and the rotational speed on the right subtracting from the effective speed. This extra force causes something kinda like a pivot point somewhere near the left edge of the disc and pulls the disc left.

Dave,

I've been studying Hummel and I'm not so sure that friction or anything about the velocity on the left and right edge are even factors. I've certainly got lots of questions about what Rameka initially stated and you've just said. I think the velocity changes have more to do with gyroscopic effects (Hummel, 2.3) and angular momentum than Bernoulli and lift.

What do you think of the following (2.2.6 Miscellaneous Aerodynamics)?

"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. "

 

[swellerdiscgolf]

I think I just clicked onto a physics website. LOL. My eyes are so big now after reading these, that I can see the discs spinning in my head. Oh wait those are the lights on the ceiling, I think I fall over go boom.

But seriously, this stuff is great keep up the good work. Two questions: Why does the disc, after skipping, seem to continue to go more to the left? and Why do some discs dive more into the ground with their left wing then others?

 

[Omega SuperSloth]

rameka i like you your allright but next time you drop acid go to a laser show instead of the dgc but seriously i think i agree with most of what your sayin i think. does anyone want to take a crack at disc dynamics in space why were at it?

 

[Omega SuperSloth]

I think I just clicked onto a physics website. LOL. My eyes are so big now after reading these, that I can see the discs spinning in my head. Oh wait those are the lights on the ceiling, I think I fall over go boom.

But seriously, this stuff is great keep up the good work. Two questions: Why does the disc, after skipping, seem to continue to go more to the left? and Why do some discs dive more into the ground with their left wing then others?

when the disc hits the ground at an angle it grips the edge a little creating added counter clockwise spin assuming you didnt anny it into the ground

 

[Omega SuperSloth]

btw climo(6'2")jenkins(6'3")orum(6'2")reading(6'4")schultz(6'1")doss(?) i guess i was wrong about height advantage, mommy whats leverage and how does torque work ?

 

[Olorin]

Here's another good resource from the Discwing guy. I've just started reading it, but it looks very informative.

Potts, J.R., Crowther, W.J. 2002. Frisbee Aerodynamics AIAA Paper 2002-3150. In Proceedings of the 20th AIAA Applied Aerodynamics Conference, St. Louis, Missouri.

 

[Jungle Tim]

btw climo(6'2")jenkins(6'3")orum(6'2")reading(6'4")schultz(6'1")doss(?) i guess i was wrong about height advantage, mommy whats leverage and how does torque work ?

man this game is turning out like basketball

 

[Rameka]

Olorin: After a quick skim of your recent posts, I am slightly blown away. I don't have time to read everything through right now; I'm actually just off to go play the local course! I'll take an in-depth look at your replies tonight.

It's awesome that you're as into it as I am

 

[Donovan]

It is obvious that discs of the same mold but different plastics have different flight characteristics but I have noticed something. It may just be coincidence but I have noticed that a plastics ability to absorb permenant marker seems to be directly proportional to it's drag. If you take two discs of the same mold like a champion wraith and a dx wraith and write your name on them with a sharpie and then use acetone to remove the sharpie, the disc with the least amount of sharpie left in it (DX plastic) will fly farther and have less fade than the other one(Champion plastic).

My theory is that at a microscopic level air will absorb into the plastic just as the sharpie ink did and adhere better and therefore slow the disc down faster.

So if this is true, if you could create a plastic that sharpie will not stick to then you would have the ultimate long flying plastic.

First off I am loving all this reading and appreciate the hard work and great writing. This was really good stuff.

Brother Sidewinding,
I thought for sure you would get more bites on this baited hook.

 

[Rameka]

Olorin: If the COP actually shifts right in a turn, then I am stumped. That seems completely unintuitive, based on the explanations I've read. I mean, if the velocity over the left wing is faster, shouldn't the pressure be lower for that side, and consequently cause a positive roll moment? My number 1 question now is the same as yours--why does a disc turn right?

Also, that's a very interesting point about the incorrectness of the direct inverse proportionality of velocity to pressure. I don't know Euler equations at all, but I'm sure I will learn them at some point. It's comforting to know that at least the general principle behind that theory is correct, though...it's just the math that's been "hand-waved" into over-simplicity.

I will continue to read and make comments on the links you've posted over the next few days. It's a lot of information to digest at once...even someone as OCD as I am about this stuff can get a headache after a while.

 

[Olorin]

For those who really want to explore the aerodynamics of flying discs in greater depth I'd suggest first starting by studying Potts, J.R., Crowther, W.J. 2002. Frisbee Aerodynamics
then Hummel, Sarah Ann "Frisbee Flight Simulation and Throw Biomechanics", Masters Thesis