DiscChucker
Eagle Member
This is some great information, albeit some of it is way over my head. I had never known about the "rings of Headrick." That's some interesting trivia fodder. I'll never look at a Frisbee the same way again now.
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Explanation of the physics of flying discs (FIXED)
- Thread starter Rameka
- Start date
colodiscgolfer
Eagle Member
Olorin, I'm really dumbing down my answers so folks can understand them better in that thread. The rotational rate would be measured in degrees or radians per second (or even rpm), and the actual velocity at any given point will vary along the radius. I am just trying to put the general concept into something more palatable for the average disc golfer to understand by selecting a point on the outside of the rim to analyze. The cumulative effect will be in the same direction. I am not completely sure of what the average rotational speed of disc golf disc is either, and would love to know. I've seen some analysis of rec disc throwing, but nothing specific to disc golf discs that would probably have a much higher rotation rate than a rec disc. I have to get back to work here, but will take a look over the other link you gave sometime in the near future.
progolfer33
Bogey Member
- Joined
- Jul 11, 2009
- Messages
- 90
So, just a thought on another reason why a disc tends to be more understable as it "beats in". It's kind of a simple theory, but sometimes those are ok, right? I apologize if someone already mentioned this...this is too long of a thread to read everything.
I'm sure everyone has experience with discs "tacoing". You smack a disc up against a tree and the lip bends down (dorsally). Repeated incidences of hitting trees, especially in the long run where the impact point should be fairly symmetrical across the rim would tend to shape the disc into a more domed shape. As Rameka already mentioned, a domed disc will tend to be more understable.
I have personal experience that this happens. I tacoed a Wizard really bad on a tree and it turned into an Aviar lol.
I'm sure everyone has experience with discs "tacoing". You smack a disc up against a tree and the lip bends down (dorsally). Repeated incidences of hitting trees, especially in the long run where the impact point should be fairly symmetrical across the rim would tend to shape the disc into a more domed shape. As Rameka already mentioned, a domed disc will tend to be more understable.
I have personal experience that this happens. I tacoed a Wizard really bad on a tree and it turned into an Aviar lol.
ChainMan
Eagle Member
My extremely pedestrian assumption on beat in discs turning right is that the nicks and scuffs cause a larger pocket of negative air pressure above the disc. Since the left side is spinning into the wind the negative air pressure on that side is more pronounced on that side causing greater lift and turns accordingly.
I've heard the theory progolfer mentioned as well. I hope someone can come up with the definitive answer because this kind of enigma fascinates me to no end!
I've heard the theory progolfer mentioned as well. I hope someone can come up with the definitive answer because this kind of enigma fascinates me to no end!
Oh lord, not this thread again. Will no one accept my theory of turn and fade occurring thanks to the invisible Hand of God? Guess I'm the only creationist disc golfer. 
justin
Double Eagle Member
BUMP!
I only just found this thread. Thanks so much for this. It's a great resource and I thought it was written very well and I'm certainly not a scientist.
The talk about Quest's dimples, Innova's groove in the rim, and beat-up discs reminded me of this Marshall Street article:
http://marshallstreetdiscgolf.com/htmlpages/torque_archive/torque_archive_0802.html
I only just found this thread. Thanks so much for this. It's a great resource and I thought it was written very well and I'm certainly not a scientist.
The talk about Quest's dimples, Innova's groove in the rim, and beat-up discs reminded me of this Marshall Street article:
http://marshallstreetdiscgolf.com/htmlpages/torque_archive/torque_archive_0802.html
This is great!! Why didn't I read this thread before?! Ok, so I spent a few hours going over all the really well-collected stuff you put together, Olorin. I just couldn't put it down. I think I have an understanding of some things.
I think I'll try to explain my understanding. You may already be past all this, but it helps me to write it out anyway. I'll try to make it readable and not get too precise about terminology and stuff, especially since my grasp on this isn't too great yet. Please, correct me if I'm wrong!
It'd be helpful to look at this image when reading: http://picasaweb.google.com/orcsroc/DiscAerodynamics#5319157673425650690
1. Why does a disc turn?
The center of pressure (ie, where the lift force is centered; CP in the image) is ahead of the center of gravity (CG in the image). That means the lift generated by the disc tends to make it rotate (ie, a torque will be applied) in such a way that the nose goes up or down (Nose Up in the image). So if the disc was thrown without spin, this would cause a rapid change in pitch: basically the disc would flip end-over-end and not go anywhere. But because the disc is spinning, it behaves like a gyroscope. Torque applied to a gyroscope along its axis of spin cause rotation at right angles to the axis (called gyroscopic precession). What this means for the disc is the torque that would change the pitch actually cause it to roll. Or in terms of the image, the spin transfers "Nose Up" torque into "Bank Left" torque.
2. Why does a disc turn right at high speeds?
The disc turns right at first because at angles of attack near zero (ie, nose flat), the flight properties of the disc actually makes it pitch nose down. So the precession or spin transfers nose down torque (aka negative "Nose Up") to bank right torque (aka negative "Bank Left").
This happens more at high speeds because lift is proportional to the square of velocity. So if you throw twice as fast, the disc will generate four times the lift. Lift is the force ultimately causes the roll, so more speed means more lift means more roll.
3. Why does a disc fade left at low speeds?
The disc fades left late because the angle of attack increases over the flight of the disc (see #5). At angles of attack over 10 degrees or so (depending on the disc), the flight properties of the disc make it pitch nose up - relatively hard, too, as the angle of attack increases past 10 degrees. Again the precession transfers this "Nose Up" torque into a roll to the left.
4. Why do some discs turn or fade more than others?
The disc shape and mold changes the flight properties of the disc to have varying centers of pressure, lift and pitch moments at different angles of attack. In the Potts and Crowther papers Olorin linked to, they tested three shapes: a throw-and-catch frisbee, a flat plate, and something in between those two. They each had very different flight properties, so there is a lot of play in disc design to give discs different flight properties. For example, I suspect a disc that holds its line (like the Buzzz) may have its center of pressure closer to the center of gravity, making less pitch torque which results in less roll. That's just speculation, but you can imagine the effect varying some of these properties would have on the flight of a disc.
5. Why does a disc's angle of attack increase during flight?
I don't know. I haven't seen an explanation for it, only a statement that it occurs. One idea is that there is a measurable roll moment when spinning, according to Potts and Crowther, which might pitch the disc because of precession.
I think I'll try to explain my understanding. You may already be past all this, but it helps me to write it out anyway. I'll try to make it readable and not get too precise about terminology and stuff, especially since my grasp on this isn't too great yet.
Please, correct me if I'm wrong!It'd be helpful to look at this image when reading: http://picasaweb.google.com/orcsroc/DiscAerodynamics#5319157673425650690
1. Why does a disc turn?
The center of pressure (ie, where the lift force is centered; CP in the image) is ahead of the center of gravity (CG in the image). That means the lift generated by the disc tends to make it rotate (ie, a torque will be applied) in such a way that the nose goes up or down (Nose Up in the image). So if the disc was thrown without spin, this would cause a rapid change in pitch: basically the disc would flip end-over-end and not go anywhere. But because the disc is spinning, it behaves like a gyroscope. Torque applied to a gyroscope along its axis of spin cause rotation at right angles to the axis (called gyroscopic precession). What this means for the disc is the torque that would change the pitch actually cause it to roll. Or in terms of the image, the spin transfers "Nose Up" torque into "Bank Left" torque.
2. Why does a disc turn right at high speeds?
The disc turns right at first because at angles of attack near zero (ie, nose flat), the flight properties of the disc actually makes it pitch nose down. So the precession or spin transfers nose down torque (aka negative "Nose Up") to bank right torque (aka negative "Bank Left").
This happens more at high speeds because lift is proportional to the square of velocity. So if you throw twice as fast, the disc will generate four times the lift. Lift is the force ultimately causes the roll, so more speed means more lift means more roll.
3. Why does a disc fade left at low speeds?
The disc fades left late because the angle of attack increases over the flight of the disc (see #5). At angles of attack over 10 degrees or so (depending on the disc), the flight properties of the disc make it pitch nose up - relatively hard, too, as the angle of attack increases past 10 degrees. Again the precession transfers this "Nose Up" torque into a roll to the left.
4. Why do some discs turn or fade more than others?
The disc shape and mold changes the flight properties of the disc to have varying centers of pressure, lift and pitch moments at different angles of attack. In the Potts and Crowther papers Olorin linked to, they tested three shapes: a throw-and-catch frisbee, a flat plate, and something in between those two. They each had very different flight properties, so there is a lot of play in disc design to give discs different flight properties. For example, I suspect a disc that holds its line (like the Buzzz) may have its center of pressure closer to the center of gravity, making less pitch torque which results in less roll. That's just speculation, but you can imagine the effect varying some of these properties would have on the flight of a disc.
5. Why does a disc's angle of attack increase during flight?
I don't know. I haven't seen an explanation for it, only a statement that it occurs. One idea is that there is a measurable roll moment when spinning, according to Potts and Crowther, which might pitch the disc because of precession.
Clark
Par Member
- Joined
- Nov 12, 2009
- Messages
- 124
First of all, thank you SO MUCH, rybob, for making this post. Thanks to Olorin for finding those resources. I was actually reading this thread two days ago when I searched for "physics" because I wanted to know why discs flew the way they did.
I am an aerospace engineer, and my colleagues and I were discussing disc flight this week. It wasn't until I read that Potts & Crowther paper that I really got the answer I was looking for. Unfortunately, Rameka's understanding was a bit lacking in his lengthy, but wrong, explanation of disc flight mechanics.
Points 1-4 above are spot on!
The angle of attack is defined as the angle between the plate of the disc and the flight path. If you throw flat, the angle of attack is zero. If you spin the disc and drop it straight to the ground, the angle of attack would be close to 90 degrees.
You will notice that the disc fades back to the left only after it has reached its maximum height. This is because the angle of attack is increasing past that 9-10 degrees point that marks the zero-pitching-moment angle. Due to the spin on the disc, it doesn't nose up or down (for the most part) during its flight.
Assume your disc is still spinning flat as it drops from its apex. The air going past the disc is rushing up at it. If you can imagine that air going straight from right to left, then the disc would be angled up compared to it. This is a positive angle of attack. Your point #3 takes over from here and you get fade on the disc.
Well done!
I am an aerospace engineer, and my colleagues and I were discussing disc flight this week. It wasn't until I read that Potts & Crowther paper that I really got the answer I was looking for. Unfortunately, Rameka's understanding was a bit lacking in his lengthy, but wrong, explanation of disc flight mechanics.
Points 1-4 above are spot on!
The angle of attack is defined as the angle between the plate of the disc and the flight path. If you throw flat, the angle of attack is zero. If you spin the disc and drop it straight to the ground, the angle of attack would be close to 90 degrees.
You will notice that the disc fades back to the left only after it has reached its maximum height. This is because the angle of attack is increasing past that 9-10 degrees point that marks the zero-pitching-moment angle. Due to the spin on the disc, it doesn't nose up or down (for the most part) during its flight.
Assume your disc is still spinning flat as it drops from its apex. The air going past the disc is rushing up at it. If you can imagine that air going straight from right to left, then the disc would be angled up compared to it. This is a positive angle of attack. Your point #3 takes over from here and you get fade on the disc.
Well done!
NothinButChing
* Ace Member *
I think about all of that every drive
Pete Kwaz
Birdie Member
Good read man. You really did your homework on this from what I see. I agree with what you said.
- Joined
- Jan 10, 2007
- Messages
- 2,776
I just compiled a more thorough list of Resources for further research.
Thanks for putting all that in one place.
Oh lord, not this thread again. Will no one accept my theory of turn and fade occurring thanks to the invisible Hand of God? Guess I'm the only creationist disc golfer.
I'd agree with you, but I think that God placed the forces of nature in existence and only allowed the miraculous to happen on the internet. That is why everyone can throw further, more accurately, putt better, and beat anyone else so long as they don't leave the lovely world of the wide web.
Disclaimer-Don't induct anything about my actual theological beliefs from that statement, unless you want to make another joke.
This thread needs resurrection... WOW is all I have to say...
I hadn't seen this thread yet. Very informative and answers many questions I've had but didn't feel like researching myself.
Thanks!
:hfive:
pspunch
Double Eagle Member
good find. glad i got to see this. :thmbup:
I have read the whole thread and I have a basic understanding of physics. That being said much of it is over my head. I am digging into the articles and I hope to further educate myself. It is fascinating that is for sure.
TeamScottSmith
Newbie
- Joined
- May 20, 2010
- Messages
- 2
Well, there goes two hours of my life I'll never get back.
Kidding aside, this was a greatly informative - though old - thread, and was just what I was looking for. Great job guys.
Your research was appreciated.
Kidding aside, this was a greatly informative - though old - thread, and was just what I was looking for. Great job guys.
Your research was appreciated.
Old Bassman
Eagle Member
I have not seen this in a long time. Thanx. Time for some reading.
