Lol - we can't agree on what causes turn or what side of a disc moves further for a normal RHBH throw.
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Disc Physics...???
- Thread starter Toro71
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Lol - we can't agree on what causes turn or what side of a disc moves further for a normal RHBH throw.
I refuse to accept the Magnus effect as a significant contributor to a disc's flight. The sidewall height of a disc is waaaaaay too small for this to have a real effect.
Headwinds and tailwinds affect the airspeed the disc sees. Changing the airspeed changes the lift characteristics (moves the center of pressure forward or backward). The movement of the CP affects the turn of the disc.
Toro71
* Ace Member *
This makes sense as I'm conceptualizing it now.
No, I can't 'tube @ work, I'll email to myself @ home and check it out, though.
You are probably right. But the magnus effect wouldn't only touch the very small vertical edge, but also the top and bottom beveled edges. Like the curved side of a baseball of soccerball.
well if some of the innova molds with X bottom and Y top tell you anything. . . .
This video explains the issue very nicely, especially the demo with the bike tire. What this is basically saying is:
Early in the flight (turn) the center of pressure (and therefore lift) is behind the center of the disc. This additional force on the back is translated 90* via gyroscopic precession which lifts the left hand side of the disc - turning it right.
As the disc slows, the center of pressure (and lift) moves forward. When the center of lift is in front of the center of the disc that same gyroscopic precession translates that force to a lift of the right hand side of the disc - fading back left.
The only thing I haven't seen explained well is why more US discs keep the center of lift behind the center of the disc for longer - and why this moves forward as the disc slows.
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It is a difficult concept to explain, cut me a little slack . . .
If true, this would almost certainly be miniscule to the point of not being observable.
I really only brought that up (after pointing out the lunacy of even going down that rabbit hole) to point out the error of thinking that air movement in relation to the surface of the disc mattered. Of course it doesn't, and you are, as you know, correct that the Magnus Effect, if present, would cause the disc to move to the right and not the left. I tend to doubt that the Magnus Effect would be anything other than miniscule due to narrow edge of most discs and probably even miniscule on blunt edged discs like lids and ultimate discs. But this is just speculation.
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I casually hinted to Harold Duvall a few years back that I'm kinda good at that stuff if they need anyone. He was all like, "Well, Dave's got that covered pretty well."
There you get into the magic of aerodynamics. That's a bit on the complicated side. I probably couldn't give you a good answer without looking at CFD results.
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Pure speculation follows: I think that it is no coincidence that understable discs tend to have more "glide" than overstable discs. This is because they probably have more lift. Does this cause the center of lift to mover further back at high speed? Does it make the initial, zero-lift, nose-down angle greater and cause turn when the disc slows enough to make the initial nose down angle a negative lift one, with a center of pressure on the top and forward of the spin axis?
It would be interesting to know although knowing probably wouldn't help my game any.
Toro71
* Ace Member *
Which is probably true of this whole thread, more or less, but I love this stuff. Thanks for all the responses, people.
One more question:
I may be incorrect in this but when I throw a disc with a poor release and it is fluttering, it turns more (goes right with a RHBH throw). If I'm not crazy and this is what's happening, how does that fit into what's been discussed so far.
I was originally in the party of "well different air speeds relative to disc surface so more lift on left side" but have been completely turned off that with the realization that lift is indeed dependent on the difference in pressure above and below disc so any effects from rotational speed are equal on top and on bottom.
I may be incorrect in this but when I throw a disc with a poor release and it is fluttering, it turns more (goes right with a RHBH throw). If I'm not crazy and this is what's happening, how does that fit into what's been discussed so far.
I was originally in the party of "well different air speeds relative to disc surface so more lift on left side" but have been completely turned off that with the realization that lift is indeed dependent on the difference in pressure above and below disc so any effects from rotational speed are equal on top and on bottom.
jeverett
Double Eagle Member
As no one seems to have mentioned it yet, some of the best/only actual research on the aerodynamics of disc golf was conducted by Jonathan Potts (PhD) of the British company Discwing (makers of the Quarter K). It appears the company domain is defunct now, but their site is preserved here:
https://reddwarf.1st4domains.co.uk/discwing.com/research/aerodynamics.html
The first article there (Frisbee Aerodynamics), for example, suggests that the 'pitching moment' is responsible for both 'turn' and 'fade'. I admit to not fully understanding the physics he's talking about, however, and will defer to anyone better able to understand/interpret that research than I.
https://reddwarf.1st4domains.co.uk/discwing.com/research/aerodynamics.html
The first article there (Frisbee Aerodynamics), for example, suggests that the 'pitching moment' is responsible for both 'turn' and 'fade'. I admit to not fully understanding the physics he's talking about, however, and will defer to anyone better able to understand/interpret that research than I.
I had seen that article before, closed the tab before I read it, and could never remember where it came from...As no one seems to have mentioned it yet, some of the best/only actual research on the aerodynamics of disc golf was conducted by Jonathan Potts (PhD) of the British company Discwing (makers of the Quarter K). It appears the company domain is defunct now, but their site is preserved here:
https://reddwarf.1st4domains.co.uk/discwing.com/research/aerodynamics.html
The first article there (Frisbee Aerodynamics), for example, suggests that the 'pitching moment' is responsible for both 'turn' and 'fade'. I admit to not fully understanding the physics he's talking about, however, and will defer to anyone better able to understand/interpret that research than I.
His conclusions agree with this thread.
Pitching Moment: Pitch is the same as nose-up and nose-down. A positive pitching moment means the lift wants to lift the nose up; the lift is in front of the CG. A negative pitching moment wants to push the nose down; the lift is behind the CG.
From his conclusions section:
The typical S shaped flightpath exhibited from a back-hand throw is dictated by the pitching moment. For a right-handed throw, the negative pitching moment [nose-down, lift is behind CG] on release causes the disc to roll (gyroscopic precession) and bank right, whereas late in the flight the positive pitching moment [nose-up, lift is in front of CG] causes the disc to bank left.
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This morning I posted a link here to a page that has pdfs of the articles by Potts, Hummel's thesis, and other research in disc aerodynamics. Apparently it got overlooked because I didn't describe it very much.
1. I ignored it. Saw Hummel at the top, decided I'd read quite enough of that paper.
2. The Potts links are dead.
DesertFox
Birdie Member
Hmm...I think I'll just throw my disc and hope it does what I want it to.
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Thanks for the heads up. I guess Discwing is out of business.
I added 9 files to the DG Resources Aerodynamics page so that what I have is right there.
Did some reading on the Magnus Effect. Two questions:
1. The Magnus Effect is not dependent on friction, is it? Like with the baseball analogy, it would still work without seams (and with a perfectly smooth covering)?
2. It seems that the amount of air affected by the Magnus Effect is incredibly small, in terms of the total air effects on the disc. Is it enough to cause turn?
1. The Magnus Effect is not dependent on friction, is it? Like with the baseball analogy, it would still work without seams (and with a perfectly smooth covering)?
2. It seems that the amount of air affected by the Magnus Effect is incredibly small, in terms of the total air effects on the disc. Is it enough to cause turn?
