Light discs can be thrown faster creating far too much lift for thier weight.

I have 150 class and 170 gm in the three following discs...Gazelle, TeeBird, and XS

all of the light weight discs rise higher than do the heavier ones. Is this because the aerodymamics are exactly the same on light discs as they are on their heavier counterparts?

Can anyone say if there is a particular disk that has aerodynamics that are better for 150class discs. Stability is not so much a problem as it is controllable, but I have no ability to keep a disk from rising to high when thrown flat and level...Even when thrown nose down a touch, I notice that the light discs eventually rise too high

Is this an equipement problem or a technique issue?

All I know to tell you is that my 150 class cheetah seems to fly s-curves better than anything else in my bag except my 174 valkyrie and it's easier to throw farther...but that's probably more due to my inexperience with the valk than to the disc weights.

The way it was explained to me is this. For a RH/BH thrower, after you release the disc, the left side of the flight plate is exposed to more air rushing over it (because of the spinning motion) which creates lift on the left side of the disc. The lighter the disc, the more it lifts the left side of the disc. Hope this helps.
Scott

That explanation is completely wrong.

There is no more lift on the left side of the disc than the right. The lift is caused by the general profile of the disc moving through the air, it is NOT caused by the speed of the actual plastic at each part of the disc. The SPIN of the disc has nothing to do with lift. Lift is not caused by the spin of the disc, it's caused by the speed of the profile of the disc moving through the air, and both sides of the profile move at the same speed like an airplane wing. The spin has nothing to do with it.

Where the SPIN on the disc comes into play is with gyroscopic effects like procession. Nose up causes the disc to process to the left (RHBH) and nose down causes it to process to the right. Has nothing to do with lift!

with no wind light discs fly the first half of their journey faster than a max weight but they fly slower than a max weight on the second half of the flight, unless you are in a vacuum in which they both fly at the same speed, as does the feather

Wow, two in a row with correct info on this subject. Could be a record. /msgboard/images/clipart/happy.gif

Except for my spelling. It's precession not procession. I was drinking again last night.

Although I understand the principle that the disc has an overall profile that affects how it cuts through the air (and thus lift, etc.), I find it hard to believe that the rotation of the disc has NO effect on lift, as Morgan stated and Dave D seemed to agree to. There would seem to be some at least some differential between the two sides of the disc in terms of lift because of the spin. I can see that it might not be the dominant factor in flight stability and direction, but surely it is a factor (and one that changes as spin lessens, speed lowers, etc. -- some big-time math calculations would be needed even if all the physics were accounted for properly, which I am not sure they have yet been!)

Dave D, you seemed to agree with Morgan that spin is no aerodynamic factor in relation to differential lift -- is there something you can point to that would justify your position? I am not trying to start a brouhaha, I am simply trying to learn more about this fascinating topic of disc flight.

Thanks for any help you can provide.

-- Karl Nehring

My previous message about lift and spin was incomplete, and I can anticipate getting jumped on already. Let me try to make my question more clear: I can see how Morgan's assertion that it is the overall profile of the disk that determines lift, not the spin, is correct overall. The differential in lift due to rotation speed would seem to pretty well cancel out in terms of overall lift. I think that would be the thrust of Morgan's claim (seconded by Dave D); however, I am not convinced that if you do the calculations and factor in overall air speed, spin speed, etc, that more rotational speed might at least have some relation to lift (although it is certainly not the dominant factor). I base this notion partially on the idea that there is not just a cancellation going on betwen sides of the disk (and to be fair, Morgan never said this, it is simply my guess at his logic, and I may be off-base), meaning that the overall profile is the only factor -- but rather the greater overall level of turbulence caused by the higher rate of spin also has an effect on lift, though probably not anywhere nearly as large an effect as that attributable to overall profile and wind speed of the disc itself.

Sorry to beat this into the ground -- this is a complex topic that does not lend itself well to armchair physics on a newsgroup. But I would like to learn more about this, and wonder whether Dave D or anyone else can point to a more rigorous analysis of disc flight than I have been able to come across so far.

Thanks again.

Karl Nehring

Since the left side of the disc, as it is going away from the RHBH thrower, is encountering more 'airspeed' due to spin, this would 'seem' like more lift is theoretically being produced, thus contributing to turnover, though a discs' overall stability (rating) would prevail. A slightly tacoed disc could be explained similarily: there is more lift on the left side, thus more turnover. Others have stated that more spin makes a disc more overstable, which of course would negate this whole theory...

When I see some longer throwing pros unleash a disc that goes out straight, straight, straight, then goes right; I ask myself what is contributing to this phenomenon!? Is it their overall disc speed, or is it added spin, OR is it some phangled combination of these 2 factors in addition to others... Likely it is the third! But, it is human nature to reduce variables to a more simplistic model for easier comprehension, and doggone it, I wanna understand better!!

My cheezy two cents worth.

If spin had anything to do with lift, then I am quite certain that aeronautical engineers would have figured out a way to incorporate the idea into an aircraft. Heck, wouldnt it make sence to mount a spinning disc to the side of an airplane rather than a fixed wing if it could provide more lift?

The gyroscopic effects of a disc alter only its stability and keeps it from wobbling uncontrolably.

Lift is generated by the difference in air pressure above and below the disc/wing...This requires smooth transition of air past the disc, so if the stability of the disc is directly responsibly for that smooth flow of air, then one could stand firm that spin does effect lift, but has nothing to do with the creation of lift. I guess in a sence, one cannot happen without the other.

Now back to my original question...are there disc profiles that are more suited for lighter discs?
I mean, all the science in the world will not matter a hill of beans on the course if you don't have the right discs in your bag.

A fellow "lefty" DGer who uses 150 class, and can throw 400' likes Valks and Cheetahs...even into the wind. His throwing style necessitates an understable disc though. He flicks the disc starting from behind his "left" hip, resulting in a "lefty" backhand style throw, but thrown with a significant amount of hyzer. A very unique style that serves him well, because he usually runs the course, and after his throw, he just keeps on running, carrying his other 3-4 discs!

> If spin had anything to do with lift, then I am quite certain that aeronautical engineers
> would have figured out a way to incorporate the idea into an aircraft.

You mean like a helicopter?

NO, not like a helicopter!!!

Take a closer look at a helicopters blades when at rest. You will notice that they are actually little airplane wings that create lift by moving into the wind. It just so happens that they are driven from an axial point that keeps them going around in a circle. but it is actually their forward motion within the arc that they travel that creates the airflow for lift. This has nothing to do with the gyroscopic effects of them spinning, but rather just the fact that they spin in order to keep the blades moving forward. This is a principle by which a cluster of blades can work together, not by which one (as in a disc) can

Now unless an aeronautical engineer wants to jump on the bandwagon and offer succinct information pertaining to this thread, then lets get off of the bunny trail and quit beating the dead horse.

Since a RHBH throw is spinning clockwise, and assuming there is no wind for simplicity sake, the left side of the disc would be encountering more airspeed due to that (left) side spinning 'toward' the direction of flight, while the right side is spinning 'away' from the projected path. Since there would be more air (relative to the disc) passing over the left side of the disc/'wing', wouldn't there be more lift on the left side? The amount of lift may be negligible, but this 'seems' plausible...and EVEN MORE 'plausible' for a broken-in disc, whose irregularities may account for even more left-sided lift, thus causing a noticeable increase in understability, by causing the left side to lift, changing the flight toward the right (or straighter for an overstable disc).
Would some physicist please put me out of my misery!!??

Oh no, they've stumbled upon the flying saucer theory./msgboard/images/clipart/proud.gif
The leading edge of a disc, which is the same because its round, duh, gives it all its flight charateristics.
A blunter rounded edge will get its lift much quicker than a sharper edge will. Air flow over the steeper rounded edge will create more lift at slower speeds, hence more midrange and putter type discs.
The sharper edge requires more forward motion to maintain flight, will also fly further and at higher speeds.

Its like the difference between an old corsair fighter plane, which can acheive lift at about say 100mph, but is low powered and slow. Now take an F-15. It cant acheive lift until about 200mph, but is much faster and acheives high speeds. The amout of air caught under the wings, like the flight plate of a disc, determines how fast it will rise with air flowing under it, and how well it will glide at slow speeds.
Then you factor in weight. Weight is relevant to how soon and how fast these edge charateristics affect the flight of the disc. The spin put on your disc comes into play here as a balancing agent. More spin, more balance, more stable a flight. When the disc stops spinning it will come back to earth because they will not fly without stability/spin.
Geez, I feel like Mr Wizard.
Just dont throw light stuff when the winds blowin./msgboard/images/clipart/happy.gif

Spin has nothing to do with lift. Spin creates angular momentum, which is what give a disc its stability. For a quick overiview of the physics involved, see, Aerodynamics in Sports Equipment: The Frisbee (http://wings.avkids.com/Book/Sports/instructor/frisbee-01.html), Frisbee Physics (http://www.pbs.org/ktca/newtons/9/frisbee.html), and The Ultimate Handbook: the Physics of Flight (http://www.ultimatehandbook.com/Webpages/Beginner/physics.html); for a fuller discussion see, _Scientific American_, April 1999 (http://www.sciam.com/article.cfm?articleID=000155A0-6D59-1C71-9EB7809EC588F2D7. ).

A beat/tacoed disc turns over because the deformation in the disc produces off-axis torque (flutter) acting in the direction of the spin.

Nah. The beat disc turns over because the front edge of the disc isn't sharp anymore. The sharp front edge of a new disc passes more air underneath it, causing more nose up, and the beat disc allows more air to flow over the top and there's less nose up. Nose up pushes the front edge of the disc upward and changes the gyroscopic stability so the the right edge of the disc moves up. If you put nose up on a disc, the right edge of the disc moves up due to precession, the disc goes to the left. The beat disc has nose down and precesses to the right. That's entirely from gyroscopic action, and has nothing to do with aerodynamics.

<FONT FACE="Courier New">
___________
...........\
............\
............/ new disc, air flows under
.........../
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__________
...........\
............|
............| beat disc, less air flows under
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Wow, RG, you almost sounded like Mr. Wizard, too! /msgboard/images/clipart/happy.gif

I didnt have the visuals though like Morgan./msgboard/images/clipart/proud.gif

Circle 2 wrote:

"When I see some longer throwing pros unleash a disc that goes out straight, straight, straight, then goes right; I ask myself what is contributing to this phenomenon!?"

Now this is a real basic explanation:

From what I've been told is that disc flight deals with airspeed and spin. Since spin effects flight characteristics (i/e stability) the phenomenon you are seeing is the airspeed is so high that the spin can not alter the flight with it's stability characteristics. Once airspeed reaches a certain value the spins stability characteristics take effect for the remainder of the flight.

This is why you see shots like inline s-curves, and late anhyzers. Their putting a lot of spin on the disc, but they are also creating a HUGE amount of airspeed.

Again, this is a real basic explanation.

A couple of thoughts: The sillouette (front view) is the most important aspect in fluid dynamics (high profile disc/putter vs low profile/driver). The leading edge contibutes to having turbulent flow (for putting) and laminar flow (for drives and higher speeds). The angle of release changes the profile immediately (throw the right disc 'flat' for distance). The wing angle and profile of a Cessna is not the same as for an F-16. There would be no lift changes from side to side on a disc if drag is assumed to be at zero accross the disc. I think friction differences would be minimal, but it would contribute some....lefty discs go right, righty discs go left (discs would all go exactly straight if there were no differences). Weight distribution of the disc (stability) leads to keeping the disc in 'wing' formation longer. A flat thrown extremely over stable OR extremely understable disc will hyzer or anhyzer quickly. So, we try to maintain the horizontal wing longer by throwing a little more anhyzer or a little hyzer to attain the 'S' for distance.
Armchair fluid dynamics at it's best? I'm probably all wrong...been about 15 years since I had any of this stuff!

All I know is that a 142g KC Cheetah kicks a<FONT SIZE=" 0">s</FONT>s with a 20 mph tailwind.

* From what I've been told is that disc flight deals with airspeed and spin. Since spin effects flight characteristics (i/e stability)... *

There is much more going on than just spin and air speed. The spinning surface of disc in static air harbors a whole bunch of air that spins off the edge of the disc by centripetal force. The faster the disc spins, the faster this air spins off the edge.

When one has a moving disc, the air that on the outer edge of the disc spinning into the static air it is traveling thru creates a fair amount of air pressure that acts on the disc to cause it to tip one way or the other, while the spinning edge that is going with the flight will provide very little resistance to the static air it is traveling thru.

A disc's flight pattern is somewhat intimately related to the balance of the air pressure of the opposing and following edges and the ability of the disc's centripetal force to counter the plus and minus of these forces acting on the disc.

Because the speed of the disc flying thru the air varies much more than the speed of the spin (and countering air pressure plowing off the opposing edge) during the flight, one has the common observation that disc stability changes during flight from beginning to end from stable to unstable and back again, assuming one has enough arm speed to exceed the inherent overstability of most discs.

It's also worth considering some grips/releases (such as the modified power grip) impart a predictable spin speed whose outer edge spins roughly at the same speed of the disc flight at release. Such techniques result in a reasonably predictable and repeatable flight pattern, regardless of disc weight. In other words, controlled flight for both light and heavy discs of the same mold, albethey of slightly different patterns.

Techniques that don't produce a predictable relationship of disc spin to speed (regardless of disc wieght) are destined to be less to much predictable in flight pattern.

114g Gateway Sabre with a tailwind carries quite a way as well :-) Not only that but you can submerge it completely underwater and it will pop back up to the surface.

But back on topic...

At least with the warped or beaten discs becoming understable...it seems like there's a good chance a beaten disc simply ends up acting through it's whole flight as if it's fluttering (like after a poor release). Without a good balance in flight, the gyroscopic force can't fight the high speed turn toward understability.

In my experience with a bunch of light discs...some ultralight, you get the most distance out of less armspeed, more spin, and a bit of height. Since the disc is lighter, it gets more lift, and stays in the air much longer. The end result with no wind for most people might not be much different distance when compared to a heavier disc, but it certainly feels a lot easier on the arm. One of the better rounds I've played at Jimmy Porter in Carrollton was with a 149g Cyclone. I would imagine all discs that are more dome-y than low profile do pretty well in the lighter weights. If you're interested in extreme downwind distance however, 150 class CE Valkyries seem to do the trick. Though the shot seemed to lack all control, one of my friends could routinely rip it out at a huge hyzer angle, have it flip all the way over to anhyzer while climbing, then slowly turn back toward the ground about 50 ft. further than any other disc he had.

Hey this post is from even longer ago than the last phantom post that resurfaced years later.

NO, not like a helicopter!!!



Spin is bad in helicopters, actually. Precession causes all kinds of problems.

Oh jeez...headache topic... :eek: