An Open Letter to Three Putt/Garubladder

[Disc Dog]

I have question. But please understand I am not a physics Phd. I am a laymen who reads and is not as dumb as some with Phd's would suppose. ( if you would like a debate on Maslow's Hierarchy of Needs, The Peter Principle, or the Law's of Thermodynamics I can hold my own)

I have read every post here and most in the other threads about this subject and I think:\ I have a basic grasp of the ideas. But I was raised around sailboats and there is a very common misconception that the
wind pushes the boat. This is only true when the wind is directly behind the boat. When you are traveling with the wind to the side, such as when tacking, you actually are being pulled into a vacumn that is created on the downwind side of the sail. This is created because the sail blocks the air flow causing the pressure to drop on the leeward side and the boat moves into that spot. If that is true of a sailboat would that not also be true on a disc? The air moves over a disc causing lift and the spin allows the disc to move through the air without causing a directional change (fade). As the spin decreases and it can no longer compensate for the leeward sides lower pressure and lighter weight the result would be a fade into that lower pressure. Thus causing a directional change we call fade.

Am I way off here? Or is this contributing factor?

 

[Disc Dog]

Like Garu said, it won't help.

Your decision to throw a disc because a wing angle of X* makes it less stable, than a disc with X.XX* of wing angle for a particular anhyzer shot doesn't mean it will perform that shot any better, if you don't have technique to make it work, lol. Also, ask any pro how much they understand about disc physics and I'd say in terms of our classifications of terms we apply to them, they have a great understanding. But, in a scientific terms I'd be willing to bet that most of them don't know, and don't care.

Because, after practicing with a disc they'll get an idea of how the disc will perform in their hands. Understanding which disc perform better could make you come to a conclusion of which disc just might be better suited to make a particular shot, or be more versatile. But, everyone else can get that knowledge much easier by practice, lol. Over thinking some things lead to failure. Determining which disc to pull out because of it's profile, or wing angles, or dome really isn't any different than saying. Well, this particular shot I can make my Roc flip just enough, "BING, use a Roc." One method is just easier and the other won't have that much affect over the competition as long as they know how and why to perform a certain shot in a given condition with a particular disc without knowing the small nuances of scientific physics of flight.

All this is trumped by your physical and mental capacity to perform the shot. Having the knowledge of how to throw certain lines, how to manipulate your form. And, then ultimately in the end being able to physically perform the shot. The variables in your throw you have to over come can make or break the throw completely. The throw could make the disc work or not. Knowing you could perform the shot, you could argue that you might not know what disc to throw just because you know how to throw, and can. Well, understanding the scientific physics won't make that much easier, as I said earlier anyone can get that knowledge easier by practice.

Over all the knowledge gained by the scientific data from how or why a disc flies the way it does, it trumped by your physical ability to perform the shot. Looks good on paper, and in your head. But, until you can go out and do it, it won't make a bit of difference. Then you can explain why it done it to someone, and they'll look at you and laugh. I do fully understand the search for knowledge. I like to know how things work myself.

I would take umbridge with your statement above about practice and an understanding of flight characteristics.

You state "Because, after practicing with a disc they'll get an idea of how the disc will perform in their hands. Understanding which disc perform better could make you come to a conclusion of which disc just might be better suited to make a particular shot, or be more versatile. But, everyone else can get that knowledge much easier by practice, lol." This can only apply if have the disc to practice with. The cost of purchasing every disc on the market to try is prohibitive. Having even a basic knowledge of flight characteristics would alleviate much expense and time by enabling a person to pick the disc that best suits their ability.

While the marketing strategies of the manufactures is not precise it does allow a person some guidance in making a proper decision in their disc selection. Once they have begun and therefore go from beginner to novice to intermediate etc. They can continue to choose discs with the knowledge they have gained about discs and their experience. So to state categorically that this knowledge is not necessary is a falicy.

 

[sidewinder22]

I have read every post here and most in the other threads about this subject and I think:\ I have a basic grasp of the ideas. But I was raised around sailboats and there is a very common misconception that the
wind pushes the boat. This is only true when the wind is directly behind the boat. When you are traveling with the wind to the side, such as when tacking, you actually are being pulled into a vacumn that is created on the downwind side of the sail. This is created because the sail blocks the air flow causing the pressure to drop on the leeward side and the boat moves into that spot. If that is true of a sailboat would that not also be true on a disc? The air moves over a disc causing lift and the spin allows the disc to move through the air without causing a directional change (fade). As the spin decreases and it can no longer compensate for the leeward sides lower pressure and lighter weight the result would be a fade into that lower pressure. Thus causing a directional change we call fade.

Am I way off here? Or is this contributing factor?

You are pretty close with that analogy. Generally there is drag/lift on left side of the disc(RHBH) and eddies on the right side with the disc spinning which is one reason a disc may turn right with spin. It basically takes a combination of speed, spin and wing design for HS turn.

 

[Disc Dog]

:thmbup:*Disc Dig feels IQ raise to new heights*

 

[sidewinder22]

Given two discs, is it possible for one disc to BOTH "Turn" more, and "Fade" more, with respect to the other disc? With the important assumption that everything else between the discs is equal (speed, spin, angle, etc.).

If so, what physical characteristics could/would cause such a difference?

I wrote the UC-Davis girl and asked her. She said she'd have to think about it. That was 4 years ago.

Not really without putting some oat on one disc or changing the speed. Turn and Fade are pretty dependent on each other thrown the same. You might get a Katana to turn and fade more than a Tbird but its not thrown the same and are different speed discs.

 

[hangwind]

Speed = drag (less lift at slow speed)
Glide = lift (can be a combination of speed and stability)
Turn = curved flight path
Stability = how resistant the flight of the disc is to go from a straight line flight path
Fade = loss of stable flight as the disc slows at the end of the flight

All intra-related.

Good topic.

 

[BogeyNoMore]

You know those marketing terms that Innova has: Speed, Turn, Fade, Glide? Let's talk about "Turn" and "Fade".

Given two discs, is it possible for one disc to BOTH "Turn" more, and "Fade" more, with respect to the other disc? With the important assumption that everything else between the discs is equal (speed, spin, angle, etc.).

If so, what physical characteristics could/would cause such a difference?

I wrote the UC-Davis girl and asked her. She said she'd have to think about it. That was 4 years ago.

Not really without putting some oat on one disc or changing the speed. Turn and Fade are pretty dependent on each other thrown the same. You might get a Katana to turn and fade more than a Tbird but its not thrown the same and are different speed discs.

If there's ANY truth whatsoever to Innova's numbering scheme, or the LSS and HSS numbers posted on Joe's Flight Chart and DiscGolfCenter's Flight Characteristics, it would seem that High Speed Turn is not necessarily directly linked to Low Speed Fade. I would imagine there are several variables that affect both similarly, but I can't imagine the two vary directly and in lockstep with each other.

Let's not discount practical knowledge: Most of us have thrown different discs that have similar high speed turn characteristics, but entrely different low speed fade characteristics.

While far from being solid empirical data, and things like wind that's substantially different at the end of the flight vs. the middle of the flight, or greater altitude at the end leading to increrased fade, etc., might account for some of these differences, those variables have less effect when the number of observations (sample size) is large enough.

 

[sidewinder22]

If there's ANY truth whatsoever to Innova's numbering scheme, or the LSS and HSS numbers posted on Joe's Flight Chart and DiscGolfCenter's Flight Characteristics, it would seem that High Speed Turn is not necessarily directly linked to Low Speed Fade. I would imagine there are several variables that affect both similarly, but I can't imagine the two vary directly and in lockstep with each other.

Let's not discount practical knowledge: Most of us have thrown different discs that have similar high speed turn characteristics, but entrely different low speed fade characteristics.

There are slight speed(wing length) variations that account for the different turn/fade numbers within the same speed rated discs. For instance the eagle vs teebird are both rated speed 7, but the eagle is has a slightly shorter wing making it slightly slower and easier to turn while it fades hard when it slows down. Now say you don't get the eagle up to its 7 speed rating, it has no high speed turn and fades out fast.

The numbers from innova and joe's aren't exactly scientific with no bias either. There is no way to throw all those discs exactly as they are supposed to be flown and the number of other variables is high. Innova rates both the Teebird and TL with a 0 HS turn. You have to be crazy to believe the TL has no HS turn.

 

[jubuttib]

Not really without putting some oat on one disc or changing the speed. Turn and Fade are pretty dependent on each other thrown the same. You might get a Katana to turn and fade more than a Tbird but its not thrown the same and are different speed discs.

They're linked somewhat, but it's not impossible. For example my medium IONs are both more HSS and less LSS than my soft ION, which easily turns more but also hooks way harder when it slows down. And I do believe I throw both of them the same, and that they're the same speed.

 

[sidewinder22]

They're linked somewhat, but it's not impossible. For example my medium IONs are both more HSS and less LSS than my soft ION, which easily turns more but also hooks way harder when it slows down. And I do believe I throw both of them the same, and that they're the same speed.

Different plastic will change flight which is another variable. Soft plastic will flex and tend to turn over/less gyroscopic, but loses speed faster for more fade.

 

[JHern]

...What I really want to know is what disc features contribute to different flight characteristics.
SPEED
GLIDE
TURN
FADE
Stability

On disc ratings and actual physical flight properties...

Note that Innova's rating system, and Joe's Flight Chart, and all other systems, are only subjective and relative. Speed=5 simply means the disc seems to have less drag than Speed=6, and more than Speed=4. These numbers are worked out by throwing in a field, and the numbering guru scratches his head, squints a little, and says "I'll call this a 4" or "I'll give this a 2," etc.. Nothing fancy here, it is just a way of characterizing characteristics of the disc that people think are important for practical purposes. Of course, this is just fine for most uses. But, there is no connection between these numbers and actual physically measurable quantities of disc flight. It might be possible to do this one day, but more work needs to be done first to study how real physical quantities and parameters governing disc flight affect things we might call speed, glide, turn, fade, etc..

You can describe the shape of any disc using a single line, and applying axi-symmetry to it sweeps out the shape of the full disc (except for weird discs like the Epic that aren't axi-symmetric). To every disc belongs a set of functions that describe the air drag (proportional to the disc's actual wind speed-squared, also nose angle sensitive), the physical lift (in units of lbs or Newtons, also proportional to speed-squared and nose angle sensitive), and the net torques on the disc (also a function of speed and nose angle). It is the torques on the disc that make it turn or fade...the rate of turning or fading is inversely proportional to the spin and the moment of inertia (i.e., how much mass/plastic is distributed on the outside relative to the inside).

In principle, if I had access to a super-computer I could simulate the aerodynamics of each disc shape, and calculate all of the above quantities. Then I could predict exactly how that disc shape should fly in real life. If the model is really good, then we would expect a good agreement. This would be a fun way to learn about how disc shape changes the flight characteristics.

Another way of doing things is to set the disc in a wind tunnel and put some instruments to measure the above quantities directly. This is probably much easier than doing a super-computer simulation, however, the computer would help you to understand what the air is actually doing around the disc and why different shapes yield different net forces and torques on the disc.

In any case, say you did either of the above with 500 different molds and you had their shapes stored in some sort of parameterized set of values. So long as the shape variations run the gamut in terms of yielding all sorts of flight properties, then you could in principle use all that data to figure out how each aerodynamical property changes with respect to changes in disc shape. Interestingly, you could even tune a disc's shape using this data in order to get certain aerodynamical behaviors by an inversion process.

I'd love to do this work myself, but there is nobody willing to pay me to do it, and I can't afford to spend that much time without a higher level of support. If I could do it, then I could answer your question properly, and I could even define a completely new system to describe the properties of a disc that could actually be used to predict exactly how it will fly if thrown with X hyzer, Y nose angle, and Z speed. This would be superior to the relative subjective ratings currently in use by Innova and by Joe's Flight Chart. More interestingly, however, with the real models in hand it should also be possible to try and use the old subjective ratings, by comparing with actual physical quantities, and generate a mapping between the two.

 

[Jungle Tim]

I don't know. I don't know of an instance where it's been measured. My best guess is that forehand shots tend to turn over more because people have more OAT in their forehand throws.

IMO, this is the most important quote of the thread so far:

Not sure if anyone has mentioned this - but there was a thread about measuring spin about a year or 2 ago on DGR.

The guy, i believe he was a big arm european, put a rotational measuring device on the middle of his disc with a dragging tail fin. When thrown, the fin stayed co-linear to the direction of travel whilst the number of revolutions were counted by the measuring device with the tail fin as reference.

I *think* that he concluded that there was absolutely heaps more spin on a backhand throw...

 

[zenbot]

On disc ratings and actual physical flight properties...

Note that Innova's rating system, and Joe's Flight Chart, and all other systems, are only subjective and relative. Speed=5 simply means the disc seems to have less drag than Speed=6, and more than Speed=4. These numbers are worked out by throwing in a field, and the numbering guru scratches his head, squints a little, and says "I'll call this a 4" or "I'll give this a 2," etc.. Nothing fancy here, it is just a way of characterizing characteristics of the disc that people think are important for practical purposes. Of course, this is just fine for most uses. But, there is no connection between these numbers and actual physically measurable quantities of disc flight. It might be possible to do this one day, but more work needs to be done first to study how real physical quantities and parameters governing disc flight affect things we might call speed, glide, turn, fade, etc..

You can describe the shape of any disc using a single line, and applying axi-symmetry to it sweeps out the shape of the full disc (except for weird discs like the Epic that aren't axi-symmetric). To every disc belongs a set of functions that describe the air drag (proportional to the disc's actual wind speed-squared, also nose angle sensitive), the physical lift (in units of lbs or Newtons, also proportional to speed-squared and nose angle sensitive), and the net torques on the disc (also a function of speed and nose angle). It is the torques on the disc that make it turn or fade...the rate of turning or fading is inversely proportional to the spin and the moment of inertia (i.e., how much mass/plastic is distributed on the outside relative to the inside).

In principle, if I had access to a super-computer I could simulate the aerodynamics of each disc shape, and calculate all of the above quantities. Then I could predict exactly how that disc shape should fly in real life. If the model is really good, then we would expect a good agreement. This would be a fun way to learn about how disc shape changes the flight characteristics.

Another way of doing things is to set the disc in a wind tunnel and put some instruments to measure the above quantities directly. This is probably much easier than doing a super-computer simulation, however, the computer would help you to understand what the air is actually doing around the disc and why different shapes yield different net forces and torques on the disc.

In any case, say you did either of the above with 500 different molds and you had their shapes stored in some sort of parameterized set of values. So long as the shape variations run the gamut in terms of yielding all sorts of flight properties, then you could in principle use all that data to figure out how each aerodynamical property changes with respect to changes in disc shape. Interestingly, you could even tune a disc's shape using this data in order to get certain aerodynamical behaviors by an inversion process.

I'd love to do this work myself, but there is nobody willing to pay me to do it, and I can't afford to spend that much time without a higher level of support. If I could do it, then I could answer your question properly, and I could even define a completely new system to describe the properties of a disc that could actually be used to predict exactly how it will fly if thrown with X hyzer, Y nose angle, and Z speed. This would be superior to the relative subjective ratings currently in use by Innova and by Joe's Flight Chart. More interestingly, however, with the real models in hand it should also be possible to try and use the old subjective ratings, by comparing with actual physical quantities, and generate a mapping between the two.

Once I find the giant box of money that I'm pretty sure is buried in my back yard you've got yourself a job.

BTW Thanks for posting. You always explain things very well so even dumb guys like me can follow. Your 300' thread has helped my drive more than anything.