Δ in Altitude/Temp/Humidity Make Discs Fly _____ ?

[bcr123psu]

I probably should have posted this here first. I tried this on DGCR and despite my request to limit verbose replies steeped in conjecture and ill-informed nonsense, that's exactly what I got. I know that these topics have all been covered on DGR before, but I need to get this info all in one place so I can respond to a question a buddy asked me. Specifically, I'd like to know how the weather variables below impact the flight of a disc from the following standpoints: More/Less Distance, More Overstable/More Understable, More/Less Glide. Assuming all other variables are at some national and seasonally-adjusted average and held constant, can someone fill in the following details to indicate how changes to each of the following environmental variables would impact disc flight?


Higher Altitudes = _____ Distance, _____stable, _____ Glide
Lower Altitudes = _____ Distance, _____stable, _____ Glide

Hotter Temps = _____ Distance, _____stable, _____ Glide
Colder Temps = _____ Distance, _____stable, _____ Glide

Higher Humidity = _____ Distance, _____stable, _____ Glide
Lower Humidty = _____ Distance, _____stable, _____ Glide

 

[bcr123psu]

Thanks keltic for replying over there.

 

[PMantle1]

I probably should have posted this here first. I tried this on DGCR and despite my request to limit verbose replies steeped in conjecture and ill-informed nonsense, that's exactly what I got.

I'm still being amused by the discs speeding up after they leave the hand.

 

[bcr123psu]

Of course, some more intelligent responses start to show up in the DGCR thread the instant I post this one...

 

[kern97871]

I'll try to keep this relatively brief.

The key variables in this is air density and air resistance (which will be directly related).

Higher temperature, higher elevation, and higher humidity = lower air density = lower air resistance. The opposite is true as well.

Higher air density means the disc will slow down faster, but the cruising speed window is lower as well, meaning the disc will begin to turn at a lower speed threshold, and will begin to fade at a lower speed threshold as well. Discs will also move more left or right based on the same relative hyzer/anhyzer angle than in lower air density (think about trying to turn on ice vs asphalt; higher density = more "traction" due to air resistance (yes I know "traction isn't the correct term, but it gets the point across)).

Lower air density would be the opposite. The disc will maintain speed better (meaning out of the hand speed is the same). The cruising speed window is overall higher. Discs require more speed to turn and fade at a relatively higher speed as well. Discs will also not move quite as much left or right based on hyzer or anhyzer angle.

The reason I won't speculate on distance for either of these is both conditions have their pros and cons with regards to maximizing. I would assume you could manipulate variables to account for differences and have the same distance potential. Don't quote me on that though.

 

[keltik1]

I probably should have posted this here first. I tried this on DGCR and despite my request to limit verbose replies steeped in conjecture and ill-informed nonsense, that's exactly what I got.

I'm still being amused by the discs speeding up after they leave the hand.

they speed up negatively...

 

[PMantle1]

So, is this enough to be noticed at all?

 

[luma1]

Higher temperature, higher elevation, and higher humidity = lower air density = lower air resistance

My logical thinking would tell me that LOWER humidity means lower air density. When you have lower humidity, you have less molecules in the same space like you have when its more humid...right? Or did my brain mess anything up...?

So for me then, it would be..:

Higher Altitudes = + Distance, + stable, - Glide
Lower Altitudes = - Distance, - stable, + Glide

Hotter Temps = + Distance, + stable, - Glide
Colder Temps = - Distance, - stable, + Glide

Higher Humidity = - Distance, - stable, + Glide
Lower Humidty = + Distance, + stable, - Glide

But as kern already explained, distance +/- isn't necessarily correct, it always depends on how you throw. Like he already said, higher air density means that there are more molecules in the air that can carry the disc but will also result in more drag on the disc.

I can imagine altitude and temp have an effect when the Δ is dramatic (can't tell you any numbers, maybe the more experienced players can though), but humidity...not that sure

 

[isobar1]

Luma, it's counter intuitive but he is correct. water vapors are actually lighter than dry air molecules. Hydrogen is much lighter than everything else in air. So say a dry air is composed 80% Nitrogen and 20% Oxygen (Just a ballpark, there's many other chemicals involved.) once you start increasing the humidity, it's going to need to replace those other heavier molecules with a much lighter Hydrogen. Avogadro's Law explains that you can't just add to this dry air mixture, the hydrogen actually has to replace something and I'm simplifying it pretty hardcore.

Basically, if I have 100 "dry air molecules" compiled of 80% nitrogen(14amu), 20% Oxygen(16amu)=~1460amu. versus 100 "humid air molecules" that are composed of 79% nitrogen, 19% oxygen and 2% hydrogen(1amu)=~1432amu.

 

[kern97871]

Most people are used to dealing with gases mixing in a closed environment with a fixed volume. In this case, you can add water vapor (increase humidity), and to compensate for the added mass, you increase pressure, since volume is fixed.

The reason humidity making air less dense seems counter intuitive is that we are looking at the same gaseous pressure problem in a completely different manner. If you look at a system with a fixed pressure, and add water vapor, you are increasing volume, therefore adding less dense molecules (water vapor) to more dense molecules (dry air) will cause a decrease in density.

The best example I can give to help visualize this is a balloon. A balloon forms a closed system where, conditions being impossibly ideal, the air pressure inside the balloon and outside the balloon are at equilibrium, because the balloon can change volume to compensate for this. If you increase pressure outside the balloon, without changing the mass of the gas inside, the balloon will shrink, so as to equalize the pressures pushing in from the outside and out from the inside of the balloon.

Because of this, you can say that a balloon is a system with a (relatively) fixed pressure.

For dealing with fixed pressure, we can do this. (I'm throwing the ideal gas law out there, google it if you want to know more about it)

PV=nRT

P= Pressure
V= Volume
n=moles of gas; for those non-chemists/physicists, this is a way of counting the actual number of molecules in a sample regardless of mass
R=a constant
T= Temperature

We'll have 3 constants in this equation; pressure, temperature, and R, so we can rewrite the equation like this:

P/(RT) = n/V = n(1)/V(1) = n(2)/V(2)

The last two part of that equation will be the parts we'll focus on. IF we start with 1 mole of gas in 1 L, and add another mole of gas, the volume of the system will double to 2 L. It would look like this:

1 mole/1 Liter = 2 moles/2 Liters

Hopefully this is seeming more intuitive looking at it this way. What you should be taking from this is that adding gas increases volume. Self explanatory. More importantly, the volume of the gas increases with absolutely no relation to the mass of the gas. If you are adding a lightweight gas (water vapor in this case) you are increasing the volume more significantly than you are increasing the mass. Density is mass/volume if you recall. Anytime you are increasing volume more, you are lowering density.

Probably WAY more of an explanation than anybody was looking for, but there it is in a nutshell (sorta).

 

[JHern]

... _____ Distance, _____stable, _____ Glide...

The unfortunate truth is that terms such as "stable" and "glide" are meaningless. Next time somebody tells you a disc has a stability (or glide) of 3 (for example) just ask them: 3 what? What are the units, what exactly is this measuring, and how can you reproduce their measurement? And while "distance" can be measured, it is known to be a complex mixture of many factors. Ratings using Speed/Glide/Turn/Fade are pretty stupid, and a lot of important real physics are glossed over in the process of using it. Discs are so much more than just 4 meaningless numbers, and everybody who has thrown a lot knows that such a primitive rating doesn't cover a lot of variety that occurs in real discs.

As others mentioned, altitude, heat, and humidity all decrease the density of air. Meteorology has constructed very accurate equations for the effects of all these things, you can find some calculators posted on some websites if you google.

Provided that the change in density doesn't change the planform of air flow around a disc appreciably, then for a disc flying at a given air speed and angle of attack, a lower air density results in relatively:
1) smaller lift force (but what matters is relative to weight of the disc, this can be compensated by lighter plastic)
2) smaller drag force (flies "faster")
3) smaller torques (turns over less, fades less)

Think about taking it to the limiting extreme of disc "flying" in a vacuum (outer space), which has no lift, no drag, and no torque...by lowering density, this is the direction you're going.

To compensate for low air density, use lighter plastic and bring some under-stable discs that will turn over more easily. And bring older slower discs, too...I was always amazed at how far I could throw a Comet at the Tahoe courses (they're going to bid for 2015 Worlds).

 

[PMantle1]

The unfortunate truth is that terms such as "stable" and "glide" are meaningless. Next time somebody tells you a disc has a stability (or glide) of 3 (for example) just ask them: 3 what? What are the units, what exactly is this measuring, and how can you reproduce their measurement?

Right, but there's no denying that the few discs rated at 6 glide like crazy compared to the 3s, no matter what is actually being measured. I find it valuable even if not ideal.

 

[luma1]

Ouch, I'm really ashamed but actually I'm at university studying material sciences, and last half year I've had thermodynamics there, but our prof. was kind of an idiot so I've never been there.... but I knew that pV=nRT stuff for the exam And now that you explained...well, sometimes my brain takes it way to easy.

 

[Widdershins]

... _____ Distance, _____stable, _____ Glide...

To compensate for low air density, use lighter plastic and bring some under-stable discs that will turn over more easily. And bring older slower discs, too...I was always amazed at how far I could throw a Comet at the Tahoe courses (they're going to bid for 2015 Worlds).

If Tahoe is high altitude then I pray they don't get Worlds.

No offense to Tahoe (or any high altitude location). I played Denver a few years back and none of my discs flew even close to normally. I don't need to learn a bunch of new courses AND re-learn to throw every disc in my bag.

 

[Cgkdisc]

I thought Pittsburgh had 2015 Pro Worlds. So maybe Tahoe is going for 2015 Am Worlds?

 

[turso]

... _____ Distance, _____stable, _____ Glide...

To compensate for low air density, use lighter plastic and bring some under-stable discs that will turn over more easily. And bring older slower discs, too...I was always amazed at how far I could throw a Comet at the Tahoe courses (they're going to bid for 2015 Worlds).

If Tahoe is high altitude then I pray they don't get Worlds.

No offense to Tahoe (or any high altitude location). I played Denver a few years back and none of my discs flew even close to normally. I don't need to learn a bunch of new courses AND re-learn to throw every disc in my bag.

You make me slightly disappointed by this comment, pros need to adapt to the circumstances, and it's not like the physics of it work randomly. In my opinion it's a nice addition to the challenge of the elements, I wish we had something else than flat ground in finland so I could experience the difference in flight.

 

[JHern]

If Tahoe is high altitude then I pray they don't get Worlds.

No offense to Tahoe (or any high altitude location). I played Denver a few years back and none of my discs flew even close to normally. I don't need to learn a bunch of new courses AND re-learn to throw every disc in my bag.

Tahoe is 7000-8000' altitude. You're crazy Mark, Tahoe is simply the world's best disc golf destination, I dream about it all year long even though I live in Santa Cruz.

If Tahoe is high altitude then I pray they don't get Worlds...

...pros need to adapt to the circumstance...it's a nice addition to the challenge of the elements...

Exactly, how well do you know how a disc flies? This is part of the mastery of the sport of disc golf.

I thought Pittsburgh had 2015 Pro Worlds. So maybe Tahoe is going for 2015 Am Worlds?

I don't know the details, I think Am 2015, Pro 2016.

 

[Widdershins]

If Tahoe is high altitude then I pray they don't get Worlds.

No offense to Tahoe (or any high altitude location). I played Denver a few years back and none of my discs flew even close to normally. I don't need to learn a bunch of new courses AND re-learn to throw every disc in my bag.

Tahoe is 7000-8000' altitude. You're crazy Mark, Tahoe is simply the world's best disc golf destination, I dream about it all year long even though I live in Santa Cruz.

If Tahoe is high altitude then I pray they don't get Worlds...

...pros need to adapt to the circumstance...it's a nice addition to the challenge of the elements...

Exactly, how well do you know how a disc flies? This is part of the mastery of the sport of disc golf.

I thought Pittsburgh had 2015 Pro Worlds. So maybe Tahoe is going for 2015 Am Worlds?

I don't know the details, I think Am 2015, Pro 2016.

Adapting is part of the game but not all adaptations are rewarding. Japan has the 150 class limit. This is one of the reasons I have never been tempted to play the Japan Open. The flutter on my forehand makes 150 class discs into scud missiles. Sure I could spend months trying to figure it out but what long term benefit would I see? Like everyone else as soon as I returned those 150 class discs would be put in a box and my regular discs gratefully restored to the bag.

I spent a week in Denver (the Mile High City it calls itself), playing every day. Every disc flies as though it is MUCH more overstable. So my primary discs became meathooks and useless. My flippiest discs flew straight and much farther than normal. Nothing in my bag would turn over unless I forced it. Nothing flew the way it normally did.

For a World Championships hundreds of players arrive for the tournament, often at the last minute, due to scheduling limitations imposed by obligation and expense.

If we are seeking odd challenges there are many ways to accomplish this; One disc tournaments, Superclass, 150 class, putter only, etc. If you want weirder then tie everyone's wrists together or blindfold them. Those are challenges, too, just not very rewarding.

Worlds should be a test of skill, not a gimmick tournament.

 

[Cgkdisc]

It will be interesting to see the discussions regarding a Worlds bid from any site above 5000' elevation. I know after Pro Worlds in Flagstaff the general feeling was that a World Championship should not be held at that altitude or above primarily for the reason stated by Mark. There were players who also experienced adjustment and health issues due to the altitude and Worlds includes players up to 80 years old. Most players don't have the time to come a week in advance of Worlds and adjust to the conditions and learn how to throw their discs in the thin air. No problem hosting any other pro events including NTs at that elevation, with the exception of Majors, since players have a choice to attend or not. With Worlds and other Majors as once per year events, there's no choice if you want to go for those titles. I think the PDGA might be more likely to favorably view an Am Worlds bid since variety of experiences seems to rank higher in the way Ams generally view the various tradeoffs for Worlds venues.

 

[JHern]

...Japan has the 150 class limit...

Actually, 159.9g

This is one of the reasons I have never been tempted to play the Japan Open...what long term benefit would I see?

Long term benefit? Sheesh, have you forgotten what this is all about?

I hear that the Japan Open is simply the best disc golf tournament on planet Earth, in every way possible. If that's not enough to satisfy you, or to provide the long term benefit of having experienced the greatest our sport has to offer, while also visiting one of the most amazing places on Earth, fair enough.

...Worlds should be a test of skill, not a gimmick tournament.

Tell that to the tens of thousands of disc golfers in the western US, who have learned how to adapt to altitude changes, and which is firmly ingrained into their skill set. It is a part of disc golf, whether flatlanders like you realize it, or not. The one to judge whether something is a skill is not the one who doesn't even possess it.

Air is what supports the flight of a disc, it is not a gimmick. Air is not a fixed thing, it is fluid and ever-changing (like wind, weather, and climate). Changing air density is like adding another dimension to your bag, it opens an entire new world and dimension of behaviors that you can learn to exploit to your advantange.

As far as disc adjustments, it's actually quite easy, get your beat plastic out, your turn-over and roller discs are money at altitude. After a few dozen throws you'll recalibrate and be ready to go.

Anyways Mark, you didn't come in 2011 when Worlds was at sea level, and perhaps you're not likely to attend, regardless of altitude.