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  #11  
Old 02-13-2013, 02:42 PM
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Quote:
Originally Posted by bradharris View Post
Glide is essentially a "parachute affect" where air under the flightplate helps to counteract the pull of gravity. With less dense air, there is less to hold it up.

As for distance, I would think it depends on the disc. Overstable discs need a lot of airflow to stay flat, so with less dense air, they presumably would hyzer out more quickly. However, an understable disc that tends to flip quickly in dense air, may be more resistant to turn, holding a longer flight line. So a person's max distance will probably end up being the same, it just might take different discs to achieve that distance.
Me thinks so.
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  #12  
Old 02-13-2013, 04:00 PM
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Those who say that air density is the biggest factor in how a disc behaves are correct. Hot air is less dense than cold air. Higher altitude (lower pressure) is less dense than lower altitude ( higher pressure). Dry air is less dense than humid air. The higher the speed the disc is moving relative to the air, the more effectively dense the air is.

However, one aspect we have not really considered is viscosity....how easily the disc slices through the air. Skin effect. Micro-turbulence. What is interesting is that hot air is more viscous than cold air. I really do not know what proportion that is and how that interacts with different types of plastics (and surface abrasion)....if it is proportionally relevant. And then there is the viscosity caused by humidity.....which I am sure is quite significant to what the OP asks.

Drag primarily acts on the forward velocity of the disc. Viscosity works on both the forward and rotational velocity of the disc.

The aerodynamics of a flying disc are incredibly complex.....especially when you consider all the variables including temperature, air pressure, humidity as well as forward velocity, rotational velocity, material, angle (yaw, pitch, roll), and then all the different molds/shapes and levels of beat-in-ness. Mind boggling!

Take a look at this for a little on the aerodynamics of lift:
http://en.wikipedia.org/wiki/Lift_(force))

It would be so cool if some really smart dude/tte were to do a PhD thesis on this....and then publish it in a dumbed down version the rest of us could understand....and that the industry could implement in designing new discs.

All that said, I am most impressed with how the OP got the little delta sign in the title.

Last edited by Dave242; 02-13-2013 at 04:02 PM.
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  #13  
Old 02-13-2013, 11:56 PM
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Thanks to everyone for their feedback thus far. I appreciate all the detailed information. Would someone knowledgeable be willing to dumb it down for me an just fill in the blanks? Please?



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Originally Posted by bcr123psu View Post

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
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Old 02-14-2013, 12:11 AM
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I'll answer a few.
Higher humidity = +stability and -glide
Lower humidity = -stability and +glide

Why? Cuz humid air is less dense!
As for distance that's a good question.
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Old 02-14-2013, 01:07 AM
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Quote:
Originally Posted by bcr123psu View Post
Thanks to everyone for their feedback thus far. I appreciate all the detailed information. Would someone knowledgeable be willing to dumb it down for me an just fill in the blanks? Please?
bcr its not easy because all three categories are variables. when considering humidity, is the altitude constant high or low? and the temp high or low?

the optimal combination for distance in my opinion is high elevation, low humidity, moderate heat. (thin air, low drag, viscous air yet resistant enough to control stability ratios)
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Old 02-14-2013, 09:31 AM
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Good point jrawk. Assume all other other variables are around their national/annual mean values and are held constant.
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Old 02-14-2013, 09:52 AM
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I wish someone would design some kind of launcher and take actual data over a long period to settle some of this.

Outside of that I find most of people's declarations about how discs fly in this air condition or that air condition to be generally anecdotal and suspect. Like others have said their are just too many variables. The only way to tease out all the variables would be methodical research.

The theory is all well and good but seems to not mean too much when applied to real life with so many variables involved.
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Old 02-14-2013, 10:44 AM
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Quote:
Originally Posted by bcr123psu View Post
Thanks to everyone for their feedback thus far. I appreciate all the detailed information. Would someone knowledgeable be willing to dumb it down for me an just fill in the blanks? Please?
The dumbest way to put it is like this

Low Air Density = more stable and less glide
High Air Density = less stable and more glide

Air Density is inversely related to Altitude, Temperature, and Humidity, meaning:
Air Density decreases as Altitude increases
Air Density decreases as Temperature increases
Air Density decreases as Humidity increases

http://en.wikipedia.org/wiki/Density_of_air
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Old 02-14-2013, 10:48 AM
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Stability is easy to observe. It is easy to see S-curves, straight lines, hyzering out/fading early or late, etc....

Glide is so much more difficult for me to get a handle on. The hardest thing about glide is that it is so affected by cross wind, head wind, tail wind, and even thermals (rising air). The same disc that leaves your hand in seemingly the same way will often glide nicely or sometimes just fall out of the air.
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  #20  
Old 02-14-2013, 10:49 AM
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The effect on "glide" really just depends on how you define "glide".

It seems like the consensus is that a discs propensity to stay aloft at low speeds is the glide. If so, my original post has it backwards. I was thinking about glide as the ability to go farther with the same throw which in retrospect is basically the same as 'distance'.

Anyway, if you'd like to get really technical, the parameter that you're playing with is the Reynolds number which includes the air density and viscosity as well as the disc's velocity.
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