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  #21  
Old 02-14-2013, 10:53 AM
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Quote:
Originally Posted by keltik View Post
The dumbest way to put it is like this

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

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
Thanks for this. In this regard, would my updates above be correct?
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  #22  
Old 02-14-2013, 11:00 AM
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Humidity and temperature are directly related. Humidity is measured in a percentage. 100% humidity is the most amount of moisture air can hold at a given temperature. The warmer the air, the more dense it is, the more water it can hold. Vise versa. 90 degree air temperature can hold lot more moisture than a 10 degree air temperature. Hence the "muggy" feeling of hot humid days. http://www.tis-gdv.de/tis_e/misc/klima.htm

The density of the air primarily effects the loft, more than the speed, of the disc. The disc rim (assuming a driver) is very aerodynamic and is minimal in comparison to the effects of gravity on all 170g grams of disc. Warmer air can hold more water and can hold "more" disc. Less dense also means that it is easier to get more torque on a disc (i.e. more speed) making them less stable. However, in less dense air, higher torque is needed to keep the disc aloft. So in colder weather, discs are less stable but fly shorter.

Have you ever noticed how well discs (especially ultimate discs) fly on evening of a hot day? The discs seem to glide effortlessly. My theory is that the earth is warm from the all-day sun, but the air is cooling. Heat rises, so heat (more dense air) is rising from the earth causes discs to have extra loft.

In short:
Winter = less dense air, less stable (easier to achieve torque), less glide (harder to maintain torque)
Summer = more dense air, more stable (harder to achieve torque), more glide (easier to maintain torque)

However, the footing and cold-hand point previously made can be a bigger affect on the flight...

Last edited by theabacus; 02-14-2013 at 11:04 AM.
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  #23  
Old 02-14-2013, 11:00 AM
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Jtencer has it in post #3.

Air is more dense at lower altitudes, colder temps and low humidity.
Air is less dense at higher altitudes, hotter temps and 100% humidity.
Distance records should be set at high altitude where it's hot and humid, maybe Equador?

Denser air makes a disc less stable out of your hand. But because the speed drops faster, the disc will become more stable at the end of the flight. Think of a shallow S-curve flight as a 350' flexible wire in warm temps. As the air cools down and gets denser, imagine someone at 350' pressing on the wire as he walks back toward the tee. The wire bulges out to the left and right a little more as this person is now 340' from the tee. As it gets colder, the S-curve widens a little more as this person is now 330' from the tee.

Last edited by Cgkdisc; 02-14-2013 at 11:02 AM.
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  #24  
Old 02-14-2013, 11:02 AM
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I'm finding this very interesting.
Chuck, are you certain more humid air is less dense?
I would say:
Low Air Density = less stable, less glide, more distance
High Air Density = more stable, more glide, less distance


we could discuss the heck out if it, but the above are my observations, even if some of them seem a bit contradictory.

even though discs glide better on more dense air, they don't seem to go quite as far... I can speak to cold v. hot. not enough experience playing at differing altitudes.

Last edited by BogeyNoMore; 02-14-2013 at 11:07 AM.
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  #25  
Old 02-14-2013, 11:11 AM
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Quote:
Originally Posted by Cgkdisc View Post
Jtencer has it in post #3.

Air is more dense at lower altitudes, colder temps and low humidity.
Air is less dense at higher altitudes, hotter temps and 100% humidity.
Distance records should be set at high altitude where it's hot and humid, maybe Equador?
I do not buy it. How is it that when the air has more water in it, it is less dense? Wouldn't more water per volume make it more dense?

I am talking about absolute humidity here (how much water in 1 cubic meter), not relative humidity (how much water in 1 cubic meter compared to the total amount possible before condensation happens).
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  #26  
Old 02-14-2013, 11:13 AM
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You also have to consider barometric pressure. Warm humid air is generally associated with low pressure, while drier, cooler air is associated with high pressure. Higher pressure creates more density.
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  #27  
Old 02-14-2013, 11:15 AM
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Quote:
Originally Posted by Dave242 View Post
I do not buy it. How is it that when the air has more water in it, it is less dense? Wouldn't more water per volume make it more dense?
Look at the atoms in H2O, and what those are replacing.
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  #28  
Old 02-14-2013, 11:17 AM
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Quote:
Originally Posted by PMantle View Post
Look at the atoms in H2O, and what those are replacing.
You're now getting into atomic weight, which is not density.
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  #29  
Old 02-14-2013, 11:20 AM
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Quote:
Originally Posted by bradharris View Post
You're now getting into atomic weight, which is not density.
Uhm...

Quote:
The amount of water vapor in air influences density. Water vapor is a relatively light gas compared to diatomic Oxygen and diatomic Nitrogen - the dominant components in air.

When water vapor content increases in the moist air the amount of Oxygen and Nitrogen decreases per unit volume and the density decreases because the mass is decreasing.
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  #30  
Old 02-14-2013, 11:22 AM
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Quote:
Originally Posted by PMantle View Post
Uhm...
Gotcha, makes sense.
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