Does density of air affect kite power?

[dandaka]

Many times I have heard, that air is more/less "dense", so kite has more/less power with same size and wind speed. Does it really affects kite power?

http://en.wikipedia.org/wiki/Air_density

[John-B]

Yes - I have been to places with thermal winds where I have been on a 14m in 20 knots wind speed and just managing to hold ground. If I was to try with the same kite in the same wind speed here on the west coast of Scotalnd I would be stupidly overpowered!

Been to many other palces where it has been like this and even here I notice a difference between our so called summer and winter - when I have been out kiting in air temps close to freezing the wind packs so much more 'punch'.

I suppose this is why you have to be careful when reading reviews or recommendations for kites on this forum as there is such geographical diversity. My 'big' kite is an 11m C shape and I can hold ground easily on this and even unhook in about 12 knots (80kg 135 TT), but in some places they'd struggle on a 17m 'lightwind' kite.

I also think this shapes people's expectations and skill with kites - in Egypt last year a guy of similar weight to me was on a 17m and door style board and I was on my 11m and 135 - he could get a bit more upwind but he get lost all this when jumping (long and low) and had to work to get back wheras I could jump, (higher) unhook, back roll kiteloop etc and use my kites speed and agility to not loose as much ground. IMO I was having way more fun on my 'smaller' kite.

Are you flying or being pulled?

[dandaka]

I don't have anemometer, so I estimate wind speed in terms of kite sizes

If air density (which is dependent on temperature and humidity?) is affecting kite power, why and how it is working?

[John-B]

The force of the wind (or any other fluid) is proportional to its density times the square of the velocity. Cold air is obvioulsy denser than hot air so a cold wind blows stronger than hot air.

http://weather.mailasail.com/Franks-Wea ... ht-Of-Wind

[dandaka]

Thank you, John-B!

From this article it seems, that effect from different temperature of air is not that significant (±10%).

[Pogibro]

It's possible. Density, temperature, altitude all affect the lift generated by An aircraft. The power of a kite is simply the lift it is generating as an airfoil.

[John-B]

Thank you, John-B!

From this article it seems, that effect from different temperature of air is not that significant (±10%).

These combined with the convective gusts are what make the difference - it is something you have to experience to appreciate.

In Thailand the wind was just over 20 knots and I was setting up my 9m when a local guy asked if that was the biggest kite I had and when he found out I had a 14m he said stick that up - he was tiny and on a 12m so I did. This was a good few years back and it was a very grunty 14m bow kite and it was weird having it above me in that wind but with hardly any pull when there was no way I could have put it up back home.

We can have 10 knot gusts easily here and with the power being exponential you can see why sessions with gusts from the mid 20's to low 30's are interesting - makes for difficult progression and some accidentially massive unhooked tricks with hot landings!!!!

[DrLightWind]

MORE about Lapse Rate-HERE
Which affect pulling power of a kite Big Time,

DrLW

[tomatkins]

...anemometer....

To me, a question, at least as interesting as the title of this thread, is:

"Does the density of air affect the wind speed exhibited by the "wind speed meters"?"

Consider that, commonly used by kiters, there are at least 3 different types of air-speed-recording-devices, each based on a slightly different physical principle, to reflect the speed of the air mass. Do you think that any of these recording devices actually record not air speed, but air "power"?

The 3 types of devices, that I am thinking of air "bladed" (propellers), "cupped" (classic anemometers), and "vacuumed" cylinders (Halls). I don't think any one uses "Doppler" mechanisms.

[edt]

Yes it does, the difference from winter to summer is on the order of 2 percent or so, but moving up or down in altitude is a lot more significant, on the order of 10 percent or more depending on the altitude. Humidity also affects power, since water vapor is LESS dense than regular air, the reason for this is that even though water is more dense as a liquid, its molecule is H2O vs most of air N2, and those hydrogens are real light, so humid air a bit less power, even though we feel humidity very easily it doesn't get much above 2 or 3 percent. I did all the calculations for figuring this out a year or two ago, maybe it's not exact but it's the right order of magnitude.

Most of the time kiters mistake wind gradients for temperature changes. So for instance a winter wind will pull a lot harder than a summer wind but the reason is not because of the dense cold (and dry) air, but that because the leaves from the trees have fallen, you get a better wind gradient and stronger smoother air.

Mountain kiters though know intimately how much less pressure is in their air, they have to put up kites several sizes bigger than for the same wind speed at sea level.

The hall wind meter measures actual air pressure, just like a kite does, but the fan or propeller or cupped style wind meters measure wind velocity and not the pressure of the wind.