On 2003-01-21 20:48, aklbob wrote:
Very good! I often don't trust my wind meter, and often add 5 knots to its reading windspeed if it says it's 15, and I know I can use my X2-12, but if it's hitting 20 then I can't go out!!
It would be interesting to see a graph taking into account air temperature/power produced.. I was in Rarotonga once with the same windmeter, and it was reading 20 knots steady, and I could still put up my 11.8 Airblast and just hang on to it..
Okay Aklbob - you got me going this time...
Here you can see how a 14.0 m2 kite (at sea level 20C/68°F) would feel like in different temperatures and location heights :
The factors that influences power, NOT related to wind speed, can be clarified in an (extreme) example:
1. At 1500 meter, low pressure 955mb(at sea level), 30°C, Humid air - wind speed 10 m/s.
2. At sea level, high pressure 1050mb, 0°C, Dry air - wind speed 10 m/s.
If you have a kite in the first situation, then the same size will lift exactly 50% more in situation 2, so a 10m2 will lift as a 15m2 !
If the air was totally dry in 1500 meter, and humid at sea level, the difference would be about 47% - so humidity plays no important role, only 3% in extreme cases.
The height difference gives about 21% power difference, the "weather" pressure about 10%, the temperature about 10%, and the humidity about 3% - in this example which is a fictive and extreme case.
But it gives us an idea of where the levels are, and what we are talking about.
I like to understand how things work, at least some dedicated issues !
Apart from that, I think Fo is very right, when he says that mother nature laughs at us - because things are often very very different.
Especially gusts - they often penetrate from higher wind layers, and they blow upwards again at some point, which will give a slight change in wind direction, and lift at some point too.
It is an issue that have been studied a lot, in order to perform better tactical on a race course.
You don't really have thermals on the sea, but gusts can in fact give more lift than just what happens because of the increased wind.
This is why parking your kite at 12 on land should be avoided !
Here there are tons of evident things that can get you lifted high in a split second - and if mother nature has one of her tricky days too - then you are history !
It is winter here now, with only rare good kitesurf sessions, as you can guess