Il semble qu'un autre rider s'est penché sur le problème et sa conclusion: 1 ou 2 PSI max.
Mais bon, il y a d'autres phénomènes qui pourrait causer problème dont la résistance à la chaleur des bladders.
Ma recommandation: dans le de doute, ne pas déposer le leading edge directement sur le sable extra-chaud. (ex. mettre la planche entre le sable et le leading edge).
Mais bon, vous pouvez dormir tranquille pour un bon bout de temps au QC. Brrr qui fait frette!
Voici ses calculs :
"To calculate how much 5C difference in air temperature affects kite pressure, use avogadro's law pV=nRT which tells you the change in temperature (in kelvin) is proportional to the change in air pressure (don't forget to add the 15psi of one atmosphere to your kite pressure)
So for a kite that goes from 20C to 25C that's 293K to 298K or a 2% change so 2% of (8+15) is one half of a psi. A 10C change will give a full 1 psi and a 20C change will be 2 psi."
On first thought I would say sure why not because I have definitely been out on a summer day where the pavement is too hot to touch, something above 55C and the air is a comfortable 25C a 30C change would be 3psi if you go from 8psi to 11 that could do it thought it's not likely.
But . . . you have to remember that there are two surfaces to the kite, there is the surface facing the sun which is taking in heat, and the surface away from the sun which is radiating it away so it's not like a hot pavement. And as you might know white does not radiate heat well, while black radiates heat very well.
So we would have to solve the blackbody radiator. The stefan-boltzmann law gives you j=oT^4 At noon the sun's energy gives you about 1,000 watts per square meter, if the leading edge gets up to about 300 degrees kelvin (that's 40C) this means it will radiate about 500 watts per square meter on both sides both the side towards the sun and the side away from it, so if it gets hot enough, it can't get hotter because it radiates it away. This might be why the air in the leading edge really can't get tremendously hot, not like pavement or a hot car can, for the simple reason that in addition to receiving radiation from the sun, it also radiates very well.
A 25C to 40C change would only be 1.5 psi, so my second thought is that the kite should be able to handle it even on a sunny day in Spain assuming it is set down on place that is at air temperature.
But, what if the sand is radiating heat into the kite? Then I could see the kite getting extremely hot, receiving heat both from the sand and the sun. I suppose I could try and figure out how much energy the sand radiates, but I'll stop at this point and I haven't even started on convection cooling.
What if it's not the hot sun blowing up kites, but the fact that when you drop a kite on sand that is 50 or 60C it melts the fabric of the leading edge, and it is the direct contact with sand that does it, having nothing to do with the color of the kite?
So, heck I dunno. I think I just did a lot of math for nothing.''
