In my mountainbikedays, there was this engineerguy with to much time for himself that made an investegation of the brilliant idea of of using helium in his tires... to..., have no fckuing idea really... what he wanted to do... fly uphilll or something?
Basically heliummolecules(?) are so small that they will escape anything, (they'll evaporate trough your bladders...) But sure, it will take some time, and as long as you have a kiteparkinghouse on your beach... go ahead. When you get bored, inhale some of the gas and do the "Donald Duck".
(Me myself have used it to check leaks in highquality tubing for other gases.)
1. Gases don't evaporate.
2. There's no appreciable difference in the size of the molecule from a materials standpoint - balloons, like bladders, hold helium, hydrogen, and air, all well. Though helium will escape faster, it won't matter for a session of kiting.
3. Lots of cyclists use helium to save weight, as a few grams matters to them in, say, the Tour de France
4. If your average kite bladder holds about 100L? (I have no idea), you would save maybe a few hundred grams max.
If we all remember our chemistry.. He is about 4 g/M and air is around 32 g/M and a mole at STP is 22.4L.