[Clint N. Suhks]

V= πr²h is the equation for volume of a cylinder. 20' by 5' ballon should be around 1500 cubic feet of volume. 35 cf per kilo of lift. That's around 45 kilos or 112 pounds it could lift. Minus the weight of the craft and that it wasn't a perfect cylinder there seems to be enough to lift a 60 pound boy.

[steve86]

there seems to be enough to lift a 60 pound boy.

I haven't read all the preceding thread. But would it lift off from a density altitude of 5000+ feet? (and do more than drift sideways)