Bloo, I agreed, a fuel tank could not possibly be airtight. If so, it would collapse or the fuel could not be sucked out.
A "flaperon" is a control surface attached to the wing, it is not an integral part of it and thus could never be used as a fuel tank.
But I dont think it is extraordinary that it floated .
Just the opposite ....I'm not surprised at all .
I agree totally.
