This thread is going for years and still not getting anywhere.

What about flat aerofoils on propellers of foamies? If profile of the wing doesnt matter, so should profile of propeller blade.

And if weight is zero, why one need wings? Helicopters have no wings and I bet they have greater than 1 thrust to weight ratio. They fly. Althogh CG placement probably matters for helis.

And hot air baloon fly too! No thrust and very lite indeed.