Morgans wrote:

Believe it or not, every additional blade means a loss of efficiency. One
blade should hover and fly on less HP than two blade. That says nothing
for smoothness, and I would think that setup would be totally
unacceptable, for that one.

I have seen propellers for a model airplane that had only one blade, with
a counter weight... has it ever been made for a full scale aircraft?

--Sylvain