You are right, up to a certain point. On 'most' propellers, maximum efficiency occurs with about 4/5 blades, because above this number, the blades start taking up so much area of the radius that there is not enough space for air to be accelerated through, thereby reducing the efficiency. How much of the propeller disk is 'taken up by blade' is referred to as the solidity of the propeller. Solidity can therefore be increased by increasing the chord of the blades, and/or increasing the number of blades.
Hope this helps!
Cheers, Jack.
Last edited by Halfbaked_Boy; 25th June 2006 at 02:26.