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On the 'odd props' front, the Supermarine Sea Otter prototype was fitted with a 'Scissor' type four bladed prop, where the two sets of two blades weren't at 90 degrees to each other, as normal, but closer.
It appears the British were fond of "stacking" propellers as evidenced by the wonderful H.P. 42.....

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In theory a one bladed prop is the most aerodymanically efficient, but it puts an asymetric load on the thrust bearing and wears them out,
Actually, don't all diametrically opposed blades apply asymetrical loads on the propshaft on all attitudes other than perfect trim cruise? IE: during climbout, due to one blade ascending and the other descending, the blades will have different angles of attack (ascending has less and descending greater).