Summary of propeller design:
Fewer blades = more efficiency
Fewer blades = lower power loading
More blades = better power loading
More blades = less efficiency
Larger disc size = better power loading
Larger disc size = faster tip speeds = lower efficiency = good for low speed work
Smaller disc = slower tip speeds = higher efficiency = good for high speed work
Propellers are undoubtedly the most complicated piece of engineering on an aircraft.
You can also bet that all the engineers during WWII did their homework. I know Mtt and Focke Wulf both tested 4 bladed designs on their aircraft. It was found that what one design made up in efficiency, it lost in power loading and vice versa. As such Focke Wulf concluded that was no appreciable difference other than weight savings on the 3 bladed propeller.
The German propeller designer took the approach of widening the blade chord to increase power loading and using a better material. The allies added more blades and accepted the weight increase. Both are perfectly acceptable approaches to increasing performance with very little to choose from.
The most efficient propeller would have one very long and wide blade. It would revolve rather slowly and acelerate rather poorly.
All the best,
Crumpp
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