There was a lot of variation in design prior to and shortly after WW1, and lots of aerodynamic theories surrounding efficiency. In the 30s and 40s most wooden propellers assumed the same general shape, primarily for reasons of efficiency. At low RPMs of early aircraft engines, the efficiency was more theoretical than real. Increased engine speeds coincided with the development of "modern" style design.
Also, I think the early scimitar shape was abandoned primarily for cost reasons, as considerably more lumber was required (and wasted) in their construction.
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