You can see the edge is cupped.
Cupping is on the trailing edge, between 1/3 to 1/2 of the blade length only as the blade gets to thick as you get to hub.
Cupping, increases grip, effectively adds pitch,increases efficiency, lowers rpm, increases top speed.
Think of it like getting 2 pitches in one prop.
Take a 15x13 prop. Adding cup gives you all the low end pull of a 13 pitch and gives you top speed benefit of maybe a 14 pitch,best of both worlds.
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