I know a 30" * 12" airplane propeller means the prop has a diameter of 30inches and will travel 12inches forward per revolution, but what I don't know is - what angle of attack does the propeller require to attain that screw pitch of 12". Forget the propeller twist(I figure that will make it more complicated). Let the 30" * 12" propeller have a constant AoA from root to tip but a tapering cord length form root to tip. So, at what AoA will the 30" * 12" specification hold true for the prop? Or is screw pitch the same as AoA(angle of attack)?
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This is something the Aviation SE site probably has an answer to. https://aviation.stackexchange.com/ – Aug 26 '17 at 19:32
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An angle of attack of zero, just like the AoA of a woodscrew that you drive into a piece of timber. This assumes that blade twist is proportioned correctly, which is often not the case near the propeller hub since that would require fancy twisting in an area that does not matter much.
By far the largest amount of thrust is generated near the outer portion of the propeller, so a good reference point for general pitch angle is found there. Tip angle can be one, since the tip speed is found in equations for propeller thrust, power and torque. But the tip AoA may be modified to alleviate Mach compression effects, so the best reference point for generic propeller pitch is the 0.75 blade radius point.
Koyovis
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