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# Popellers CFM

## Popellers CFM

(OP)
I conducting a little experiment and want to know how to calculate my propellers air flow (CFM cubic feet minute) at a given RPM. I’m using an eight inch prop with a six percent pitch with two blades and eighty percent efficiency.
Replies continue below

### RE: Popellers CFM

Your best bet is to get a pitot tube and run a traverse across it to verify your flowrate. You'll get a significant variation across the disk in speed, depending on the design.

### RE: Popellers CFM

(OP)
Is there any known equations to calculate it on paper.

### RE: Popellers CFM

flow is
cross sectional area
x distance/revolution
x rotational speed
x efficiency.

blade count is irrelevant for calculation.

for your specifics, r = 0.33 feet.

Area = pi * r squared = 0.35 ft2
Distance = 2 * pi * r  * pitch/100  = 0.12 ft/revolution
efficiency = 0.8

net is about 0.035 ft3/revolution, or
35 f3/min per 1000 rpm.

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