In front of the prop, about 4" in from the tips. Air moving more in than back.
In front of the prop, just about even with the tips. Air only moving in.
Prop tuft experiment
I was test running in a paramotor on the test stand (fence) for several hours and getting very bored. Just for fun, I decided to do a little test to determine just how much prop was actually working to provide thrust.
Due to the fact that this is done static, as opposed to at say twenty some MPH, and the fence has to be affecting airflow to some extent, it's not scientific. I was surprised at what I found.
The prop tips are about 2-1/2" from the inside of the cage and the witness stripes in the handle are 1". The tuft is about 2-1/2"long.
The 48" prop is spinning at 2000 RPM. The tuft is a bundle of strands of nylon masons line tapped to a wooden dowel handle.
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In front of the prop, about 4" in from the tips. Air moving more in than back. |
In front of the prop, just about even with the tips. Air only moving in. |
Lined up with the tips fore and aft,about 2"outside. Air moving in and forward. |
Behind the prop, a little outside the tips. Air moving in the wrong direction. |
Definately behind the prop, and the air is going backwards. |
In a little further and the air is beginning to get turbulent, but still backwards. |
A little further and the turbulance has the airflow about stagnent. |
A little more and the flow is front to rear, but very turbulant. The tuft is actually flailing in a circle. |
Still flailing in a circle but more to the rear. |
More than 6" in from the tips to get to where the air is going smoothly in the right direction. |
Last fiddled with 03 Nov. 03 Click here to go back one page.