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Old Feb 17, 2013, 04:35 PM
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3-Blade or 2-Blade Props? 10 propellers tested

We often see questions about 3-blade props.
Answers concerning airplanes props are easily found unlike multicopters ones.
Wanting to improve my knowledge, I have tested 10 props, four 3-blade and six 2-blade.

DT700 motor and 3S battery, often seen on multis, have been used for this test.
Two levels, mid throttle (1.5ms) usually used for hover and full throttle (2ms) for max thrust.
Airflow being without any interference, thrust and efficiency values are optimal.
Here is what I've got:



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Last edited by Mortimer; Feb 17, 2013 at 05:16 PM.
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Old Feb 17, 2013, 05:43 PM
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Thank you for your hard work and effect here. Your results confirmed my Intuition when taking into consideration the Pitch and diameter of a given prop in the same class, there is little measurable differences. Example, the Master Airscrew 10x7 and the APC 10x4.7, if the pitch was the same, there would be little differences.
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Old Feb 17, 2013, 07:07 PM
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Great work Gary; it expands on Old Man Mike's work from years ago. His data and yours points to two blades being more efficient in general than three blades.

Dan
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Old Feb 17, 2013, 07:52 PM
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It's been known for a long time that 2 blades are more efficient than 3 blades and 1 blade is the most efficient. Single blade props are a challenge to balance, but they have been used.
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Old Feb 18, 2013, 08:33 AM
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[QUOTE=nfhill;24167202]It's been known for a long time that 2 blades are more efficient than 3 blades and 1 blade is the most efficient. Single blade props are a challenge to balance, but they have been used.[/QUOT

Agreed but there are many non believers out there.

Dan
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Old Feb 18, 2013, 09:05 AM
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There is another factor few people consider when discussing 2 and 3 bladed props and that is Disk loading.
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Old Feb 18, 2013, 11:25 AM
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Thanks so much Mortimer for doing this great work and publishing
Jim
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Old Mar 16, 2015, 05:12 PM
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Without taking airflow speed into consideration this test doesn't prove anything. Low pitched propellers will always give more thrust at 0 speed. Only test that could be considered given circumstances is GWS 9*5 vs APC 9*4.7, and we see really close performance here, but considering difference in quality between APC and GWS I really don't know... Correct test would be to check amp draw of the prop while doing same same thrust AND airflow speed.
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Old Mar 17, 2015, 02:13 AM
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What airflow have you when hovering ?
These props are tested for multicopter purpose, not for planes, check forum/context where you are.
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Old Mar 17, 2015, 03:39 AM
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There is another factor few people consider when discussing 2 and 3 bladed props and that is Disk loading.
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Old Mar 17, 2015, 04:47 AM
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Bigger for 3s, so again less efficient, but more wind resistant.

I would be more interested to see a versus analyse, which is more efficient when you need more load in restricted space, which is better, increasing voltage (3s to 4s) or blades count (2 to 3) Both decrease efficiency, but curious which is better.
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Old Mar 17, 2015, 07:26 AM
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Quote:
Originally Posted by pteadsgo View Post
There is another factor few people consider when discussing 2 and 3 bladed props and that is Disk loading.
Amen and is why I like the Master Airscrews even though their efficiency is lower than the slow-fly props.
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Old Mar 17, 2015, 05:13 PM
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Quote:
Originally Posted by renatoa View Post
What airflow have you when hovering ?
These props are tested for multicopter purpose, not for planes, check forum/context where you are.
Never knew quads have changed laws of physics.
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Old Mar 18, 2015, 01:32 AM
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So you think hovering/forward flying has same prop requirements ?
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Old Mar 18, 2015, 04:13 AM
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Could you please be more specific with your question, to the one you asked I can answer only that in both cases it is required for the prop to spin Airflow, in our case, is a speed of air that is being pushed through the prop which, is not the same as airspeed that I assume you have mistaken it for.
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