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Maybe unusual question but it's related to Aviation world, even if is more directly related to Drones one.

Why almost all consumer drones like DJI's and Yuneec's ones (but it's true also for other manufacturers) uses two blade propellers only?

I'd think that tri-blade or quad-blade could spin slower and so quiter.

Exist 3rd party multi-blade propellers compatible with commercial drones, so is possible to use them but what advantages/disadvantages they have? and again... why default ones are only two-blade?

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    $\begingroup$ I googled "3-blade propeller for drones" and got plenty of hits for sites selling and folks using them and discussing using them, so I'd say your premise is incorrect. $\endgroup$ – CrossRoads May 10 '18 at 12:07
  • $\begingroup$ The more blades you add, the less efficient you get. More blades is helpful if you have the power to drive them (or need to spread the power out), but ideally you'd want as few blades as possible for the best efficiency. $\endgroup$ – Ron Beyer May 10 '18 at 14:50
  • $\begingroup$ In the world of full size planes, two blades will deliver a faster cruise speed but three blades will deliver better acceleration and climb performance. The assumption here is that an engine is not so powerful as to REQUIRE three blades...only that a two or three blade option exists (think IO-520). The performance gains in either direction are so minor that most pilots make a prop decision based on how it looks or how the extra weight changes the W&B. $\endgroup$ – acpilot May 10 '18 at 15:51
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There are a number of related questions on the site for more information about this. I'll link them below.

The short answer is that two blades will be the most efficient use of energy. If the drone needs a better climb rate then adding extra blades is an option, since you can't make them any longer. The downside is that it will reduce efficiency and thus your battery time.

I can't find the question at the moment, but Peter Kämpf mentioned in an answer that theoretically one blade would actually be most efficient except that you would have to provide counterweight to balance it. The counterweight with no excess thrust would negate the advantage, but that's just an illustration of how the fewer blades the more efficiency.

Here are the links for more reading:

What's the difference between a two-blade prop and three-blade?

Is a propeller with two long blades more efficient than one with three shorter blades?

How does blade solidity ratio relate to thrust/power/torque of a propeller?

Why are three-bladed helicopters relatively rare?

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  • $\begingroup$ Here's a quadcopter with single-blade props: youtube.com/watch?v=ab8Dff8X5j0 $\endgroup$ – Steve May 11 '18 at 18:22
  • $\begingroup$ @Steve They managed to make it fly. They didn't mention if it was truly more efficient or not. With a duct taped prop, probably not though. $\endgroup$ – TomMcW May 11 '18 at 18:58
  • $\begingroup$ It's the only example I know of :) $\endgroup$ – Steve May 11 '18 at 20:43
  • $\begingroup$ I think the answer you were looking for is this one: aviation.stackexchange.com/a/23015/3394 $\endgroup$ – Manu H Oct 11 at 11:21
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If the weight of a 3 blade prop is equal to or less than the weight of a two blade prop you're replacing and the pitch is equal to or greater then the 2 blade prop to increase thrust proportionally then theoridically it will give better overall performance without sacrificing battery life. With the 3 blade prop made of a strong super lightweight material in theory it is possible.

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    $\begingroup$ Do you have something you can cite for this? The most efficient propeller is a single blade. More blades generally reduce efficiency. $\endgroup$ – CatchAsCatchCan Oct 9 at 22:11
  • $\begingroup$ I can say for a fact that 3 blades are slower in cruise than 2 blades, despite a specific example of a composite 3-blade prop being 11 pounds lighter than an aluminum 2 blade prop. There is a Cessna Cardinal forum where this has been demonstrated on several planes with 180 and 200 HP engines. The 3-blade does accelerate faster on takeoff and improves climb rate some (perhaps 100 ft/min better), but once at cruise is slower. Also increases drag lot when in the pattern and slowing down for a landing. I can't say how much this carries over into RC craft. $\endgroup$ – CrossRoads Oct 9 at 23:26

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