Mavic Pro (Series 1) propellor modification

[Eraser339]

Hi All,

I have a Mavic Pro series 1. I bought some low noise propellers(Platinum) for it. After about 10 flights I noticed that the tip was bent down. Probably from storage and still having a hot heat exchanger under the quad. I had watched a youtube video years ago from rcmodelreview about propeller efficiencies. I remember something about the noise of a propeller depending on weight of propeller and speed etc. One of the propellers discussed had the tip curled down. The premise was it reduced the flow of air from the high pressure zone to the low(bottom to top). It turned out it wasn't more efficient, maybe the reduced effective propeller width, but it appeared(subjectively) to be quieter.

So when I saw my bent propeller I thought, gee they bend easily and that I would do it to all four. See photo below. Notice I also manage to bend the bit before the tip up. That was unintentional.

I took it out for a flight today and the noise did appear less. This was of course subjective, hence my problem. Also my forward speed seem less(maybe some drag due to the attack angle), but not my climb speed, again subjective.

I don't know the name of this propeller design. But the DJI low noise propeller is well documented as a "Scimitar propeller". It is supposed to "delay the onset of shocks wave at the propeller tip" and "reduce drag". These propellers also don't suffer as much from high blade counts.

So my question is, HAS ANYONE TRIED THIS AND WHAT WERE YOUR IMPRESSIONS. Also does anyone have an "anechoic chamber" to test this.

 

[brett8883]

Hi All,

I have a Mavic Pro series 1. I bought some low noise propellers(Platinum) for it. After about 10 flights I noticed that the tip was bent down. Probably from storage and still having a hot heat exchanger under the quad. I had watched a youtube video years ago from rcmodelreview about propeller efficiencies. I remember something about the noise of a propeller depending on weight of propeller and speed etc. One of the propellers discussed had the tip curled down. The premise was it reduced the flow of air from the high pressure zone to the low(bottom to top). It turned out it wasn't more efficient, maybe the reduced effective propeller width, but it appeared(subjectively) to be quieter.

So when I saw my bent propeller I thought, gee they bend easily and that I would do it to all four. See photo below. Notice I also manage to bend the bit before the tip up. That was unintentional.

I took it out for a flight today and the noise did appear less. This was of course subjective, hence my problem. Also my forward speed seem less, but not my climb speed, again subjective.

I don't know the name of this propeller design. But the DJI low noise propeller is well documented as a "Scimitar propeller". It is supposed to "delay the onset of shocks wave at the propeller tip" and "reduce drag". These propellers also don't suffer as much from high blade counts.

So my question is, HAS ANYONE TRIED THIS AND WHAT WERE YOUR IMPRESSIONS. Also does anyone have an "anechoic chamber" to test this.



View attachment 68953

I tried this and it was a bad idea. The purpose of a winglet, usually points up btw, is to increase the efficiency when installing a longer wing or prop isnt feasible but will never be as good as a longer prop. What you’ve done there is decreased the prop length even though you didn’t need to.

Also unless done perfectly you probably have unbalanced props now.

 

[Eraser339]

Thanks. Worth a shot. I know about the winglets on planes, the Boeing737Max are still redesigning them. See Boeing: The most efficient winglet on any airplane

Also I have seen some TED talks about reversing the camber so you don't need a tail fin. Just like birds, soaring Eagles do it best with large prime feathers.

So once bent by accident I mean, how do you correct? I guess the carbon fibre low noise propellers are the best option.

 

[brett8883]

Thanks. Worth a shot. I know about the winglets on planes, the Boeing737Max are still redesigning them. See Boeing: The most efficient winglet on any airplane

Also I have seen some TED talks about reversing the camber so you don't need a tail fin. Just like birds, soaring Eagles do it best with large prime feathers.

So once bent by accident I mean, how do you correct? I guess the carbon fibre low noise propellers are the best option.

You can just buy new ones. They come in sets of two so you don’t have to replace them all. Propellers are just a consumable part like air filters or tires

 

[Eraser339]

Thanks. I already have some spares.

 

[brett8883]

Thanks. I already have some spares.

I consider myself a prop connoisseur. I tried MPP props, I tried what you tried, I even put the Mavic 2 blades on my Mavic Pro(worked better then you’d think.)

But what worked best for me are these Master Airscrew props. They have a winglet design but they are longer and wider than the MPP props so you don’t give up anything. They also have an even steeper pitch than the Mavic 2 props which makes them noticibly quieter than the MPP props. They are rigid so they dont bend at all.

I think it was @FoxhallGH who got me into these and they are the forum favorite for the Mavic Pro and Mavic Pro Platinum. Some people swear by them and I might be close to that point. At any rate they are worth a try.

 

[Eraser339]

Thanks. I will check it out. BTW I found the RCMODELREVIEWS article I mentioned. He mentions an autogyro with Q-tips. Looking at the thumbnail photo the curve at the tip is two dimensional. So my attempt seems pretty random.

 

[Eraser339]

Also found the video about no rudder. I thought it was TED but it was NASA.

and

 

[Eraser339]

Random grab. ISS uses minimum noise fans(Prandtl Propellers) in there computers so the Astronauts can sleep.

Also Dyson bladeless fan uses Helmholtz cavities to filter certain noise frequencies. What if the fan was inside the body of the aircraft(with noise silencing). This has a 15 times output flow (cfpm) to input. And no propeller drag!

How the Dyson Bladeless Fan Works

The Dyson Air Multiplier works like a fan, but it has no blades. Can it be as effective as a traditional fan? What's so different about it?

electronics.howstuffworks.com

 

[brett8883]

View attachment 68981

Random grab. ISS uses minimum noise fans(Prandtl Propellers) in there computers so the Astronauts can sleep.

Also Dyson bladeless fan uses Helmholtz cavities to filter certain noise frequencies. What if the fan was inside the body of the aircraft(with noise silencing). This has a 15 times output flow (cfpm) to input. And no propeller drag!

How the Dyson Bladeless Fan Works

The Dyson Air Multiplier works like a fan, but it has no blades. Can it be as effective as a traditional fan? What's so different about it?

electronics.howstuffworks.com

While there’s no propeller drag that big cylindrical thing has a ton of drag. Remember that the Mavics motors are multi speed so you have to consider the start stop energy loss. Also a large winglet produces forward thrust not vertical thrust which is ok on a plane where the thrust vector is perpendicular to the lift vector but on the mavic the thrust and lift vectors are the same.

 

[Eraser339]

While there’s no propeller drag that big cylindrical thing has a ton of drag. Remember that the Mavics motors are multi speed so you have to consider the start stop energy loss. Also a large winglet produces forward thrust not vertical thrust which is ok on a plane where the thrust vector is perpendicular to the lift vector but on the mavic the thrust and lift vectors are the same.

True. I think the dyson is a reach, but proplematic, meaning you would have to do the research. As for horizontal thrust of the winglet, it is angled to do that. The RCModelReview, which is a hypothesis, says that the centrifugal force of the high pressure air is deflected in the direction of the curve, while low pressure follows the curve due to Bernoulli or Coriolis effect which causes drag opposite to thrust. Random research says that most of the air noise comes from the tip. If you reverse load the tip greater than 4% better at 12% you remove vortex noise. Problem one is in horizontal flight the angle of attack is different and you may not have reverse load. My curving of the tips down does not reverse load the tip. Seeing these blades are compromised, I'll straighten them out and twist them opposite to the current curve of the propeller.

 

[brett8883]

True. I think the dyson is a reach, but proplematic, meaning you would have to do the research. As for horizontal thrust of the winglet, it is angled to do that. The RCModelReview, which is a hypothesis, says that the centrifugal force of the high pressure air is deflected in the direction of the curve, while low pressure follows the curve due to Bernoulli or Coriolis effect which causes drag opposite to thrust.

Your nasa guy explains that at the end of a wing tip there is up wash not down wash. This is the reason the winglets are always pointed up (737 max might have both but the larger one is pointed up) because the air there is moving in the opposite direction you would think because high pressure wants to go to low pressure. So having the winglet pointed up creates a more gradual equilibrium between the low and the high pressure.

 

[Eraser339]

Good eyes, did not notice one winglet was bigger than the other. cya