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Prop Experiment

Rodger

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I have a new DJI Phantom 4 Pro Obsidian. While waiting for my registration stickers to arrive and affixed to the Phantom before it's first flight I decided to tune the props a bit. I removed the flashing left from the mold from the leading and trailing edges. I used sanding sticks polishing the edges to a finish that is the same as the rest of the prop. I the polished and waxed the props. I don't know if the performance is going tone any better but, it definitely sounds different. More of a purr than a buzz. Maybe a waste of time, but I needed to do something with it while waiting to make things legal.
 
I have a new DJI Phantom 4 Pro Obsidian. While waiting for my registration stickers to arrive and affixed to the Phantom before it's first flight I decided to tune the props a bit. I removed the flashing left from the mold from the leading and trailing edges. I used sanding sticks polishing the edges to a finish that is the same as the rest of the prop. I the polished and waxed the props. I don't know if the performance is going tone any better but, it definitely sounds different. More of a purr than a buzz. Maybe a waste of time, but I needed to do something with it while waiting to make things legal.

Did you balance the props after? If not you could of potentially introduced alot of vibration to the air frame and stress the motors.
 
I have a new DJI Phantom 4 Pro Obsidian. While waiting for my registration stickers to arrive and affixed to the Phantom before it's first flight... I needed to do something with it while waiting to make things legal.

Congratulations on the new P4P Rodger! Did you special order your FA number sticker? FAA registration took me about 10 minutes, and they e-mailed my registration instantly. I dug through my wife's crafts stuff and found some letter sticker sheets and added them on. Time spent 30 minutes.
 
Polishing props is dumb IMO. A little texture inhibits air flow separation resulting in smooth and efficient laminar flow. Take the golf ball, a blunt flying object. By adding dimples and tripping the laminar boundary layers - reduces drag. Airplane wings and our props are less prone to separation since they aren't as "blunt" and as a result skin-friction drag is more important.High gloss makes them less sticky with regards to the air/skin boundary. More noise and less efficient, though the numbers are very small and in my opinion insignificant. You want the air to stick to the surface.

Take a look at this video and prepare to have your polished mind blown.

And what about golf balls (I knew you were thinking it)?
Why aren't airplanes like golf balls?

There does exist other types of devices commonly used on wings that create a similar effect to the dimples used on golf balls. Though these wing devices also create turbulence in order to delay flow separation, the purpose is not to decrease drag but to increase lift. One of the most popular of these devices is the vortex generator.



javelin_18.jpg

A Gloster Javelin showing the three sets of vortex generators located along the outer portion of the wing

I've sanded with 600 grit and left it at that. Wow, what an improvement! I'm just not convinced I should be waxing/polishing my props. I recall while in college learning a little about he physics of air flow over curved surfaces; aircraft wings - where by keeping the air attached, smoother airflow and better lift resulted. High gloss doesn't help keep the air attached.

Maybe that rough trailing edge will act as a spoiler like we see on the Subaru WRX? ;-P

I've read the polished props are best for keeping bugs from sticking. Definitely a benefit there, especially if you live/fly in buggy areas. Not a big problem here in Colorado. If you live in a buggy area, I suggest keeping a "Magic Eraser" in your kit.

Seriously, these drones use brute force and a little sanding here and polishing there isn't going to amount to anything that can be measured. But if it floats your boat go for it. FWIW, I do sand down the flashing and ridges that often accompany DJI props.
 
Polishing props is dumb IMO. A little texture inhibits air flow separation resulting in smooth and efficient laminar flow. Take the golf ball, a blunt flying object. By adding dimples and tripping the laminar boundary layers - reduces drag. Airplane wings and our props are less prone to separation since they aren't as "blunt" and as a result skin-friction drag is more important.High gloss makes them less sticky with regards to the air/skin boundary. More noise and less efficient, though the numbers are very small and in my opinion insignificant. You want the air to stick to the surface.

Take a look at this video and prepare to have your polished mind blown.

And what about golf balls (I knew you were thinking it)?
Why aren't airplanes like golf balls?

There does exist other types of devices commonly used on wings that create a similar effect to the dimples used on golf balls. Though these wing devices also create turbulence in order to delay flow separation, the purpose is not to decrease drag but to increase lift. One of the most popular of these devices is the vortex generator.



javelin_18.jpg

A Gloster Javelin showing the three sets of vortex generators located along the outer portion of the wing

I've sanded with 600 grit and left it at that. Wow, what an improvement! I'm just not convinced I should be waxing/polishing my props. I recall while in college learning a little about he physics of air flow over curved surfaces; aircraft wings - where by keeping the air attached, smoother airflow and better lift resulted. High gloss doesn't help keep the air attached.

Maybe that rough trailing edge will act as a spoiler like we see on the Subaru WRX? ;-P

I've read the polished props are best for keeping bugs from sticking. Definitely a benefit there, especially if you live/fly in buggy areas. Not a big problem here in Colorado. If you live in a buggy area, I suggest keeping a "Magic Eraser" in your kit.

Seriously, these drones use brute force and a little sanding here and polishing there isn't going to amount to anything that can be measured. But if it floats your boat go for it. FWIW, I do sand down the flashing and ridges that often accompany DJI props.


Just an observation as a Mechanical Engineer:

You have it right: Golf balls need dimples to create a little turbulent layer because they are blunt thereby creating smoother airflow (I know, counter-intuitive). Wings need smooth laminar flow in order to create an efficient vacuum above the wing. Winglets are on the outer portion of the wing to lower the vortex effect.

Question is: Mother's or Turtle wax? o_O
 

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