Phantom 4 Blades NOT FINISHED EFFICIENTLY

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Here is an interesting issue: Factory direct and third party purchased blades for Phantom 4 are not finished properly. The trailing edges are rough and have a definite "ridge" along the trailing edge on most of them . . some worse than others but you can feel it with your finger or thumb by running it over the surface in the direction of the normal airflow. I thought I was just imagining it at first but took some closeups and it's really there. . . more exaggerated on some but it's on every one I've purchased so far. This makes them less efficient, adds noise and wastes a bit battery energy. There are 8 turbulence generating surfaces like that on set of P4 blades.

So, I took some 400 sandpaper and just "brushed" them off in the direction of airflow gently along the trailing edge from root to tip. Does not take much . . go gently and feel it with the edge of your thumb after each pass. Drag in the direction of the airfoil till you cant feel it any more. It should only take 2-3 light passes. ( see comparison photos)

RESULT: quieter sound, and can't prove it but seems really quick and my fastest speed is logged as 56.38mph and before the best I saw was 47.73. Not a valid comparison really (just comparing 2 flights) . . but it does seems faster.

upload_2016-11-19_20-24-40.png
 

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That's correct. A rough trailing edge won't generate any appreciable turbulence in a subsonic propeller. OTOH, smoothing it a little won't hurt anything either.
 
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Blade's leading edge and surface is important. Trailing edge will not make significant impact.


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I've spent a few years designing and manufacturing a small wind turbine called WIND ARROW and our blade testing showed that the air must depart that training edge as cleanly as it separates at the leading edge . . (and it should match the upper and lower surface departure angle as closely as possible) . . or turbulence is generated that robs lift. We built our own blade shape/design of 1m long carbon fiber each weighing barely 450grams each. Besides shape and weight . . stiffness, surface coating and final shape finishing accuracy also contribute to efficiency.
Wind Arrow 1kW

Monitoring blade turbulence and flutter in the wind tunnel
upload_2016-11-20_7-6-41.png

Blade finishing at various stages
upload_2016-11-20_7-1-0.png

 
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I've spent a few years designing and manufacturing a small wind turbine called WIND ARROW and our blade testing showed that the air must depart that training edge as cleanly as it separates at the leading edge . . (and it should match the upper and lower surface departure angle as closely as possible) . . or turbulence is generated that robs lift. We built our own blade shape/design of 1m long carbon fiber each weighing barely 450grams each. Besides shape and weight . . stiffness, surface coating and final shape finishing accuracy also contribute to efficiency.
Wind Arrow 1kW

Monitoring blade turbulence and flutter in the wind tunnel
View attachment 69028
Blade finishing at various stages
View attachment 69027

Absolutely correct!
 
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I have never had any issues with DJI blades for the P4. They always fly steady as a rock. I have about 4 or 5 sets I rotate when they get debris, bug splatter build up I switch them out until I can properly clean them.
 
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alokbhargava

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I've spent a few years designing and manufacturing a small wind turbine called WIND ARROW and our blade testing showed that the air must depart that training edge as cleanly as it separates at the leading edge . . (and it should match the upper and lower surface departure angle as closely as possible) . . or turbulence is generated that robs lift. We built our own blade shape/design of 1m long carbon fiber each weighing barely 450grams each. Besides shape and weight . . stiffness, surface coating and final shape finishing accuracy also contribute to efficiency.
Wind Arrow 1kW

Monitoring blade turbulence and flutter in the wind tunnel
View attachment 69028
Blade finishing at various stages
View attachment 69027

Wow. Wish I can visit your lab. Doing all this at personal level means a great achievement. Salutes!!!


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I'm 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. Maybe that rough trailing edge will act as a spoiler like we see on the Subaru WRX? ;-P
 
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I'm 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. Maybe that rough trailing edge will act as a spoiler like we see on the Subaru WRX? ;-P
 
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I am not an aerodynamicist, but if it is good enough for Boeing it works for me. As a pilot for over 50 years, it's all about airflow.
I'm with you gsreinke . . .even a pig will go super-sonic, if you get it going fast enough . .
Actually, I think P4 blades are an excellent trade-off of materials, finish, performance and cost . . just the one tiny improvement is so easy to do, that they really should have seen to it at the factory
 
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I once worked at a small airport washing and waxing planes in exchange for flight time. Pilots wanted the planes skin waxed as well as the props to have better airflow dynamic. And you better believe the props were balanced.
 
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Oh, you haven't heard about my list. I'm takin' names and there will be no mercy! Hey, I just received my DJI Phantom 4 9450s Quick-release propellers. There IS a slight ridge on the training edge. I'll sand that down, but probably will use 220 grit.
 
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I once worked at a small airport washing and waxing planes in exchange for flight time. Pilots wanted the planes skin waxed as well as the props to have better airflow dynamic. And you better believe the props were balanced.
What the He11 do pilots know about aerodynamics?
 

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