Plastic vs Carbon Props - Vibration Test

I am sure I am not the first one facing the dilemma – plastic vs. carbon – when choosing multicopter props. Carbon fiber is twice as expensive. On the other hand, props are the key moving part and may significantly affect your rig’s performance, battery life, and most of all video quality. To put the issue to rest once and for all I did my own test using an iPhone vibrometer app and two sets of 10x45 plastic and carbon fiber props, 12 vs 8 grams a piece respectively.

Both sets (hexacopter) have never been balanced before and ran at the same minimum throttle speed. Plastic props vibrated at 1.6-1.8 m/s2. They also produced more noise.  

Carbon fiber props ran at healthy 0.2 - 0.3 m/s2 and sounded much better. Also, they are significantly lighter and stronger than plastic.

Cautionary note – carbon fiber props are very stiff and sharp. Carbon fiber is 100 times stronger than aluminum and can cause bodily harm at high speeds. You should handle them with extra care. 

See for yourself 

https://www.youtube.com/watch?v=dkQqD96AEd4

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  • There are a couple of other things to take  into account:

    First the fabrication methods. You can make plate by layering sheets one upon another, and even if you angle the weave for the best strength, and squeegie the final product, it may not be as strong as a sheet made well. A sheet should be cured with pressure, and the resin is very important. Even though it isn't the strongest element in the process.

    Second. CF doesn't resist abresion well. Care has to be taken around holes or any surface where one element rubs on another.

  • Rob, I think you are onto something close to what I have felt for a while now about CF props in comparison to good quality plastic props. The one main dislike I have for CF props is they can fracture at the motor shaft collar while tightening the nuts and you wont be able to tell this until after it breaks off completely while in flight.

    I have a theory that the rigidity of the CF props might in fact be less energy efficient. Ive yet to put this to some good testing to prove it, but since Ive switch a lot of my copters back over to plastic props, they do seem to fly more easily and I get slightly better flight times out of them.

    Here is where the foundation of my theory comes from. There is a big Eagles nest in the forest just out front of my apartment building and I often watch them catch thermals out the front of the building to go of hunting for the day. They often come within 5-10 meters from my balcony.

    I noticed while watching them, they have long flexible wing tip feathers that seem to act like shock absorbers as they hit uneven pockets of air as they fly in and out of the thermals.

    I could imagine how much easier this would be for them to manage those sudden changes in air movement and density and it would require much less energy fighting this say than if they had very rigid wings. Sudden gusts and change in air movement would be very tiring and hard to mange much like riding in a car without shock absorbers.

    I feel the flexibility of plastic props might work in the same way where they give a slightly easier forgiving ride and as such likely they don't expend quite as much energy in doing so.

    When I have some more time I'm going to work out a method to put this theory to test and see if it proves me right or not. .

    • Interesting, while doing battery testing on my basic 450 quad - hovering in one place - i noticed I get consistently slightly less flight time with CF props than I do with plastic props - 16mins vs 18mins and it's more exaggerated in a breeze/wind.

      Also interesting that airplane manufacturers interested in efficiency make wings that are disconcertingly flexible (to a nervous flyer!).

      • Nice observations Dom.

        It sort of make me ask the question where did the idea to use carbon fiber come from for use in multirotor props to begin with?  Was it simply to have stronger more damage resistant props?  Was it just from an assumption CF is so good in many other areas it should automatically be a given it would be the best material for multirotor aircraft props as well? 

        I have never seen any significant test data to prove they are more efficient or not eitherway.  But just going on my own observations and experience with using the exact same aircraft, I actually get less flight times using CF props. Seems you have now found the same which support the same as my findings. .

  • I've had very good results with these on my smaller quads. I've been using them for a year. Very quiet and stiff and not expensive. I use these on my octo but am changing them out for APC props 12x3.8 to see if I can get more efficiency.

  • Test your endurance with both the plastic and CF props.

    I bought some CF props to test, was amazed by their strength and lightness and looking forward to never having to worry about breaking a prop in flight, but my flight times were only 75% of what I got using APC plastic props. The CFs looked identical in shape (like they copied the APC moulds) but just didn't perform as well.

  • What's the general consensus on carbon and nylon mix propellers such as these made by GemFan?

    http://www.gemfanhobby.com/proInfoE-id-207.html

    Many thanks,

    Steve
  • Which plastic props did you use?  If you didn't use genuine APC's, or Graupners then you've proved nothing.  All the no-name props are junk and barely suitable for a rubber-band powered airplane.

    Yeah, no time to balance props in the field.  That's why you balance them ahead of time if you are serious.

    And Carbon Fiber absolutely is not 100 times as strong as Aluminum.  Not even close.  Maybe 5 times.  And due to the way these things are actually made, I suspect CF props are actually not much stronger than plastic.  Carbon Fiber can be a very gimmicky material, and misused in many cases.

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