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 

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

Tags: carbon, fiber, multicopter, plastic, propeller, props, test

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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. .

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.

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

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.

I suspect the same. I will be testing my new CF props in the next 2 days and will report here. I suspect this has something to do with plastic curvature caused by G forces. CF fiber is stiff and does not adjust the same way. 

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.

Those black "CF Reinforced" plastic props are the one that snapped mid-air on my quad, leading to it's death.

I work for a contract manufacturer specializing in composites manufacturing, and I can tell you that properly engineered products made using carbon fibre products are not only lighter but far stronger than when made using conventional materials. If it's cheap it's defiantly not a true composite product. By the lb or linear yard CF is far more expensive than any other common material. Besides the advantage of weight the primary and often most forgotten benefit of manufacturing with composites id the fact that you can align the materials to best suit the stress points of the design and you can provide maximum strength and stiffness on the axis of load. Much of what we see in hobby related products are purely cosmetic application of carbon or carbon look materials. Carbon in thin unidirectional layers is very fragile and susceptible to breakage, however if properly designed it can be both strong in the long axis as well as in torsion. That said, it's a lot like building and flying a plane, we build them to fly not crash. If that's part of the design intent and survivability isn't a factor then we can use a very thin, lightweight design (less rotational mass = better efficiency and higher performance) and reap the benefits of the material to the max. A reinforced nylon prop usually consists of nylon with randomly oriented short fiberglass strands this helps bond the prop together and helps when an edge or tip becomes chipped but does little to add any real strength or stiffness to the prop. It's always a compromise when choosing the materials for any design, and as always we must choose our props based on our use. If we looking for durability and low cost we might be on one end of the spectrum and if we are looking for higher performance and cost or durability isn't as much of a factor we might be on the other end of the spectrum. On a side not I have played around with a large variety of props and can say that the right prop can yield 20% or greater increase in performance and or efficiency. The search for the Holy Grail is a full time job!

Regards,

Nathaniel ~KD2DEY

I've never had that happen with these using the smaller diydrones motors but I've had that happen to diydrones props that I got a couple of years ago. I think it was from a slight hit they took on a soft crash or hitting something and since I didn't notice, it then failed in the air. Also it can happen if you crank down too much on the collet. Things from my learning days that I'm sure didn't happen in your case but it can happen if you don't check them carefully after a soft crash where nothing really broke but a prop took a hit that weekend it's hub.

I find the weight of the Prop  to be a big issue. I have spent some time working on vibration in my quads with different motors.  I have changed the motor bearings for abec 5 quality and balance the props. when  I  try a CF prop compared to a light electric  the lighter prop is always significantly less vibration.

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