Frame Material: Carbon Fibre and Fibreglass

by Oscar

Carbon fiber and Fiberglass are two popular materials for quadcopter frames. The choice between carbon fiber and fiberglass depends on many factors, in this article we will look into some of the most important aspects and differences between these materials

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Carbon fiber is lighter than fiberglass, it’s 70% lighter than steel, 40% lighter than Aluminum. The nature of carbon fiber is low in weight, rigid, and strong. This is why most weight-critical performance products use carbon fiber, and it’s a far more popular choice of material for mini quad frames.

Strength vs Rigidity

Rigidity is also known as stiffness. Carbon fiber and fiberglass are both very strong, but Carbon fiber is more rigid. Carbon fiber is about 3 times stiffer than steel and aluminum for a given weight.

In applications where a small amount of flexibility is allowed, carbon fiber is a top choice. Fiberglass is better suited to extreme flex patterns, while carbon fiber has a relatively small flex window.


The shape of Carbon fiber doesn’t deteriorate over time. That means the shape of carbon fibre doesn’t change when consistent and constant force is applied on it.

Fibreglass however being more flexible, it means that glass-fiber typically has a higher ultimate breaking point than a similarly shaped carbon fiber product, therefore having higher strength-to-weight ratio. In general it is a “tougher” material. The incredible rigidity of carbon makes it less capable of enduring certain abuses than fiberglass. I guess therefore you could say CF “more brittle”

Thermal and Electrical Characteristics

As opposed to most other materials, carbon fiber has a negative coefficient of thermal expansion which means they don’t expand or shrink as much as fibreglass when the temperature changes. This is a desirable quality for applications that have to operate in a wide range of temperatures .

Fiberglass composites are insulators, which means they do not respond to an electric field and resist the flow of electric charge. Fiberglass composites are very radiolucent, which means they allow radiation to pass through it freely. This makes fiberglass rods a useful material for antennas. CF is conductive and it’s a problem for mini quad frames.


Fiberglass is more cost effective. Long strands of carbon fibers are very difficult and expensive to manufacture, while fiberglass processes much easier. As a result, fiberglass is considerably less expensive than carbon fiber. Fiberglass composites are less expensive than carbon composites in most cases.

More on Carbon Fiber Specification

3K, 6K?

These numbers indicate how many carbon strands per tow are in the weave. Lower the number “K” in carbon sheet the thicker and stronger the weave. To simplify it, 3K is stronger than 6K, 1K is stronger than 3K etc. However, 3K is pretty much the standard weave people use for general applications so if you pick up some random carbon it will most likely be 3K.

Twill Carbon fiber?

Some argue mini quad frame parts should be cut in twill pattern (diagonal shaped pattern), and that could maximize the strength. While others argue it just looks different but still provide the same strength properties. This remains a myth until someone can provide some scientific proof.

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Uzma Khan 28th May 2023 - 4:02 pm

I love the way you differentiate between carbon fiber and fiber glass. It is simple and understandable. However, how can get more specific details?

Me Myself 20th September 2021 - 1:58 pm

Thy should have made the new Corvette out of carbon fiber. It would justify the premiums people are paying for them. What happens when it needs pair though.

John Doe 26th January 2020 - 8:45 am

“Hi guys, just a quick question would you use carbon fibre or fibreglass for a walking cane for someone who has knee and back problems. Yours Sincerely, Paul Smith.”

for that problem, I’m suggesting you use walking cane that made from aluminum. You could go to a store which sell only medical/health equipment and you could ask guidance which cane is good for your case

Paul Smith 5th November 2019 - 11:01 pm

Hi guys, just a quick question would you use carbon fibre or fibreglass for a walking cane for someone who has knee and back problems. Yours Sincerely, Paul Smith.

peter 7th June 2019 - 9:05 pm

just one question( or 2 ):
if i have a 0.5m tube with 3K, thickness of 3mm,
what can one expect in terms of compression
before the tube “breaks” ???
where can one find such data ???

thanks in advance

Ashvin 9th January 2019 - 6:53 pm

Thank you for sharing these important information. Actually i am trying to make a rod which is a bit flexible and can twist also, but the rod should be strong enough to carry a a constant load and counter the effect of wind at a certain height. Is Fibreglass a good choice or should i consider other material also ?

Ilyas 7th September 2018 - 10:39 pm


Good blog, thanks. However, can anyone explain, what is the weight difference between carbon fiber and Fiber glass?

Spencer L. 4th January 2018 - 8:09 am

Hi Oscar, I’m hoping to build an octocopter out of carbon fiber that can accommodate 18 inch propellers. What diameter should the drone be? Also, what carbon fiber tube size should I use? I’m thinking 25mm, as a lot of other drone builds use this size, but is there any reason to go above 25mm? What thickness should the tubes have? What thickness should the center plates have? Thanks for taking the time to help me out.

Chris Rowell 28th April 2018 - 1:40 pm

Well if you haven’t started building the drone yet i will give you an idea. I built a hexacopter that has 17in props and the total diameter is 38inches. So you are probably lookin at arpund a 48 inch diameter to have a octo with 18in blades. I would probably go with larger carbon fiber such as 30mm so the arms willm atch the size of the drone. For the center plate i would go 1.5 to 2mm for the center plate. You don’t need them to be too thick because once you attach all your tube clamps and any stand offs you will have a prtty sturdy structure once its all done. I used 1.3mm plate and had 3 of them stacked( bottom center and top plate) ao i could put all the componenta and wires on the inside so the frame looks more professionally built and so it covers everything from different weather elements. Its all about trial amd error to be able to build a drone that big that looks good and thats safe because you deffinently dont want something that big falling from the sky. Lol

Red Owl FPV 7th November 2017 - 1:10 pm

Hi Oscar!

I’m Red Owl FPV, from Spain. Congratulations for your blog! It’s amazing.

I have a doubt. You said that the K number represents how many carbon strands per tow are in the weave. All right, but, 4K are 4000 strands, more than 3k… why is 4K less stronger than 3k? I don’t understand. Can you explain me, please?


Oscar 12th November 2017 - 4:29 pm

Think of it like the material in your shirt. A heavy shirt has more material in it. Like wise the higher the number “K” in carbon sheet the heavier and stronger the weave but also thicker so in 4mm carbon plate you get less layers of carbon and since there is different types of weave and both cloth and unidirectional in carbon plates, if you used a much thicker weave you have less layers available to you.

jose P 27th July 2017 - 11:03 pm

Valuable info. Thx Oscar.

Awal Muhammad 21st January 2017 - 7:41 am

Good morning.
I feel much pleasure to find this web while I was searching for which material I have to choose for structuring body for for electric car. I have manage the electric motor and other parts.
I will be more thankful if you let me know whether I have to choose Carbon Fiber or Fiberglass including its specifications.
Let me know if you can guide me for other materials for mould as different adhesive, resin, tool and CSM and weight etc for carbon fiber / glassfibe.

Awal Muhammad

SamXu 29th September 2015 - 8:42 pm

Hi Oscar Im considering buying some 5045 HQ props that exist in two versions. Glass Fiber Mix (Glass Fiber & Plastic) and Carbon Fiber Mix (Carbon Fiber and Plastic). The price is the same! Wich of them would you recommend?

Oscar 1st October 2015 - 12:53 pm

Glass Fiber

willer 8th July 2015 - 4:57 am

Still stick to GF rod for my drone arm instead of CF.
much flexible, cheaper and survival rate higher then CB after crash!!