Carbon Fibre, the good and the bad.

 

I am not setting out to either slate other peoples work or big up my own.

I just want to help people understand the basic different kinds of carbon fibre that’s out there to buy.

 

There are basically two different kinds....

Wet-lay and Pre-preg.

Wet-lay is layers of dry material are layered into the mould and the resin is brushed on. The resin is mixed by hand and mistakes can be made during measuring and mixing. The fibres of the material can also distort during the brushing in process if the resin. Then it can be put in a vacuum but doesn’t have to be baked as the resin will cure naturally once the hardener is added. 

This can make the parts heavy as there is no way of making sure you don't have too much resin in it. Meaning the whole process is less controlled.

 

Pre-preg is where the resin is ‘Pre-impregnated' into the material in the factory where it is made and then they can get the exact amount of resin into the material. This is then bought by the laminator and then again layered into the mould, this has to be put in a vacuum and baked. 

The cooking process is much more complicated and the process I use is 16 hours long at varying temperatures. The part is a light as it can be as it has the exact amount of resin in it. So therefore the finish quality is much higher and makes a much stronger part.

 

Wet-lay, the dry carbon fibre material is anywhere between £3-£10 per square metre and the resin is between £5-30 for 5 liters.

 

Pre-preg material is £20-£80 per square metre. The resin is all ready in the material. 

The material I use is £75 per square metre.

 

The disadvantage  of wet-lay is it is easy-ish to make very cheap parts as you can put one layer of carbon into the mould (surface layer) then just add layers of fibreglass then add the resin then leave to cure. When it is cured you can just paint the back of it with black resin. This makes it heavier and weaker than Pre-preg parts.

When I was making wet-lay stuff all of mine was 100% carbon fibre.

 

You cannot mix other materials with pre-preg so each part is 100% carbon fibre.

 

Lets talk pricing now. Without mentioning labour, oven time and consumables, please remember Pre-preg is a longer and more costly process but results in higher quality parts.

Pre-preg is baked in a vacuum at varying temperatures, for different amount of time, I bake mine for 16 hours at 5 different temperatures. Wet-lay doesn’t need to be baked or even put in a vacuum.

 

Take a front mudguard.

Wet-lay uses about £7-8 of carbon, £5 of fibreglass and a maximum £5.00 of resin. 

 

Pre-preg uses about £70-80 of material, resin included.

 

I would say about 95% of carbon on eBay/ Facebook Marketplace is wet-lay with one layer of carbon and the rest fibreglass and then painted with black resin on the back.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This part itself looks like nice and shiny carbon fibre. Yes it is, well the surface layer is, with lots of lacquer on too. If you look at the areas I've circled, you can see the different texture of the inside of the mudguard,. It's black and it is fibreglass matting, painted black.. Also, the holes that have been drilled in it, to mount it to the forks, are white; this shows the fibreglass and CANNOT be hidden. You can also see that some of the weave is distorted.

 

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This my pre-preg mudguard. This is just as it came out of the mould after polishing. There is no lacquer. You can see the weave looks deeper and better quality.

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Another example, this is the underside of a tool tray. This still has the weave showing but with a matt finish. This is because the resin is more towards the mould side of the material.

 

 

 

 

 

 

 

 

 

 

 

 

 

      

 

 

 

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This is the rear of a wet-lay part that has major faults. 

You can clearly see the fibreglass (the multidirectional strands) and the black resin, it looks nothing like the rear of the tool tray.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sometimes if the parts are shaped they will look wrinkled. If you look at the velocity stacks, you can see the inside is really nice, shiny and smooth (thats the side that was against the mould). The outside has a slightly wrinkled texture, this is where the release film was applied, the pressure of the vacuum bag has squashed it leaving it wrinkled. This does not weaken the part in any way, it is purely cosmetic and cannot be helped unless you have very expensive 2 or 3 piece moulds.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Finally onto different materials. There are two basic types: 'Plain' and 'Twill' weave. 
I use twill weave for all my parts as its the best material for my manufacturing process.

I also find it looks nicer as I can make the weave 'flow' with the parts and allows me to express my passion for nice looking carbon parts.

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                         Plain Weave                                                          Twill Weave                            

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So there we have it....

 

99% of wet-lay is poor quality and pre-preg is high quality. 

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If in doubt just ask the seller, if it’s pre-preg they'll probably tell you in the advert. If they say 'finished on the back with black epoxy' or '100% carbon weave' it isn't pre-preg.
 

Also lots of the items found on Ebay and FaceBook Marketplace are mass produced in China and may not fit very well.

 

This is the reason why I started making carbon parts myself as I was fed up of paying silly money for parts that were poor quality and poor fitting.

 

At least now you have an idea of what to look for and hopefully will it help you to make the right choice.

 

If it's cheap it won't be 100% carbon fibre and just because its super shiny it doesn’t mean it’s good quality.

 

 

Jolly Giant.