Been lucky enough to have been invited on a couple of courses at EC, one of which was pre preg. So I can say with confidence that the parts shown are done using pre preg and no clear coat just a buff/polish after demoulding.

Carbon Copies Ltd

The part in the second photo you showed (epfibre), is a pretty crap effort.
Although they are both wetlay, I would aim towards something that looks like the first photo.
you can get carbon to bend like that, but you will need to do some relief cuts right where the holes are. Just nib it with the tip of a knife
You might want to vacuum bag it to make sure the corners are consolidated.
But like Warren said its easier if you fill the holes and leave a 1-2mm recess.

On a flat object like that and will very good release agents and good preparation you can do recesses if they are shallow.  Obviously you would fill the hole itself leaving just the countersunk recess.

A prime example is the recess on our subaru alternator cover:




And the shallower ones on our MR2 engine cover:



So it is possible to mould them and get a successful repeatable release.


The practicality of getting the carbon to stick exactly where you want it means it would be very hard to do those parts wetlay or resin infused, however pre-preg is dead easy as you can cut the fabric to any shape and it easily sticks where you want. Also lots of brute force can be used with blunt tools to force it into corners, the same kind of force that would shread normal fabrics.

If you wanted to do such things wetlay or infused then you would find it much easier with a ProFinish Carbon Fibre 2/2 TwillProFinish Carbon Fibre 2/2 Twill and some form of spray tack or applying when resin is tacky.  ProFinish can be neatly cut like pre-pregs and wont fall apart like normal fabrics do, so you can do some quite precise work with them.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

If you are sacrificing the original you could cut them off and bond them onto the new CF one. There is a chance that if you scrape of the layer of silver they will be black ABS underneath.

Carbon Copies Ltd

thanks for your help  

The fixing recesses will almost certainly have been made separately and then bonded on afterwards.  ( or they use a two part compression mould) I have done similar using carbon tube cut and shaped to fit and then bonded in place. If you use a hole saw the same size as the tube on some flat CF sheet you can make some" washers " that you can then bond onto the bottom of the tubes to finish the mounts.

Carbon Copies Ltd

Sorry for digging this up again, but i notice that a few companies offer this part with the same fitment as the standard part, how exactly do you think they do it? I'll attach a picture of their parts. 

Thank you all for all your help, will have a go with the body filler as i don't actually need the part again! 

I notice the holes are countersunk.
You might need to get washers and longer screws to secure the composite part to the car.
As for the grooves, I would go the car body filler / primer way, that way you will have a smooth mould. You'll also get rid of the ABS plastic texture.