Carbon overlaying
^ANT^'s guide to Carbon Fibre Overlaying
OK so some of you have asked for a dummies guide to carbon overlaying, so I’ve just spent the last couple of hours writing up this guide to doing the job with West Systems gear which was sent out in the group buy kits.
What we start out with
Once you have selected the parts you want to overlay, you need to key them up so that the resin has a good surface to bond to, the Audi trims all had a glossy wood finish so it was just a case of keying them up with 150 grit so they have an nice even dull finish then a quick burst with 80 grit which gives a really nice key for the resin. If you have a part that doesn’t have a smooth surface, you will need to spend more time with the grit paper sanding it back smooth, a lot of parts on the gen 5 Celica have a textured finish e.g. gear surround, a/b/c pillars. These will all need some time spent on them to get them all smoothed out.
Here is pic of the finish after sanding with 150 grit
And after 80 grit sanding
Once all the parts are keyed you will need to removed any grit left behind from sanding, so they will need to be wash/scrubbed and then dried, then wiped over a couple of times with acetone or panel wipe so there isn’t any contaminants left on the part.
Now we move on to cutting out the fabric, so lay your carbon out on a nice clean flat surface and then lay the part onto it smooth surface down, you want to leave some extra fabric around the edges so it drapes a little, be very careful at this point the weave of the twill gets disturbed very easily, I mark out the fabric with a silver sharpie, but you can just do it on the fly if your only doing a small part.
Parts laid out and marked
Once you have your material all cut out its time to lay your parts/part out ready for its base coat. I attach blocks to the bottom of my parts to lift them off of the table top so you can drape the fabric over and let it hang later on, tacky tape or a double sided tape is ideal for attaching the parts to the blocks.
So now that’s all done we can move onto mixing up the base coat. The west systems epoxy is mixed 5 parts resin to 1 part hardener (by volume or weight) once you mix the hardener into the resin you can then add a very small amount of the black epoxy pigment, you only need a very thin layer of base coat so you wont need to mix up much resin, for example you will only need about 30 ml to cover 2 A pillar trims so 25 ml or resin and 5 ml of hardener, then a dash of black pigment until it blackens the resin.
To avoid mixing in bubbles to the resin, mix very slowly I do 30 turns one way then 30 in the other direction and then make sure I scrape the sides and the bottom so that the hardener gets fully mixed in. You also have to make sure you mix the right ratios of resin to hardener, if you mix in too much hardener it wont make the resin harden any quicker quite the opposite actually it will just never harden.
( I’ve seen the results of this and its not pretty, a guy was trying to leap before he could walk and went out and spent £600 on materials to make a carbon bonnet, he didn’t read the ratio’s for the epoxy and consequently mixed the wrong ratio, he was left with a gloopy expensive mess that was only good for the bin)
Here is the first part coated in the base coat.
So once the base coat is down, you will need to leave the part to hit what is called ‘b’ stage with west systems epoxy this is usually about 1-2 hours ( you can speed up the drying process with a hair dryer or heat gun) this is where the resin has started to gel but not fully hardened, you should be able to touch the part and it will still feel tacky but shouldn’t leave any black on your finger.
Fabric draped onto the parts
Once the parts/part have hit ‘b’ stage you can now move onto laying down the fabric, be very careful as you only really have one shot at this as the fabric will stick like s**t to a blanket smile.gif so carefully align it and once happy drop it down onto the fabric and smooth over the fabric with your hand making sure you hit all the edges and so fourth, but be careful not to damage the weave in the process.
At this point if you have a hair dryer or heat gun and start warming the parts. A regular blow dryer works well because you won't cook the resin as easily. Some heat guns get pretty hot and you can easily hurt something with too much heat. Just warm each part in rotation and make sure no fabric pops up on curves and such (make sure you have good ventilation as the fumes aren’t good for you)
Once your happy that everything is as it should be and all the fabric is stuck around
all the edges we you can now move onto the first coat of resin, 3-5 thin layers are
better than 2-3 thick layers because if you have any bubbles in the resin they will
pop out of thin layers of resin a lot easier than if you lay down thick layers ( using a
hair dryer on bubbles will also help them to pop them for any stubborn ones)
So here is the first layer of resin on the parts mixed as before but no black tint this time.
Once you have your first layer on and its hit ‘B’ stage you can mix up more resin and do another thin layer, repeat this process another few times, each time waiting for the part to hit ‘B’ stage.
Once you are happy with the thickness of the resin let it fully cure 24-48 hours if the part is small enough to fit in the airing cupboard then stick it in there for a day.
Here is a part that has cured and ready for sanding, as you can see it is quite lumpy, don’t worry about this as it will all be taken care of with the sanding process, you’ll also notice that the part has been trimmed, missed photos of this out but I usually use a nice new sharp Stanley blade to trim off the excess, as long as you haven’t got too much resin on the excess material a Stanley blade works well, if the Stanley blade wont cut very well a Dremmel with cutting disc also works very well.
Now onto the finishing ( here is where we start again lol)
I first start with the 150 grit wet sanding all the lumps and bumps out so it has a nice uniform smooth finish and then move through the grits (220/320)
The start of 150 grit
after a good sanding with 150
now with the 220 and 320 washing in between grits so you don’t have any left over grit on the piece
You do have to be careful not to sand down to the weave as this will wreck the piece and you will have to start all over again, so only take off the bear minimum so you get a nice uniform finish.
After 320 grit you can stop here and finish with coating the part with rattle can lacquer as this will give the part more UV stability so it wont yellow when the part is subjected to the sun. Here is what I was left with after sanding
And after first coat of lacquer
And after 3rd coat
Now its just onto the final finishing I use 1000/1200 and 1500 grit and then finish off with Meguiars ultimate compound on the polisher to get the fine scratches out and then a nice coat of Colinite 746s wax
The finished pieces
So hope that all made sense and helps you to get started.
