SORT YOUR MOULD
WAIT TILL IT CURES THEN REPEAT THE PROCESS UNTIL YOU ACHIEVE THE FOUR- TO FIVE-LAYER THICKNESS
In this case, the mould was taken from the quarter panel, which was already wearing a fiberglass widebody over fender. It’s important that your surface is perfect. Any imperfection, no matter the size, will directly transfer onto your mould and then onto your carbon product. Zac says: “Make sure you have used 2k paint on the plug [original part], if not the paint will undoubtedly fry up.” Next, you’ll want to use plasticine or modelling clay to fill all of your gaps. What you are trying to achieve here is to stop having your mould mechanically lock to the plug. You can’t have anywhere where the resin or glass can go back in on itself or you’ll never separate the two without damaging the mould. For this particular project, there were two areas to sort. The dimples where the widebody bolted to the original body and the seam where the over fenders and body meet. Ensure your modelling clay is nice and smooth.
On edges where your new carbon part will run right to the edge of the body, you’ll need to create some flanges. These do not need to be flash. Zac simply hotglued them on from foam that will be removed from the body later. Masking tape will protect your paint work, if that’s a concern.
Once you’re all prepped and ready to lay glass on your plug, the first step is to create a non-stick barrier on your paint surface using a release agent. “PVA release agent is hands down the most foolproof release system — it’s also my go-to if I’m unsure of the substrate.” For best results, spray the PVA on, but if you don’t have a spray gun, a foam brush will net you a great result. Aim for a smooth, even coating — again, any texture introduced here will transfer onto your mould. A single coat will be plenty. The next layer is the gel coat. This will become the surface on your mould that you lay your carbon on further down the track. Zac went with, and recommends going with, polyester for both the resin and gel coat. Be very precise when measuring out the quantities and don’t try to mix too much at once — never more than one litre at a time! Your mix ratio of catalyst is only two percent. “You want to brush the gel coat on nice and even. You’re aiming for a thickness of .5mm; anything less will fail. Half a litre per m² coverage is a good way to gauge quantity.” Once cured, it’s now time for the chop strand (CSM). The aim here is for four or five layers, but you’ll need to lay up each layer and let it cure before laying the next. Doing it all at once will end in tears (trust us). “You’ll need a laminating roller, which you can get from a composite supplier, or cheap chip brushes work great too. Pre-wet the gel coat with resin and lay on the dry CSM, then wet out with more resin, ensuring you remove all the air bubbles.” Wait till it cures and repeat the process until you achieve the four- to five-layer thickness.
Once it’s fully cured, it’s time to demould. Do this using small wedges of wood, carefully driving them between the two surfaces. Depending on the shape, it should be removed with ease. Trim and sand your mould edges, giving them a sand to ensure you don’t have to deal with sharp edges — this stuff will cut you.