OK, this is a big project with a lot involved but I’ll try to cover it as best as I can. If you go ahead and buy these materials (or something similar) from us then we’d be only too happy to provide more detailed information on each step, as you go.
Getting the Pattern RightTo make your own replacement carbon fibre body panels the first thing you’ll need is the ‘pattern’ of the parts. As you probably know the pattern is the male form of the part, exactly as you want the finished part to be (even though it can be made out of just about anything). Given that you’re starting with an MR2 but want to modify it then the obvious thing is to just start using foam (normally PU foam) and bodyfiller to alter the styling or proportions of the existing bodywork until you’ve got it to the shape you want the new body kit to be. Modifying the existing panels in this way is going to be a messy process and not really reversible without a lot of work.
Once you’ve got the shape how you want it, you’ll need to get the finish right too before you’re ready to pull moulds off the pattern. We would strongly recommend using a 2-pack (2k) filler primer sprayed through a gun. These are the primers that bodyshops use when they’ve done repairs – they’re high-build (so the fill any texture in the surface) and are very polish-able when they’re cured. You may well need to spray a couple of thick coats, then flat the surface, then spray again (and maybe flat and spray yet again) until you get the new contours really smooth (no ‘wobble’) and glossy. Given the size of the panels you’re going to be making, I recommend investing in a random orbit palm sander like the Mirka Ceros (an amazing bit of kit) because by hand you’re probably looking at hundreds of hours of flatting and polishing.
Once you’ve got the pattern (i.e. your modified body panels) looking really nice, you’re ready to take moulds off them…
Making Moulds of Car Body PanelsCar body panels, particularly a whole car’s worth, represent a lot of moulds and are in themselves quite large moulds. This means that you need a tooling system (a mould making system) that’s cost effective and zero shrink (normal polyester resin and chopped strand mat will shrink, particularly on larger moulds, which means the replacement panels you make using them would not fit back on the car properly). Our system for making large, zero shrink moulds is called Uni-Mould. Not only is it cost effective, it’s also designed to be compatible with any resin system meaning that once you’ve made the moulds, you could use them to make top end carbon fibre/epoxy parts or low-end csm/polyester panels.
You would need to add flanges to all of the panels. There are various ways to do this but probably the most common is bendy-board (thin MDF with lots of grooves in one side) or fibreboard (like the bottom of the drawers in cheap furniture) which are fixed in place with a hot-melt glue gun and then made ‘none-stick’ using masking tape with mould release wax on the masking tape.
To give you a really rough idea about how much Uni-Mould you would need to make a whole set of moulds for a car, I would think it would be something like 100kgs of Uni-Mould Tooling Resin, 25kgs of Uni-Mould Coupling Coat and 10kg of Uni-Mould Tooling Gel Coat. In addition you’d want about 10kgs of 150g CSM (Chopped Strand Mat) and 35kg of 450g CSM.
Here's links to the materials used in the Uni-Mould system:
Uni-Mould Tooling Gel CoatUni-Mould Coupling CoatUni-Mould Tooling ResinBefore pulling the mould, you would obviously prepare the surface of the pattern panels with a suitable release agent. Our Easy-Lease would work well or you could use wax and PVA.
There are some specific steps to follow when using the Uni-Mould system but most of the process is just like normal fibre-glassing. If you want to read up in advance then take a look at the Introduction and Application guide for the system.
Making the Replacement Carbon Fibre Car Body PanelsNow you get to the fun part, making the carbon fibre replacement panels. For panels this size where you’re after a show quality finish and want them to be as strong and light as possible then you really only have one choice for making them and that is to use a process known as resin infusion. In this process the moulds (made from Uni-Mould as described in the previous section) are prepared with a chemical release agent before carbon fibre fabric is laid dry into the mould (along with any other reinforcement that are being used such as glass or Kevlar and any core materials) and then the whole mould is enclosed in a special vacuum bag. The bag is connected to a vacuum pump and the pump sucks all of the air out of the bag, pressing the carbon and other reinforcements hard against the mould’s surface.
Once this has been done a special ‘infusion’ epoxy resin is allowed to be sucked into the mould and infuses through the reinforcement, wetting it as it goes. The resin supply is then clamped off and in many instance the pump is clamped off to and can be switched off. Once the panel has cured it can be removed from the mould. If the mould has a smooth, glossy surface then the part will have exactly the same smooth glossy surface. Resin infused panels will pretty much be as strong and light as any carbon fibre part could be with no trapped air-bubbles and no voids or defects.
To get a good understanding of the resin infusion process, please take a look at the video for our Resin Infusion Starter Kit which shows us making a large carbon fibre bonnet scoop using this technique. Although whole body panels are larger than the scoop we make in the video, the process would be exactly the same and the vacuum pump we include in the kit would be more than adequate for any size car panel.
The reinforcement for the panels themselves could be almost any combination of carbon, Kevlar and core material, depending on how strong or how light you want the finished panels to be. For race car parts we sometimes only use 1 layer of 200g and 1 layer of 450g. This makes for a carbon panel only 0.75mm thick, clearly this is very thin (and so very light) but it certainly wouldn’t be enough for daily use.
A really nice combination for body panels (which I know we supply to many companies making such parts) is a single layer of 200g carbon, a single layer of
3mm Soric SF core material and then a final layer of 200g carbon on the inside to balance the laminate (make is symmetrical). This layup has two advantages, one is that the 3.5mm overall thickness seems to be a nice thickness for a body panel, proving to be plenty strong enough and yet, because the core is low density, very light. The other advantage of using Soric is that it acts as an internal flow media for the resin infusion process meaning that you don’t need peel ply or infusion mesh – instead the resin runs through the Soric and wets out the surrounding carbon.
To give you an idea of costings on the panels themselves, you’d be using a combination of 1m wide, 1.25m wide and possible (in places) 1.5m wide carbon cloth. The classic fabric for the surface of your moulds is 200g 2/2 twill. There’s some links to those fabrics below:
1m Wide 200g 2/2 Twill Carbon Fibre Fabric1.25m Wide 200g 2/2 Twill Carbon Fibre Fabric1.5m Wide 200g 2/2 Twill Carbon Fibre FabricIf you went with the layup I’ve suggested (200g carbon, 3mm Soric SF, 200g carbon) then you’d need 2sqm of carbon cloth and 1sqm of Soric for every 1sqm of body panel you’ll be making. If we have a wild guess at 15m sqm of body panel on your car then you’re talking 30sqm of 2/2 twill, 15m of Soric SF and 21kg of
IN2 Epoxy Infusion Resin in the finished panels. Given waste and the way the different shapes will come out of the material I think you’d need to consider at least 30kgs of infusion resin, 20m of Soric SF and up to 40sqm of carbon fibre cloth.
It’s a considerably investment but then, including purchasing all of the mould materials, vacuum equipment and materials to make the parts you’re still going to be looking at considerably less than the cost of purchasing those parts and they’re likely to be much stronger and lighter (and of course made to your unique shape) than anything you could buy.
I hope this helps and look forward to supplying you.
Matt StathamEasy Composites / Carbon Mods - Technical Sales