September 06, 2020

DIY Carbon Fiber - 5 Tips and Tricks

10 MIN READ

guides , diy , wrx

When I first tried my hand at carbon fiber skinning, I didn’t really appreciate how much work it would be. There were a few cautionary forum posts and YouTube videos I’d watched that warned me - “It’s not for the faint of heart” and “It’s a lot more work than you think”. Boy were they ever right…

Working on a few carbon fiber parts

The good news is that my pain is your gain! After over a year of experimentation, I’ll be going over five of the most important lessons I’ve learned. I won’t be rehashing any of the basics, so if you’re just getting started, I’d recommend checking out the DIY Carbon Fiber post first.

#1 - Don’t Reuse Brushes

Trying to be frugal with materials can lead to a lot of frustration. It’s almost always safer to cut the carbon fiber oversized, mix more epoxy than you need, and use a new brush every layup.

Initially, I had decent results cleaning out my brushes. Spritzing the bristles with a spray bottle of 50/50 isopropyl alcohol and water or paint thinner, I was able to get two to three uses out of a single brush.

Unfortunately, I began to realize that any leftover epoxy in the brush would turn to gel and eventually harden. Trying to apply the second or third layer of epoxy with bristles like this messed up the weave of the carbon on more than one occasion. Because of this, I’d recommend stocking up on brushes (I picked up this bulk pack on Amazon) and dispose of them after each use.

Bulk pack of paint brushes

On the other hand, mixing cups are easily reusable. I’ve mixed dozens of batches in a single cup with no issues. You just have to be diligent about cleaning them out after each use.

Sometimes though it’s safer to stick with single-use cups. Especially when applying the final layers of epoxy, keeping the cup and mixed epoxy as clean as possible means less sanding after everything cures.

#2 - Base Coat + Spray Adhesive

Laying a chunk of carbon fiber seems pretty straightforward. Unfortunately, parts with lots of curves or sharp edges can be problematic. As the resin cures, it can pull and lift the carbon fiber leaving you with gaps and air bubbles.

The carbon fiber bubbled as it cured

There’s a few ways to prevent this, the easiest of which is to use a spray adhesive like 3M Super 77. Apply a thin layer to the back of your carbon fiber and use your fingers to gently work the fabric onto the part.

An alternative method is to lay a base layer of resin, let it cure to tack, and then lay your carbon fiber. One advantage of this approach is you can use black pigment to die the epoxy. This will help mask lighter colored parts from showing through the final weave.

Black tinted epoxy resin

Unfortunately epoxy isn’t as “maneuverable” as spray adhesive, and it can be harder to conform the carbon fiber around curves and edges. Another drawback is that the ideal cure window for resin is pretty short. If you try to lay the carbon fiber early, the epoxy won’t be sticky enough and the carbon won’t stay put. Too late and the carbon won’t adhere at all.

I’ve found the best solution is a combination of both. Laying a base layer of black-tinted epoxy, letting it dry to a tack and then using spray adhesive to help fix the carbon fiber into place.

One cautionary note - if you’re laying up carbon over tinted epoxy, you’ll want to avoid pressing too hard on the fabric.

Recently I was experimenting with techniques to fully saturate the carbon fiber, and used some release film to really press the fabric into the base coat. This resulted in the darker epoxy bleeding through the gaps in the carbon fiber, and left a blotched-looking finish.

Black epoxy bleeding through the carbon fiber

#2 - Vacuum Bagging

When doing my initial research on carbon fiber, a lot of the tutorials I was watching made no mention of vacuum bagging. In fact, for a while I was convinced it was really only necessary if you were an F1 team or building supercars. After all, the cost of investing in professional vacuum pumps and bagging materials is pretty significant.

Since then, I’ve found that using vacuum bags as part of the layup process is not only beneficial, but entirely feasible on a budget! In fact, for the average DIY’er, there’s a couple of options that are just as effective as the professional tools.

The first solution is to use the same type of store-bought vacuum bags you’d put extra clothes in. They come in all different sizes, and most include a hand pump, which can be very helpful.

Using store-bought vacuum bags

Pumping the air out by hand means you have more control than hooking up your household vacuum cleaner and hoping for the best. Here’s a set I picked up that’s worked great for me.

The second option is to use plastic food wrap or window shrink film. This option won’t work for parts with complex curves or lots of holes, but for simple stuff, it’s a great option. Using a variety of tape and clamps can help keep things from shifting.

Saran wrap + painters tape and some clamps

In either case, you’ll want to make sure you utilize some form of peel ply and breather cloth in between the bag and your parts. These are specialized fabrics that allow excess resin to be pulled out of the carbon as it cures. Doing this helps create a nice even finish while simultaneously eliminating air bubbles - meaning less frustration when sanding. Speaking of which…

#3 - Sanding, But Not Too Much

This is the area I need the most improvement. There’s been too many times where I’ve gotten overzealous and ended up burning right through the epoxy and carbon fiber.

Because of my many failures, I’d recommend laying as many layers of resin as you can before you do any serious sanding. This should build up enough material for the first round of leveling sanding, but you’ll need to be careful you don’t go too aggressive with the sandpaper grit (220 or 320 max).

Wet sanding to a matte finish

Be sure to take extra care when sanding in corners or near the edges of your parts. These are areas that get less resin and are super easy to burn through with sandpaper. When in doubt, sand as little and lightly as possible and add more epoxy.

Once you’ve applied a few layers of resin and cleaned up your edges, make sure to test fit everything in the car. Depending on where/how the part is installed, the tolerances can be tight. Figuring out how much material you need to remove at this point is a much less of a headache than waiting until the finishing steps!

Test fitting before final sanding

#4 - Clearcoat Alternatives

When it comes to choosing a finish for your parts, it’s important to remember the application. If any portion will be exposed to sunlight, you’ll want to make sure you finish the part with a UV protectant.

In the past I’ve utilized a 2k rattle can clear coat. This is a reliable option and leaves a super strong glossy finish. Unfortunately, you only get about 48 hours of use out of a single can. At over $20 a pop, this gets expensive quick! And to make matters worse, you only get one or two shots to do it right as you probably won’t have enough time to re-coat if there’s any sanding needed.

Because of these limitations, I’ve been experimenting with a UV-resistant epoxy from Composite Envisions - UVPoxy. The main benefit of this solution being you can mix only what you need, and there’s less pressure to get a perfect finish the first time round.

UVPoxy from Composite Envisions

I’ve found that the UVPoxy is pretty durable, but it doesn’t quite match the hardness or clarity of the 2k clear. This means some wet sanding and polishing to create the perfect finish.

Ultimately, if money was no object I’d invest in a proper compressor/spray gun setup and shoot all my parts with a proper clear coat. However, I’m very happy with he flexibility and gloss of the UVPoxy, even if it does require a bit more elbow grease to get that perfect finish.

UVPoxy finish

#5 - Don’t Be Afraid to Experiment

There’s no substitute for practice. After months and months of experimentation, and over a dozen different projects, I’m still learning something new every time and making plenty of mistakes along the way.

Scouring eBay for used interior parts can be a great way to find new stuff to wrap. Not to mention, you can save a few bucks and buy scratch and dent items since you’ll be covering it all up with carbon fiber anyways!

eBay is a great place to find cheap parts to wrap

The bottom line is this: The more mistakes you make early on, the more quickly you’ll improve. Expecting perfect results right away will just set you up for disappointment.

I’d also recommend searching YouTube and Instagram for inspiration and tips. I’ve learned a ton from just watching other people work. Here’s a list of a few of my favorites, in no particular order:

Conclusion

These are just 5 of the lessons I’ve learned over the last year. There’s lots of little ways I’ve improved my process too, like figuring out the best way to mix the resin to prevent air bubbles, types of brushes and mixing cups to use, etc.

While I’m far from and expert at this stuff, each project has been less intimidating than the last. The results are always rewarding, and it’s awesome to be able to make some unique carbon fiber goodies for friends too!

Finally just for fun, here’s a few pics of the kinds of parts I’ve been working on over the last 12 months:

Carbon fiber hazard buttons

Carbon fiber door handles

Carbon fiber dash trim

Carbon fiber dash trim

Carbon fiber shifter trim

If you’ve got specific questions or just want to share your own carbon fiber projects, shoot me an email at [email protected] or a DM on Instagram! I’d love to see what you’re working on!

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