How to Make a Cheap Carbon Fiber Splitter: The Quick and Dirty Way!

So you have your track car out, getting laps in on a beautiful day, and everything just seems to be going well, smooth and consistent… almost too consistent. You notice you are no longer reducing your lap times; you are hitting a proverbial wall. What can you do between now and the track day you have next weekend?

Oh yeah… you’re broke too, you know, because you have a track car and a racing hobby, and those tires? They aren’t getting any cheaper either.

There are a few options, but they all cost money. Plus, you know you have been getting some understeer lately too as you picked up time.

Well, a lightweight prepreg carbon fiber splitter with a robust foam core and machined inserts, especially designed by an aerodynamicist to create the shape of the splitter to flow just right, optimally balancing drag and downforce, would certainly fix your problem and likely get you a little more time. But I can’t justify that cost for a non-professional track car.

What if I told you there was a quick and dirty way to make a functional splitter, cheap and easy, and surprisingly quick?

I like to consider the value of the splitter, and as a consumable item that WILL get destroyed, I would prefer something cheaper, MUCH cheaper. So instead, I recommend you take yourself to Home Depot and grab yourself a big 4×8 sheet of 1/2-inch or similar balsa wood or whatever they have that may be most water resistant.

In this article, I’ll show you how to make “carbon fiber” splitters the quick and dirty way. I’ll be using some common tools for this one, so you can see how this can be done by anyone without special tools or equipment. I have also made a video covering this process as well, so take a look there for more visual information.

Please note that in the video and images shown, I am reusing a frame I made for a previous splitter. There are many ways to mount and attach your splitter, and I will not be covering the frame in this article, but you can see roughly how I do it. It’s just a box frame of aluminum square tube that bolts to the splitter with large washers and pass-through bolts and attaches to my chassis-mounted quick-release mounts. There are many available; the ones shown here are from The Build Journal. Other vendors, such as Professional Awesome, make some universal mounts that are highly recommended!

Getting Started

There are many ways to make a simple splitter, but if you are running your car in any particular series that has a rule book, double check the rules on splitters for your class and ensure that you are abiding by them.

The cheap and easy way to do this is to get some chipboard or cardboard to lay out your general shape. I prefer to use chipboard for most of my templates because it is clean, flat, and can be had in large shapes without fluting like cardboard, but you do generally have to buy these (I usually buy these from Hobby Lobby) vs. getting them for free if you have large cardboard lying around.

Lay the chipboard out underneath the edge of the bumper, lip, or whatever your lowest part of the bumper is, then with a block of wood, ruler, or something to consistently distance the marker from the edge, trace an offset shape. I did about 10 inches to fit within the ruleset of my class (GLTA Limited Class).

You will notice I did one side only; this is so that I can just flip the template over and the layout will be symmetrical. Once you have the template, lay it over your sheet of wood and start tracing your shape.

Cut your splitter shape

Once you have the front shape laid out, measure the width from the outer edge to the center of the car so you can cut the shape to extend as far back as you want. In my case, I am maximizing the ruleset that allows the splitter to extend to the front center axle line but not beyond. You will also need to measure the clearance along the frame to allow for your wheels to turn completely without making contact.

With the shape traced over the wood, use a saw to cut out the rough shape. Take your time here, and it will save you time later when we sand the shape smooth. Any wood-cutting saw will work, even a handsaw, but that will take a lot of time. I used a circular saw and a simple jigsaw with wood blades to cut mine out just to save time, but these are not necessary.

Inspect your edges closely; look for dents or knobs in the wood that will impact the smoothness of the front edge profile. I had a few dents that I keyed and applied some wood filler to and let it cure before moving on. You will want to spend the time to get the front edge as smooth and consistent as you can since the dents or defects will be visible with the carbon.

Finishing the Edges

There are a lot of good articles out there covering the shape and profile of a front splitter’s leading edge, but for this quick and dirty one, just follow the fundamentals and you will have the majority of the benefits without much hassle. The 80/20 Pareto principle is applied here.

Sand all of the edges of the wood so they are smooth. Pay particular attention to the front profile and add a large radius edge on the BOTTOM and a very small radius edge on the top; the front profile is important to the performance and effectiveness of the splitter. For all other edges of the splitter, you want to sand them so they are smooth and not squared off so that the carbon fiber fabric can adhere and blend properly.

This will likely take you the longest time to do; use whatever tools or sanding aids you have here. You CAN do this all by hand, and you will see I did do a lot of the splitter by hand, but a power or air sander will make your life easier if you have them.

Measure, mark, and drill your holes for your mounting solution; this will be unique to whatever car, attachment system, and even bumper differences, so I will not cover that here in detail. You will want these holes in place so future steps are easier.

Prepare for Carbon Fiber

Since we are effectively using the wood as a core material for our carbon fiber, you will want to prepare the surface for maximum adhesion. Thoroughly sand the surface with 80 grit for a strong mechanical bond with the epoxy. I also added a couple drops of black dye to the epoxy resin, as I did not want the light colored wood to show through.

In retrospect, I do not think this was necessary, and frankly, it caused more challenges than it helped. If you notice in the final stages, I had a bit of black dye resin ‘bleed’ through the carbon and create dark splotches, just for your awareness.

For this front splitter project, I used the US Composites 3:1 medium cure epoxy resin system. Mixed thoroughly, I spread it across the bottom side of the splitter first. Let the resin dry to a tack on the wood, then drape your carbon fiber fabric over the length of the splitter. Cut the excess fabric off, leaving enough material to weigh down the sides and hold it tight to the edge.

You can do this with whichever material you have or feel confident with. I used a heavy 12k 2×2 twill carbon fiber fabric from Composite Envisions. I am not sponsored or affiliated with Composite Envisions or US Composites; I just use their products often and highly recommend them.

Wetting Out the Resin

As the carbon fiber is draped and trimmed over the front splitter, mix another batch of resin and start to apply it over the fabric. Using a flexible body filler spreader is common practice, but a brush or even wood mixers can be used; this is often called “wetting out” the fabric. You want to apply light pressure with whatever tool to press the resin through the fabric and make a complete bond with the resin you applied directly to the wood underneath.

Be diligent and ensure you have no air pockets under the fabric or in the resin. Take your time here, but be aware of the working time your resin system allows.

With the fabric completely saturated and pressed down, allow the resin to cure. This begins an iterative process of applying resin, curing, sanding flat, then reapplying, curing, sanding, and repeating until you have a consistent flat surface. After curing, you will want to sand, cut, and remove the overhanging carbon fiber so the opposing side can drape and layer the edges.

Once completely cured & trimmed and you are satisfied with the surface quality, flip the front splitter over to the top side. This is the visible and cosmetic side. Ideally, any learning curve, mistakes, or tricks you have discovered occurred on the less visible side, and your learnings can be applied to the visible side for a better end result.

Repeat the same process of resin on the wood, then drape the carbon fiber and wet it out as you did before.

Finishing the Splitter

Following a full cure of both sides of carbon and the edges having been trimmed & smoothed and your mounting holes drilled, we can move onto the finishing touches.

Inspect the carbon for remaining resin drips and sand them down flush, round, and smooth; all of the edges should be carefully dusted with black epoxy paint over the edges and the drilled holes to blend the seam between top and bottom, covering any wood or edges of carbon. This not only protects and seals the wood more completely, but it also looks much better as well.

The last step is clearcoat; you will want to sand the surfaces with about 400 grit, keying the resin surface and the black paint in preparation for the clearcoat. If you have a compressor and HVLP paint gun with 2-part automotive clear coat and hardener, by all means use it. However, for the purposes of this article being quick and dirty, we are using 2k clearcoat in a can. Specifically, we are using Spray Max high gloss 368-0061 clearcoat, as it still uses a 2-part clearcoat with hardener but without any special equipment. You will need more cans than you think, so pay attention to the coverage details on the can.

Allow the clearcoat to fully cure, then repeat on the other side.

For mine, you may notice that I chose to use a clear satin on the bottom and a high gloss on the top; that was only because I had satin cans lying around, and I wanted to use them up.

Final Touches

Now that your front splitter is complete, you can choose to wet sand, cut, and polish it. I chose to do so and finished it with a black wax for a little extra cosmetic pop.

You will also notice I drilled holes along the front edge; this is so I can install some sacrificial pucks to absorb contact rash from the road. These also help reduce flutter from bottoming out and seal air from traveling underneath; for this I used AJ Hartman’s splitter scuff plates.

Lastly, I installed splitter end plates that I made, and my mounting setup uses 4x splitter rods, two of which are hidden behind the bumper and two out front. These are also AJ Hartman’s compressible splitter rods; however, I modified the bases by pressing out the roll pin and adding a removable pin with a detent retaining ball that was safety wired to the rod. This allows me to quickly detach the entire front splitter without tools, making it much easier to get on and off of a trailer if needed.

Wrapping This Up

There are definitely better, more ‘correct’ ways to do this, but this is a quick and dirty way of getting a chassis-mounted carbon fiber splitter onto your track car relatively cheaply and easily, giving you some much needed downforce!

With the wide tires, chassis-mounted aero front and rear, along with the MK60 Motorsports braking setup, this V8 powered M3 is a ton of fun on track!

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