Light’n up. Building a Carbon Fiber roof.

For me, metal fabrication is more like 3rd nature. The past two and a half years has been a lot of metal fabrication and I’ve learned quite a bit. 2nd nature to me is composite fabrication. I’m finally at the point in the build where I can flex some carbon fiber skills. A hand full of years back, I owned my own business, where I developed and manufactured Moto GP body work, open wheel aero parts, R&D for factory Yamaha racing, just to name a few projects. Carbon fiber was a “black art” when I was first learning. Youtube has done a great job of showing people who want to get into composites step by step processes. I won’t get into the nitty gritty, but I’ll show you guys a few techniques that I learned in the 7 years that I was doing this for a living.

In my last post I was finishing the bodywork on the Z. The roof and quarter panels are laser straight and smooth so, I’m ready to make carbon fiber parts now. For all of the other parts I’ll be making, I will be using a technique called “Vacuum Infusion”. On the roof and quarter panels, I’ll be using a technique where I use the surface of the original body panels as the mold, as opposed to making a fiber glass mold off of the body panel.

That seems to be an unconventional method, right? I’ll be using this technique because the most important surface when fitting a carbon fiber part over an existing surface (like a roof) is the inner surface. It’s very hard to control the inner surface of a part that is made in a conventional mold. So let’s get started.

Step 1: I made sure my roof was very clean. I then applied mold release. It’s simple, wax on, then buff off by hand. I typically apply three coats. If you skip this step, you will be in a lot of trouble because the carbon fiber part will not release.DSC01640

Step 2: I then sprayed the roof with PVA (Poly Vinyl Alcohol). This is a sprayable mold release, and makes parts very easy to remove. It’s almost like a sprayable saran wrap. I typically spray a mist coat, then 2 full coats. Be sure to let each coat fully dry before applying the next coat.DSC01643

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Step 3: Once I had the PVA down, and it was fully dried, I mixed up the resin. I like to use surfboard grade polyester resin. I like this resin because is it is very UV stable. We have all seen a carbon fiber hood that has turned yellow. This resin won’t “blush” or yellow over time. The other reason I like this type of resin is it is crystal clear.DSC01680

Step 4: Once you have mixed up your resin, just brush it on. You want a nice thin and even coat. Use cheap brushes because you will go through a lot. Just be sure to pull any loose bristles out of the brush before you get started. If you don’t, you will be picking them out of your resin later.

You want your resin to be tacky before you lay down your first sheet of fabric. This generally takes about an hour or two (depending on temperatures and humidity). I use the finger print test. If you touch it and the resin comes off on your finger, wait longer. If you touch the resin and it just leaves your finger print, you’re ready to go. DSC01649

Step 5: I used 4 layers of 2X2 twill weave 5.7oz Carbon Fiber. I cut the carbon fiber fabric to the appropriate size, typically leaving an extra 2-3 inches of extra fabric in case “shit happens”.  Now is the time to call your buddy over for an extra set of hands, you will need the help when placing the fabric. DSC01654

We draped the carbon sheet over the roof and worked the fabric smooth. ** It is incredibly important that the carbon fiber is worked into tight areas and hand smoothed into the base layer of resin. If you leave any voids between the resin and fabric, you will have air pockets. The key is to take your time. You have one shot at this. You will not be able to pull the fabric off of the resin. Be methodical on your placement. DSC01652

Step 6. I let the first layer (seen above) sit over night. The next day I started off by mixing up resin and I “wet out” the dry fabric. You need to find a happy medium. Do not over saturate the fabric and do not leave any dry spots on the fabric. DSC01655

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Step 7: It get’s kind of redundant here. Once the resin gets tacky (about 1-2 hours), you add another layer of carbon fiber. You repeat this process until you have 4 layers (or desired layers). On the last layer, you will add 2 coast of resin, then a final wax coat. The extra coats will add depth to the part. You will need to sand the part, in my case the roof. The extra coats of resin will make sure you’re not sanding into the carbon fiber itself. If you sand into the carbon fiber, it will mess up all of your hard work and distort the weave.

Step 8: The wax coat is very important. The polyester resin will remain in a tacky state. On the final coat, I mixed a wax additive in to the resin. This ensures the part is rock hard. You will notice the wax coat gives it a dull finish. Don’t worry, once sanded, it will be clear. Once I laid down the wax coat, I let it air dry over night.DSC01661

Step 9: This is the most fun step: removing the part. I suggest starting with the least complex shape of the part, then working your way around. It’s going to make some pops, and you will feel the part releasing.DSC01662

Step 10: Step back and marvel at your hard work, as your just getting started.

Step 11: The least fun step: trimming the part. If you haven’t worked with composites before, it can be miserable. I highly suggest a respirator, latex gloves, safety glasses (I use a full safety shield), long sleeves, and pants.

Pro tip: Use baby powder on your arms and neck. This will clog your pores. Carbon fiber dust can be VERY itchy. I typically do the cutting outside with a Dremel tool and shop vac. DSC01671.JPG

See how tight the tolerance is? It fits prefect. DSC01674

Step 12: This is where you put your sanding skills to the test! I use a DA (dual action) sander and Dura-block foam sanding blocks. I started off with 80 grit sand paper to knock down all of the high spots, then I moved to 180 grit, and finished it off with 320 grit. Don’t mind the water spots.DSC01678

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So just to recap on the layering order.

  • Mold release wax. Wax and hand buff 3 coats.
  • PVA release. Apply with a spray gun. 1 mist coat and 2 full coats.
  • Resin (I used Polyester UV Stable) tack coat.
  • Carbon fiber fabric (let it sit overnight).
  • Resin coat.
  • Carbon fiber fabric.
  • Resin coat.
  • Carbon fiber fabric.
  • Resin coat.
  • Carbon fiber fabric.
  • Resin coat.
  • Resin coat with wax additive.

Of course, these are just the basics, over the years, I have learned a lot of tips and tricks.

I didn’t make this roof just for looks… Although it will look killer.  I wanted to shed some unwanted weight, so I put my good friend Mike to work by cutting away the old roof.DSC01667

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The next step will be to clear coat the roof. As I’m typing this I’m building the rear quarter panels using the same method. I’ll clear coat all those parts at the same time.

So what’s the verdict? I removed 23lbs of the steel roof and support structure. The carbon fiber roof weighs in at 6lbs. That’s a weight savings of 17lbs. I’ll have similar weight savings on each side of the quarter panels.

I just wiped the roof down with wax grease remover for this photo. I still need to clear coat it, but you get the idea.DSC01692.JPG

I’m really happy with the fit and finish. Now I’m onto the rear quarter panels. I hope this post inspires you to start a carbon fiber project. Early in 2018 I’ll show you guy a more advanced technique of vacuum bagging and vacuum infusion. As always, thanks for the read and be sure to post any questions you have in the comments section below.

6 thoughts on “Light’n up. Building a Carbon Fiber roof.

Add yours

  1. What would be the average cost for a piece like this to do it myself, material wise? I’ve always wanted to build some carbon stuff for my own car since there’s a few pieces that companies simply do not make and sell. I feel like the process of carbon fiber is just this untold secret legend that you have to somehow learn from someone experienced. I’m so glad to see it shared.

    Liked by 1 person

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