Surface prep

Shoutout to Maciek and Nikita, our W2021 co-op, who are doing the heavy lifting on this (including writing this confluence page )

Sanding

As originally, the side panels were only sanded and primed where the actual panel was going to be, the tolerances were too small for a carbon fiber layup so we decided to prepare the mold so we can make flanges during our carbon fiber layup. Below are the areas that needed some additional sanding and the blue lines were the biggest issue as they were quite rough and needed to be somewhat smooth for the carbon fiber. We began with 150 grit sandpaper to sand down those bumps evenly and then worked upwards to 600 grit for a light polish and finished off with 1000 grit for even more of a polish.

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Bondo

For those who don’t know, bondo is an auto body filler used in various applications. Our main application of it is filling small cracks as shown in the two pictures below.

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You start by taking the Bondo putty out of the can and then putting the tiniest amount of cream hardener in it and then mixing it up with a plastic spreader. You finally apply it to the crack and watch out because it cures extremely quickly. it takes approximately 15 minutes for it to fully harden. Below is one of our results from applying Bondo:

This is the Bondo after applying it to the crack. As you can see, it’s not perfect and it’s still a bit rough. Thankfully, Bondo sands away really easily so it should be sufficient to get rid of big imperfections using 150 grit sandpaper and then polishing with 600 grit should be fine as a final polish.

For reference, below is a good video that teaches how to properly use bondo.

Mixing and Applying Body Filler - Bondo

Sealing

Next up is the sealing. Since MDF is a very porous material, without a sealer, primer and resin would just seep through and get absorbed into the MDF. For this step, only the edges shown in the sanding part had to be sealed. Below are two pictures showing where the sealer was applied on the front half and rear half of one side panel, the sealer was applied on the dark spots.

The front panel (pictured above and to the left) had around 450-500 mL of sealer applied in two coat, the first being near 300-350 mL and the second being near 100-150 mL. Meanwhile, the rear panel (pictured above and to the right) used around 150 mL of sealer for both it’s coats, the first being around 100 mL and the second being around 50 mL.

Priming

Primer is next, for this step, we started dealing with the whole mold, not just the edges, so, we added two coats of primer on pretty much everything. Pictures below are two of the molds that have been primed.

The rear half needed 300 mL of primer for each coat, so 600 mL in total and the front half needed around 200 mL of primer each coat.