Or just making it look cleaner by installing an undertray. I have no basis for knowing whether I’m truly helping ground effects with this addition to the car, but it does make for a cleaner look in my opinion.

Here’s whats going on. The car essentially has a flat bottom all the way from the very front of the to where the engine bay begins. This includes the front splitter, the area under the driver compartment and the area under the fuel tank which is between the driver compartment and the engine. As a side note, I had a special order done on my car to have the same 1/4″ aluminum that’s the monocoque under the driver also welded under the fuel tank. Typically this is a thinner gauge (1/8″), but I figure it’s a good safety measure at a $150 total cost to make it 1/4″ welded aluminum.

Looking further towards the back of the car, I wanted to have the flat floor “undertray” go as far as possible so I decided to add a roughly 22″ square panel in front of each rear wheel well. The reason for not doing a full side-to-side panel is that you want to leave the part under the engine open to allow for air flow around the engine.

Off I went to research how to buy custom cut aluminum and as it turns out what looks to be San Francisco’s premier metal supply shop, Bayshore Metals, is less than 5 minutes from my place. Two hours and $80 later I what I needed: custom cut 1/4″ 6061 aluminum. 6061 is colloquially “aircraft aluminum”, i.e. the stronger variety that isn’t bent as easily. It was recommended by fellow builders to save money and go with a thinner gauge here since it’s not structural, has no safety implications and since it has a greater chance to be banged around a little, replacement is easy. That’s also part of the reason I screwed it in with 3 through-bolts on each side with a layer of silicone between the frame rails and the plate to prevent vibration noise.

That was all. Pretty simple job. Now I have an even longer and cleaner car floor. And zero clue whether this is helping ground effects in any way, but it looks cool, right?