If I am reading your plans correctly, the step between the two plates will be 1/2". I don't think that's enough to matter on a structure as aerodynamically "dirty" as a Miata underbody. On an Indycar or NASCAR, both very finely tuned aerodynamic shapes, yes.
I think 1/2" is overkill for the two plates. That's 1" on birch. If clamped together over a wide enough area, they effectively become one. That's a lot of mass. I'd consider doing both plates of 3/8" and making the lip section a bit less area. Just to save mass. When it's all bolted together and on the car, it should still support your weight when it's extended around 4" from the dam.

Thanks for your advice. I will do my best to minimize the mass. I went with 1/2" for two reasons.
1. I only wanted to buy one sheet of plywood.
2. I was worried that after countersinking the grooves in the splitter with 3/8", there would only be about 1/8" of material clamped under the washers. That seemed like a bit thin. 1/2" gives me more like 1/4" of material.
Another option would be to use 3/8 on both panels, but not countersink the grooves. The bolt heads would protrude but not by much.
Or, if you think 1/8" of material at attachment points (using 2 layers of 3/8") + cables out front would still suffice, I will try that.

Thanks again.

I would think dome head bolts and the thinner lighter ply would be better,IMO anyway.

Thanks for the post, it reminds me to make a better version of our basic splitter as well. Same reason, adjustability/fine tuning but mostly for getting on and off the trailer as well :)

Thanks.

This image was released today of the new Supercar DJR Penske Mustang at Adelaide. I thought the raised edge of the splitter was interesting, not to mention the intake, rad/cooling and size of the brake ducts.

The splitter leading edge has me intrigued though. Any thoughts...?




https://cimg9.ibsrv.net/gimg/www.mia...0025144ca1.jpg

Just finished this splitter design with the help of a friend. Its 1/2 birch and runs under the oil pan. However, I want to try something new so I purchased 2 sheets of 6mm Alupoly. I will report back how it holds up.
https://cimg8.ibsrv.net/gimg/www.mia...f0ea1414bf.jpg
https://cimg4.ibsrv.net/gimg/www.mia...b004e604b7.jpg
https://cimg6.ibsrv.net/gimg/www.mia...ab726626be.jpg

It looks like that Alupoly is just as heavy as 1/2" birch and isn't nearly as tough. Alumalite is what you want if you're looking for lighter.

I will make sure to post the weight differences once I complete the splitter.

Reducing spill-over (and thus pressure loss) of the high pressure on the splitter by a fractional amount.
Those brake ducts are indeed massive.
I'd be interested to see what the ducting behind the grille looks like.

Density and other data for Alupoly
https://www.piedmontplastics.com/blo...upoly-overview

So my 1/2 inch birch splitter comes in at 12.5 lbs vs the 1/4 inch Alupoly at 15.2 lbs. The Alupoly has some flex but it's usable and passes the body weight test.
https://cimg2.ibsrv.net/gimg/www.mia...61f5167977.jpg
https://cimg3.ibsrv.net/gimg/www.mia...32f31fba54.jpg
https://cimg4.ibsrv.net/gimg/www.mia...cca822fa2e.jpg
https://cimg5.ibsrv.net/gimg/www.mia...fad8a84fc5.jpg
https://cimg6.ibsrv.net/gimg/www.mia...1635e057ec.jpg

Your using the wrong material if a quarter inch is heavier then a half inch of ply.
10mm alumalite is lighter and stiffer then ply.

I agree the material and weight is not ideal. However I bought 2 sheets so I will use it for now. If all else fails I'll return to my birch splitter. The s2000 community has been using this for sometime so I have a little hope.

Thanks for the input

New carbon fiber foam core splitter designed by Robert Thorne and myself. Splitter blade made by Ryan Neff and Mike Forsythe and Zebulon MSC. Tunnels designed and made by Robert Thorne.

This splitter literally hit the tire wall at turn 5 at Road Atlanta this last weekend and did not sustain damage. You can jack the front of the car up using the splitter or stand two guys at the outer edges no problem.

https://cimg9.ibsrv.net/gimg/www.mia...f8107c38dc.jpg

https://cimg5.ibsrv.net/gimg/www.mia...10fbce4b19.jpg
https://cimg3.ibsrv.net/gimg/www.mia...5134ff3ba0.jpg
https://cimg4.ibsrv.net/gimg/www.mia...a1404770a4.jpg
https://cimg5.ibsrv.net/gimg/www.mia...d76b5e07c1.jpg
https://cimg6.ibsrv.net/gimg/www.mia...1b1247998a.jpghttps://cimg4.ibsrv.net/gimg/www.mia...173f31b85f.jpg
https://cimg5.ibsrv.net/gimg/www.mia...e890e67612.jpg

This is exactly what I'm planning on doing next for my car. What thickness core did you go with, # of layers and type of carbon weave, and why carbon over s/e-glass? I'm likely going to be using a couple large ProAwe diffusers so I don't have to design my own from scratch.

Nice job! Thanks for confirming that the pink insulating foam is a useful stiffener! I was planning on giving it a try for barge boards.

1” pink foam core, 2 layers on top, 2x2 twill 3k and 12k I think, 2 12k on bottom. Ran out of carbon on the tunnels so that’s why on the s/e glass

So the splitter has a 1" thick foam core? Looks a lot thinner than that. Nicely done!!

I have a question about my design. Would it be worth it to get rid of my homebrew canards/lip and use the .100 HPDE sheet instead of the lower half of my factory bumper? Splitter is paired with a Singulär Motorsports Wing in the rear.

Pictures don't show ducting but it will be there before my next event. I just cut the front crossbar off and need to make new ducting.

I usually pull the wing and splitter off for street driving but I could get a spare front bumper and just swap that out too for the track. Thoughts?

https://cimg8.ibsrv.net/gimg/www.mia...cc98ee5638.jpg
This picture is from before I bolted the new front splitter mounts to the splitter.
https://cimg4.ibsrv.net/gimg/www.mia...26a4b4a425.jpg
Current splitter design with new front mounts. Weight tested with my bodyweight (it was nerve wracking to stand on it)

Youve just blown my mind! Last projects I’ve used closed cell foam and the prices are outrageous. This looks roughly 1/10th the price. Any prepping needed to the foam. I was thinking it came with a plastic lining on it.