Splitter support rods, how to make them go away
 

Splitter support rods.
We rarely use them @ BFW but I see all the time, splitters getting mounted via external support rods.
There are only very specific reasons why we would use them at all and in 90-95% of the cases I see they can and should be eliminated.

Problem:
External mounts such as support rods or cables increase drag / decrease efficiency.

Question:
Are they even needed?

Answer:
Unless you're running a gigantic splitter (think Bullet) you can probably do without them, and even if you are running a gigantic splitter there are still ways to avoid them, but it takes more work and planning (think HyperMiata and Morpheus / Creampuff).
Your typical 4"-6" Birch / FG top splitter will easily support itself with proper mounting without the use of any external support.

Solution:
Tuck all mounts and supports behind the bumper, right behind the bumper.

How to:
A typical splitter has a mushroom shape when viewed from above.
There are many solutions as to how to mount the "stem" of the mushroom at the subframe, so I won't go into this, but it's the front of the mushroom that sees all the load and thus needs the support.
What we typically do is to build an arch shape frame that tucks right behind the bumper / air dam / lower lip, bolt the splitter to the arch, and hang the arch on the core support / front frame.
It doesn't even need to be a full arch, you can just have a few individual mounts along the way.
The idea is that the closer the support is to the front, the less unsupported area there is to worry about..

Example:
Creampheus' old splitter was 3/8" Baltic birch (higher layer count than your typical HD variety, thus stiffer to start with) with one layer of CF, but can be done the same way with FG.
Despite the fact that this splitter is even bigger than the typical ones (5.5" on center, 8.5" sides), and has BIG diffusers and end plates to increase the load even further, there are no external mounts past the air dam -

https://cimg3.ibsrv.net/gimg/www.mia...e00519c50e.jpg

https://cimg6.ibsrv.net/gimg/www.mia...b76d0c0d5c.jpg

HTH!

Unless your splitter is fricking huge it's not hard at all to hide all supports behind an airdam, even for a streetcar.
Behind the airdam, 4 turnbuckles for main support, attached to the frame, 2 secondary metal trips to support the corners of the "mushroom"
https://cimg5.ibsrv.net/gimg/www.mia...4a473f108c.jpg
All supports hidden once the airdam/bumper is on.
https://cimg0.ibsrv.net/gimg/www.mia...57de324a96.jpg
(To be clear this is an agreement with Moti, just showing a slightly different method).

Dont even need an air dam to hide them all. Not shown in this picture are the outside cables that go to the end of the aluminum angle.

https://cimg9.ibsrv.net/gimg/www.mia...104a62578b.jpg
https://cimg0.ibsrv.net/gimg/www.mia...bcae342b44.jpg

My design is the same, with the exception that my strut rods go to two separate locations, each attached via a clamp to a round tube frame rail, since my RX7 is round tube from the strut tower forward. My 250# self could stand on the COT front splitter at 4 1/2" overhang without issue, and that is without the luxury of being supported at engine crossmember from a full underpan up front. I will be making a lighter version as I transition to full pan birch/CF combo very much like what Moti has in that picture.

Sidetracking a little bit, but Moti, why is plywood the go to base material for splitters? Would alumalite not still be the prefured materal as it's lighter and stronger then plywood? Or does the resin not play nice with alumalite's smoother surface and bond better to the more porus plywood? Seems like there's a good bit of weight to be shed moving to 6mm alumalite wrapped in carbon.

Alumalite is lighter, but the 3/8" Baltic Birch / CF is definitely stronger.
Birch / FG are also cheaper and readily available at your local HDM.
I wouldn't use 6mm Alumalite for a splitter either, it's just not strong enough, for splitter I'd use only a 10mm.
There's no need for a layer of composite on top when using Alumalite, it's not porous.

There's definitely a good amount of weight to shed going to other materials, the Hammerhead splitters that Ryan and I built for our car are MUCH lighter despite their colossal sizing.
The pricing, however, would make most Miata owners cry tears of blood.
Still no external supports :)

https://cimg4.ibsrv.net/gimg/www.mia...e0db1b9dc4.jpg

Going to take this as a lesson learned thread for me. I currently use 2 support cables out the front of grille opening on my "first attempt at aero" setup, but moving forward with my V2.0 10mm alumalite design I noticed that's not needed.

Well good, the whole point of sharing my knowledge is to help users like you, so I'm glad to hear this :)