ThePass

iTrader: (3)

I don't think I have pics of it but on Sean's we did a similar thing in the rear to what JPreston did in the pic he linked to except we made a steel bracket that attached to the splitter and the bracket slotted above the front subframe lip instead of the splitter itself doing that. That allowed us to run the splitter lower than that point.

Jpreston's is an example of brackets sufficient for an undertray only - no extension forwards of the bumper. You don't need much in that situation. However, it would not hold up well in offs. Dip two off where there's a bit of a drop to the dirt or find yourself straddling big rumble strips.. anything that pressed up on the splitter against the car's weight, and the straps that serve as brackets will likely fold/compress. Although, his is a bit higher than we run ours, so in his situation you might hit the subframe first.. (BTDT)

jpreston

iTrader: (4)

True. I'll do cables like E suggested, or a much stronger rigid setup on my next attempt. That undertray definitely bottomed out and hit curbs a few times though, and it held up fine.

aidandj

iTrader: (5)

Thanks for the advice guys. Picked up a 4x8 of 1/2" birch, 8ft of square tube, and a gallon of kilz. I was going to just do an undertray but I don't want to have to do this twice.

Would a front splitter and no rear aero unbalance the car significantly? I plan to make it easily removable, so I could always give it a shot and take it off if its too much. More front grip sounds nice though.

jpreston

iTrader: (4)

Definitely. I ran my PTE air dam (with the above undertray) without the rear wing once and the car was damn near undriveable. A well-designed splitter would be even worse. You could make other setup changes to work around it but you really need something on the back for good balance.

aidandj

iTrader: (5)

Thats what I was worried about. Hmmm. Guess I'll just stick to an undertray. Don't think I will have time to sort rear aero out.

ThePass

iTrader: (3)

SuperMiatas run an airdam with an undertray and need a lexan rear spoiler to balance. To balance anything more than a very small splitter you need a wing.

aidandj

iTrader: (5)

Hmmm. Good to know. What would you consider a very small splitter. I won't be running an air dam, just a regular NA front end.

Maybe I'll start decent sized and bring my battery powered jigsaw to the track. Cut off splitter material until it balances

doward

My GV lip + under tray and hood vent was balanced with a CoT wing at -2*.

aidandj

iTrader: (5)

Hmmm, I'm probably underestimating what a splitter will do for front aero. I'll read through the thread again.

Dustin1824

iTrader: (2)

For those thinking of bamboo, I considered it a year or so ago and found a local exotic hardwoods place and they had about 60 sheets of 1/4" stuff, I think it had 3 plys, definately not 5 ply. They basically wanted to give them away at $20 per 4x8 sheet, they had apparently been sitting for a long time because some rich guy ordered them but didn't get them exactly on the day he was promised, so cancelled on them and refused to pay. They weren't stored very well so they had some waviness.

Unfortunately, they were not stiff at all. They were pretty flimsy. This is just 1 data point though, it could have been because of weak glue or because the storage conditions, or many other factors. It was very pretty though!

If you look up stiffness values for bamboo, it should make a great material for a splitter, not sure why the stuff I found sucked.

Edit: just remembered the stuff I found was horizontal layout. I think vertical would be more stiff.

ThePass

iTrader: (3)

That bamboo place got back to me saying their 5-ply stuff had been laid up incorrectly and was pretty flexible. They say the 1/4" stuff is "pretty rigid", so apparently 5ply =/= 1/4"

cordycord

iTrader: (2)

I'd still check it out. Ryan, you've seen the aluminum tray under the front end of my Catfish, right? It bolts to the front bodywork and then is connected under the steering rack with the two M6 nuts that are sitting there. Have you guys considered doing this for your cars, and then just making an edge splitter that extends from the front of the car?



The big part stays under the bodywork, and the small splitter can be removed somewhat easily

aidandj

iTrader: (5)

I was thinking about something like that. Couldnt come up with a great way to connect the plywood together off the top of my head.

cordycord

iTrader: (2)

I'd consider aluminum under the bodywork and wood/tegris/other for the splitter. It seems like you guys could come up with something removable in a couple of days, the way you work.

Dustin1824

iTrader: (2)

Did some more searching today in the name of science.

1/4" bamboo plywood can come in single ply, 3 ply, and 5 ply. I found out that 3/8" thickness is pretty rare.

Aside from that, it can come in a horizontal layout or vertical layout. Keep in mind the layup can also be optimized for being stiff along the length or the width, just like any plywood and also composites. Cool stuff, but it's pretty expensive right now and not many places have it.

ThePass

iTrader: (3)

I may be having deja vu but I'd swear you and I have had this conversation before.. you're just messing with me now aren't you?

Aluminum isn't a popular splitter material. I'm a BIG fan of aluminum in general, but I don't like it for this application... You have to go way too thick (heavy) to get the rigidity you need.
0.125" thick (rough guess) aluminum at ~1.75 lbs per sq. ft. doesn't win any weight contests, and that's still not nearly rigid enough at that thickness to extend very far beyond the bumper without additional supports. I'm not doing the stand/bounce test on a 0.125" aluminum splitter edge...

Re: removable extension, I've thought about it before, but the answer has always come down to it just adds unnecessary weight. You have to overlap the two layers a considerable amount to get enough rigidity in the layer that extends outwards of the bumper, and all of that double-thickness is twice the weight of what you'd have had there if it was one piece. And again, now you need a substantial amount more support along the outer edge than you would've needed if it was all one continuous piece - we can run more than 6" of extension beyond the airdam without any support at all.

My current splitter transitions to half thickness in all the portion behind the bumper. At ~0.75 lbs per sq. ft. that is hard to beat without going composite.

aidandj

iTrader: (5)

How do you transition from 1/4 to bigger?

ThePass

iTrader: (3)

ApexAddict

Not really 100% DIY since I bought the diffuser off a buddy but whatever.

Dollars spent: $180 (diffuser, paint, and splitter rods)
Hours spent: 20-25
How effective: 2
Materials used: Paint, l-brackets, u-bolts, windlace, edge trim, splitter rods, and diffuser
Tracks tested on: None but will be tested at Thunderhill this weekend
Race/TT class built for: Just HPDE, nothing serious yet

ThePass

iTrader: (3)

Love the Lotus diffuser's look on the Miata. Had one on mine many moons ago. Good exhaust setup to make use of the existing center hole as well.