Thats because you want polypropylene sheet. Hdpe isn't typically flexible enough for this, and if it is is specialty. If you can't find it at a race shop your local plastics supplier should be able to get it.

I have sheets of this stuff at work, the hdpe. 1/16 and 1/8". Rolls up reasonably for me. I mean, you can't be a pussy about it.

The stuff from speedway is 1/8" hdpe. In rolls.

Two parter for you guys - first: What are your thoughts on a flat floor inlet that it slightly higher than the middle of the system? I have a situation loosely depicted as attached (blue line), where the splitter height is not the lowest point in the system, as there needs to be a dip to clear some exhaust and bellhousing components. I can continue the floor relatively flat from there (maybe two inches or so below the floors "rails" due to exhaust clearance again) before increasing the angle starting just forward of the rear diff, with a clean shot out the back of the car from there. Will I end up with a parachute effect and frontal lift with a flat floor, or a pseudo venturi effect? The car will have a slight forward rake to it as well. For a number of practical reasons, I do not want the splitter and engine bay under tray any lower than it is.

Also, any creative mounting suggestions for a "drop floor" other than the obvious c-shaped brackets scattered throughout?

There's potential for it to act as a venturi, but with the positioning of the different levels dictated more by necessity than by ideal placement, it's likely to cause more drag without more benefit compared to just being flat front to back. To have the best shot at a minimal venturi effect, try to make the transitions with long gradual angles instead of an abrupt change and move your diffuser throat as far forward as possible. The forward rake helps.

I can likely smooth the transitions out some, but I guess the burning question, is do the pros of having a "flat-ish" floor as depicted above and clean air to the diffuser outweigh having nothing under there at all? I would like to think that the despite the elevation change in floor height, the smoothing of the undertray will do more good than harm?

Yes, better than not having it, particularly if you have a diffuser you're trying to make function properly

After a mixup at my steel supplier, I've got $240 worth of 4'x8' dibond sitting in my garage, so there's going to be one there if it kills me!

Had a lot of fun last Saturday at the Autodrome St-Félicien and my wife took that picture where you can see the new aero at work.

The car feels a really more stable in the turns and is a lot quicker. I also see that I've still got a lot of body roll, those 504/336 V-Maxx Xtreme Track Pack seem overwhelmed.

Speedway motors plastic roll and Home Depot Lexan for the win! Need a hard top to finish the aero package on this one...

https://c5.staticflickr.com/9/8841/2...bf2c668a_b.jpg
DSC_0768 by Claudia Blanchette, sur Flickr

Hey guys,

Just making up a new splitter and I just thought I would put the plug up for any criticism/advise before I start making the mold.

It will be CF vacuum infused from a mold, so what is in the picture is the top shape.

The front will be 100mm from the front of the car, as per 2b rules for the class I run in, and the back will be at the leading edge of the front tires, again class rule.

I'm not sure you want the raised channels opening up into the leading edge of the tyre. The point of these is to create a low pressure zone under the splitter so that you get a larger pressure differential from top to bottom. In order for that to work you need clean laminar air flow running through those channels and if it hits the leading edge of the tyre on one side it will back up into the channel reducing the effect. Ideally you want it exiting well inside the edge of the tyre. The flaring is good as it helps generate that low pressure air as long as you don't take it too far.

I'm planning on something similar once I destroy my plyboard splitter.

Edit: I'd also try and smooth the entrance angle a little. You look like you have around 12 degree change in angle and this might be at the limit of the air flow separating and stalling. You just need a 50mm strip that chamfers the two angles so it blends a bit nicer.

Whiskers
 

https://cimg7.ibsrv.net/gimg/www.mia...f14be9e977.jpg

https://cimg8.ibsrv.net/gimg/www.mia...15f8119db9.jpgThe Catfish FINALLY has some whiskers!

As Madjak said, angle transition is too abrupt and angle is too steep. Don't get greedy on the angle, more is not better. Maximum 10 degrees, and if you're making it from a composite then there's no excuse not to make it with a nice gradual curve rather than a sharp angle change.

Can't tell from the pic, is the center section angled as well?

Yes the tire's presence does reduce the effectiveness of the diffusers, but it's still very effective. At the front of the car you're pretty much stuck with having the tires in the way, but you'll still net more downforce with more diffuser area than if you were to do, say, a small narrow diffuser that only directed air where the tire doesn't obstruct the flow.

Madjak I don't know how you did it but you're pretty much spot on with the 12 degrees. I did intend to go 10, and measured it out for that, however I forgot to take into account material thickness.

I was also looking at the tires and thinking contemplating the same, but I came to the conclusion that no matter what air was going to hit it, and I guessed that everything was a trade off, I just didn't know which was better, more diffusing or less tire.

ThePass, yep the center part is raised, unlike the last design though it will not go straight into the steering rack and will be just under it (if i didn't stuff up the material thickness that is). I'm just concern that I'm trying the raised bit at the front to grab some more air so I want a bit of diffusing straight after it.

I could make the two end diffusers take more and push them out to the sides instead?

I totally forgot about making a nice smooth transition as you both pointed out, and I will make the channels something like the attached picture.

Thanks for the feed back guys, Il'll post up the changes once I get them sorted.

Hey guys, I've joined up since this seems the best (and only!) Proper DIY aero thread on the whole of the internet and I've been lurking to follow progress for many months now. I've got a Nissan 200sx and am working on a front splitter/diffuser currently, with flat floor and rear diffuser etc planned for the future. I'm lucky that I live in the UK's "Motorsport triangle" so have loads of suppliers local.

Tim, with your front splitter, why not use a strake along the line of the front wheel edge? That'll tidy up the flow in the clean inside channel, whilst still allowing the outside to generate some downforce if the tyre blockage isn't too great?

Did a size comparison between the GT-1000 that Morpheus is getting to the factory wing on a customer's GT3RS :rofl:

https://cimg3.ibsrv.net/gimg/www.mia...5962685d58.jpg

Maybe I missed this, but what span are you using? Looks like you need a bigger car to match :)

71" width.

Geez that thing's huge! Are there plans for bigger endplates?

Those are just the pieces of plywood that APR ships the wing with to hold the two elements together, not the actual end plates.
I typically run much bigger end plates -

https://cimg0.ibsrv.net/gimg/www.mia...9e22478389.jpg

That was my thinking too, will probably be two strakes making them 3 sections.