Simple front splitter design

[R59]

OK then, what's the best source of info for making a front splitter?

I want a robust design, that's simple and effective. Doesn't have the be a world beater, just something that works.

I was thinking about a simple plywood sheet that extends forwards from under my exising airdam.

[phoenix]

Absolutely nothing wrong with using ply. It's strong enough and cheap to replace. A damaged splitter can be next to useless (and they are easily damaged) so it's better to have one you can cheaply replace than run with a damaged carbon fibre one, for example.

[1200Datto27]

Ply is also a lot cheaper and easier to test and modify to find the most effective design.

[ss_collins]

Try Aerobytes (in Racecar Engineering) - Simon McBeath covered splitter design recently - PM me and I'll send you an copy of it

[greenamex2]

Rob, the splitter on kit car which balances out a 100lb of downforce at 100MPH rear wing was originally made out of ply coated in green Cuprinol to match the cars colour. It extended fowarded about 3 inches at the front and an inch round the sides to help stop the displaced air slipping back under the car.

Coupled with a two inch 'step' at the front to form a simple venturi this is producing more downforce than the rear wing and is going to require a venturi at the rear to balance out.

The steering is also now so heavy due to downforce in fast corners that the car can be difficult to steer. Hopefully the forthcoming baby lifting exercise will fix that!

The splitter is now fibreglass and slightly lighter as a result but works the same.

Note that a real working splitter MUST have supports or it either isn't working or it will vibrate, reduce efficiency and break after a while.

I tried a splitter on the Corolla and it wasn't really deep enough to have a massive effect. The 40mm allowed by the regs was too little for a car with such poor underbody aerodynamics.

[richard_sykes]

For what car?

[R59]

Originally Posted by richard_sykes

For what car?

My ex-Thundersaloon Vauxhall Astra Saloon (nee. Belmont).

[enlashok]

if you want to make a front splitter you can also use lexan and paint it it is lighter and more durable then plywood albit slightly more expensive. be sure you are mounting the splitter to the bumper very securely also

[phoenix]

Originally Posted by enlashok

if you want to make a front splitter you can also use lexan and paint it it is lighter and more durable then plywood albit slightly more expensive. be sure you are mounting the splitter to the bumper very securely also

Does polycarbonate (Lexan) offer the same degree of stiffness as ply, for a given thickness?

[phoenix]

The reason that I ask is that the weight per cubic foot of some materials you might choose for a splitter are as follows:

Glass Fibre 105 lbs
Carbon Fibre 95 lbs
Perspex/Lexan 74 lbs
Plywood 55 lbs

[Al Weyman]

Rob,

I am in the sign business and we use a very versatile material called Foamulux, which is similar to the white cladding used in building and is a plastic close cell struture material with a finished outer skin, This stuff can be cut, planed, heat bent and retains its shape and I have sold sheets of it in the past to car prep companies, it comes in 8 x 4 sheets or 10 x 5 feet. I have used it to make up internal door pannels including bending over the top and shaped foot wells, cut to size then apply heat with a heat gun and push into the well, great. It is available in different colours. I don't know where you are but I always have a few scraps lying about you could use. Another great material although not so workable but a lot strionger is 3mm Raynobond which is an ally faced composite material with a resin core, light and strong.

[enlashok]

you are forgetting something. You dont use the same amount of lexan as you would plywood because it is much much stronger same with carbon fiber.
GLass would work well too dependinging on how well you can lay it

[phoenix]

I am not forgetting anything; I asked IS Lexan as stiff as plywood; If a lexan splitter has to be thicker that a plywood one to get the same stiffness then it may end up weighing more than a plywood one. If someone has the stiffness figures for each material we can work it out. We use lexan windows 4mm thick and I believe plywood 5mm thick is stiffer, so a plywood splitter would be stiffer, weight for weight, than lexan.

Ridgidity of the splitter is very important; it generates a lot of downforce but if it becomes deformed under pressure a significant amount of downforce can be lost. I am sure lexan is stronger weight for weight than plywood i.e. it has a higher strength under bending loads and will not break so easily, but I think this is largely because it is a more flexible material and it will be deflected easier than plywood; the laminations make plywood very stiff. Properly layed up carbon would be the stiffest I am sure, weight for weight, I have seen carbon splitters and wing endplates shatter on impact.

[noquarter]

I have first hand experience in playing around with splitters. I ran an OW autocross car and after totalling a wing once I decided to build a splitter for an upcoming event.
I used 5mm Meranti mahogany plywood (real cheap) I found in the garage cut to 22 inch and 48 inch wide. My front track was 56 inches so I had to notch out a bit to clear the inside on the tires. The leading edge was 15 inches from the front tires.
I bent a 50thou Al channel 1.5"x1"and epoxied and rivetted it halfway across the span.
For the venturi I bent up a 50thou Al angle to provide an exit height of 1.75inches (I couldn't get the angle to hold more than that).
I mounted the whole thing with .125 Al plate to the nose box.
The thing was NOT fragile.

You know what....it produced more downforce at lower speed than the front wing. Enough that I had to increase the rear wing flap(s) angle....and it looked ugly....
So much so my kids told me to build a new wing !!!!

Total weight was 10.5 pounds. Weight for the wing (Aluminum, foam and FG) 18 pounds. The splitter has a lower CG too...

[R59]

OK, so I have some ideas on materials.

What I'm looking for are some simple designs now....

Rob.

[cannardd]

Marine Plywood is probably the best choice as it will survive getting wet better than normal plywood. Marine ply uses waterproof glues, normal ply doesn't.

[a_ahmed]

I know this is an old thread, but I am wondering how your progress came along. I hope you guys post some pictures.

I don't understand how this whole venturi thing works.

I want to build a front spliter on my s13 240sx (i think this is a UK forum? They are known as 200sx in europe).

I want to put a really big wing on the back... and I want to make a spliter/front aero that'll generate maximum downforce as possible. I run really stiff spring rates and r comp tires... so I want to extract as much grip and cornering speed as possible... heck it even helps with braking and stability in general...

I'd really like to see what you guys did...

[JohnD]

No one mentioned covering plywood with glass fibre.
Probably no actual fibre needed, just resin, as the wood provides its own 'fibres' for the composite, though a layer of tissue may help. The resin, several coats if necessary, gives a smooth surface that is hard, knock resistant and adds to the stiffness.
Cheap and repairable, though not the lightest possible.

John

[R59]

Holy thread revival Batman!

I didn't get that far with it. Having other problems to resolve first - mostly engine.

It's still on the list of "things to do", and ply is probably the way I'm going to go. I've also toyed with the idea of making a complete undertray with rear diffuser. Though it'll probably wait until I start on the next chassis.

[Supercar]

I have been running a 1/2" thick marine-grade plywood splitter for the last 3 years. Very happy with it. It survived a couple off gravel traps, no problem. Saved my low-hanging dry sump pump. An 8 or 10mm plywood would have been lighter and just as effective probably.

A friend and I tried a lexan splitter as a prototype, but he cracked it while driving around town, lexan is brittle. Lexan was also expensive, too flimsy or too thick, and quite heavy. So plywood it is.

A carbon fiber sandwich panel was quoted at $800 each, so no thank you. It would have saved me some 10-15 lbs, but I'd rather put that $800 into the engine or into a more lasting weight reduction like a CF hood.

My splitter extends 6" forward of the car. I read that they stop being any more effective if they are longer than 4-6". It ends at the centerline of the front wheels. I am thinking about using a thin plywood to make a smooth flat bottom and a diffusor, but I would like to reroute the hot exhaust away from it first.

[tzei]

Originally Posted by Supercar

I have been running a 1/2" thick marine-grade plywood splitter for the last 3 years. Very happy with it. It survived a couple off gravel traps, no problem. Saved my low-hanging dry sump pump. An 8 or 10mm plywood would have been lighter and just as effective probably.

A friend and I tried a lexan splitter as a prototype, but he cracked it while driving around town, lexan is brittle. Lexan was also expensive, too flimsy or too thick, and quite heavy. So plywood it is.

A carbon fiber sandwich panel was quoted at $800 each, so no thank you. It would have saved me some 10-15 lbs, but I'd rather put that $800 into the engine or into a more lasting weight reduction like a CF hood.

My splitter extends 6" forward of the car. I read that they stop being any more effective if they are longer than 4-6". It ends at the centerline of the front wheels. I am thinking about using a thin plywood to make a smooth flat bottom and a diffusor, but I would like to reroute the hot exhaust away from it first.

I've been running with 10mm ply that i painted first with water proofing paint (one that is used to preserve wood in moist conditions). This might be a bit lighter than marine grade - haven't looked into that thou. And by using stiff support rods i can alter its angle.

I believe that some sort of a household chimney insulating materials have been used in success to cope with temps when having a flat bottom.

[St Eval]

Any plywood with a WBP stamp on it is made with waterproof glue (that's most of them) this will be generally lighter in weight than a marine ply and certainly cheaper and more available.