belly pan for race car

[Bennett_Racing]

hello all,

need to ask a question about making full belly pan for our race car. top speed is likely to be 220mph+

my question is this, will a full belly pan create lift? I REALLY cant have any lift as dangerous.

ok the purpose of it is to smooth air flow under the car.

advice please!?

photo of car


and bare chassis too


thanks

[ConnClark]

Hmm.... Thats a good question. I don't know for certain but my gut tells me it won't create lift.

I would view it like holding two pieces of paper parallel to each other with a small gap in between then blowing between them. Keeping the velocity of the air under the car might create a vacuum.

Edit: I should say reduce lift because you will have fast air moving over the yop of the car

[CapriRacer]

Well, MY gut says it depends on the angle of attack.

The body is going to act like a wing - and since the top is a longer distance than the bottom, you need to make sure the angle of attack cancels out the lift. There's no easy way to find this out, so you need to be looking else where for ideas on how to measure the lift. I don't think you can predict it easily without knowing what the full body is like.

[darcane]

Interesting...

This weekend I looked at an Altered that my Brother-In-Law is planning to buy since I am close to where the car is at and he isn't. The body is a little more aerodynamic than yours ('34 Bantam Roadster, hard to tell in this pic, but the body is as wide as the rear wheels) but otherwise pretty similar to your car. When it was last running, he was at about 210mph in the quarter.

His car didn't have a "belly pan" but it has an aluminum tray that is the full width of the chassis and extends from just behind the front wheels to the back of the engine where it meets up with the floor under the driver. The purpose is to catch oil and metal bits in the event of a catastrophic engine failure and the rules allow a tray like this instead of a diaper. Effectively though, it behaves as a belly pan. His car is lower up front than it is in the rear and I believe this tray generates some level of downforce based on the angle of attack.

The other feature I was a little surprised by, his car had no nose piece on it and no canard wings like yours. His car had no need for these and was quite stable without them.

[k.civic.f4i]

i say you're fine. plus you have that massive wing in the back and those 2 canard type things before the front wheels. people who run at the Bonneville salt flats SEEM to run with less than what you already have but of course that's a different application. do it!!!

[Bennett_Racing]

Originally Posted by ConnClark

Hmm.... Thats a good question. I don't know for certain but my gut tells me it won't create lift.

I would view it like holding two pieces of paper parallel to each other with a small gap in between then blowing between them. Keeping the velocity of the air under the car might create a vacuum.

Edit: I should say reduce lift because you will have fast air moving over the yop of the car

I do think so either but wanted to ask opinions....

Please note that the car does already have a 'belly pan' front front of engine to drivers feet so already about 1/3 to 1/2 of chassis,

[Bennett_Racing]

Originally Posted by CapriRacer

Well, MY gut says it depends on the angle of attack.

The body is going to act like a wing - and since the top is a longer distance than the bottom, you need to make sure the angle of attack cancels out the lift. There's no easy way to find this out, so you need to be looking else where for ideas on how to measure the lift. I don't think you can predict it easily without knowing what the full body is like.

The car does get bouncy at the top end, I have a photo somewhere with all 4 wheels off of the floor...

We are planning on moving the rear wing further back too, to create more downforce

[Bennett_Racing]

Originally Posted by darcane

Interesting...

This weekend I looked at an Altered that my Brother-In-Law is planning to buy since I am close to where the car is at and he isn't. The body is a little more aerodynamic than yours ('34 Bantam Roadster, hard to tell in this pic, but the body is as wide as the rear wheels) but otherwise pretty similar to your car. When it was last running, he was at about 210mph in the quarter.

His car didn't have a "belly pan" but it has an aluminum tray that is the full width of the chassis and extends from just behind the front wheels to the back of the engine where it meets up with the floor under the driver. The purpose is to catch oil and metal bits in the event of a catastrophic engine failure and the rules allow a tray like this instead of a diaper. Effectively though, it behaves as a belly pan. His car is lower up front than it is in the rear and I believe this tray generates some level of downforce based on the angle of attack.

The other feature I was a little surprised by, his car had no nose piece on it and no canard wings like yours. His car had no need for these and was quite stable without them.

We have a car like this (shown below) and yes probably better aero wise. We just dont want to add if it wont help (extra weight)

[Bennett_Racing]

Originally Posted by k.civic.f4i

i say you're fine. plus you have that massive wing in the back and those 2 canard type things before the front wheels. people who run at the Bonneville salt flats SEEM to run with less than what you already have but of course that's a different application. do it!!!

True. We are changing the front canards too, changing to large front wing mounted in front of everything else

[DonR]

Read your rules very carefully, you may be able to make a venturi shaped floor pan with side skirts. Similar to old ground affect F1 cars. This should create some downforce. If I remember some of those cars would begin to porpoise if not done right. You may want to think about that too.