Amount and distribution of downforce in a 2003 F1 car

[rich1701]

It's awesome that there is a 2003 mod in the works, I hope you take in to consideration the different balance properties of each car too, Though i don't know what capacity rfactor has to realistically replicate that.

[GGSF1]

It's awesome that there is a 2003 mod in the works, I hope you take in to consideration the different balance properties of each car too, Though i don't know what capacity rfactor has to realistically replicate that.

Well, this is just a school project which was proposed by 2 of my teachers, then I dediced to use rFactor.

But this doesn't mean that the project won't be continued, I would like to continue it to make a full mod, but it will be difficult because it would take a lot of time.

[GGSF1]

Hello, it's me again.

I just found this table:



And I just feel something is wrong there. I think that the 3000 kg value is right but the information of that table confuses me. I just don't know how they did the calculations, I measured the plan area of an F1 car (I used the F2002) and it's 4.1 square meters (without tires), so if you use some of the data of the table (for example, lift coefficient 2.63, speed 306 kph = 85 m/s, area 4.1) you get very high values (using the values I previously said you get 4849 kg). So there's something wrong on the values (which match the values of the F2000 posted in page 1).

I just hope someone can understand that table because I just don't know how have values been calculated.

Thanks in advance.

[newbie]

the area term in Cl and Cd is frontal area, not plan (top-down) area. this is around 1.4 m^2.

[GGSF1]

Earlier in that topic it was said that the measure lift you must use plan area, and to measure drag you must use front area I think.

The coefficient of lift wont be calculated for an F1 car, it will be found in the wind-tunnel or CFD because it runs directly from chord length and plan area etc - something that isn't directly applicable.

Oh and I've been an eejit, it's F = 1/2*rho*A*U^2*Cl - woops

The area is the plan area - the surface area that the air is subject to. 2.75 (or whatever it is after you redo it without my idiocy included) on a car that is 4.5x1.8 metres does seem a bit low but when you consider the size of the floor and the wings, it might not be too far off.

[newbie]

For racecars the convention that I have come across in the UK is to use frontal area for both drag and lift. there is no point in using one area for lift and another for drag because then your Cl/Cd (efficiency) ratio is useless.

"A is the reference area. NB for an aerofoil this is always taken as plan area because this is how the coefficients are expressed, but in the case of whole vehicles the convention is to use frontal area for both drag and lift"
- Simon McBeath, "Competition Car Downforce"

[Crazy Bored]

My friend has spent quite a bit of time modding the 2007-2009 seasons, updating the mod as the rules changed. He has wrote up a few things relevant to rFactor, you might find this post useful for making the diffuser.

http://f1elites.com/4d/?p=48

[monza17]

Hello together,

i like the effort you all are showing. GGSF1 i think the table you show (which i find wery interesting) has in the last column the downforce at the speed in the column left to it(which is also the maximum speed at that particular track).

I think A(kg) comes from french: Appuis=Downforce.
And that would explain all of it. 1500-1600kg is more realistic than 3000 because at 3000kg downforce (+600kg the car itself) the car would corner (with 1.5 tyre coefficient) with 9g theoreticly which is impossible, so with the 1500kg downforce like you shown it in the table the car would corner with 4,5g so its more like probably

[GGSF1]

This is exactly the way I used to check if the values were realistic or not.

I tried both values and there wasn't too much difference in handling (or I didn't notice much difference). But htere was a huge difference in the cornering, in the setup menu of rFactor there's a way to see the maximum cornering that the car can generate, with 1600 kg the value is roughly 4.8 g, and with 3000 kg the value is more than 7 g. So, if the tires are right, it looks like 1600 kg is more realistic.

But well, who knows, maybe the whole game is wrong and it can't be used as a simulator

[asdf10101]

I was just stating that if it's constant, it's an easy interpolation - none of the variables in F = rho*A*U^2*Cl change, apart from the velocity.

So, what's the units used to calculate Cl? Any guesses?
I used rho=1.21 kg/m^3, U=83.3m/sec, F=30kN and got A=2.75, probably square meters=)))
I guess it's too small for F1 car?

The coefficient of lift wont be calculated for an F1 car, it will be found in the wind-tunnel or CFD because it runs directly from chord length and plan area etc - something that isn't directly applicable.

Oh and I've been an eejit, it's F = 1/2*rho*A*U^2*Cl - woops

The area is the plan area - the surface area that the air is subject to. 2.75 (or whatever it is after you redo it without my idiocy included) on a car that is 4.5x1.8 metres does seem a bit low but when you consider the size of the floor and the wings, it might not be too far off.

2.6 sq m is the value for planform area? how come its that small cause ive model an f1 car (maybe not accurate but at least 80% is same as the regulation) and the planform area is around 5.4 sq m (auto calculation from CFD program)..

by using the value (timbo) " I used rho=1.21 kg/m^3, U=83.3m/sec, F=30kN "

Fd = Downforce
P = rho
V = velocity
A = planform area
Cl = lift coefficient

Fd = [ P*(V^2)*A*Cl ] / 2


30,000) = [ 1.21*(83.3^2)*5.4*Cl ] / 2

=> Cl = 1.323

why most reply stated that Cl is around 2.7?


by the way this is what i got from my cfd analysis and i dont know whether its correct or not..

1:5 scale model and its a half body

A = 0.109261 ( its /25/2 from full body)
P = 1.1458
V = 38.013 scaled from 85 m/s
Cl = 3.7

Fd = [ P*(V^2)*A*Cl ] / 2

= [ 1.1458*(38.013^2)*0.109261*3.7 ] / 2

= 343.709 (for scaled and half)

# im not sure if this is correct but if i want to find for the real size car, i need to multiply with 2 ( half body ) and multiply by 25 ( which is for scale )

so

Fd = 343.709*2*25

= 17,815.45 / 9.81

= 1705.73 kg