What is the drag coefficient in an F-1 car?

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Greg Locock
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Joined: 30 Jun 2012, 00:48

Re: What is the drag coefficient in an F-1 car?

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I am fully aware that real aerodynamcists often use F/(1/2 rho v^2) when comparing things, nonetheless on cars even an aerodynamicist like Katz uses frontal area basis when comparing them. Sure for individual wings use S. It doesn't matter what you use so long as you know what you are using. But pedantic statements like yours are just silly.

thepowerofnone
23
Joined: 24 Apr 2013, 17:21

Re: What is the drag coefficient in an F-1 car?

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Greg Locock wrote:I am fully aware that real aerodynamcists often use F/(1/2 rho v^2) when comparing things, nonetheless on cars even an aerodynamicist like Katz uses frontal area basis when comparing them. Sure for individual wings use S. It doesn't matter what you use so long as you know what you are using. But pedantic statements like yours are just silly.
There was nothing pedantic about that statement: this is a forum based on F1-specific facts, and the statement, or implication, that F1 uses C_L or C_D to compare between vehicles is incorrect, not to mention misleading if you know aerodynamics. Sure, Katz can use frontal areas, and yes, of course I believe Katz knows what he is on about, but no, that is not how F1 quotes its values. If I were to try and analyse RBR's current car you can be 100% confident that I wouldn't figure out the frontal area, I would try to correlate its sector times to a generic C_x and C_z. The frontal area is irrelevant information to the performance, unless you are specifically looking at does my element X work the air more efficiently than element Y on the RBR, which is exactly what C_L and C_D are useful for but not the question asked by the forum poster.
Per wrote:Now you are being REALLY confusing. First you say L/D changes because they have changed the wings and the diffuser (with which I agree), then you say L/D doesn't change from year to year. And how on earth does the power curve influence L/D? It changes the optimum setup for a certain track, so they can opt to run more downforce (and as a result, more drag) but L/D will not change nearly as much as L and D individually.

What you're saying about coefficients is just another way of saying that they don't look at Cd only, but at S*Cd. :wink:
Yes, that's exactly what I'm saying about the coefficients, but almost coming from it the other way, you never really consider the C_D of the individual elements, or the planform (or frontal) area, you just observe the forces they produce. This is for two reasons: 1) when you use a wind tunnel to test, you can't isolate the forces produced by each element, so you can't state use planform areas; you could use frontal area, but it's less useful when you come to 2) at the end of the day, you're looking to improve the performance of the car, so you don't really care about anything other than that headline value of C_X and C_Z.

As far as L/D is concerned, yes it has fallen since the end of the double-diffuser era, because drag has gone up, but your target wouldn't change if the power unit (/some other big performance component) didn't change. Imagine a circuit full of long straights: your performance is probably limited by your top speed, so there is a premium on dropping drag, even if it costs you quite a bit of downforce. Now of course, if you could add downforce without increasing drag, and in doing so you increase your L/D, you'd do it, but generally the two are related, and you try to find the sweet-spot between losing drag and losing even more downforce, where you do it until losing downforce becomes more detrimental than the benefits of losing drag.

Now, change to a circuit full of corners (which the driver can't take flat), where you aren't limited by engine power, you're limited by the cornering speed you can sustain with your tyres: here adding on downforce could well improve lap times, even if it brought a hefty drag penalty, all the way until you were taking corners flat. Basically, circuit downforce/drag targets are sensitive to the circuit profile, so you might elect for a lower than optimal L/D ratio for more ideal absolute L or D values.

The reason the engine can change these ratios is that if you had unlimited power (and therefore torque), you would never been top speed limited, and traction would be extremely important, do you would obviously slap on downforce, even if it cost you a tonne of drag. Changes to aero regulations also change these ratios as the L-D relationship of any car is not going to be linear.

thepowerofnone
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Joined: 24 Apr 2013, 17:21

Re: What is the drag coefficient in an F-1 car?

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Ok so this has been bothering me all evening, so I'll just take one more stab at explaining myself through the medium of a fictional set of events, then if you still disagree Greg, we can just agree to disagree and you can think I'm an idiot if you like.

Fiat, a big company with fingers in lots of vastly contrasting pies, wants to decide which design team under the company's umbrella did the best job, to give them the biggest bonuses. They decide to compare one of the big 550 trucks from Fiat's truck division, a Fiat Doblo, and a Ferrari 458. To make the decision, they bring in a race engineer, an aerodynamicist, and an accountant, and they look at three key values, C_X, as I defined it, C_D, defined by frontal area, and C_D/€ millions spent in development, as summarised in this table:

[blank]; C_X; C_D; C_D/€
550 truck; 1.2; 0.2; 2.5
Doblo; 0.6; 0.4; 0.1
458; 0.4; 0.3; 5.0

So who did the best job? Well, the race engineer picks the 458, because it has the least drag force acting on it, so for the same torque has the highest top speed; the aerodynamicist picks the 550 truck, because it is the most efficient at managing its airflow and efficiency is very important for transporters; the accountant picks the Doblo, because the designers did the most with the funds that were given to them.

The point of all of this is that it matters what question you are asking when determining which metric to use to measure success, but fundamentally on an F1 car, the only thing anyone really cares about trackside is C_X. Yeah, you're going to look at how to improve your C_D and where your rivals might be making gains on you there, or rivals who spend their money more efficiently than you do, but C_X wins races. That's why its the headline number, along with C_Z, in F1, and that's why it wasn't pedantic of me to mention that correction.

Greg Locock
230
Joined: 30 Jun 2012, 00:48

Re: What is the drag coefficient in an F-1 car?

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Shrugs, like I say, the aerodynamicists I know wouldn't get pedantic about it, if they are using frontal area basis they say so, if they are using drag area they say so (or you can tell from the units), it just isn't a big deal and there are NO rules.

flyboy2160
84
Joined: 25 Apr 2011, 17:05

Re: What is the drag coefficient in an F-1 car?

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I'm with tpon on this issue of the useless concept of a frontal area based drag coefficient for F1. I've tried to explain this privately without success, so I'm glad he's brought it up here in public.

Per
Per
35
Joined: 07 Mar 2009, 18:20
Location: Delft, the Netherlands

Re: What is the drag coefficient in an F-1 car?

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Everyone here agrees with him, I just don't understand why he has to devote so much text to it.

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Andres125sx
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Joined: 13 Aug 2013, 10:15
Location: Madrid, Spain

Re: What is the drag coefficient in an F-1 car?

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I can´t remind where did I read it, but I read a long time ago an F1 car, from 200 or 250 km/h (?), just releasing the throttle decreases the speed faster than any production car with full brakes applied.

Quite impressive if you ask me, and that´s due to the huge drag from wings (and wheels). It was one of those parameter that made me realice what an F1 really is, because you instantly think.... and then they still can apply those impressive carbon brakes :o


That togheter with another comparison between a Porsche 911 and a F1 cornering speeds (80 vs 100 on a slow corner, 140 vs 260 on a fast one) I think are the most illustrative comparisons I´ve ever read about how fast a F1 really is. This was specially illustrative since a corner where a 911 struggles at 140 is not that wide, so thinking any car could go 260 there was mindblowing to me


Sorry for the OT, this just remind me one of those things I found so impressive I can´t forget

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fausto cedros
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Joined: 30 Jan 2010, 10:22
Location: Brindisi, Italy

Re: What is the drag coefficient in an F-1 car?

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For an f3 car you can assume 0,38 - 0,40 ( referenze area 1 square meter). The se are first hand data. F1 must not be' that different, if you just want to figure out.
"Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere" Anthony Bruce Colin Chapman

NoDivergence
50
Joined: 02 Feb 2011, 01:52

Re: What is the drag coefficient in an F-1 car?

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The drag coefficient of a F1 car is much much higher than that of a F3 car.

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Ciro Pabón
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Joined: 11 May 2005, 00:31

Re: What is the drag coefficient in an F-1 car?

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F1 cars have drag coefficients of 0.7.

Zombie threads have a larger drag, so I'm not afraid of them.

What really scares me are zombie cats: apparently they have a drag coefficient of 0.0001. That chopper is doomed.
Image
Ciro

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Andres125sx
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Joined: 13 Aug 2013, 10:15
Location: Madrid, Spain

Re: What is the drag coefficient in an F-1 car?

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Ciro Pabón wrote:F1 cars have drag coefficients of 0.7.

Zombie threads have a larger drag, so I'm not afraid of them.

What really scares me are zombie cats: apparently they have a drag coefficient of 0.0001. That chopper is doomed.
http://sites.google.com/site/ciropabon/zombiecats.jpeg
:shock:

:lol: :lol: :lol: :lol:

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turbof1
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Joined: 19 Jul 2012, 21:36
Location: MountDoom CFD Matrix

Re: What is the drag coefficient in an F-1 car?

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Normally I would remove off-topic posts, but in this case Ciro's awesomeness overwrites any moderation. People, if you like to legitimate make off topic posts: the standard has been set right there.
#AeroFrodo