115 replies to this topic

[Pingguest]

I'm looking for any data to know how the downforce levels developed since 1968. As far as I could find Formula 1 cars created almost 2000 kg of downforce in 1999, but I couldn't find any more information. Could anyone help with some data?

Thanks!

[Greg Locock]

p24 in Peter Wright's "Formula 1 Technology" is probably what you want. It specifies downforce at 150 mph, vs year. It wanders around between 2000 and 3500 lbf over the years 1978-2000.

[Ogami musashi]

max downforce from the two last years (2005-2006) levels were around 1500kg for tracks like monaco and 1200kg on tracks like monza.

2004 were a bit higher.

During the 97-98 seaons the typical levels were 1600Kg.

According to pilots the lotus 79 produced only 500kg of max downforce, but in 1980 most of the wing cars produced 1000 kg and the next year about 2000kg (in which you saw some front wing disappear).

I have no clue about the 83-93 periods before skid pad was enforced.

The minimum weight fluctued from 500 to 650kg and today is 605 of course with driver and fuel&oil onboard.

[Greg Locock]

at what speed are you quoting downforce? It is a square thing...

[karlth]

According to the GP79 owners's manual the strongest car in 1979, the Williams FW07, produced 2278kgs of downforce with only 285kgs of drag at 150mph.

[Fat Boy]

Originally posted by karlth
According to the GP79 owners's manual the strongest car in 1979, the Williams FW07, produced 2278kgs of downforce with only 285kgs of drag at 150mph.

Do the L/D calculation on that and get back with me.

[OO7]

Originally posted by karlth
According to the GP79 owners's manual the strongest car in 1979, the Williams FW07, produced 2278kgs of downforce with only 285kgs of drag at 150mph.

According to the book Competition Car Downforce the Lotus 79 produced 3600lbs of downforce at 180 mph and one 1996 F1 car "produced a figure 'approaching 4000lbs' of downforce at 200 mph" in the low downforce Monza and Hockenheim configuration.

Obi

[DOHC]

Originally posted by Fat Boy


Do the L/D calculation on that and get back with me.

Looks like that drag figure could refer to the drag of wings only; in some sense this could be thought correct, for without the wings, you'd lose "2278 kgs of downforce" but merely gain a drag reduction of "285 kgs." That kind of argument is entirely different from looking at total downforce and drag of the entire system.

[Ogami musashi]

Originally posted by Greg Locock
at what speed are you quoting downforce? It is a square thing...

max means maximum so whatever the speed, it is the max downforce aviable, i don't have stepped speed figures unfortunately.

As for the lotus 79 500Kg figure it was maybe by niki lauda, or nelson piquet, i don't recall..

[karlth]

Originally posted by Fat Boy


Do the L/D calculation on that and get back with me.

What numbers in particular don't you agree with?

Here is the full quote:

If we take a Sauber C9 sports car as an example here ... we find the following:

1.253 Kgs @ 150mph with 313 Kgs of drag



Lift-to-drag ratio:4:1

As a comparison, a modern day Formula 1 car generates similar levels of downforce but, significantly, greater drag. With smaller surfaces along with less design constraints, the pinnacle of the ground effects cars of 1979 - the Williams Cosworth FW07 - boasted an unprecedented lift-to-drag ratio.

2.278 Kgs @ 150mph with 285 Kgs of drag



Lift-to-drag ratio:8:1

[Ogami musashi]

I think the FW08D (the siw wheeler) took it to 13:1

[Fat Boy]

OK, let's accept that the Sauber number is real. An L/D of 4 with a car that has closed wheels, tunnels, and is a 'Lemans Special' is very good, but not impossible.

An open-wheeled car from 1979 does not have the L/D numbers you have quoted and there isn't a racecar that ever existed that had an L/D of 13. There might have been aspects of the car that were that efficient (as DOHC said), but not the car as a whole. 1979 was a time when the rules were quite loose with respect to aerodynamics, but the bigger influence was the knowledge of racecar aerodynamics. They just did not have the knowledge or capability to produce the numbers you're quoting. Remember, in this time frame you're talking about an aluminum monocoque with a seperate fiberglass body and little if any wind tunnel time.

Again, I get the feeling that the drivers are being quoted here on technical aspects of the car. The only people that are worse to quote about technical aspects of the car are in the marketing department.

[Fat Boy]

Originally posted by Greg Locock
at what speed are you quoting downforce? It is a square thing...

The downforce was measured at 400 mph and the drag is measured at 100 mph. That clears it all up, huh?

[karlth]

Originally posted by Fat Boy
An open-wheeled car from 1979 does not have the L/D numbers you have quoted and there isn't a racecar that ever existed that had an L/D of 13. There might have been aspects of the car that were that efficient (as DOHC said), but not the car as a whole. 1979 was a time when the rules were quite loose with respect to aerodynamics, but the bigger influence was the knowledge of racecar aerodynamics. They just did not have the knowledge or capability to produce the numbers you're quoting. Remember, in this time frame you're talking about an aluminum monocoque with a seperate fiberglass body and little if any wind tunnel time.

Again, I get the feeling that the drivers are being quoted here on technical aspects of the car. The only people that are worse to quote about technical aspects of the car are in the marketing department.

The numbers seem to be too accurate to be pulled out of a hat or quoted by a driver.

Here is another article

The relevant paragraph

Their six-wheeled car promised a leap forward in grip comparable to that which had been seen when ground effects first arrived. Williams’ 1982 car had a lift to drag ratio of 8.2 - the six-wheeler’s was 13.4. At the end of 1982, ground effects were banned, and Williams’ 1983 car had a lift to drag ratio of 1.1.

Take a look at probably the most extreme of the 1979 cars, Arrows A2


Source F1tip.ch

Not a lot of drag there compared to the Sauber.

[DOHC]

The point that Fat Boy tries to make is that one should compare total downforce to total drag. Bodywork, wheels, sidepod cooling ducts, engine air intake, driver, suspension arms, brake cooling ducts &c. all contribute to total drag but don't generate much downforce.

In an airplane, you'd be very proud to generate a 20:1 L/D ratio. Some gliders reach 40:1 or even higher, but that is exceptional. Commercial airliners rarely go above 17:1 in cruise conditions. In landing manouevers, with slats and flaps deployed (this is similar to the low-speed aero of a racing car and its wing configurations), L/D may drop to 4:1, and yet such a design is usually distinctly better, aerodynamically, than an F1 car, which typically has the drag of a brick wall. The space shuttle flies in at roughly a 1:1 ratio...

Flat Boy's comment is therefore certainly warranted.

[Fat Boy]

Originally posted by karlth


Source F1tip.ch

Not a lot of drag there compared to the Sauber.

You mean except for the exposed tires, open cockpit, no engine cover, open wheel internals, and 50mm spoiler on the rear upswept tail? The numbers you are throwing around are **massive** efficiencies.

Look, I appreciate that you think this gets the numbers you are quoting. Without showing any animosity at all, I just don't believe it, sorry. In truth, I'm not really sure what you evidence you could produce that would make me believe it. I suppose if you had a good chunk of information directly from the aero guys that put the car together along with wind tunnel data I would have to stop arguing, but even then, I doubt if I would believe it. A write-up from a website just doesn't do much for me in terms of validation of your claims.

[Ogami musashi]

as for myself i never said that i was sure it was for the complete system nor did i backed up the L/D number except the 13:1 that i just saw on the 8W site.
It may refer to some reference area you're right, but i don't know and i don't think you know it either.
Could you believe a sukhoi 27 fighter jet has a max L/D of 12 for the entire plane? When you see it you can point many parts not streamlined or located at the right place, but then the plane drags not so much (in that particular condition which is of course a cruise one) and lifts well.

Aerodynamics are not done by the eyes.

What i say is that we lack data, that's all.

[DOHC]

Best glide ratio (L/D) for a Cessna 172 is about 8:1. Drop an upside-down F1 car through the air, and I bet that it won't fly as well as the Cessna.

[karlth]

Originally posted by Fat Boy


You mean except for the exposed tires, open cockpit, no engine cover, open wheel internals, and 50mm spoiler on the rear upswept tail? The numbers you are throwing around are **massive** efficiencies.

Look, I appreciate that you think this gets the numbers you are quoting. Without showing any animosity at all, I just don't believe it, sorry. In truth, I'm not really sure what you evidence you could produce that would make me believe it. I suppose if you had a good chunk of information directly from the aero guys that put the car together along with wind tunnel data I would have to stop arguing, but even then, I doubt if I would believe it. A write-up from a website just doesn't do much for me in terms of validation of your claims.

Fair enough. I will be the first to admit that I would never consider myself an expert in aerodynamics but I certainly believe those numbers.

Do consider this if you find the 285kg of drag @150mph unbelievable for an open wheeler:


Source: Ideeos.com

The Penske[Ganassi pictured] 2001 CART racecar, in superspeedway configuration, produced only 430kg of drag @230mph

Reference (Racer Tech Magazine)

[Ogami musashi]

Originally posted by DOHC
Best glide ratio (L/D) for a Cessna 172 is about 8:1. Drop an upside-down F1 car through the air, and I bet that it won't fly as well as the Cessna.

thats completely out of the subject. aerodynamics are done in accordance with ground proximity to transfert a load on tyres, 30% of the total drag of an F1 car comes fromthe rear wing's form and induced drag.

don't compare apples and bananas.

[Greg Locock]

I'm sure both of Peter Wright's books discuss this. I've lent mine out. Papers by Katz or Hucho would also be worth looking at.

Milliken fig 15.29 says that for a good ground effect car the total L/D was around 3.4 max - so an F1 car would fly about half as well as a Cessna, or slightly worse than a hang glider.

[Ogami musashi]

Yes 3.4 is possible, but why "for a ground effect car"? i mean the drag generators we are talking about have nothing to do with ground effects, so what is this reference for? is there any specific GE car cited like the lotus 79 or else?

[Fat Boy]

Originally posted by karlth
Do consider this if you find the 285kg of drag @150mph unbelievable for an open wheeler:


Source: Ideeos.com

The Penske[Ganassi pictured] 2001 CART racecar, in superspeedway configuration, produced only 430kg of drag @230mph

Reference (Racer Tech Magazine)

It's not that I find a certain drag number unbelievable. It's the L/D's that you are quoting I find unbelievable.

I don't have any Champcar superspeedway aero data here to look at, but I've got plenty of road course stuff. A Lola running 30mm front ride and 60mm rear ride in road course trim made 5291 lbs. of downforce at 200mph. Drag was 1707. L/D was 3.1. My source on this is the 2003 Lola B02/00 Aerodynamic Supplement, which should count as a reasonably valid source. I would expect for other numbers for open wheel racecars to be somewhat in line with these. You'll find variations, of course, but the general trend is going to be somewhere along these lines.

On superspeedways they were slick drag-wise, no question (your example was 717 pounds at 200mph, which seems a little optimistic). At an L/D of 3.5, we're talking 2500# down. I think that also might also be a bit light, but it's probably not far off in terms of efficiency. So, to put this in perspective you are saying that the type of car that set the all time closed course record for an open wheel racecar (I believe Pacwest w/ Gugelmin has that honor?) was less efficient by about a factor of between 2 & 4 when compared to another open wheeled racecar produced 20 years prior racing strictly on road courses. Is there any question as to why I find these numbers suspect?

Another thing to take into consideration. Just as taking aero numbers without a corresponding speed in meaningless, taking aero numbers without designating ride heights is also a little meaningless. If you stick the rear of the car 5 inches into the air and the front on the deck you can start throwing around some pretty impressive numbers. They're meaningless, though, because there's no way in hell that you could actually run the car in that trim.

I'm not trying to be contrary or offensive, I'm just trying to add a little perspective using information which I trust as being true.

[karlth]

Originally posted by Fat Boy


It's not that I find a certain drag number unbelievable. It's the L/D's that you are quoting I find unbelievable.

We know that the ground effect cars were producing a lot more downforce than the F1 cars today so I don't see why the ratio should be so unbelieveable?

...
So, to put this in perspective you are saying that the type of car that set the all time closed course record for an open wheel racecar (I believe Pacwest w/ Gugelmin has that honor?) was less efficient by about a factor of between 2 & 4 when compared to another open wheeled racecar produced 20 years prior racing strictly on road courses.

Yes, because of the ground effects. Banned technology. The numbers were there, the problem was though crude aerodynamic implementations which meant inconsistent and unstable handling, and of course suspension and tyre technology which now is considerably more advanced.

I'm not trying to be contrary or offensive, I'm just trying to add a little perspective using information which I trust as being true.

I totally understand. I am glad we are able to debate/discuss this subject like adults.

[Greg Locock]

"Yes 3.4 is possible, but why "for a ground effect car"?


Because that's what they tested?????

[Fat Boy]

Just curious. I'm not sure what the hell we're arguing about. Are we arguing whether or not the skirted tunnel cars were the all time downforce champions?

[Fat Boy]

I just clicked on the 'Mulsanne Corner' website. Those 2001 'Renske' numbers are very suspect.

They go from road course to short oval to superspeedway. As they take downforce off, the efficiency gets worse. I've never seen that before on anything. Generally speaking, as you get less and less downforce, the L/D goes up. You ditch the draggy stuff and keep the efficient stuff so that overall efficiency goes up. 1000# down at 230mph is not reality, of this I am certain.

[DOHC]

Originally posted by karlth
The Penske[Ganassi pictured] 2001 CART racecar, in superspeedway configuration, produced only 430kg of drag @230mph

But that car is in low downforce config. As for the quoted numbers (drag=4,300 N, velocity=100 m/s) you get power = drag*velocity = 430 kW, or approximately 580 hp. This is the engine power required to overcome the quoted drag. At such speeds the greater part of the engine's power is used to overcome drag, as rolling resistance and transmission losses are much smaller. How much downforce that car produces is hard to tell but I would be surprised if it much exceeded L/D=2.

I don't have any complete data but typical best performance for open-wheel cars are

total L/D < 2.5-2.8
front wing L/D only < 10-12
high camber rear wing L/D < 3

(Figures may of course vary a little outside these numbers depending on speed and downforce config.) Although it is always questionable to quote numbers for a separate component (front wing, rear wing), an indication of relevant figures can be obtained either through CFD or wind tunnel testing where the component is either on the car or removed.

It's also worth noting that the L/D number isn't the full story. Consider a wing for "high speed" applications. It would be sleek and have small camber and operate at a small angle of attack, just like in the pic of the Ganassi car. Such a wing has a high L/D, but needs "very high speed" to produce a significant lift. In "low speed" conditions, you would instead run a high camber multi-element wing at a higher angle of attack. You can buy yourself the same downforce, but you will pay dearly in terms of drag.

Compare to what the wing config looks like on an airliner in cruise conditions. No flaps, no slats, essentially a biconvex, slender profile. The drag penalty, which basically determines the airliner's fuel consumption (and therefore is terribly important economically as well as environmentally), is compensated by the thrust, and you want to run the engines much below maximum output (only used at take off) for fuel efficiency. Total L/D for let's say a 747 is something like 17 in such cruise conditions.

At low speed, however, you run into some problems. Because you have to keep the plane up, lift L must equal the plane's weight. L is proportional to v^2 (so is D), which means that lift drops significantly when you reduce the speed. At cruise, you go 900 km/h, but you don't want to land at that speed. You want to land at something like 300 km/h or less. That's three times slower, so you only have 1/9 of the lift if you don't do anything to the wing (you'd simply drop like stone!). How do you fix that?

There are two things you can do: increase the angle of attack, or change the wing configuration. In practice, you have to do both. So you deploy flaps and leading edge slats to get a concave-convex, high camber wing profile, and you run it at a greater angle of attack. (Such a wing resembles the typical F1 rear wing, and doesn't look like the Penske-Ganassi's high speed rear wing). In that new configuration you can still keep the plane up at low speed, so the lift is the same as it was in cruise.

Because L=c*v^2, where the constant c depends on the geometry of the wing, you have

L=C1*v^2 at cruise and L=C2*v^2 at landing

so C2 must be something like 9 times bigger than C1. For the drag, you have D=k*v^2, where again the constant k depends on the wing geometry. However, drag is not the same in cruise as in landing. Therefore

D1=K1*v^2 at cruise and D2=K2*v^2 at landing

At cruise (high speed) you try to maximize L/D for fuel economy. Maybe you reach L/D1 = 20, implying that C1/K1=20. The high camber wing used in landing, however, has a relatively low L/D. Fuel consumption isn't the main concern then, but maneuverability. The wing may have L/D=4, implying that C2/K2=4. But because we know that C2=9*C1, we find

C1/K1 = 20 and 9*C1/K2 = 4, so K2/K1 = 45!

That means you pay a lot in terms of drag for using that high-camber wing to generate the same lift at low speeds. Check out above and you find that the drag at low speed is actually five times bigger than at high speed. As a consequence, you have to use much more thrust to overcome that drag, and I'm sure you've noticed that an airliner's engines run at much higher revs during the landing maneuver.

All of this is simplified of course, with some made-up numbers, but aero isn't much different (except for ground effects ;) ) between cars and planes.

Except for at Monza, F1 cars run high camber wings. Fuel efficiency isn't a great concern, and the speed is (from the aerodynamical point of view) low, so in order to squeeze out some downforce you have to use such configurations. But at that configuration L/D cannot be high, and that's why you have the "unimpressive" L/D<3 above for the rear wing.

The front wing uses less camber, runs close to the ground and can therefore boost its performance via the ground effect, and often runs at a smaller angle of attack. So you get a higher L/D there, but mind you, L/D=10 is quite high! Diffuser and undertray also produce downforce, but don't forget that you have to drag along that lump of bodywork that envelops the chassis and driver, with all its sprouting parts, including wheels, air intakes and cooling ducts. Those parts generate drag, drag, drag, but no lift...

In all, I think it's fair to say that a total L/D of 2.5-3 in a racing car is quite an aerodynamic achievement. A total L/D of 8 or 10 or something such is just a wet dream and won't happen unless we change Bernoulli's law or replace the atmosphere by a more racing-friendly gas...

[cheapracer]

http://www.pbase.com.../image/20939155

Although the Lotus 79 always gets the kudos when ever ground effects is spoken of as being the first, I cant help but feel the March 701 was actually the first and that the designer missed a great chance to accelerate aero's at that time (1971?).

[karlth]

Originally posted by DOHC


But that car is in low downforce config.

That is exactly the point. The ground effect cars had almost no downforce from the wings, as in many cases there hardly were any. The massive downforce quoted came from the ground effects.

So take the Penske open wheeler which in that oval configuration is producing very little drag but hardly any downforce either. Slap ground effects on the design and the extremely low drag will hardly be changed while the downforce figures will explode.

[karlth]

Originally posted by Fat Boy
Just curious. I'm not sure what the hell we're arguing about. Are we arguing whether or not the skirted tunnel cars were the all time downforce champions?

Hmmmm well something like that. Or perhaps if Lift-to-drag ratio of 8:1 is possible on a ground effects open wheeler like the FW07.

Now would be a good time for Nick Wirth to post something in this thread like he did a long time ago. And set the matter straight.

[Paolo]

Originally posted by Fat Boy
I just clicked on the 'Mulsanne Corner' website. Those 2001 'Renske' numbers are very suspect.

They go from road course to short oval to superspeedway. As they take downforce off, the efficiency gets worse. I've never seen that before on anything. Generally speaking, as you get less and less downforce, the L/D goes up. You ditch the draggy stuff and keep the efficient stuff so that overall efficiency goes up. 1000# down at 230mph is not reality, of this I am certain.

Not true for racecars.
To be clearer I will here refer to a non ground effect racecar, say a 1970 F1.
A racecar of this kind has many parts (body, wheels, wings) which produce drag.
Yet only wings produce downforce.
Take away the wings, you will still have the drag from the rest, but no downforce: zero L/D ratio.
And that's if you are lucky, as many car bodies actually show upward lift.
The more wing you put, the more (negative) lift you get. Drag will increase, but still -L/D will increase.
Usually a racecar's maximum efficiency happens near maximum downforce settings.
The presence of body downforce shifts this balance a bit, yet not much.

By the way, thie "less downforce = more efficiency" argument is not even true for wings and planes: at an angle of attack which produces zero lift you will still have drag, and therefore zero efficiency.
An airplane wing wich stalls at 20° can roughly be expected to hit maximum efficiency at 8°.

[Ogami musashi]

Fat boy:

You are here still talking about planes that can change their angle of attack (thus having a V² evolution of induced drag) with cars that cannot change their angle of attack and from were the major drag is a form drag, and as said just above, the profil drag is not dependent on lift (there's of course an amount of induced drag in the total drag of a F1 car but that's far from being the major consideration).

Additionally, you take linear curves for granted were they're not (as said just above again, Cz is not linear past a certain angle, and it is often were a wing of F1 car is set, at the highest Cz possible).


You also ignore any lift enhancement like Vortex lift which today's F1 cars are just overloaded (endplates, barge boards, indy wings, mid wings, sidepods wings etc..all are vortex generators) that boost the L/D ratio.

Modern F1 cars ratio vary from 3.5 to 4 which is quite considerable given bluff design.

But more that that, the L/D ratio quoted first are from ground effects cars.
In which the lift produced certainly not results from a wing like flow circulation.


Again i'm not saying that i'm sure 100% about those numbers, but it doesn't seem impossible to me.

[Gecko]

Listen to Ogami, he is coming from a proper aerodynamic background by the look of things

What some of you are forgetting is that with properly sealed sides one can get downforce for virtually no induced drag at all. Induced drag comes about due to the vortices that are shed (mostly) by the wingtips. An ideal sealed underbody works fully in ground effect and doesn't shed any vortices at all. A glider may reach a lift to drag ratio of 40, but that is away from the ground. A glider with its wing in close proximity to the ground will already experience a much better lift to drag ratio.

The drag on a proper ground effects F1 car will mostly be due to parasitic drag, namely the drag due to the surfaces that actually do not produce any downforce (wheels, cockpit, cooling). It is quite independent from the lift that is produced by the underbody, whose magnitude then mostly depends on the area below the car and the proper shaping. That is why lift to drag ratios of 10 and more would not surprise me at all. I do not claim that that is what they were, it is however entirely plausible that those cars were much more efficient aerodynamically than the cars of today.

P.S.: Taking dowforce off the car resulting in a worse lift to drag ratio is expected at some point, and is certainly true of the ground effects example above. Again, some of the drag is the induced component due to the lift and depends on the amount of lift, while there exists a fairly constant parasitic component due to nonlifting surfaces. Once lift is decreased such that the induced drag becomes comparable to parasitic drag, the lift to drag ratio of the whole car will start becoming worse with decreasing lift, even if the overall drag is reduced, simply because lift is dropping faster than drag at that point.

[DOHC]

Originally posted by karlth
So take the Penske open wheeler which in that oval configuration is producing very little drag but hardly any downforce either. Slap ground effects on the design and the extremely low drag will hardly be changed while the downforce figures will explode.

That car already has venturi tunnels, and my guess is that ground effect produces most of the downforce on that car.

[karlth]

Originally posted by DOHC


That car already has venturi tunnels, and my guess is that ground effect produces most of the downforce on that car.

It was my understanding that the ground effects in CART were (are) severely limited.

[phantom II]

One of the members on this thread has a PhD another has a degree in aerodynamics . There are two members who have not posted yet with PhDs in CFD. Careful what you say.

Originally posted by Gecko
Listen to Ogami, he is coming from a proper aerodynamic background by the look of things

What some of you are forgetting is that with properly sealed sides one can get downforce for virtually no induced drag at all. Induced drag comes about due to the vortices that are shed (mostly) by the wingtips. An ideal sealed underbody works fully in ground effect and doesn't shed any vortices at all. A glider may reach a lift to drag ratio of 40, but that is away from the ground. A glider with its wing in close proximity to the ground will already experience a much better lift to drag ratio.

The drag on a proper ground effects F1 car will mostly be due to parasitic drag, namely the drag due to the surfaces that actually do not produce any downforce (wheels, cockpit, cooling). It is quite independent from the lift that is produced by the underbody, whose magnitude then mostly depends on the area below the car and the proper shaping. That is why lift to drag ratios of 10 and more would not surprise me at all. I do not claim that that is what they were, it is however entirely plausible that those cars were much more efficient aerodynamically than the cars of today.

P.S.: Taking dowforce off the car resulting in a worse lift to drag ratio is expected at some point, and is certainly true of the ground effects example above. Again, some of the drag is the induced component due to the lift and depends on the amount of lift, while there exists a fairly constant parasitic component due to nonlifting surfaces. Once lift is decreased such that the induced drag becomes comparable to parasitic drag, the lift to drag ratio of the whole car will start becoming worse with decreasing lift, even if the overall drag is reduced, simply because lift is dropping faster than drag at that point.

[phantom II]

You mentioned a C172. The Indicated airspeed that you fly at constant altitude with the least amount of thrust is the max efficiency of the aircraft.IE: Max L/D. This speed(about 72kts) is also max range and best glide ratio and Vy(max rate of climb on a standard day gradient below 5000ft. where above that, VY and Vx drop off drastically because of thrust availability. Obviously, it will take you forever to get anywhere at 72 kts.
I just got back from Africa and the 747 chooses a power setting, routing( wind) and altitude for the lowest fuel burn. As the plane burns off fuel, it can fly higher. The air density drops off so the plane flies at a slightly higher angle of attack but lower total drag. The higher ground speed makes up for the reduced thrust.
The aero package on a car will be the most efficient at a given speed and atmospheric conditions including wind direction. The package is set for section of the track that the package will achieve the most advantage. Tracks like Indy has half the distance that requires no down force and half the distance at max downforce.
Tunnel or venturi or GE cars are expensive to design and except for front and rear wing trim the car is pretty much locked in which means the package is compromised for the whole season. Indy cars are different.
Two different aero packages may have the same L/D at one speed but vastly different above or below that. Current F1 packages give the most margin for adjustment from track to track.



This ASW 15 is an aerobatic glider so its glide ratio is less than efficient at 35:1 but a whole lot more fun than seeking any records. I have even less hair now. Each aero package is compromised.



Lift and drag values from Peter Wrights Ferrari Formula 1 book.

Originally posted by DOHC


But that car is in low downforce config. As for the quoted numbers (drag=4,300 N, velocity=100 m/s) you get power = drag*velocity = 430 kW, or approximately 580 hp. This is the engine power required to overcome the quoted drag. At such speeds the greater part of the engine's power is used to overcome drag, as rolling resistance and transmission losses are much smaller. How much downforce that car produces is hard to tell but I would be surprised if it much exceeded L/D=2.

[Fat Boy]

Originally posted by Gecko
Listen to Ogami, he is coming from a proper aerodynamic background by the look of things

What some of you are forgetting is that with properly sealed sides one can get downforce for virtually no induced drag at all.

P.S.: Taking dowforce off the car resulting in a worse lift to drag ratio is expected at some point, and is certainly true of the ground effects example above.

Modern tunnel cars, which include the Lola/Reynard/Swift/Penske CART cars and the present Panoz Champ Car all have real ground effect tunnels. The Panoz is by far the most pronounced. It should be noted that the Toyota-Atlantic and Mazda-Atlantic cars also have very large underwing tunnels. These are all the real deal in terms of ground effects. While these cars don't have sliding skirts, what they do have is vortex generators at the entry of the tunnel that does a pretty effective job of sealing the outer edge of the floor. It's one of those deals of trying to put the toothpaste back in the tube. The sliding skirts were the first way of sealing the floor, but they aren't the only way.

Getting downforce from the tunnels is cheap in terms of drag, but it isn't free. You can never get something for nothing. Anyone that tells you differently is selling something.

For sure that at some point you will lose your L/D as you reduce downforce. There is going to be a certain 'D' number that has nothing to do with downforce. As the 'L' goes to 0 the 'D' will stay constant. However, I'm talking realities, not hypotheticals. When you run a car at maximum downforce (say, for a slow street course) there are many gurneys and wing angles that you choose to run in spite of their efficiency. At some tracks, you get more speed by sticking more wing on the car and efficiency be damned. For a given car, as you remove gurneys and reduce wing angles, you gain efficiency at the cost of total downforce. At the racetrack, you never get to the point of reducing downforce to the point where you actually hurt efficiency in any car I've ever had any dealings with. It's a moot point. By the time you've gotten that low in downforce, you're going to be dead slow.

[McGuire]

Originally posted by phantom II
One of the members on this thread has a PhD another has a degree in aerodynamics . There are two members who have not posted yet with PhDs in CFD. Careful what you say.

The technical deficiency is large and this is looked at in the particular: wings to spoon, taperings, bar extensions, fireplaces, wings in several sequence and other. For the studies in merit, they are chosen of the not suitable methods. All it is entrusted to the fantasy; to the experience of it puts into effect them technical. The result is one aerodynamic mistaken, from the snout to the posterior end.

[RDV]

Ok DOHC, I blame you...and I'm sure Zmeej is lurking somewhere in the background...
Suspicious timing for all this to start reaching a crescendo!
I'll get back to all of you NEXT week...a bit busy at the moment, plus far from my records.
Basicaly skirted ground effect cars were reaching 7:1 L/D, flat bottom went to 4:1.... dont think anyone reached 11... and I'm talking wind tunnel figures validated by on track measuring... and sorry Fat Boy, L/D on single-seaters goes down as you trim wing off, or go from Hi-downforce to lo... just think about it , in the end you are left just with those exposed wheels and assorted suspension iron(carbon)-mongery..
more later but I gotta sleep, its 2AM...arghhh

[Ross Stonefeld]

Originally posted by Fat Boy


So, to put this in perspective you are saying that the type of car that set the all time closed course record for an open wheel racecar (I believe Pacwest w/ Gugelmin has that honor?) was less efficient by about a factor of between 2 & 4 when compared to another open wheeled racecar produced 20 years prior racing strictly on road courses.

Somewhat head scratching, for me, is I think it was actually de Ferran in 2000 in a Penske-Reynard with a godzilla Honda engine and, err, the Handford wing. I recall he only did one hot lap and parked it.

[Gecko]

Originally posted by Fat Boy


Modern tunnel cars, which include the Lola/Reynard/Swift/Penske CART cars and the present Panoz Champ Car all have real ground effect tunnels. The Panoz is by far the most pronounced. It should be noted that the Toyota-Atlantic and Mazda-Atlantic cars also have very large underwing tunnels. These are all the real deal in terms of ground effects. While these cars don't have sliding skirts, what they do have is vortex generators at the entry of the tunnel that does a pretty effective job of sealing the outer edge of the floor. It's one of those deals of trying to put the toothpaste back in the tube. The sliding skirts were the first way of sealing the floor, but they aren't the only way.

Getting downforce from the tunnels is cheap in terms of drag, but it isn't free. You can never get something for nothing. Anyone that tells you differently is selling something.

For sure that at some point you will lose your L/D as you reduce downforce. There is going to be a certain 'D' number that has nothing to do with downforce. As the 'L' goes to 0 the 'D' will stay constant. However, I'm talking realities, not hypotheticals. When you run a car at maximum downforce (say, for a slow street course) there are many gurneys and wing angles that you choose to run in spite of their efficiency. At some tracks, you get more speed by sticking more wing on the car and efficiency be damned. For a given car, as you remove gurneys and reduce wing angles, you gain efficiency at the cost of total downforce. At the racetrack, you never get to the point of reducing downforce to the point where you actually hurt efficiency in any car I've ever had any dealings with. It's a moot point. By the time you've gotten that low in downforce, you're going to be dead slow.

I do agree with what you write, no question about it. There is just some details in my post that you perhaps missed.

If you create an underbody which is a thin sealed Venturi tunnel (and not a diffuser) you will get very little induced drag. Drag as such is of course always present the moment you have a wetted surface in the stream. But the drag due to the creation of vortices (induced drag) in the sealed skirt type of car with an inverted wing underbody is not dominant at all. You get the pressure drag due to flow separation as well as skin friction drag, you can certainly never avoid that, but the induced drag can be eliminated to a very large degree. There will of course be more induced drag the higher up the exit opening is from the ground, but the main difference to using a normal wing is that the largest part of the downforce does not arise from giving vertical momentum to the moving air, but rather due to the interaction with the ground via the air flow, thereby not using up energy.

You are right about most cars never going into the regime where the lift is reduced to the point that the lift to drag efficiency is reduced. A superspeedway, however, may perhaps not be your typical application. There may be sufficient mechanical grip available that very little wing downforce is necessary in order to make the turns, which is completely the opposite case to regular circuits that are almost always grip limited. In that case, getting away with as little extra downforce as possible to make the turns is the target, and efficiency should not matter directly.

[Fat Boy]

Originally posted by RDV
... and sorry Fat Boy, L/D on single-seaters goes down as you trim wing off, or go from Hi-downforce to lo... just think about it , in the end you are left just with those exposed wheels and assorted suspension iron(carbon)-mongery..

First, RDV is one of the people I was talking about could at least make me shut up when it comes to talking about high L/D's. Not that I necessarily believe it all( ), but he's one with real experience on the matter.

Secondly, I don't think my example was explained well. I'm not talking about physically removing wings. I'm talking about reducing gurney sizes and angles. Many of the gurney additions and higher wing angles of attack on cars I have numbers on come in at L/D's around 2.0 to 1.0. The car as a whole might be 3.4. In these cases, decreasing something like gurney sizes does both reduce overall downforce and increase efficiency.

Really, I'm not making this up. If I had the ability to stick an Excel graph in here that shows it, I would.

[Boro]

1) get on excel with the graph
2) press print screen
3) open paint, press ctrl-v (or paste)
4) save the file in jpg
5) go to imageshack.us, u/l the picture
6) come back here and post the link to said pic

voila.

[Fat Boy]

God, you ask a lot out of guy. Hold your horses and I'll get to it.

[phantom II]

Size of Gurney is the height of separation or boundery layer thickness which depends on A of A. It is always at one angle. 90' to the trailing edge otherwise it doesnt generate as much low pressure under the wing and all you have is induced lift which is high drag lift.. With a typical F1 thick wing section, it actually reduces drag while increasing lift without changing nose pitch. AIAA paper(76-406) patent 1935. Efficiency is the most amount of lift for the least amount of drag.

Originally posted by Fat Boy
I'm not talking about physically removing wings. I'm talking about reducing gurney sizes and angles. Many of the gurney additions and higher wing angles of attack on cars I have numbers on come in at L/D's around 2.0 to 1.0. The car as a whole might be 3.4. In these cases, decreasing something like gurney sizes does both reduce overall downforce and increase efficiency.

Really, I'm not making this up. If I had the ability to stick an Excel graph in here that shows it, I would.

[Fat Boy]

[IMG]http://img237.images...iencynm2.th.jpg[/IMG]

Here ya go.

[DOHC]

Could you supply a little bit of additional explanation to what we see in that graph?

[Fat Boy]

Not a lot of time to write. It's the relative L/D of common changes to a given car as produced by the supplier. The changes are all adding downforce, but this gives you an idea of the efficiency of each particular component/change.

Be back in a day or so.