Reducing the drag of a two element wing through stall

[cornermarker]

Good job on both of those. I never did figure out what exactly the louvres were for until I saw that.

I think the curvature also has to do with the lift distribution along the span as well. The center of the wing always tends to have more separation in the case of an F1 wing. The stronger upwash is where the wing profile meets the end-plates.

Ah, I see. That's helpful, thanks. One of the abstracts I read did say that the best place to put the slot was just before the area where flow separates. So there's yet another piece of the puzzle in place, I hope So I wonder, is the location of the slot on the 25 about where flow would separate at high speed on such a high df wing?

Kelpster

[raymondu999]

Hey all, after watching the Chinese GP again, in the damp, this shows up right at the end of the straight, when presumably the f-duct is opened again. This is on lap 10 just Hamster overtakes Webbo.

[cornermarker]

Hey all, after watching the Chinese GP again, in the damp, this shows up right at the end of the straight, when presumably the f-duct is opened again. This is on lap 10 just Hamster overtakes Webbo.

Those are the tip vortices I mentioned. They tended to disappear down the straight, so I figure operation of the slot cancels those out some how.

[wrcsti]

Those are due to the wing having such drastic pressure changes. If they disapear down the straight it means the F-duct is blowing to stall the wing, adding pressure down there to levels low enough so the vortices dont condensate the water in the air

[raymondu999]

I'm quite interested, actually, to see what they would do at fast corners, say Eau Rouge, 130R, etc. Would they stall the wing, or keep it normal

[forty-two]

I know it's been a while since anyone made any comments on this thread, largely since it seems like the concept which is the subject of this thread is now basically understood by all.

But, during the buildup to yesterday's Monza GP, Martin Brundle on his grid-walk spoke with Jenson Button and made reference to Jenson "using his leg" to operate his f-duct, to which Jenson pulled him up and told him something along the lines of "yeah, that might be the case IF I used my leg".

We really do seem to still not know how the McLaren F-Duct system is activated by the drivers, or indeed if it is driver controlled or not.

Does anyone have any images of the various cars (including McLaren of course) to show how they are controlled by the driver?

[ringo]

I think Mclaren switched to hand operation. I have no reason as to why, since i think the knee operated duct is more convenient.

[horse]

I think Mclaren switched to hand operation. I have no reason as to why, since i think the knee operated duct is more convenient.

Or it's operated by the braking foot. There is definitely some 'operation' going on. Jenson has always been pretty coy about the system anyway.

If they have moved to hand operation, it may be to reduce lag to the fluidic switch, perhaps? Not sure if an extra metre of pipe would make a massive difference???

[forty-two]

Or it's operated by the braking foot. There is definitely some 'operation' going on. Jenson has always been pretty coy about the system anyway.

If they have moved to hand operation, it may be to reduce lag to the fluidic switch, perhaps? Not sure if an extra metre of pipe would make a massive difference???

An interesting point about lag to the fluidic switch Horse. Initially I considered that if you suddenly increase the pressure at one end of the pipe, it would immediately increase along it's length, which would ALMOST be true if we were actually talking about a fluid, but we're not, so air would compress near to the "hole" (albeit slightly) and take a measurable time before that increase in pressure made it all the way to the switch.

But let's not forget that we don't actually KNOW that it's driver controlled at all. This could be McLaren's strong suit, in that they might have managed to tune their system to switch automatically.

[horse]

But let's not forget that we don't actually KNOW that it's driver controlled at all. This could be McLaren's strong suit, in that they might have managed to tune their system to switch automatically.

Unless it's a computer that knows the lap, I just can't see how a passive system would be able to judge when the wing should be operating. Wing operating below a certain velocity doesn't make sense if you want it off when leaving a slow corner like a hairpin. Wing operating under deceleration doesn't work either if you are accelerating out of an opening radius corner. I just think the logic is too complicated to avoid the use of either computer or human control.

[forty-two]

Unless it's a computer that knows the lap, I just can't see how a passive system would be able to judge when the wing should be operating. Wing operating below a certain velocity doesn't make sense if you want it off when leaving a slow corner like a hairpin. Wing operating under deceleration doesn't work either if you are accelerating out of an opening radius corner. I just think the logic is too complicated to avoid the use of either computer or human control.

Not necessarily. The suggestion was made a long time ago on this thread. I'm pretty sure that the following quote was not the first mention, but anyway, the idea given here is plausible IMO. Posted on March the 24th 2010:

Any thoughts on the possibility the snorkel is just a cooling duct, and Whitmarsh is sending everyone on a wild goose chase?

It is an interesting theory that you postulate, but if it is indeed a passive system, then it would have to be tuned to only go into effect at some velocity above the highest cornering velocity for a given circuit, plus some margin of safety. Imagine going through Eau Rouge or 130R and suddenly losing some downforce percentage. This constraint could limit the usefulness of the system, while a driver operated system could allow for use on shorter straights for which the maximum cornering velocity was not exceeded.

And other(s) suggested that it could be a combination of both, whereby the system is tuned to stall automatically once the car is above a given speed for a given circuit, but the driver operating the "device" could provide a manual override (either for "Stall now despite being under speed" or "don't stall now, I need the downforce").

Allowing the driver to concentrate fully on driving and not messing about covering holes with whichever appendage they may or may not be using would surely be an advantage?

[horse]

I actually think a driver operated system would be easier to drive because you are in control of the characteristics of the car. For instance, under heavy breaking an automatic f-duct will turn off somewhere and the characteristics of the car will change completely. Under acceleration in a straight line this is not so bad, but if you were still somewhere through a turn it might be a bit of a surprise. No, I think the driver having control of it is the only sensible way to go.

[747heavy]

a "semi automatic" system which stall above a certain speed, indepentend from the driver action is technically possible - IMHO

One drawback, is you would lose braking performance at high speed IMO, as the drag of the wing would be most benefical at max speed. A speed sensitive system would only "switch on" the df/drag below the reference speed, so you lose the effect at higher speeds, this would also affect the brake balance.

With a purely speed sensitive system you would lose the advantage in the first part of the straight, until you reach your activation speed.

It´s doable, sure, but I would see the behavior in brakeing as a "problem"/drawback

[forty-two]

a "semi automatic" system which stall above a certain speed, indepentend from the driver action is technically possible - IMHO

One drawback, is you would lose braking performance at high speed IMO, as the drag of the wing would be most benefical at max speed. A speed sensitive system would only "switch on" the df/drag below the reference speed, so you lose the effect at higher speeds, this would also affect the brake balance.

With a purely speed sensitive system you would lose the advantage in the first part of the straight, until you reach your activation speed.

It´s doable, sure, but I would see the behavior in brakeing as a "problem"/drawback

Good points, but I am merely pointing out that many posters on here, and indeed it seems the overwhelming majority of journalists still insist on saying that McLaren use their "left knee" or "left leg" but the fact is, McLaren have managed to keep this particular fact a secret, despite all the other teams being in a position to copy it in their own way.

This could be and probably is a bit of one-upmanship on the part of McLaren, but if the reason for their keeping this "secret" so close to their chest is that whatever they are doing does indeed give them an "advantage", then that would suggest to me that perhaps their car would be significantly off the pace were it not for whatever "secret" this actually is?

[hollus]

If you can have it manually controlled, why would you prefer an automatic, tuned system? Left hand activation (or left whatever) is just so simple, elegant, and, obviously, effective (See Ferraris, Saubers, Bulls, Renaults...).