F-Duct Is Misunderstood

[Flood1]

The F-Duct is generally considered to be intended to increase straightline speeds. But, that is a misconception.

http://www.formula1journal.com/2010/08/ ... lood1.html

Please discuss on the Apex.

 

[FB]

I think this is best described as cause and effect. Higher wing angles allow for greater downforce in the corners and higher cornering speeds. The wing stalling device negates the effect of the wing potentially leading to higher top speeds on the straights.

The question I have is how effective is the "F-Duct"? Does it make the car run as if the wing isn't there or does it reduce the effectiveness of the wing making it provide a similar level of down force to a lower wing angle? If the latter of these two options it would result in similar straight line speeds between an F-Ducted and non-F-Ducted car (wouldn't it?) but, as Flood points out in his article, higher cornering speeds for the F-Ducted car.

Is there a fluid dynamicist in the house?

 

[snowy]

Nothing in the article is actually wrong...
Though I have to say McLaren isn't particularly quick through fast corners and was regularly very much quicker down the straight and through the speed traps. Which tends to indicate that McLaren weren't being particularly aggressive with downforce in fast corners. And I have no idea why that might be.

 

[rufus_mcdufus]

I think this is best described as cause and effect. Higher wing angles allow for greater downforce in the corners and higher cornering speeds. The wing stalling device negates the effect of the wing potentially leading to higher top speeds on the straights.

The question I have is how effective is the "F-Duct"? Does it make the car run as if the wing isn't there or does it reduce the effectiveness of the wing making it provide a similar level of down force to a lower wing angle? If the latter of these two options it would result in similar straight line speeds between an F-Ducted and non-F-Ducted car (wouldn't it?) but, as Flood points out in his article, higher cornering speeds for the F-Ducted car.

Is there a fluid dynamicist in the house?

You've nearly asked the same question as I've always wanted to - but were slightly embarrassed to. Surely if the wing is stalling, that's not terribly efficient aerodynamically and could lead to more unpredictable results? What I'm sort of trying to say is, purely in terms of drag (and hence straightline speed) is the following true?

Wing with lower angle of attack is better than stalling wing with high angle of attack is better than fixed wing with same high angle of attack but not being deliberately stalled?

 

[Chad Stewarthill]

I think we could be arguing about semantics here, but surely the lowering of drag which enables higher wing angles to be used for increased downforce in the corners, does by definition also produce higher straightline speeds relative to what could be achieved without the device?

What baffles me a bit though is why Mclaren have run too little downforce at some races (Hockenheim?) resulting in very high straightline speeds at the expense of performance round the corners, which would seem to defeat the whole object of having it on the car.

It has also been suggested in some quarters that at Monza, which is already a very low downforce circuit, there may be no benefit in using the device at all.

It is also interesting to note that Mclaren themselves have never called the device the 'F-duct'. They have always referred to it as the J-switch (and no, I don't know what the 'J' stands for).

 

[FB]

The nice people at ScarbsF1 have given a pretty full explanantion as to how stalling a wing works and why McLaren needed it to be driver operated . Just follow the Link

 

[MajorDanby]

Although I am not by trade a Fluid dynamist, I have made a brief study of the subject. Without any data to draw on however, it makes reaching a conclusion difficult.

To the question of why the McLaren always seems to have a higher top speed, and in effect don't run more wing to increase cornering speed, I imagine the issue comes from compromised efficiency of the rear wing. To me this is the only logical explanation for why they don't seem to run higher downforce levels.

We all know that the effect of the driver closing off the f-duct is to change the airflow over the rear wing, directing the flow through the slotted gap, reducing effective downforce. Now my question would be, how does the airflow change with cornering (air no longer flowing linearly across the car), and how does the rear work in an effective cross wind?

The stability of the McLaren in high, and especially medium speed corners this season has been nowhere near the level of the RBR. Is it possible that this is a direct consequence of the switched rear wing? It is highly possible that with variable airflow across the wing, in a non-linear approach, has the effect of creating varying levels of downforce through the corner. The difficulties that this bring would be analogues of the difficulty found with variable levels of downforce gained from the EBD on and off throttle.

Obviously, with this effect, the varying downforce levels would be more pronounced running higher wing angles on the switched rear wing. Is it possible that McLaren have found that the car actually gains better lap times running similar wing levels as the rest of the teams, and gaining a higher top speed, than it does going for a higher wing level, with a lower top speed, and more variable levels of downforce through the high and medium speed corners?

With the other teams, with a less effective f-duct system, maybe variable levels of rear downforce are less pronounced?

A further consequence of the switched rear wing would be exemplified in high speed corners. If you are carrying higher levels of wing and drag through those corners than is necessary, but are unable to switch the rear wing for fear of loosing all downforce, than of course you would simply not be as quick through those corners.

I guess my point is, that with the switched rear wing, it is all a question of compromise, and I imagine McLaren have been caught in no mans land, several times this season.

 

[Brogan]

You've nearly asked the same question as I've always wanted to - but were slightly embarrassed to.

No need to be embarrassed rufus.
We have a thread just for asking those questions that you always wanted to: Ask The Apex

 

[Flood1]

In my thinking, high cornering speeds are more useful than top speed in getting a fast lap, but Kubica said this:

Renault's Robert Kubica said at the Hungarian Grand Prix that he had no doubts about the importance of the F-duct.

When asked which of technical innovations seens in 2010 was the most important, he said: "If it is working properly, it's the F-duct. The longer straights you have, the more of an advantage you have."

As well as using the F-duct for a pure top speed advantage, teams can also utilise the concept to help them run with more downforce for the corners – because the knock-on increase in drag is eradicated on the straights by the stalling of the rear wing.

 

[Brogan]

I'm surprised at that to be honest.

I think it's clear for all to see that a flexible front wing has far more effect on the overall aero/downforce than an F-Duct which only effects the air "exiting" the car.

The flexible front wing produces significantly more downforce with a negligible increase in drag.

 

[MajorDanby]

Also, it balances the front and rear downforce in full throttle high speed corners from the EBD. I imagine it gives more of a performance gain that is generally thought

 

[Chad Stewarthill]

Well, well, well; no Mclaren F-duct for Monza, as predicted:

http://www.autosport.com/news/report.php/id/86076