Mclaren MP4-25 rear wing design controversy explained

[Tension_36th]

Earlier in the internet circles there were talks of Mclaren using a small opening in the nose section which was believed to be intended for electronics cooling and cockpit cooling, could be secretly used as a channel to send air under the rear wing and stall it via some sort of elaborate airduct to the rear region.

F1 Wing Stall in simple terms is to say stop the wing from generating downforce.

Every team is trying to increase downforce so you will ask why do they want to decrease it now?. It is actually simple, while your wing is doing such a dandy job of generating downforce it is also causing that much drag to free-flow motion. You getting good grip but you also slowing down the car that much. And your engine has to work ever more to punch the car through all that air and resistance to keep up the top speeds on the straights.

Now what if there was a way to make that wing "stall" or say stop it from being a downforce generator on the straights? Nice way to get more top speed as the drag is reduced and the resistance to free motion is reduced further. This also means you dont have to over work your engine for getting higher speeds on the straights. Fuel economy anyone? Yes.

How do they stall it? Remember in the technical review for 2010 we talked about how downforce was generated? The difference of airspeed over and below the wing. The air above the wing is slower than the speed below the wing.

Higher the speed ---> lower the pressure and vice versa (for simplicity)

Now this airflow above and below the wing is in the form of a thin layer of airstream that "sticks" to the surface of the wing. This adhesive power is weak and can easily go off if the angle of the wing (known as angle of attack or 'AOA') is too steep. So if you can change the angle and make it unreasonably steep the wing can stall and it will stop downforce generation.

But in the F1 car the rear wing angle cannot be changed like the front wing flaps that the driver can control. The front wing drag is not as significant as the rear wing drag, which is why rear wing is of great interest to the engineers.

So you cant change the wing angle, now how do you deal with the wing and try and stall it? There are a couples of ways to stall the wing.

Lets look at some wing design background:

A basic single plane wing looks like this below, the angle is not too steep and the curvature is not too much. Making a longer highly curved wing will definitely stall it since the air stream has to adhesively travel all along the length of that wing and generate downforce.




In F1 for a long time now since the times of advanced aerodynamic designs, they have been splitting the main wing into multi plane wings as shown in the example below where we have two planes.




What is being achieved here is that while we cant have a high steep angles and high curvature from one single plane, we split that up and form a highly curved and steep design. The air rushes not only from under the wing but also from between the slot gaps that have now formed. This rushing in of air maintains the adhesive air stream over to the next higher plane and then next one so on and so forth. So you can see how you place many planes and achieve really extreme curvatures and angles without stalling the wing.

In F1 today the regulations allow only two planes at a maximum. You can see this in action on an airplane when its about to land. Notice how they drop down the flaps and you hear the engine thrust increased even though the aircraft is slowing down? If the wing didnt have that high curvature by aid of multi planes, the wings wont generate enough lift at those slower speeds and the wing would fail to work.

This video shows this happening with an airplane wing.



So this generates lift, in an F1 car its the reverse we are trying to generate downforce. Which is the opposite, but the idea is more or less the same.

So for an F1 car what if on the straights these planes closed these slots between the wing planes? The wing stalls because the adhesive air stream is no longer maintained. In the recent past Redbull and Ferrari flexi-wings on the rear wing for example did just that on the straights. At high aerodynamic loads the upper planes bent down due to which the slots gets blocked and there by blocking the air stream in between resulting in the wing stalling. This practice was then banned by introducing struts to ensure the gap between the planes are not closed in anyway during high speed motion.

You can do this with more than two planes as well. The ideas and end results are the same.

So going back to Mclaren's concept. We know:

1) we cant flex the wing planes (as per regulations)
2) we cant change the angle of attack.
3) We cant have more than two planes (also refereed to as flaps)

So now the trick would be to some how disrupt the adhesive air stream behind the wing and there by stall the wing. Plus this has to be done only on high speed straights. A hard thing to balance.

Mclaren have come up with what may work if done right. The upper wing plane from the front looks like one solid piece and is connected to the shark fin. They have an air duct inside this fin connected to the upper channel of the engine airbox hole. Now look at the wing plane from behind, you can see a very thin line of what is another slot (highlighted in bluish grey). This upper wing plane is not solid like it appears on other team's wings, it has a small air channel inside it that is fed by the shark fin and its spitting out air through this thin slot that we can see.




This looks like a 3rd plane which is not allowed as this would make for a 2nd slot when only 2 planes are allowed. Its made 'legal' because this slot is not visible from the front and it is also not complete as it does not go all the way to the rear wing end plates (look on zones highlighted on the either sides in green).



Look at this pic from the front of the rear wing you dont see that thin fake slot you can only see the larger gap between the two allowed wing planes. Also notice the location of the air channel on the engine air box that acts as the supply for the sharkfin air duct.




Watch this 'fake' slot in action, it does work. Look at the viz paint that been pushed out by the air stream coming out of it.



The idea is to disrupt the adhesive air stream by using the air rushing out of this 'fake' slot.

Here is the cutway for the Mclaren sharkfin-rearwing structure



Now this slot will be putting out air stream on a straight and even on a high speed corner. You don't want your wing stalling on the parabolica at Monza or on Eu rouge at Spa. Thats going to take your car right off the track. This should ideally work only whilst on the staights. Very hard to achieve since there is no intelligent system that tells apart the difference between a run through the straights or though a high speed corner. The engine airbox can only scoop up enough air when the car is at higher speeds. So at low speeds we can expect the fake slot to put out only a weak amount air therefore not stalling the wing. But the problem still exists that the wing can stall on a high speed corner. Besides there are medium speed corners, how can the determination be made for what can be a medium speed turn and fairly fast short straight?

There could be a valve controlled by the driver when on the straights thats either leg operated via a pedal or hand operated via steering wheel levers or buttons. This would be illegal technically, as the driver is manipulating the aerodynamics at free will.

So you need a system which is independent of driver control and is sufficiently intelligent enough to tell apart from a straight line run and a fairly fast corner.

This is where the small opening on the front nose may be possibly coming into play.

The small opening in question is shown here below, look like a submarine's snorkel so to speak.



Some initially speculated this maybe the duct that is connected to the shark fin and not the engine air box. The claim is fairly ok but there is one problem in saying this small hole is the one that supplies air to the fake rear wing slot.

1) the opening is too small to get enough volume of air needed to stall the wing
2) It is doubtful that the air pressure from such a tiny feed can disrupt the air stream under the wing.
3) the amount of distance, twisting and turning of the air duct before it reaches the rear wing will ensure the air has lost most of its energy and speed. Just look a the location of this snorkel and the place it finally needs to get to, the rear wing.

So we can dismiss this idea completely, it is not feasible.

But what this small snorkel can do is act as a "trigger" sensor. It can house a mechanism that triggers a valve somewhere within the engine cover that opens and closes the air duct to the rear wing. But thats only going to solve how to detect the air speed or car velocity. It still cant tell apart from going on a straight or a corner.

If they connect the steering wheel input (sampling the input voltage feedback) to the valve mechanism, then such a system can tell the difference between being on a straight and going into a corner. So by setting a certain level of +/- steering degree as default for determining if the car is in a straight line you can control when the valve opens to the rear wing.

But you have yet another problem. What if the driver performs a quick turn on the straight like when he is overtaking someone following their slipstream? That can be interpreted by this intelligent system as beginning to go into a high speed corner. This can suddenly bring the downforce back up and it defeats the purpose of the system. So there needs to be a timing delay before this system is activated.

You can see this system is complicated, and the benefits are not as great as they make it out to be, precisely why Redbull are not so overtly concerned about this. But this can be Mclaren's answer to the absence of a KERS button on the straights. The electronic overheads and the extra value mechanism surely will take up some space, but since the duct is small the valve is also small.

One thing is for sure, it wont be driver operated or else it would be instantly illegal. It is driver independent. It is a grey area and Mclaren have exploited it reasonably well. We will have to see just by how much it has helped them on the straights.

Make no mistake, it will help them gain top speeds but the real gain is the fuel economy. That is the killer aspect of this concept because they can achieve the same top speed that they could before without the need for higher power levels from their engine. This means they can detune their engines a bit to achieve higher mileage. All thanks to reduced drag on the straights. Also there is no specific regulation that says you cant stall the wing, it only says you cant bend the wing or change the AOA to achieve that.

Does it brake the spirit of the rules? Yes it does. But is it illegal? Nope.

[icegirljenni]

I feel like i was in a physics class.

[funkyfish]

So Tension, do you think they'll get to keep it as Red Bull are already 'seeking clarification' from the FIA about it?

[Tension_36th]

They will get to keep it. Also they have reported they have been contact with FIA when they first designed the concept. So nothing will come of it specially since the FIA have been aware of it for sometime now.

Now lets say it was 'illegal' by regulations, this is the shamilton team. Obviously they will be let off the hook, but this time the idea is indeed legal by regulations albeit shady since this a grey area.

[icegirljenni]

I bet this MP4-25 rear wing case is gonna drag until the race start, when come to cheating , mclaren always has the upper hand, am pretty sure there is always one cheating in every season. So this rear wing will be pretty much the same case like Brawn GP 07 diffuser. Start off with illegal/legal case,FIA took own sweet time to decide, then some Paris court attend and then towards middle of the season suddenly it become legal.. and so go on...

[Tension_36th]

Mclaren rear wing has been cleared in scrutineering. Thats the end of that, even technically like I pointed out there was no issue in the first place, because it was a grey area they utilized. Depending the layout of the chassis, some teams will try and have the same on theirs by Barcelona.

Though some may not be able to do it because of the inherent design limitations with their chassis real estate.

More here

[pete]

Oh well the cheating has started wonder who will be next with a new radical piece of equipment for there car Brawn next as shuchmacher is there so more cheating from them soon

[Tension_36th]

The thing is this time its not technically cheating. Its being cheeky and clever at bending the rules. It certainly is against the spirit of the post 2006 rules on wing stalling though.

[Spyro]

Well who said bending the rules is fair play it is still a clever way of cheating i think lol

[Tension_36th]

Renault unhappy to be outwitted by Mclaren's rear wing. When have they been happy since 2006? They always complain and do a terrible job on their cars. They need to mind their own business and first improve to a point they a regular front runnner again. Then they will have earned the right to go whining.

More here

Meanwhile Redbull has played down the prospect of a protest, but Autsport dont have the understanding that the snorkel on the front of the nose does not have the pressure or the volume to drive air through the duct. The duct is connected to the airbox. Autosport has got its info wrong.

We have got the closest explanation to the actual concept.

More on redbull's views

[Tension_36th]

There is plenty of rife belief the snorkel on the nose is the one that supplies the air to the duct by driver knee.

The most hilarious aspect according to them is that the driver controls and closes this with his 'knee' apparently, you really have to be very ignorant to not understand that the knees cant hold down and seal a hole water tight when you dont need it. The driver knees are not shaped like a cork screws for goodness sakes.

Another hilarious aspect no one's paying attention to is how does the knee open the flow to the duct? Obviously there must be a lever or a pedal, this is Illegal you cant have any pedals other than for Clutch, brake, throttle and gear shifts. Or are they trying to say there are no pedals involved and that the air just decides for itself to funnel its way perfectly into some duct when the driver unmuffles the air hole with his knees?

You can see clear see how the press can be so stupid and naive.

They also think they are right because the teams spoke of not being able to change the tubs/chassis to accommodate the system if you dont have the space for it. They said so because they are actually talking about housing the non-driver controlled system that works by itself fed of steering input and the airspeed sensors in the snorkel's feed as explained in the first post.

No team actually said that the snorkel feeds the rear wing, they will not say anything about it because they dont want anyone else to get the idea of how it works in the Mclaren if they haven't already figured it out or if they have another idea to do it in another way. But the press made up its own nonsense and it has started spread like wildfire.

Well you folks read it hear first and you read the correct working of the concept right here at alonso-planet

[Tension_36th]

The latest theory being put forward by the press is that it works like a flute.

The snorkel feeds duct and is mostly kept open at the base of the driver's foot or maybe close to the left knee, the air rushes in through the snorkel and then floods the cockpit. But when the driver steps on it or blocks it with his left knee, the air goes into the shark fin and stalls the wing.

This is again people trying to make guess work here because there are problems with idea as well.

1) When air rushes in through the snorkel and goes down through any duct system there might be, its under low pressure and higher velocity, even if there is a hole in the this duct the air will go on through the rest of the duct and into the shark fin. Why? because the cockpit is at a higher pressure with less moving air. This air from the cockpit will rush into that duct hole because the air inside it is at a low pressure and higher velocity. End result is more air rushes into the duct through the hole and stalls the wing even more.

2) If this has to work, the driver has to be stepping on the hole all the time and releasing his hold to open the duct only when he needs to stall the rear wing, but what about braking?? Do you really want to stall your wing when you go into a breaking zone? Again this is pure nonsense.

3) I repeat yet again there is not enough pressure nor the volume from that measly snorkel to feed the shark fin with enough pressure to stall the wing. Do these people even look at the modeling in CFD to know the the velocities of the airstram under that rear wing? The air stream under the wing is so high and strong that it will choke the slot fed by the shark fin to the extant it wont stall at any point regardless if the driver steps on the hole or not.

In all the angles you look at it this is not how it works, we wont know the precise details of the system mclaren has, but what i explained is what they will doing or somewhere along those lines. The exact system is their clever piece of engineering. But a snorkel hole fed system, it most certainly is not. Already debunked by just a passing application of fluid dynamics.

The entire assumption is based on the fact that the snorkel has enough feed to stall the engine, but their theory falls apart when you consider that a hole in the duct kept open will start sucking in even more air from the cockpit not flooding it.

[Tension_36th]

That picture of Vettel is yet another indicator, Redbull knows the design is not controlled by the driver. Its automated. What the press haven't thought of yet is the interpretation like so: A device is already supplying air to the rear wing slot so that is manipulation and there are no rules saying you cant have a pseudo slot. So any means to control the airflow to it via valves independent of the driver is also not in breach of the rules, since the duct is already an aerodynamic device. The valve doesnt move anymore than a oil pump having its oil moving around and causing a slight disturbance in weight distribution in real time. Also the definition of Movable part is that part must physically move.

A valve as a whole doesnt move, it only closes and opens a hole. The rear slot also works in a similar fashion it has air rushing out and at other times no air rushing out. Open/close functionality. They cant apply the mass damper excuse. There the mass damper moved physically up and down. Here the valve system only opens and closes. Very easy to see how they have used a valve, electronics to control and make it an intelligent system.

Another hint which was very telling. Martin Whitmarsh was smug when he said "Adrian and the boys will have figured out how it basically works, but they wouldn't have figured it all out for its finer details..."

Exactly, you know the concept right away. All teams would have, they are all engineers of the same trade. But that clever automation is hidden totally. You have to do your own guess work on that. Which is why Redbull or any other team has its drivers spying on that car when ever they get the chance. They are looking for anamolous patch panels or wiring that can suggest a possible automation system. The impression we get is that Redbull knows for sure there is automation. Just how mclaren have done it they are unsure. There are many ways of getting it done. You have to choose what works best for you.