Mclaren Mercedes MP4-25

[Raptor22]

I don't buy into the stalled wing theory. That would require total flow separation which we are NOT seeing on the flow vis images.
Those pics clearly show attached flow. Show me the stall...

[Poleman]

Detail of the front top vent on J.B car last week in Jerez:

[bosanac1]

from feb.18 a little more detailed pics.

[ringo]

I don't buy into the stalled wing theory. That would require total flow separation which we are NOT seeing on the flow vis images.
Those pics clearly show attached flow. Show me the stall...

I have been saying this all along.
There should be a way to have the wing not create drag by equalizing pressure on both sides of the airfoil. Increasing pressure on the reverse side is what can achieve this.

Stall is not good, poor lift to drag ratio. But close to zero lift with almost no drag is what we want!
No separation neccesasry, just speed reduction with some high enough internal energy (from heat under engine cover) on the back side of the wing should be good.

It's the pressure difference that makes most of the drag. Reducing this difference behind and in front wing = reduced drag force. If this is done to leave enough DF for straight line traction and acceptable aero balance Mclaren has a Dr. Jekyll and Mr. Hyde MP4.

[ringo]

The slot in the flap of the McLaren top rear wing (and the shark fin - roll hoop duct) is there to stall the rear wing at high speed. This decreases the car's overall drag by a couple of percent and will increase the straight line top speed by around 10-20kph.

Rumour is that it is a semi-active system controlled by the driver - something to do with the driver's knee covering a hole in a pipe in the cockpit which, in some way or another, acts as a pressure switch.

More like a valve mechanically linked to the steering wheel shaft that opens at full lock or no lock. Still driver operated no?

[Raptor22]

The only way to reduce the lift is to change the angle of attack of the wing to the air flow.
Maximum downforce requires highest possible AoA without flow separation. Flap blowing achieves this by filling in air where flow separation occurs for a given wing. Its the flow separation that creates turbulent dragging flow that eventually becomes stall if the AoA is too high for the foil section.

The way they achieve this in F1 wings is to use a foil section of high chord depth, which creates a lovely hollow inside the wing with the space that results.

Wth flap blowing, a huge pressure difference is not needed, you just need to maintain it slightly above atmospheric and the low pressure behind (or on top in a normal aircraft wing) creates the gradient for air to flow out of the wing since it is open to atmposhere.

Also stalling the wing will reduce the effectiveness of the diffusor. Through stalling the fall, they will choke the diffusor which is NOT what anybod wants because the car will become unstable.

There is no stall going on here, the flap blowing is there to increase the effectiveness of the wing.
How top speed will be affected is that a more efficient wing will create similar downforce for a smaller angle of attack. The lower angle of attack has a smaller wake and less drag.

[ringo]

Yes, I agree, what you are saying pertains to increasing down force. I am going in the opposite direction. However I think they want to make less drag with a penalty on downforce.

This can be done by reducing wing performance, without stalling it.
Drag has many components, form/pressure drag, vortex drag, induced drag etc.

This is why i proposed the opposite of flap blowing, focusing on the pressure component, which indirectly affects the induced drag.
In my case i don't want increased lift, i want to reduce drag, but since the angle of the wing cannot be changed, one way to reduce some drag is get rid of the thing causing it, the wake of the vehicle. If the wake is filled will pressurized air, the drag will be reduced.
This is done with blowing but not the typical method. The blowing pressure is what i am considering, not the velocity as in typical blown flaps.

Whatever it is they are doing, passively increasing lift or decreasing drag, they're up to something! and we're up to 80+ pages and season hasn't even started yet.

[SLC]

It is definitely a stalling mechanism. Yes, this will decrease the effectiveness of the diffuser but at 300kph down a straight you don't really care about the absolute downforce level you are producing - as long as you can shed 10-15 pts of Cd.

And yes, it is driver operated. Somehow.

[SLC]

REEEEEWWWIIIIIINDD!!!

The slot in the flap of the McLaren top rear wing (and the shark fin - roll hoop duct) is there to stall the rear wing at high speed. This decreases the car's overall drag by a couple of percent and will increase the straight line top speed by around 10-20kph.

Rumour is that it is a semi-active system controlled by the driver - something to do with the driver's knee covering a hole in a pipe in the cockpit which, in some way or another, acts as a pressure switch.

Where did you hear that (and how did you get those numbers)? Another site that copied from this site or another totally different source?

Another totally different source. The media know so little when it comes to the actual technicalities involved in this sport.

[Mysticf1]

I highly doubt its controlled using steering angle, imagine correcting a slide and loosing rear grip, even for an instant this wouldnt be advantageous.

The ongoing analysis of this concept is why i love this forum

[-o< too you smart cookies on the forum.

[kalinka]

Another interesting find. This is some kind of military research document from 1964 !!! :

http://oai.dtic.mil/oai/oai?&verb=getRe ... =AD0603904

The most important detail in it I think :

"Lift coefficient increased appreciably with blowing at low values of the parameters, and then tended to level off as blowing was increased. At low angles of attack, the only additional drag induced by blowing was the momentum drag due to the rearward thrust of the jets. It was found that such blowing reduced the stability of the wing. "

From this we can assume that is no need for high velocity airflow to create the blow effect, thus the air intake above driver's helmet would be enough. Another thing : it seems the effect is leveling with increasing speed,so in long straigts there would be no additional downforce with/without blown wing. And it's good for us !!!

Of course under "lift coefficient" we must replace with "downforce coefficient" in our case.

[KJM3]

Could it be possible that the hole channeling air to the rear wing can be opened and closed?

Perhaps it's controlled via the throttle pedal?
- When the throttle is open, the hole is open as well to reduce drag and downforce and thus increasing top speed and acceleration.

- When the throttle is closed (i.e. slowing down), the hole closes to increase drag and downforce to assist in braking and handling.

Would this work and would it be allowed by the rules?

- KJ

[kalinka]

Could it be possible that the hole channeling air to the rear wing can be opened and closed?

Perhaps it's controlled via the throttle pedal?
- When the throttle is open, the hole is open as well to reduce drag and downforce and thus increasing top speed and acceleration.

- When the throttle is closed (i.e. slowing down), the hole closes to increase drag and downforce to assist in braking and handling.

Would this work and would it be allowed by the rules?

- KJ

I think maybe a simple pressure sensor-activated valve in air intake would be enough. It can be calibrated for every track during practice.

[tok-tokkie]

I don't for a moment believe it is actively controlled. I believe it simply supplies air to the slot on the back of the upper wing element to keep the airflow attached & thus create more downforce. As raptor22 so rightly points out the angle of attack of the wing can then be reduced while generating the same downforce. So drag on the straight is reduced while downforce on the corners is the same as before.

The airsupply to the slot is controlled by the size of the aperture in the airsnorkel (a separate apeture to the engine air intake - some posts here don't seem to appreciate that it is not from the airbox), the speed of the air arriving at the inlet and the resistance to airflow through the duct and slot. Macca have been playing with the aperture size. I would not be surprised if the dynamics of the system adjust automatically with the airspeed so that it progressively becomes less effective as the airspeed increases.

For those who think it is actively controlled. How about that little air inlet in front of the driver (erroneously termed a vent in many posts). Is that the air inlet to the controlling system & can the driver modulate that with his knee?

[LotusF1]

The only way to reduce the lift is to change the angle of attack of the wing to the air flow.
Maximum downforce requires highest possible AoA without flow separation. Flap blowing achieves this by filling in air where flow separation occurs for a given wing. Its the flow separation that creates turbulent dragging flow that eventually becomes stall if the AoA is too high for the foil section.

The way they achieve this in F1 wings is to use a foil section of high chord depth, which creates a lovely hollow inside the wing with the space that results.

Wth flap blowing, a huge pressure difference is not needed, you just need to maintain it slightly above atmospheric and the low pressure behind (or on top in a normal aircraft wing) creates the gradient for air to flow out of the wing since it is open to atmposhere.

Also stalling the wing will reduce the effectiveness of the diffusor. Through stalling the fall, they will choke the diffusor which is NOT what anybod wants because the car will become unstable.

There is no stall going on here, the flap blowing is there to increase the effectiveness of the wing.
How top speed will be affected is that a more efficient wing will create similar downforce for a smaller angle of attack. The lower angle of attack has a smaller wake and less drag.

I dont totally agree - a component on its own most likely true, but rear wing with diffuser isnt totally true...infact your wrong...dunno about macca flow vis, but trust me downforce isnt always about getting everything to work in PERFECT conditions...