Mclaren Mercedes MP4-25

[horse]

The jet would not add to the drag, since it's not the same thing

I don't understand. If you seperate attached airflow with a jet of some other fluid, then surely it will create drag by the vortices, etc generated in this process. It's a Helmholtz instability, maybe.

The jet vector should also be in the opposite direction, since it's the reaction force on the wing that counts. That is a different thing altogether still.

Yeah, that's my diagram being rubbish again, sorry. I wasn't try to show it imparted a force, just that it was injecting fluid into the flow and that this was separating the normal airflow.

My idea was more about pressure; pressure is not a vector quantity. However it can act on surfaces to create motion in a direction. I was thinking more like a hydraulic cylinder, the plunger will move toward the side with lower pressure. Equal pressure on both sides and the net force on the plunger is zero.

Can you really think about it just in terms of pressure though? The actual fluid motion must be important also.

And to add to this, note the MP4 25 has a fin too, to add more area for yaw stability at high speed.

This is a good observation.

The problem we are having is the use of the word stall. I am of the opinion a wing can be "stalled" where lift and drag is reduced. Similar to this bird, pressure is equal on both sides of the bird's wings, she is not not moving to the left or right, just down.

This is not stall, more like zero lift, like a symmetric aerofoil at no angle of attack in an inviscid fluid. It will, in reality, still have some drag, though, in a viscous fluid.

Also, care to take it outside, to my dedicated thread...

viewtopic.php?f=6&t=8028

[wrcsti]

Stall one element and the whole wing, including the lower wing stalls.

Stall teh entre wing and the diffusor chokes resulting in a rapid increase in pressure under the car and this makes it extremely unstable.

Someone tried to debunk my effect being similar to removal of the rear wing and missed the point. The oint is that both cases result in a sudden and massive disruption in flow around the car. Thats why when the wing falls off, cars spin off the road or at lest gives the driver more than hand full of fish tailing to contend with. Downforce at high speed is vitally important. If this stalling concept was so fantastic why do they not run stalled wings at Monza...? I rest my case.

You want enough downforce to keep the tail down, and maintain aero balance near the COG that's it. The diffuser does not choke either. When a wing breaks off and the car fish tails, that has many reasons:

the endplates go as well with the wing.
The end plates provide yaw stability with their surface area.
Just like the vertical tail on an plane.

The car has a raked floor, when the wing goes, the tail lift's more, the splitter floor is pitched down into the boundary layer and Ground effect is disturbed.

And to add to this, note the MP4 25 has a fin too, to add more area for yaw stability at high speed.

At Monza they run a wing closer to no wing at all, that is what I am looking at. Stalling is not my main argument.

Ringo, shooting a hole in the wing does not result in a pressure equalisation. for that to occur, you would need to shoot enough holes into the wing so that the surface area of the wing is reduced sufficiently to not suspend the mass of the aircraft so its not a good analogy. even if I drill a hole through the M4/25 rear wing, the wing will still produce massive downforce because.
- the pressure equalisation does not occur
- there is a still a massive vertical displacement of air /sec.

I also tested this out one of my park flyers. I drilled holes into the wingeverywhere this morning and took it for a flight. Hey its still flies... it requires a bit of up trim but it still flies. So how do you explan this? The airflow over the wing is fast enough for pressure equalisation not be significant.

Your park flyer doesn't stall because of the Reynolds number, micro scale flying is completely different concept than high Reynold's number. Take a Moth's wings for instance, they are rough, dusty, fuzzy and tattered, this works at that small scale but we can't apply rough and fuzzy wings to commercial airliners to increase performance. We do the opposite and polish them down.

When i said a hole, i meant more like a huge rip along the wing, sorry about that. The pressure equalization will occur, in the same way that an engine will lose vacuum if there are any leaks, it will try to equalize with the atmosphere; adhering to the law of entropy.

and no I do not believe in the stalled wing concept and I never will. Its science fiction and I think it was created by James Allen.

We don't know if it's science fiction yet.
Touch screen computers were science fiction in the 70s with star trek. Now we have this I pad thing and I phones.

No body that would like to move through the air wants to "Stall", not even bee's.
If Stall was desired, mother nature would have invented it. Wait, actually she did, when birds land they essentially stall their wings and use it as an airbrake.
Other useful applications of stalled wings are airbrakes on aircraft.
Stall is useful for slowing things down, not speeding them up.

right now I'm off to the Hobby store to buy new wings for my Wilga

Ahh!!! gimme a sec..... *runs to dig up some Nat. Geographic videos*

[youtube]http://www.youtube.com/watch?v=j3mTPEuFcWk[/youtube]

Perfect example of RAW straight line speed! Stalling can be good in nature

The problem we are having is the use of the word stall. I am of the opinion a wing can be "stalled" where lift and drag is reduced. Similar to this bird, pressure is equal on both sides of the bird's wings, she is not not moving to the left or right, just down.

video narator: "When it comes to raw speed no creature on earth can match the MP4 25!! "

Atleast in my flight school we are taught that a stall is when the airflow separates from the surface of the wing thus there is no more low pressure above the wing and now it only operates with newtons 3rd law which is not enough to provide lift. This means that lift decreased but drag increases exponentially! I don't think what you guys call a "stall" is really what happens. That bird for example doesnt stall its wing, it changes the chord and camber to make it thinner and almost flat, thus decreasing both lift and drag, kinda like a fighter jet wing. If the engineers did make such a deadzone it has to be an area where after a certain speed the airflow will just flow around the wing, not separate from it.

[TheMinister]

http://en.wikipedia.org/wiki/Circulation_control_wing

SLC, you seem not to have seen this; the blown slit at the back looks to me like a perfect CCW, where it exploits the coananda effect to keep the airflow stuck to the wing, thus increasing the airspeed at which the wing will stall.

Of course, that means by turning it off you could purposely stall the wing at high speeds. I have yet to see a good explanation of how this would lead to less drag- but that's not to say it couldn't. (But tbh I imagine it would only help if there was something behind the rear wing, that could be removed from the airflow when the rear wing stalled).

Also as a previous poster said, it's damaging at low speeds, where you would infact want a sucking slit, and we have seen that extra mystery outflow on the back of the car (although it could just be an exhaust). Nobody's come up with a mechanism for how it could be done, but it doesn't seem beyond the bounds of possibility.

I guess what we really need is to get a good look at a McEngine cover, on the underside. That'd let us see what internal aero devices it has. If you really are an F1 designer SLC, get yourself down to the next test and 'accidentally' wander into the McGarage, and nick one for us

[ISLAMATRON]

Bunch of aero nerds spewing stalled hot air... cant all that go in the aero section?

More pics of the 25 please

[Pup]

I agree, it would be better to keep the "stalling or not" discussion in the aero board...

viewtopic.php?f=6&t=8028

And keep this discussion to the MP4-25's particular implementation.

[Pup]

Looking at these, I think there is indeed a slot on the lower element as well - fed possibly by the center strut. Could that be why they placed the foil on it, to keep the air from heating up as it went through? That might explain the reason for the temp strip on the lower element as well. But where would that air be coming from - behind the driver's head? Could there be a connection between the center strut and the exhaust over the tail light?

[outer_bongolia]

Atleast in my flight school we are taught that a stall is when the airflow separates from the surface of the wing thus there is no more low pressure above the wing and now it only operates with newtons 3rd law which is not enough to provide lift. This means that lift decreased but drag increases exponentially! I don't think what you guys call a "stall" is really what happens. That bird for example doesnt stall its wing, it changes the chord and camber to make it thinner and almost flat, thus decreasing both lift and drag, kinda like a fighter jet wing. If the engineers did make such a deadzone it has to be an area where after a certain speed the airflow will just flow around the wing, not separate from it.

+1

Is this stall that SLC is talking about something different than the airplane wing stall? I am a thermal hydraulics guy, and the jargon of an F1 engineer with a Ph.D. in aero might be a little different to what I am used to.

[kalinka]

Just an addition to the rear aero debate :

http://www.formula1.com/news/technical/2010/0/720.html

I think though that it's more confusing than explaining

[TheMinister]

http://www.formula1.com/news/technical/2010/0/720.html

Directed towards the top of the rear wing's lower section and the diffuser (small red arrows), it intentionally interferes with airflow over these parts at certain speeds, causing them to stall.

OOooooOOOOooohhh controversial! Either there really is something in this method of purposely stalling aero parts, or F1.com are avid readers of this site. Wouldn't be the first time either- remember the nosecone holes on ferrari a few years back? The idea came from here first...

[horse]

Just an addition to the rear aero debate :

http://www.formula1.com/news/technical/2010/0/720.html

I think though that it's more confusing than explaining

I have an idea that might put the pieces together. I'll draw it tomorrow and scan it in at work.

[Pup]

Just an addition to the rear aero debate :

http://www.formula1.com/news/technical/2010/0/720.html

I think though that it's more confusing than explaining

I suspect that they're the ones who are confused.

[Pup]

http://www.formula1.com/news/technical/2010/0/720.html

Directed towards the top of the rear wing's lower section and the diffuser (small red arrows), it intentionally interferes with airflow over these parts at certain speeds, causing them to stall.

OOooooOOOOooohhh controversial! Either there really is something in this method of purposely stalling aero parts, or F1.com are avid readers of this site. Wouldn't be the first time either- remember the nosecone holes on ferrari a few years back? The idea came from here first...

In all fairness, the concept of stalling wings and diffusers and what not has been brought up many times before - that's why we have those spacers now between the wing elements after all.

[cornermarker]

Also as a previous poster said, it's damaging at low speeds, where you would infact want a sucking slit, and we have seen that extra mystery outflow on the back of the car (although it could just be an exhaust). Nobody's come up with a mechanism for how it could be done, but it doesn't seem beyond the bounds of possibility.

My guess is that it's just a venturi effect going on inside the engine cover, and that black exhaust is the exit for the fast moving, low pressure body of air (B.)that's "sucking" on a slightly higher pressure body of air (A.), which is itself drawing air through the slot.



To get it to blow air (down the straight), just raise the pressure of A. and B. higher than that at the rear of the wing, there's plenty of heat under the cover to do that with. And it should be easy, as the pressure at the wing is pretty low at high speed.

It would be an elegant solution, lightweight, not too risky, and extremely cheap. It's so easy that if they're not doing it, the should be!

Kelpster

[Raptor22]

Yaw control provided by the end plates??? Perhaps a 2ndary effect of their purpose yes. Yaw control is provided by the tyres.

When the wng falls off, a large portion of the energy required to draw the air along the underbody is removed. The air flow under the car slows down dramatically resulting in a higher pressure wave now moving underneath the car. It reaches the exit at the rear and destabilises the rear, reducing the grip.
A the shark fin won't stop fish tailing under these conditions. Slowing the car down to rebalance the underbody flow is what is required.

I think Vodafone is raking in the cash after this discussion...

more than 3x the number of posts than any other car.
What an extremely successful marketing campaign

[meves]

Just a question on the rear wing, everyone is concentrating on the slot in the rear of the wing. At the top front front they may also have a full length slot across the entire wing. Is that likely and does that explain the black strip along the top as it doesn't look like a guerney flap.