ISLAMATRON wrote:if they turn all those knobs and switches with "inside out" gloves and reach down and change the brake bias, a knee bump aint a big deal
I don't agree with the point you've made.
When dealing with switches they can choose the timing and grab the switch only when it is safer/easier to do.
Supposed knee-valve operation is quite contrary -- it is more like pedal work or steering, it should be very simple and reliable.
ISLAMATRON wrote:
And all you guys shooting down the knee switch idea have never used an air switch in a hot tub...
And all you guys (and me as well, sadly) have never driven an F1 car at 180mph+ with our arses an inch off the ground. Every little ripple in the track is transmitted to the driver and could easily lead to his knee moving on and off the "switch" which might have interesting effects on the rear wing's performance.
I walked around Silverstone with Justin Wilson (when he was racing with Minardi). As we walked around Maggotts, he commented about a really viscious bump near the apex which meant one had to be very precise with the car's position to avoid a big jolt. "What bump?" I asked, looking at the smooth tarmac. The reply was along the lines of "Trust me, at 180mph the slightest ripple feels like a pothole in these things".
So his knee moves off and on a switch at 180mph on a straight for milliseconds at a time? I don't see that being a problem worthy of worrying about. Assume it is a knee, it will be braced up by his foot. Notice over bumps the drivers foot doesn't come off the throttle, or the drivers foot doesn't come off the brake in bumpy braking zones.
They tested it in testing, and went fastest overall, and did long runs. They are so far ahead of us and this discussion, it's almost comical.
Before I do anything I ask myself “Would an idiot do that?” And if the answer is yes, I do not do that thing. - Dwight Schrute
Hi guys, just been trough 16 pages of posts and just wanted to add my view. It seems to me that we are divided into two categories on this subject:
1. McLaren have found a way to stall their wing to get less drag
2. Mclaren are using a very effective blown wing resulting in low drag
I'll count myself to the second category. (Pardon my English, but I'm from Belgium so my phrase construction is not always correct).
To me the wing is just an upside down Fowler flap (with only two elements). The slot in the main plane is just to get more air at the suction side of that plane to increase the stall margin (a bit like adding an element to the flap). Because of this very effective Fowler flap, they can work with a rear wing with lower angle of incidence, therefore having a higher finesse (L/D) and higher top speed.
The reason I don't "believe" in the stalled hypothesis is that I have a background in aeronautical and aerospace engineering (MSc thesis in experimental turbo-machinery) and that I have always been taught (and seen) drag = bad. I don't have a lot of experience in low Mach aero, so I'll keep an open mind about reducing the induced drag trough stall.
What troubles me with the stalled hypothesis is not only the size of the wake created by the stall (which could or could not be smaller), but the fact that flow velocity in that wake is going to be very low, causing low static pressure air, which is going to cause a huge form drag. I know induced drag on those stubby wings is huge, but I would be surprised they could off-set the loss in form drag with reduction in induced drag.
Just a thought, great input from all of you, it has been a fascinating read. Cheers.
At upper element stall, the lower wing element is still curving the air to fill the low pressure caused by the form drag on the upper element. The upper element is no longer creating 'lift' though.
I think one reason why this discussion is going for so long without a solid conclusion is that we are still trying to compare the F1 wing to an airplane wing and not looking at both components of the flow that creates the downforce:
(i) the shape of the wing, creating lift.
(ii) the direction of the airflow when it leaves the wing.
As far as (i) goes, yes, the wing works like an airplane wing. It simply creates downforce by being an upside down wing. If you stall it, you will lose downforce. I believe this is especially important for the lower element.
However, for (ii) the wing is designed to push the air upwards. The force required to move the air upwards with create a reaction pushing the wing down, creating additional downforce. This will not be affected as much from the stalling. Note that I said "as much" because the turbulent flow behind the wing will also mess up the flow from the front of the wing and cause it to lose some downforce.
Now, if we look at the angle of attack of the top element of the rear wing, it is something like 45 degrees or more. In case of an un-stalled wing, this will create as much force pulling the car backwards as it is pushing the car down (just draw a line vertical to the wing). So, stalling the wing and killing the lift will actually benefit the car at high speeds!
McLaren's design (or any blown wing) will delay the stall a little bit. i.e. it will allow to wing not to stall at higher angles of attack. Or if one looks at this from another point of view, it will allow them to use a smaller upper element in their rear wing to generate the same amount of downforce at a certain speed, but since the upper element is smaller, once it stalls, it will generate less drag at higher speeds.
Skeptical scrutiny is the means, in both science and religion, by which deep thoughts can be winnowed from deep nonsense. Carl Sagan
We can also compare it to Williams' blown wing. Williams has a scoop that the air from the middle of the rear wing assembly. They are actually losing some surface area to get enough air to blow through their slit.
What makes McLaren's design so nice is that they are taking some unused air from a section that already creates a drag penalty and using it somewhere else. This is a very elegant solution.
Skeptical scrutiny is the means, in both science and religion, by which deep thoughts can be winnowed from deep nonsense. Carl Sagan
So his knee moves off and on a switch at 180mph on a straight for milliseconds at a time? I don't see that being a problem worthy of worrying about. Assume it is a knee, it will be braced up by his foot. Notice over bumps the drivers foot doesn't come off the throttle, or the drivers foot doesn't come off the brake in bumpy braking zones.
They tested it in testing, and went fastest overall, and did long runs. They are so far ahead of us and this discussion, it's almost comical.
His knee will be braced by his foot? His foot can only brace his knee if it's braced itself. And what can he brace his brake foot against other than the brake pedal?
The reason the feet don't come off the pedals is because they are pushing on the pedals. In the braking zone they are pushing very hard on the pedal. Some drivers have side panels on the pedals to help keep their feet on the pedals too.
And you have no proof what they tested when going quickly other than that there was a duct on the top of the monocoque above the pedal box. That proves not one jot of the theory that there is a knee hole / squeezy pipe / unicorn in the cockpit.
The whole thing is just supposition until we get to see inside the McLaren cockpit or a driver / senior engineer confirms what it's all about.
Too many people in here are talking as if the whole thing is a done deal. It's good fun but currently nothing more than that.
If you are more fortunate than others, build a larger table not a taller fence.
ringo wrote:I'll keep modifying until i get something. I think i can change some of the geometry of the ducting and the slit it self.
Hey ringo,
Do you know what would happen if you changed the tube that comes from the roll structure a little? I think if you add a nozzle, you could increase the speed of the air coming into the rear wing at some pressure cost.
Skeptical scrutiny is the means, in both science and religion, by which deep thoughts can be winnowed from deep nonsense. Carl Sagan
This subject deserved it's own thread tbh. Good job by the mod carrying all these messages ! Cheers =D>
Anyone interested in how the airflow can be forced to change direction WITHOUT any MOVING PARTS go to page 9, there's a fluidics diagram related to this issue. If the 'knee thing' is real, then it most probably works using that logic.
This whole think might also be a diversion. But it seems to be clear that they have a straight line speed advantage. Since they can't do much with the engine, they're definitely up to something with aero.
Education is that which allows a nation free, independent, reputable life, and function as a high society; or it condemns it to captivity and poverty.
-Atatürk
Bah, I don't have time to reply properly right now - but there is a lot of misinformation in this thread and people are posting information authoritatively when in fact they do not understand the actual aerodynamic theory - a lot of you are simply applying your own "common sense" with some basic understanding of mechanics/physics. I am not trying to belittle your efforts but most of the recent posts are incorrect.
For example, it is completely nonsensical to attempt to remove an individual element of a dual element wing and think of it as an independent entity. The two elements are so closely linked in terms of load generation and effect on the surrounding flow field that they must, at all times, be considered as a whole assembly.
And again, for those of you who think the McLaren slot is acting as a blown flap (and thus helping to prevent stall) are incorrect. This is what the Williams and Sauber wing are doing, and indeed what the McLaren 2009 wing did, but this has nothing whatsoever to do in terms of applied aerodynamics to the 2010 wing.
And Gecko: I know your post was some time ago, but I'll reply here. You clearly have an understanding of what's going on, and I agree with what you say. After thinking about it, I don't mean to say that the induced drag component is negligible on the whole (when the wing is attached). However, I do think the most significant reduction in drag when the wing stalls is from the large reduction in pressure drag (due to the loading on the wing being massively decreased). Yes, the induced drag would also decrease due to this reduced loading (the decrease in loading will reduced the upwash which you get as a result of the trailing vortex system), but that component is still relatively small (I'd say 20-25% of the total drag delta). To be honest I've never had think about, let alone work out, the different components that make up the wing drag (hell, overall car Cd is all that really matters).
Anyone have a reply to my question back on page 21 with pictures comparing the F2007 snorkel intake to the MP4/25 intake? I know one person responded saying they're in totally different spots, but I posted the pictures side-by-side to show they're basically in the same spot. Thoughts?
The F2007 doesn't have an intake in the nose ? Maybe that's why they put the intake where it was (I thought someone else already mentioned this) ?
In Macca's case, they both have an intake in the nose, plus the snorkel. Could be an intake for a complicated aero device, could not. Could be extra cooling for the driver, could not. If it actually IS cooling, then it definitely does not answer how McLaren gain extra top speed in the straights.
Education is that which allows a nation free, independent, reputable life, and function as a high society; or it condemns it to captivity and poverty.
-Atatürk
A fluidic switch is just that, a switch, just like an electrical one in function.
Let's start with the intake. It directs air via a duct to a small box on front of the driver's left foot. Above the driver's left foot is a hole. Normally the driver's left foot is at rest or depressing the brakes. But with the hole above the driver's left foot, he can just lift it enough to cover the hole. That's all, and is done only in a straight line. Once approaching a braking point, the driver's left foot slides down to the brake pedal, and the hole is now open.
This box has another duct running all the way up to the airbox, where the actual fluidic valve is. The ducting is only for control, to turn the fluidic valve on or off. When the valve is on, airflow is as designed, the rear wing has tons of downforce. Close the valve, and the wing stalls, drag is reduced. The driver can only make this work when in a straight line, and definitely cannot when braking, because the foot is no longer covering the hole, but instead is on the brake pedal.
No crushable hoses, no moving parts at all. Everything rigid and as per regulations. The only variable is the location of the driver's left foot, high or low.
All this stuff is purely to control the fluidic valve built into the airbox, and as long as the drag of the intake is less than the reduction via stalling the wing, it makes sense. And for the engineers out there, this design resolves two problems with one device. Because not only does it have the ability to reduce drag in a straight line, it also furnishes cooling air for the driver.
The primary purpose of this was to reduce drag, but a welcome secondary benefit is a cooler driver.
You guys have been caught up in the assumption the knees are involved, and also that the real magic is happening up inside the airbox. What's going on down at the driver is just a pneumatic control system.
Racing should be decided on the track, not the court room.
SLC wrote:
And again, for those of you who think the McLaren slot is acting as a blown flap (and thus helping to prevent stall) are incorrect. This is what the Williams and Sauber wing are doing, and indeed what the McLaren 2009 wing did, but this has nothing whatsoever to do in terms of applied aerodynamics to the 2010 wing.
I thought I understood all the explanations and was finally on the same page as you until I read this part. So you're saying the air coming out of the slot does NOT keep the flow attached while "on". Instead, you're saying the flow out of the slot actually CAUSES the stall? I know we've been around the block a few times on this issue, but how can that happen?
