Reducing the drag of a two element wing through stall

[hybridreload]

Hi all newbie here,

think this place is great and the insight some people give is brilliant

read the entire of this thread and i believe quite a few people need to also.

comments on the last few pages about blocking the hole and not blocking and what that does needs to be clarified in some peoples minds.

i see it as the hole is blocked by the knee on the straights. This "completes" the tube allowing air from the snorkel down through the fin to the rear wing. WHen in a bend the hole into the cockpit is unblocked and the air flows into the cockpit.

Whether this flows into a fluidic switch (or even if this is needed) is unknown.

also andrew benson on the bbc text commentary got this completely wrong.

[Federico]

The helmet is already sheped to deflect air into the airbox.

[hybridreload]

Just a bit of topic here. Seening as there are two potential holes too place a Snorkel on the cockpit, on Faster circuits i.e Monza could Mclaren have two Snorkels? or will one do the job?

I believe that the general consensus is that the snorkel is supplying (or not) a "signal" to a fludic valve at the rear of the car which "switches" air from the top vent in the airbox to one of two locations. The volume of air sent for this signal is supposedly significantly lower than that being fed from the main airbox, therefore I don't think a second inlet would be advantageous.

That is all assuming that there's only two possible states for the fludic valve of course! If perhaps there could be an advantage to sending air to somewhere else under different circumstances maybe they're planning something else for the future...

following on from the question asked earlier with debris in the snorkel (not an issue), could the possibility of debris in a fluidic switch be dangerous, as is the size of the switch would need to be large enough to handle most of the flow from the airbox. You couldn't be sure if a small obstruction could change the aerodynamics within the switch that could the to lead to flow being channelled to the rear wing causing a permanently stalled wing.

[segedunum]

I don't see how this can be legal to be honest. The double diffuser situation last year had loopholes in the regulations, but effectively using a driver as a moveable aerodynamic device can't be right. We've had moveable aerodynamic device systems banned before and from what I remember of the regulations it's whether a device moves and changes the aerodynamics, not whether it's a moving part of the car or not. It's not something that moves and has an effect on the aerodynamics three or four steps down the line, perhaps like Renault's mass damper.

I find it an odd interpretation that the FIA has taken, and if they wanted to cut costs then this isn't the way to do it.

[hybridreload]

I don't see how this can be legal to be honest. The double diffuser situation last year had loopholes in the regulations, but effectively using a driver as a moveable aerodynamic device can't be right. We've had moveable aerodynamic device systems banned before and from what I remember of the regulations it's whether a device moves and changes the aerodynamics, not whether it's a moving part of the car or not. It's not something that moves and has an effect on the aerodynamics three or four steps down the line, perhaps like Renault's mass damper.

I find it an odd interpretation that the FIA has taken, and if they wanted to cut costs then this isn't the way to do it.

but the fia stated the movable part cannot be a part (sprung or not) of the car. The mass damper was a sprung part of the car. A driver is not. A driver can already alter the aero characteristic of the car by moving/turning his head, he also alters the airflow when turning the wheels as his hands pop over the cockpit rim.

[javi]

I am new here..., and half technician only
Sorry (really, lots of pages to read)if this has been asked before or if someone deems the questions "silly"

Question1: If really is the driver´s knee which is operating this device by blocking a hole in the straights (isn´t it?), Mclaren must be very sure that the driver WON´T cover that hole, per example, in a quick corner... How do you prevent a driver to block unintentionally this "hole" in a hard, wheel to wheel battle??
Question2: You don´t need drag in the straights,OK, but you NEED downforce/drag while braking... So also the driver must be very sure he "unblocks" the hole while braking hard at the end of the straights... This would work with left foot brakers, are Hamilton and Button like that? I guess...

so, driver concentration must be very very high all race... (well, they´re supposed to do so, arenñt they?)

[Just_a_fan]

I don't see how this can be legal to be honest. The double diffuser situation last year had loopholes in the regulations, but effectively using a driver as a moveable aerodynamic device can't be right. We've had moveable aerodynamic device systems banned before and from what I remember of the regulations it's whether a device moves and changes the aerodynamics, not whether it's a moving part of the car or not. It's not something that moves and has an effect on the aerodynamics three or four steps down the line, perhaps like Renault's mass damper.

I find it an odd interpretation that the FIA has taken, and if they wanted to cut costs then this isn't the way to do it.

The driver isn't a device nor is he part of the car.

The driver adjusts the front wheels and they probably have the biggest aero effect on the car. Perhaps we should ban steerable wheels...

Sorry, couldn't resist a bit of reductio there.

[Just_a_fan]

I am new here..., and half technician only
Sorry (really, lots of pages to read)if this has been asked before or if someone deems the questions "silly"

Question1: If really is the driver´s knee which is operating this device by blocking a hole in the straights (isn´t it?), Mclaren must be very sure that the driver WON´T cover that hole, per example, in a quick corner... How do you prevent a driver to block unintentionally this "hole" in a hard, wheel to wheel battle??

No one is really sure they do use their knee. Some of us have raised this sort of issue in the thread but the 'true believers' will accept no disagreement. They may still be proved correct, of course, but 'til then it is all supposition.

Question2: You don´t need drag in the straights,OK, but you NEED downforce/drag while braking... So also the driver must be very sure he "unblocks" the hole while braking hard at the end of the straights... This would work with left foot brakers, are Hamilton and Button like that?

All drivers are left foot brakers these days. I think even Rubens does now although he didn't for a long time (I think). Assuming the driver uses his knee to operate the new system, he will need to disengage his knee from the system before he brakes to ensure correct downforce distribution. The added drag will then be beneficial to the braking process anyway.

[siskue2005]

why do people have problems understanding that Driver cannot be considered as a movable aero device.....Driver can lean to one side, he can raise his head and lower it , he can do whatever he wants to inside the cockpit
Maybe the driver can move up and down and act like a mass damper ??

[RacingManiac]

I think the driver has to BE the valve in order for this to be legal. As said he is not part of the "device"(otherwise known as the car). If there is a separate valve then that part will be the movable device and thus banned from the movable aero device rule.

Assume if thats how it works anyway, aerodynamically how much flow does it need to be supplied to stall the wing? The losses must be immense from a tiny hole routing through the car when it reaches the rear wing?

[l.etranger]

Those figures seem to indicate the drag increases with stalling & the downforce reduces.

I confess, I had to run and posted before a full quality check of my math. Since the units and orders of magnitude were right, I felt good - but I went home and re-checked Katz and began to feel very uncertain about the L/D - seems low compared to similar examples he uses. Sure enough, when I rechecked today I had missed a couple parentheses and my equations were off.

I've also been looking at some more references (Abbott's 'Theory of Wing Sections' - Check Google Books), and thinking that my estimates for section drag were too low for a wing pushed as aggressively as an F1 rear wing would be. Most plots seem to show that two-element wings see their section drag climb to the .2-.3 range by the time they're pushed to peak lift. Section drag is indexed to chord (like section lift) so at my estimated 2.5 Lift coefficient, this works out to a section L/D in the 8-13 range - not 20 like I mentioned. I added this term and reran:


I think this is probably a more accurate breakdown of unstalled wing loads. However the L/D of 4.0 is on the high side for a wing of this type - enough so to make me doubt the value chosen for k, which is quite low. Perhaps endplates of this height (longer than the wing's span) no longer fit the linear formula for effective wingspan?

Unfortunately, when I made this fix to my formulas my chief finding - lower drag in stall - was reversed. I'm thinking that my estimate of the unstalled drag may be too aggressive - it applies the flat-plate estimate for a high AoA to the whole wing (23 degrees), when the mainplane actually has a pretty small angle. I'd be interested in hearing an estimate (or seeing a calculation) of the loads on a stalled wing. Using flat plate theory I'm showing that the post-stall form drag on just the flap (which I estimated at 45% chord and 55 degrees) is as high as the total drag on the unstalled wing.

[Giblet]

I am still taken back that some users on this technical site, were so sick of hearing about us talking and speculating about something technical, felt the need to complain, trying to stifle one of the best technical discussions that has been on this site in ages. We were on the cusp of figuring out in detail how it works, with a simple process of observing and discussing. Most of the more technical/intelligence inclined users were not nay-saying because they were sick of the word snorkel.

even if it was a left field idea, it was a great discussion other than a bunch of bran new users yelling "COOLING COOLING!!!!"

This isn't about told you so, it's about letting people have discussions without complaining about sore eyes. If you are not into it, don't bitch, move on.

Fine it's in a new thread, no problem, fair enough. I hope some people are seasoning and slow roasting their hats for a good dinner tonight, followed by a serving of pie with humble berries.

Now that is has come and gone, and there are details to be sorted, it's coming together. This site lists high up in google searches, and this discussion attracted a swath of new users, strengthening the site more.

Thanks to SCL, Pup, Raptor22, Scarbs, Manchild, Jason.Parker.86, autogyro, Shaddock, and many that I have missed, and those who supported me in PM's when I knew I was on to something. Also to the "F1 guys" that had some more intimate knowledge and didn't want to post publicly, thanks also.

[void]

I think this devices are ilegal. A movable aero is not only flexible wings or bodywork. The McLaren's device is activated by pushing a button (don't matter if was using fingers or knees or so by using driver's brain inputs), so it has an electrical engine and a kind of valve. Activating this device the drivers change the aerodynamics of the car using movable parts.

[remotedt]

hello all,

new user here... sorry for the lack of knowledge here... but does anyone agree that maybe the design here was purposely done to double as a cooling vent...

if the air comes in the snorkle, through an open space and into a second interior inlet, it's flow could be blocked by anything placed between the two. if the driver is used as that blocking element, then nothing is changing on the car other the the air flowing through/around it...

always block it, it does nothing... move out of the way, and let the airflow unrestricted, and you now have a different function...

[hybridreload]

I think this devices are ilegal. A movable aero is not only flexible wings or bodywork. The McLaren's device is activated by pushing a button (don't matter if was using fingers or knees or so by using driver's brain inputs), so it has an electrical engine and a kind of valve. Activating this device the drivers change the aerodynamics of the car using movable parts.

please just read the previous discussion, there is NO mechanical element. It is like blowing on a recorder (woodwind instrument), the air will pass out of the hole.The driver covers the hole (NOT pushes a button) and the air will now carry on down the tube instead of out of the hole.

this airflow may not be enough for purpose so a fluidic switch (which has NO MOVING PARTS) can be used to switch the flow of a large amount of air, using the small amount of pressure from the "driver tube".