Discussion - is there a design issue with LMP

[Aysedasi]

Well, it rolled several times during which it was airborne. As I couldn't see how the accident started, I'd prefer to reserve judgement on this one.....

[SebringMG]

Looked like it was launched by either a kerb or the gravel and not aero related imo

[dj choc ice]

we have had 4 flipovers now, 6 if you include the audi monza incident and the BK incident at sebring.

there is a definite design issue with these cars when they are sideways, something needs to be done before a car fly's either roof on into a wall at high speed or goes into a spectator area and we have many people hurt or even killed.

on a side note though it did look like the car made contact with the inside wall/tyre wall once it had spun just before it went airborne, but it didnt look like the car was launched in any way by the impact though.

[AllonFS]

I completely agree, the Peugeot crash sideways roof first into the wall probaby should (but thank goodness didn't) have done for the driver. And as others have pointed out, here is a P2 on a not particularly fast part of the circuit crashing horribly. Surely it can't be rocket science (excuse the pun) to keep cars on the ground?

[gucom]

The thing I'm wondering is... what has changed since last year that makes cars flip so much more often this year? This really is starting to worry me, it's just not gonna end up being OK every time if this continues...

[Stefvh]

SInce last year, one year of big devlopments

[gwyllion]

I think the Lola that flipped, has pretty much the same aero. Not a lot changed since last year. The LMP1/2 rules have been around since 2004.

[gucom]

Originally Posted by gwyllion

I think the Lola that flipped, has pretty much the same aero. Not a lot changed since last year. The LMP1/2 rules have been around since 2004.

exactly, which is why I don't understand why all these flips are happening now... the aero rules are unchanged as far as I know, I can't imagine all teams having made the same change within the rules that suddenly causes these cars to flip when sideways on bumps...

[Holt]

I think this is the first year where the prototypes are putting themselves into a position that exposes thier aerodynamic weaknesses.

I don't remember seeing similiar spins in last year's sports car racing.

Now we have what, 5 warning shots? Most motorsport series don't get that many chances to do something before it all goes wrong

[gucom]

Indeed... but what can be done before the LM24 start on saturday? No1 wants to see the race stopped obviously but with the number of crashes recently, and the length of the Le Mans 24 hours, I think there's a substantial chance there's gonna be another one of these crashes during the race... I don't think there's really anything they could do right now to reduce that risk...

[I love 04s]

could it be something to do with the new regulations re. underbody?

For example.

-flat very close to the road sidepods pre 2006.

Whereas now ....

Hard to see but the sidepod floor is more like a "boat" now...when travelling sideways at any speed surely its just asking for air to rush in and cause it to lift up?

Just my ten pence.

[deggis]

Video: http://youtube.com/watch?v=yxm9PjVmgW4&fmt=18

[JAG]

Originally Posted by SebringMG

Looked like it was launched by either a kerb or the gravel and not aero related imo

IMO, he simply lost control, it slid sideways, but rather than spinning off into the gravel, the car gently lifted, and threw him off into the gravel.

Looked like a text book flip, the same as we've seen seemingly at every high speed track this year.

[MulsanneMike]

Originally Posted by I love 04s

could it be something to do with the new regulations re. underbody?

For example.

-flat very close to the road sidepods pre 2006.

Whereas now ....

Hard to see but the sidepod floor is more like a "boat" now...when travelling sideways at any speed surely its just asking for air to rush in and cause it to lift up?

Just my ten pence.

It's the lift generated by the top side and the inability of the bottom to produce downforce when the car is yawed (opposite of what you want--naturally you want the underside downforce to counteract the top side lift) that causes the cars to get airborne. The underbody chamfer allows the car to maintain some degree of downforce generation when yawed sideways. The chamfer allows any built up air pressure a means to escape. Previously that wasn't the case.

Here's a simplified drawing that shows transverse x-section with 4 degrees of wind ward yaw (worse case Piper report looked at):

http://www.mulsannescorner.com/rolldetail.JPG

[prototype]

Originally Posted by JAG

IMO, he simply lost control, it slid sideways, but rather than spinning off into the gravel, the car gently lifted up, and threw him off into the gravel.

Looked like a text book flip, the same as we've seen seemingly at every high speed track this year.

I agree, textbook flip with the car going sideways.

I think if some people saw one of these LMP's flip on the Bonneville salt flats they would still say that the driver hit a curb or a bump in the grass.

[I love 04s]

Originally Posted by MulsanneMike

It's the lift generated by the top side and the inability of the bottom to produce downforce when the car is yawed (opposite of what you want--naturally you want the underside downforce to counteract the top side lift) that causes the cars to get airborne. The underbody chamfer allows the car to maintain some degree of downforce generation when yawed sideways. The chamfer allows any built up air pressure a means to escape. Previously that wasn't the case.

Here's a simplified drawing that shows transverse x-section with 4 degrees of wind ward yaw (worse case Piper report looked at):

http://www.mulsannescorner.com/rolldetail.JPG

I stand fully corrected!

[Malfunction Junction]

Thankyou Mike,

For those interested in a bit more pure theory, check out Bernoulli's Theorom. There's a school of thought that this applies to all lift, whereas another refers to "surfing" over the air. There may be a potential combination of the two taking place under and over a yawing prototype.

It seems to me that a strake would more useful at the TOP of the car - perhaps even a pair running down the outside edge of the bodywork.

Additional advantage - it would remind people of the McLaren M8 series (though I do recall at least 2 backflips there too....)

Power and cornering speed are of little consequence. The 400ish hp Porsche 908 Spyder and 420ish hp Ford P68 were notorious for getting airborne at the Nurburgring, not always at the Flugplatz' either, but I'm not really comparing apples with apples here.

Drivers will always fight a spin to the hard object they're heading for.

Question - Have there been genuinely high speed incidents this season, using the same cars, with matching the driver response, that have NOT resulted in airborne behaviour?

[MulsanneMike]

Originally Posted by Malfunction Junction

Thankyou Mike,

For those interested in a bit more pure theory, check out Bernoulli's Theorom. There's a school of thought that this applies to all lift, whereas another refers to "surfing" over the air. There may be a potential combination of the two taking place under and over a yawing prototype.

It seems to me that a strake would more useful at the TOP of the car - perhaps even a pair running down the outside edge of the bodywork.

Additional advantage - it would remind people of the McLaren M8 series (though I do recall at least 2 backflips there too....)

Power and cornering speed are of little consequence. The 400ish hp Porsche 908 Spyder and 420ish hp Ford P68 were notorious for getting airborne at the Nurburgring, not always at the Flugplatz' either, but I'm not really comparing apples with apples here.

Drivers will always fight a spin to the hard object they're heading for.

Question - Have there been genuinely high speed incidents this season, using the same cars, with matching the driver response, that have NOT resulted in airborne behaviour?

Yes, it would seem we need to look at the top side lift and with that we're back to NASCAR type "roof" flaps that automatically deploy. But it will take a very smart person to get it to work when, and only when, they are needed as the situation here is very different than the backwards NASCAR (car get's backwards [worsecase], roof flaps deploy]. Working out the logic control and implementing a flap that fits and works on all cars would be one hell of a challenge. And I've been told this was brought up to the FIA back in '02 when the Piper report was being done and there was hesitation then.

IRL runs a center line wicker down the length of the car with rather meek results (ask Buddy Rice about it!):

http://youtube.com/watch?v=pPtfWHgVCPk

[Tom87]

What about at 2008 Bed Bull/Renault style fill extending from the roll hoops (or cockpit for coupes)? This would serve a similar purpose to the larger rear wing end plates of the current LMP cars by increasing drag, but would also disrupt airflow over the lift generating surface.

[zac510]

ACO have just accounced intention to change the floor rules for 2009 and then further for 2010.

[gwyllion]

Something went wrong with your translation.

Cette sécurité passera d’abord par une réduction des performances moteur en 2009. Par la suite, en 2010, la protection latérale sera renforcée, et des réductions seront apportées d’un point de vue aérodynamique, notamment au niveau de l’aileron arrière. « Nous voulons réduire les appuis, donc tout appendice aéro sur la voiture sera supprimé, pour les LMP1 et les LMP2 » ajoutait Daniel Poissenot.

source: http://www.endurance-info.com/article.php?sid=5797

In English:

The safety will first be increased by a reduction of the engine performance in 2009. Thereafter, in 2010, the side protection will be reinforced, and aerodynamic restrictions will be introduced, in particular on the level of the rear wing. « We want to reduce the downforce, therefore any aerodynamic appendix on the car will be removed, for the LMP1s and the LMP2s » added Daniel Poissenot.

I do not have a good translation for "appendice aéro", but I think it includes the Audi non-wing

[FelixP]

Aero Devices apparently:

http://www.autosport.com/news/report.php/id/68235

[Malfunction Junction]

Tom87,

You might be onto something there.

I do recall in the early 80's there was a Kremer spaceframe chassis (one of the 908 derivatives I believe) that had an obscenely ugly nose and a strake from the roll hoop to the rear wing.

It would certainly disrupt the flow down the lifting surface as well as provide an advertising space.

I doubt it would be far enough from the centre of pressure to help to add much yaw stability, but you never know.

Mike,

Historically speaking, most of the inverted accidents in the IMSA/Group C era were from 180 degree spins resulting in blowovers were they not? I certainly can't recall one that flew from a yaw of 90 degrees.

It is now well known that some Group C cars drew their normal downforce in from the side of the chassis, so is there something about a floor designed on these principles that makes it more or less susceptible to yawing flight than a currently sculpted floor?

I wonder if the cars then were just as susceptible, but the sheer downforce numbers were enough to mask the possibility?


Experience has shown that flat floors are dangerous. For many years there have been no incidents quite like these, despite numerous instances of drivers having suspension failures, hitting kerbs, dropping off the edge of the track onto bumpy grass sections etc. It appears that the upper aerodynamic refinement of the cars has exceeded the capacity of the current floor to counter it, while the diffuser is clearly working well.

While I'm typing, I'm wondering if a series of shapes down the spine of the car might assist in breaking up a yawing airflow, something like Lisa Simpson's haircut, rather than Homer's......

[Purist]

In 1990 or so, the WSPC race at Fuji saw a Nissan Group C car cut a tire on the main straight, turn sideways, and lift off the ground.

http://www.youtube.com/watch?v=2e-Zad4mFb0

It's not exactly 90 degrees yaw, but you get the idea.

[JAG]

Originally Posted by FelixP

Aero Devices apparently:

http://www.autosport.com/news/report.php/id/68235

All aero devices on the bottom of the cars will be banned for 2009."

What does that actually mean, the front splitter, rear diffusser, what?

I can't imagine they'd have an entirely flat bottom, it's the tunnels afterall that were introduced to stop some of the previous aero issues.