Why The Increase in Rake?

[tuj]

never seen that shot of the FW15, cool!! I've seen the FW14B do it's active test, but I did not know the 15 could raise rear ride height on driver command, wow.

[crbassassin]

You can run a higher rear wing with more chassis rake.

[Powerslide]

think of it as during the era when a lot of teams were running flexible wings where on the high speed straight the wings would flex and reduce downforce but increase aerodynamics and top speed. On the corners when the car slows down the wing wont flex so much and returning higher downforce, getting the best of both worlds but then later was scrutinized and then banned.

so what red bull did is rake the entire car more aggressively, during lowers speeds the high rake would give higher wing or general attack angle increasing downforce but as the car get up to speed the rear suspension would drop low by down force and improve high speed on the straight, thats why red bulls were having lots of sparks on higher speed sections. should be pretty interesting how they would run the suspension set up, more lateral support but slightly less on vertical load

basically what they are trying to achieve is mechanical variable aerodynamics

[misterbeam]

But no one has answered the question: how can they still have a good amount of rear downforce on braking for example ? if you bring me back to the era of previous F1 cars that used to have low rakes, i would expect them to lose balance instantly with high rakes on braking ...

[Vyssion]

At the front of the car, the nose down attitude drops the Front Wing into ground effect. As the wing gets closer to the ground, the air accelerates increasing the downforce generated, whilst a vortex is generated at the joint between the wing and Endplate. Obviously in the real world there is a limit to this where boundary layers combine and other "flow restrictive" phenomenas.

Running with more Rake can become a problem during qualifying especially as this is when the car is at it's lightest (may occur during the last few race laps too). The biggest issue comes under braking as the car pitches forward and can cause the Front Wing to either collide with the ground or Stall as it's range becomes too low to work aerodynamically. However, the main problem comes from the Splitter as it is more likely to hit the track than the Front Wing wearing out the skid pad (and maybe ensuring disqualification. This is essentially the limiting factor when it comes to rake angle setup.

Concerning the underbody, a Diffusers performance has to work over a wide velocity and pitch range which both contribute to the Diffusers expansion: get the rake wrong and you can end up with the Diffuser losing efficiency or some cases stalling. If we imagine that exhausts could not contribute to the sealing of the diffuser then peak downforce generated in the Diffuser would occur at a much lower height (due to Ground Effect). The last time we saw rake used extremely was in 2011 when teams utilised Off Throttle Blown Diffusers. The easiest way to explain it is that those cars had more rear downforce by virtue of the exhaust plume assisting in Diffuser extraction.

Basically, rake may be synonymous with an increase in downforce; however, the effects of it can either be marginal or large. It could be argued that it is a simple tradeoff to be honest, keeping in ming that with raised Rake you then also have to redesign (or at least account for the change in) the rest of the car too.

But when all is said and done, teams weigh up the benefits of having a slight normal force being applied to the chassis aiding in overall downforce vs. the need to account for (or design around) a larger volume of space required to be "virtually sealed" via longitudinal vortices off bargeboards ect, or exhaust plumes. If the gains of a higher rake outweigh the downforce they could get from a more traditional approach, then obviously they will opt for it. But its on a team by team basis (as you can see for yourself).

Concerning your specific "Rear downforce under braking" part though, the change in pitch doesn't cause the rear wing to immediately lose all of its performance as if it were on ice. There is of course a change (could induce stall or even produce more downforce depending on the teams angle setup - increased drag assisting in braking as well) but given that front wing/underbody downforce make up ~70% of the overall, and the fact that front downforce is desirable for a responsive turn in along with oversteer > understeer (within reason!!), I would hazard a guess there wouldn't be too many issues that would arise. Finally, most of the braking occurs in a straight line before the corner anyway so that negates some of the potential impact as well.

[OO7]

I understand that increasing rake is beneficial, as it places the front wing closer to the ground enhancing ground effect. Despite the advantages extending downstream, why doesn't such a configuration shift the CoP too far forward and cause handling issues (I believe the early FW16 suffered from this)?

[FoxHound]

Continuing a discussion that's been held on the Merc team threads....

The concept is irrelevant.

An adverse pressure gradient is a region where static pressure increases in the direction of travel. This is problematic, because air would much rather flow from areas of high pressure to areas of low pressure, as areas of varying pressure will always seek to equalize.

Ultimately, that means air flow along an adverse pressure gradient steadily loses dynamic pressure - the kinetic energy of the air flow itself - as it overcomes the effects of the adverse pressure gradient. If boundary layer flow along an adverse pressure gradient loses too much dynamic pressure, it will separate. By separate, I mean it will reverse itself, as areas of varying pressure will always seek to equalize...

http://i.imgur.com/nuUvXQU.jpg
Exaggerated for effect

If that were to happen on a Formula One car as described in the Motorsport article, the size of the car's wake would be increased significantly, which would increase drag significantly, because it would create the mother of all bottlenecks. It's a senseless outcome.

And this is supposed to happen to RB12 as a drag-reduction strategy? After the severity of the rear wing's adverse pressure gradient has been minimized due to reduced rake from aero loading? In other words, the senseless outcome is supposed to occur magically?

http://i.imgur.com/2ya6ZUY.jpg
Less rake = lower AoA

As my friends in New Jersey would say, "Get the --- outta here!" (The idea presented actually comes closer to explaining how rear wings create downforce.)

If you have a pet, ask for its thoughts on the subject. The answer you receive will make exactly as much sense as what was written in that article.

EDITS: clarity

So what is the position then Ben?

What are you suggesting regards the drag of the Red Bull vs less steeply raked cars such as Ferrari and Mercedes?
Red Bull would have us believe that their lower top speeds is a direct result of a less powerful(up to 60bhp according to Horner...) PU.
I want to be as clear as possible why I'm struggling with some of the theories floating about.

It is interesting because I find these assumptions by Red Bull to be complete horseshite. And my reasoning on this comes from laptime data and GPS data from previous venues.
A bit of data I've collected to compare 2 separate venues with different demands on the car. Spa v Hungaroring.


The lap at Spa is 26 seconds and 2.6km longer than Hungary.
The importance of engine power is far more pronounced at a track like Spa as it has more time spent at full throttle.
33% of time is spent at full throttle around Hungaroring compared to 57% at Spa, a full 24% difference.

At Hungary, a car less dependant on overall power in comparison to Spa, the difference was 0.320 seconds Mercedes to Red Bull.
Yet at Spa, we see the difference shrink by more than 50% to 0.149.

Red Bull would probably put the difference down to engine power, Mercedes having a 3kp/h advantage with Rosberg, with Hamilton level pegging Ric. However Verstappen was 1.5 Km/h an hour down on Ric, and still beat him in Qualy by over 0.3 seconds.
http://grandepremio.uol.com.br/f1/notic ... gica-de-f1

So they're set up differently, however marginal.

Now where can anyone draw the conclusion from this data, that Mercedes engine is so superior that it is the raison d'etre of their success?
And how can a gap shrink when the importance of this supposed advantage increase?
And how is rake in anyway an explanation that an inferior engine can decrease a gap when the reliance upon said engine increases?

[OO7]

The Mercedes cars are relatively poor on the Super Soft tyres. They gain far less using the softer compounds than any other team. Rosberg's Q2 lap on the softs however was very strong. The Mercedes car had been struggling for most of the weekend so comparisons are a little difficult.

[bhall II]

What are you suggesting regards the drag of the Red Bull vs less steeply raked cars such as Ferrari and Mercedes?

Nothing at all. I've just been poking holes in your arguments.

Without hard data, there's no way to know what's what, because there's nothing inherently draggy about high rake, and there's nothing inherently "slippery" about low rake. The devil, as they say, is in the details.

However, I will say that I'm equally suspicious of Horner's power deficit claims and Lowe's rear wing AoA hand waving. In each case, it just strikes me as PR nonsense, because I've gotta believe both of them know the story is nowhere near that simple.

I'm still baffled as to why it matters, though. It's the whole car that crosses the finish line.