Formula 1

Have high rake cars had their day in Formula 1?

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Have high rake cars had their day in Formula 1?
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Co-author: Jonathan Noble

The progress Mercedes has made with its Formula 1 car this year, allied to struggles Red Bull is having taming its RB16, has re-opened the debate about high rake cars.

Ever since the current aero regulations came in to play, teams have been divided about which direction is optimum – with Mercedes at one end of the spectrum and Red Bull the other.

For Red Bull, the belief has been that a high rake car, with the rear running higher than the front, is the best way forward.

But based on early season form, and in particular the difficulties the Milton Keynes outfit is facing getting its current car to behave while Mercedes' low rake solution is flying, there have been some suggestions that perhaps the high rake solution has reached the limit of its potential.

Last week, Motorsport.com threw the theory to former Red Bull driver Daniel Ricciardo that perhaps the best days of high rake cars were behind us.

“I'm no aerodynamicist but I would say that could be quite accurate,” he said. “I know from what I feel I knew and saw over the years, especially of Red Bull success in the Vettel and Webber days, that it was all about pumping the rake higher and higher.

“Now, more more recently, Mercedes seem to have had more success with something that's less extreme. So it looks like it's going back to that...it does look the case that it reached its peak and now it's trying to find another way to go fast.”

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High rake benefits

Like most things in Formula 1, the actual answer on the high rake debate is not actually so simple. Because, whilst from the outside it often seems as though one concept has to be better than another, there are many factors as to why it’s a constantly evolving situation and why there is not a one-size-fits-all solution.

The rake angle at which you have the car set up is, simply, an aerodynamic factor. The more angle you can apply without the diffuser flow being disturbed, then the more downforce you can potentially produce as there will be more air going under the car.

But there will be a ceiling where further downforce gains cannot be achieved because there is too much disturbance in the system, so the flow under the car isn't behaving.

This could be what is happening to Red Bull this year, where the theoretical downforce peaks it can achieve in the wind tunnel are not matched by the reality of how its car performs on track at various different corner speeds.

Disturbance can be triggered by various factors, including ride height sensitivity, turbulence created by the front and rear wheels or an inefficient aerodynamic design.

For Red Bull and the teams that have followed that high rake concept, given its win ratio during its dominant years, controlling the turbulence created by the front and rear wheels was and still remains a critical factor.

 

Red Bull has learned well how to manage these factors in the past.

Exhaust blowing tactics were deployed during the V8 era to help mitigate the effects of tyre squirt on the diffuser, whilst at the front of the car, flexi-wings were a factor in helping to keep the turbulence created by the front tyres in check.

As the rules continuously changed throughout that period, so too did the teams’ approach, but the constant that remained was Red Bull’s effort to seal the edge of the floor and diffuser, where possible, from the turbulence created by the tyres.

As we moved into the hybrid era, some of those tricks were stripped away because the overall design of the cars were simplified.

This opened the door for the emergence of an aerodynamic rival to the high rake solution used by Red Bull. Mercedes, with its lower rake philosophy, made up some of the aerodynamic deficit by increasing the wheelbase, thus increasing the length of the floor and lessening the impact that the turbulence had on its floor and diffuser.

 

Mercedes had and still continues to opt for a more consistent and usable amount of downforce over a wider range of operating conditions, than the absolute peak that’s deliverable with a higher rake setup.

In the case of Mercedes, this has always been supplemented by a very compliant suspension setup too, firstly with FRIC and latterly with independent hydraulic suspension arrangements, all of which keep the platform of the car more stable.

A sealing ceiling

The 2017 regulations were originally introduced to increase the level of downforce that could be produced in order to reduce lap times. But, in making the cars wider, the rules pertaining to the edge of the floor were left unchecked. This quickly led to a range of solutions being fielded by the teams that helped to seal the floor’s edge and ramp up the downforce that’s achievable.

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Ferrari SF71H floor detail

Ferrari SF71H floor detail
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Photo by: Giorgio Piola

Ferrari SF70H floor cut

Ferrari SF70H floor cut
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Photo by: Giorgio Piola

Haas VF-17 floor details, captioned

Haas VF-17 floor details, captioned
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Photo by: Giorgio Piola

McLaren MCL32 floor details, captioned

McLaren MCL32 floor details, captioned
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Photo by: Giorgio Piola

Red Bull RB15 top view

Red Bull RB15 top view
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Photo by: Giorgio Piola

Ferrari SF90 top view

Ferrari SF90 top view
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Photo by: Giorgio Piola

These fully enclosed holes that are now allowed on the floor’s edge create a vortex skirt that keeps the wheel wake from the front tyre from being ingested by the floor. Furthermore, holes, rather than slots, ahead of the rear tyre just add a little more potency to limit the effects of tyre squirt on the diffuser. 

And, whilst this helps those cars running with higher rake, it’s actually even more of a benefit for those running with a lower rake angle, such as Mercedes.

Overall package remains king

The interesting aside, is that the dominant teams in both cases largely have the engine/power unit to thank for their relative aerodynamic successes too.

Red Bull was able to use the Renault engine to exploit the exhaust blown diffuser and aggressive rake like no-one else could. The longer architecture of the Mercedes power unit led it to take the longer wheelbase and lower rake route.

Furthermore, it’s an extremely long and costly road to travel to change from one concept to another, with rake just one ingredient in a very finely balanced recipe.

High rake has essentially become Red Bull’s hallmark and means it is unlikely to switch from it. The other teams that followed suit, which is most of the field to a varying degree, also went through the pain and expense of trading one concept for another.

Racing Point did make the switch from high to low rake, but it needed an intense spell in the windtunnel and the use of the same Mercedes rear suspension and gearbox, to be able to make it work.

And while the Mercedes concept is paying dividends now, let’s not forget that it wasn’t that long ago that Mercedes cars were labelled ‘divas’ and questions were frequently asked as to why it hadn’t increased its rake angle inline with the rest of the grid.

Key to the debate going forward will be how quickly Red Bull can get on top of its current issues. If it can sort out the balance inconsistencies that have dogged it over the start of the campaign, then it could deliver the progress needed to at least put Mercedes under some pressure.

But if it continues to struggle to understand how best to solve its headaches, then the arguments against high rake cars will likely only get louder.

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About this article

Series Formula 1
Author Matt Somerfield