With everyone but Toro Rosso and the team formerly known as Force India having now revealed details of their cars, we can see the general trends to have emerged into the second year of these wider bodywork/tyre regulations.
The overwhelming area of attention for everyone has been in the super-sensitive area between the front axle and the sidepods – and this has brought variation between teams and innovation in the layout and design of both. These two components are crucially linked and can almost be considered as one. The greater bodywork freedoms granted in this part of the car from last year onwards have brought about much greater design variation in this interlinked area.
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What is very clear is that last year’s Ferrari SF70H has turned out to be the most influential design of recent years – with most of the 2018 cars adopting its treatment of the sidepod/side impact structure. Only Mercedes and McLaren so far have not done so. The Red Bull, Williams, Haas, Sauber and Renault (as well as the new Ferrari) all incorporate a separate side impact structure ahead of the sidepods.
Not having the impact structure built into the sidepod housing allows the airflow that has been interrupted by the front wheels more distance in which to re-attach itself to the side body surfaces, for greater aero efficiency. The other way of achieving a similar effect is moving the front axle line forward relative to the sidepods – bringing a longer wheelbase, ie the Mercedes approach.
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As for the sidepods themselves, there is great variation in where the radiator inlets have been placed – high or low – how they are shaped and how big they are. Generally, the high positioning of the rad inlets allows a more extreme undercut to the lower part of the pod as seen from head-on (so with a wide top and narrow bottom). This layout promotes a low-pressure area at the bottom which the air rushes to fill, thereby increasing the speed of the air from there and down the side of the car towards the downforce-inducing surfaces at the back.
The speed of the airflow over the various surfaces determines the downforce generated. On a car travelling at 150mph, the air speed over critical surfaces may be 200 or even 300mph, as the various vanes and contours create pressure changes. More air speed over those surfaces equals more downforce.
However, placing the radiators high and shaping the bodywork around that increases the car’s centre of gravity height – not a good thing, placing extra loads on the tyres for a given cornering force. So some teams prefer to mount the radiator inlets low. The air can still be made to accelerate around the sidepods with low-mounted radiators, albeit not so easily. Last year’s Ferrari had high sidepod inlets, Mercedes low. This year, both are high.
There is a very intricate and aerodynamically sensitive relationship between the front suspension and sidepod. There is only so much air pressure to go around – and some of it has to be used to feed the radiators with cooling air. The remainder can be used to create downforce.
As the air makes its way to the radiator intakes, obviously the front wheels and suspension get in the way. Nothing much can be done about the wheels, but the placement of the suspension wishbones are very much determined by the aero demands rather than the mechanical geometry.
Last year Mercedes (and Toro Rosso) placed the upper wishbone unnaturally high, mounting it at the wheel end to an upward extension from the wheel upright. This allowed air heading for the low-mounted radiator inlets to pass beneath the suspension with minimal disruption (the more it’s disrupted, the slower the airflow will be), thereby allowing the radiators to be smaller than would otherwise be necessary. That was last year’s Mercedes approach.
The other way to skin that particular cat was to do what Ferrari did – with conventional, lower suspension, but high radiator inlets. In this concept the airflow destined for the radiators travelled above the suspension.
But what Mercedes has done with the new W09 is combine the high suspension – which also brings benefits to the airflow used for downforce creation – with high radiator inlets (also good for downforce creation). In order for that to work, the air is scooped from beneath the suspension by a dramatic long lateral vane atop the barge boards and sent directly to the sidepod inlets.
It could be that only a very long distance between the front axle and sidepod (ie long wheelbase) allows enough airflow capacity to feed such a system and create plenty of downforce.
This has allowed Mercedes to retain its long wheelbase/low rake concept – or, expressed another way, the long wheelbase has allowed this unique combination of high suspension/high inlets to address the downsides of Merc’s existing low-rake concept. A lot of attention has been paid to lowering the centre of gravity in the new Mercedes engine – to offset the effects of having both high radiators and suspension, not to mention the halo.
Ferrari has stayed faithful to the concepts of the very influential car of last year. A slight increase in wheelbase (believed to be 5cm) has allowed a greater downforce-generating floor area – and an even more aggressive treatment of the sidepods. The front suspension remains conventional, allowing the radiator airflow to go over the top.
The Williams FW41 appears to share the same sort of concept and is almost totally unrelated to last year’s FW40.
Both the Red Bull RB14 and Sauber C37 are cars with very narrow sidepods, chasing aero efficiency.
The Sauber is very innovative, with the most extreme version yet of the high front suspension – and a very low siting of the main radiator intake, with a smaller separate intake higher up. This layout makes for a ‘fatter’ rear end and will impose a very different aerodynamic philosophy. But it may well have the lowest centre of gravity of any of the 2018 cars.
The McLaren MCL33 superficially appears the least changed from its 2017 descendant but features much higher and smaller radiator inlets that have allowed a more extreme undercut.
The McLaren’s front wing has a much more dished proportion to its arrangement of multi elements – diving down from high outer to low inner – suggesting a more aggressive chase of aerodynamic load. Probably in the expectation of having more horsepower than last year to push it along.
How all this variation plays out we’ll begin to find out at Barcelona in a few days.
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