Gary Anderson: Making rear wings work with DRS

The advent of Formula 1's Drag Reduction System in 2011 forced designers to rethink their philosophies behind rear wing design. But things haven't changed as much as most people think.

The science

Under current FIA rules, a rear wing has to fit into a rectangular box when viewed from the side, and has a maximum of two closed aerodynamic sections, the main (lower) wing plane, and the upper flap; each with a specified width and depth.

In order to get maximum performance from the wing, it is essential that the slot between the plane and the flap is as far back as is possible to still enable stable attachment of the airflow to the wing. Too far back and the air will separate before the slot, meaning no downforce at all. Too far forward and the underside surface air speed will not increase enough, meaning that potential wing performance is given away.

Mercedes has yet to optimise its rear wing © LAT

The execution

The slot is there to inject high-speed, high-energy airflow onto the underside surface where the airflow would otherwise separate. When the slot is opened up to 50mm (when the DRS is activated), the velocity of the airflow going through the gap is vastly reduced and causes the airflow on the surface of the main plan to separate. The effect of this is a massive reduction in drag and a potential gain of 7mph.

Most designers will place the slot at the critical point where the air wants to detach itself from the wing, and doing this will enable you to generate the maximum amount of downforce. Some, however, are more sympathetic to the whole system and position the slot further forward. This is a lower-risk solution, but does not produce such a big reward either.

The problems

In order to produce downforce, air has to remain attached to the surface of the wing. In a straight line, however, downforce - and the resultant drag - hinders a driver's speed, so the key when the DRS is used is to make the air detach, thus reducing drag and downforce.

The big issue here - and the one that has plagued Mercedes for much of the early part of this year - is that when the DRS is deactivated and the flap closes, the process of airflow reattachment is not an instantaneous one.

The Mercedes wing is such a critical one i.e. the slot is too far back, that the drivers have had to close it at least 50m before the braking zones this year just to allow the air to reattach - and to generate some downforce - before applying the brakes. What they seem to have done to address this problem is change the configuration of the wing so that the slot is moved further forwards.

Instead of having 100 per cent downforce for 95 per cent of the time, they now have 95 per cent downforce 100 per cent of the time, which is probably the right compromise for them. With the slot away from that critical zone, it is easier for the air to reattach once the slot moves back to its 'closed' position.

The Williams wing © LAT

The financial cost

As a result of the DRS coming in, all the teams have had to go away and brew up a whole new family of rear wing designs that not only optimise the rear wing performance, but also get the best speed advantage possible when the DRS is in effect. Given that the cost of tooling and component manufacture of a given wing design will exceed £1million, and that each team will need around five different packages to suit all the circuits on the calendar, it makes it very hard for squads to adhere to the current budget reduction process.

To qualify or to race?

Most teams have optimised their rear wings to maximise the affects of the DRS during qualifying, rather than the races. This is a smart move, because if you don't use your DRS properly in qualifying - when its use is unrestricted (unlike in races) - you will give away about a second in terms of lap time, and that's a massive difference.

There are two ways of making your car work with the DRS in qualifying. The Mercedes system involves the air stalling on the rear wing when the DRS activates and opens the flap between the planes, giving the car about a 7mph boost. The other method is by having a longer cord flap, so that when the DRS activates, the main plane doesn't stall the air, it simply adjusts the amount of downforce the wing is giving. This gives you a 4mph boost, but a more consistent one. In Mercedes' case, it's probably pushed too far one way whereas some teams haven't pushed far enough. There is a happy medium to be struck though.

Optimising the way you use your wing for a race would be a pretty bold move. Firstly, you have to make sure your engine and your gearing is all pushed towards getting a higher maximum speed in the DRS zone, and this means you're almost certainly compromising your pace in other parts of the lap - and especially during qualifying. Then you have to remember that there's only a tiny window of opportunity to use that advantage too i.e. in one small part of the lap, and only if you're within a second of the guy you're behind. I my opinion, it's not worth it.

Red Bull's rear wing works as part of its overall aero package © LAT

Making it work

In short, Red Bull has been the best at implementing the system. The success of the championship leading team though, is not just down to its rear wing - you can't just simplify the whole argument by saying that one component is solely responsible - it's the whole aerodynamic package that is working in balance with itself.

It is clear though, that Red Bull has optimised its car for using the DRS during qualifying. Sebastian Vettel's had pole position for every race, and because of that, I've not seen him really having to overtake anyone properly.

As far as optimising the wing as a compromise between qualifying and the races, I'd say Ferrari has done the best job, as they seem to be the ones moving forward most on Sundays and have made a number of very effective passing moves in the DRS zone.

By contrast, I don't think McLaren has got the best out of the compromise at all. Lewis [Hamilton] and Jenson [Button] definitely have to fight more than the other front-runners in order to use the wing for overtaking. But remember, we've not really seen Red Bull, Renault or Mercedes making too many DRS moves against other front-running cars. Even in China, when Rosberg was leading, it wasn't because he'd passed people on track, and in Turkey he went backwards.