Mercedes' DRS F-Duct System

So all the buzz around the paddock over the last couple of weeks has mainly centered around one thing, Mercedes GP's DRS System. Lotus f1 and Red Bull Racing decided that there were some illegalities surrounding the system and I shall explain why they would think that.

What it does.


The concept behind it is very simple and an extension to a system which the team has run in previous seasons. The whole idea is based around stalling the front wing in order to reduce drag and gain greater straight line speed. This is similar to the F-duct principle pioneered by Mclaren in the 2010-2011 season which used a duct on the nose of the car to channel air to slots that blew the air on to the rear wing when a hole was covered by the driver's knee.

The f-duct on the MP4-25

This was beneficial due to it creating less drag on the wing and thus increasing straight line speed. This was made illegal for the 2011-2012 season onwards and was deemed a driver controlled aerodynamic device. 

The Mercedes system is similar in principle but aims to stall the front wing rather than the rear wing as the old F-duct systems did. It is designed around the DRS (Drag Reduction System) rear wing. The DRS is what the FIA brought in to replace the F-duct system and aid overtaking for the 2011-2012 season. It effectively lifts up the top element of the car's rear wing in order to minimise the main drag creating component and increase straight line speed. The Mercedes car uses the DRS system to expose holes in the rear wing end fences that feed ducting inside the end fence and rear beam wing that channels air through the body work and to slots in the front wing which stalls it for a speed boost of roughly 4-5 km/h.

How it Does it

The DRS System normally uses a pod mounted on the central section of the rear wing's upper element that encases a hinge mechanism and the hydraulic actuators to flip the wing up and open the slot gap as shown below on the mp4-27's wing.

The central 'pod' houses the DRS mechanism

The Mercedes wing however, houses the DRS mechanism in the end fence of the wing making it one complete span left to right. 

The Mercedes rear wing

The crucial part is in the end fences however and is pretty hard to spot so I have taken a photo from here and photo-shopped it so that you can see the crucial detail.

As you can see, once the flap is opened a hole in the end fence is revealed that allows air to enter the end fence itself. This is the first clue as to how the system works and what it does. There have been theories that the slot is to stall the rear wing, but with the DRS system already active when the hole is exposed, a lot of the drag has been lost from the wing already.

A further piece of detail comes from another rear end shot from a different angle.

In the area where I have brightened the picture you can clearly see two tubes leading out from where the beam wing joins the rear crash structure that houses the rain light. This is evidence of ducting leading to or from the rear end of the car and through the main body work. As I believe this ducting is for the stalling of the front wing rather than the rear, I believe that the picture below is the correct airflow of the system at the rear. 

Why do it?

There are 2 main benefits to this system. The first and obvious benefit is that it gains them straight line speed whilst the DRS is active. This increases qualifying performance and also aids in overtaking manoeuvres during the race.

The second benefit is, I believe, more tangible for the drivers. When the DRS is active, the rear wing not only loses drag but also reduces its downforce creation ability. This then presents a slight setup issue as the centre of downforce shifts forward and the car becomes, in a sense, nose heavy. This upsets the balance of the car as the teams will set up the car for optimal performance with the DRS closed as thats how it will work for the majority of the race. Stalling the front wing in tandem with the DRS at the rear helps to reclaim the balance by reducing the front downforce and moving the centre of downforce back towards the rear of the car. This makes the car less 'nervous' and 'twitchy' whilst the DRS is active and inspires greater driver confidence allowing a much greater showing when putting in a flying lap in qualifying where DRS is available whenever the driver chooses to use it.

Why the big fuss?

All the fuss is mainly because only 1 team has found the loophole surrounding the DRS and exploited it. All teams want to be at the front of the pack and if a team who was behind you last year has a system on their car which gives them an advantage you dont have, you have one of 3 options. Option 1, complain and try and get it banned. Option 2, copy it as best you can and just get on with it. Or option 3, a mixture of both to cover your bases.

This is a very simplistic view of it, but its what it boils down to!

The teams trying to get the system banned are citing the same rule that got F-ducts banned in the first place, that its a driver influenced aerodynamic device. However, if this rule was to be taken by the letter then the DRS system itself would be banned!

The clever interpretation on Mercedes' behalf comes from the use of primary and secondary purposes of the system and that the hole in the end fence is always partially open even with the DRS shut. Mercedes' argument is that it constitutes part of the DRS system as it is only a secondary function of the DRS system rather than a system in its own right. Charlie Whiting agrees and so the system is declared legal.