From being in a situation where there car has had only minor updates for several races, the Mercedes development curve has gone vertical during the course of the Magny Cours Young Driver Test (YDT). While their new exhaust solution and Drag Reduction Device were both logical development directions, the reinvention of the shark fin has come as a surprise. On the last day of testing the W03 was seen with both the new exhaust system and the truncated shark fin, this is the first such fin to be seen on a car this year.
The device has two functions, according to the designers I have talked to. One effect is the device acts like a wind vane and its side surface area prevents yaw (tail slide), which helps with stability into turns. Another effect is the device acts as a flow straightener, by aligning the airflow towards the rear wing. However opinion is split on whether one is more beneficial than the other, few designers have cited both as a benefit for their fin. However the device has been widely used in the past, so there must be a tangible benefit. It does however have some downsides, the fin will make the car sensitive to side winds and if the car does start to yaw then the rear wing will be masked by the fin and may result in loss of downforce and a spin.
Shark fins gained popularity a couple of years ago, initially in 2009 with the reduction in downforce from the new aero rules and then in 2010 when the shark fin contained the F-duct pipework. During this period teams extended the fin to join with the rear wing, creating both a larger surface area and a more direct path for the air to the rear wing. With the ban on F-ducts the FIA chose to create an exclusion area for bodywork ahead of the rear wing. This prevented the fin reaching the rear wing. In 2011 two teams tried truncated fins, Red Bull launched with one, but soon dropped their fin, while HRT chose to run the fin for much of the year.
The Mercedes 2012 iteration of the fin is much like the 2011 RBR\HRT design, with the fin reaching the maximum allowable height and extending as far back as allowed. So despite the belief amongst many fans that the fin was made illegal, this truncated version remains perfectly legal.
One additional benefit bearing in mind the Drag Reduction Device they have also tested, is the flow straightening effect will especially useful to ensure the airflow to the rear wing is correctly aligned. The “L” duct blowing upwards to stall the wing, will potentially be more effective if the airflow is not trying move sideways across the wing span.
For Mercedes the gains appear to be logical, bearing in mind their rear tyre degradation issues. With Mercedes taking time to understand their tyre problems before working on technical solutions to it, their recent focus appears to be rear end aerodynamic grip. Both the new exhaust and Drag Reduction Device will create more downforce at the rear. To a lesser extent the shark fin will improve rear downforce due to the straightened flow aimed at the rear wing, also if the rear end has moving about on corner entry, the lateral scrub can overwork the tyres, which the fin will help prevent. So both potential benefits of the fin will be useful for the team.
With the upcoming races being aero tracks with high speed turns, the added downforce and rear end stability may help the team preserve the rear tyres for as long as their rivals are able to. Allowing Mercedes to race more conventional strategies, without as many pit stops.