Williams’ Winglet Causes Stir

Date published: June 24 2015

In his latest feature, Matt Somerfield talks about Williams' winglet and side skirt that caused quite a stir.

Susie Wolff emerged from the garage in her FW37 after a rain hit first day of testing at the Red Bull ring on Tuesday, causing quite the furore. It wasn't Susie at the centre of this mini storm in a tea cup though, rather a winglet and side skirt that protruded from the FW37's floor.

The winglet and side skirt are placed in areas of the car that would be deemed illegal should they be run during an official session, bringing up the question by many, "why?"

Firstly, this is a test session and it gives the teams the opportunity to understand their cars in a way that isn't possible with the time constraints of a usual race weekend, whilst not being under the same FIA scrutiny. Furthermore, whilst research and development can be done in CFD and the Wind Tunnel away from the track, time is still a factor in gathering and processing data and real world correlation is needed to verify the findings.

I asked the team to comment on why they were using a setup that wouldn't be legal during a race weekend to which they responded: "The main focus of this test is to conduct some fundamental research to help us better understand certain aerodynamic characteristics of the car."

It doesn't get to the crux of the matter but essentially the team are simply replicating how their car may react, if they were to make certain design changes upstream of the floor region, that mirror these localised changes. 

There were two elements placed on the car, firstly the side skirt (marked in green) simulates both a wider floor section ahead of the rear tyre and then transitions into a vertical element which is prohibitive to flow getting underneath the floor. This element would be analysing how airflow moving around the car and especially the wake shed by the front tyre would impact rear performance, should they be able to change the current characteristics. 

Secondly, the larger winglet structure (marked in yellow) above the floor is in a position we used to see the teams run sidepod 'flickups' during the mid-late 00's. This would simulate how airflow thrown up and around the rear tyre will have an effect on the shape of the tyre wake and the airflow structures generated by the diffuser, brake ducts and rear wing.

These test components are a ad-hoc way of understanding how the changes could affect the car without having to take the time and money to do full blown simulation and/or build the necessary parts. Their effect on both downforce and drag could be fairly significant owing to the way the flow structures interact with the existing ones.

Whilst it's clear that these parts aren't currently legal it is also entirely plausible that Williams were acting on behalf of the Strategy Group to collate data. The promise of cars that are 5-6 seconds per lap quicker for 2017 and beyond will require some aerodynamic regulatory changes. This will be earmarked as an area to concentrate on as it's a particularly sensitive area of the car, especially in transient conditions as the tyre deforms, with the tyre impacting on the aerodynamic performance of many flow structures.

Matt Somerfield