UNDER THE HOOD
FLEXIBLE WINGS DISCOURSE IS NOTHING NEW
Pat Symonds on the flexi-wings disagreements
Every season brings a new contentious technical argument that occupies the attention of teams, the FIA and fans alike. This year there has been a focus on flexible wings, but unlike many previous discussions, such as the Mercedes dual axis steering system from last year, this one is anything but new.
We can go back as far as 1980 in the technical regulations, then known as Appendix J of the Sporting Code, when the entire set consisted of just 11 pages compared to today’s 137, to see the origins. There it is stated that the coachwork, as it was quaintly known then, must be rigidly secured to the entirely sprung part of the car and must remain immobile in relation to the car. In 1980 there was a single exemption to allow sliding skirts but even this was removed for 1981. By 1982 Formula 1 regulations were removed from the old Appendix J to stand in their own right. It was the start of ever more detail and complexity.
While there were undoubtably several designs that either intentionally or through poor design resulted in aerodynamic structures that were anything but rigid, it was not until 2000 that additional tests were introduced on the floor and front wings to examine legality.
It must be pointed out that all engineering structures will deflect when subjected to load. On a car there will be some components designed to strength criteria, some designed to stiffness criteria, but it is generally understood designers will choose the lightest structure that will satisfy those individual design criteria. In particular, for those surfaces affecting the aerodynamic performance of the car, practical weight considerations will mean some components will deflect sufficiently to modify their own aerodynamic performance, in other words to have a degree of aero-elastic response.
The real question is whether such deflection enhances or detracts from the car’s overall performance. In reality it is not the magnitude of the deflection but rather the effect that is of importance.
This means that some areas can be more flexible than others if the result of that flexibility does not make much difference to performance. Of course, this can often be difficult to determine. For example, it is accepted that the front of the floor has to have some flexibility to ensure the chassis is not damaged if the car hits a kerb. This very same flexibility, if not carefully controlled, will also allow the car to be run at a lower ride height, which instantly adds performance.
While it might be thought flexibility is used either to increase downforce or reduce drag, there are other subtleties that can be as effective. For many years we used various different composite lay ups for the front flaps so that we could tune the deflection such that they backed off at high speed. This allowed us to set the car up to reduce low-speed understeer while relying on the change in aerodynamic balance achieved by the flexi-flap to keep it stable in high-speed corners. The different lay-ups would allow us to choose the rate at which the balance changed with speed. It took a while before tests were introduced to stop this practice.
The current dispute started with a suspicion that certain rear wings were backing off and reducing drag. This is nothing new. The FIA clamped down on this practice in 2004, by introducing pull back tests on the rear wing. Ironically, a technical directive issued by the FIA at the time answers a number of questions posed by Nikolas Tombazis, then chief aerodynamics engineer at Mclaren and now, in a classic case of poacher-turned-gamekeeper, the FIA’S single-seater technical head.
There are several methods that can be used to achieve this particular aim, and exploiting the regulations to their utmost is not cheating, it is merely what technical directors are paid to do. So for example, if a rear wing mainplane has a relatively flexible construction that de-cambers the wing at speed and therefore starts to open