Video footage of the Red Bull rear wing bending down at high speed on the Barcelona straight in the previous Grand Prix courted Mercedes’ ire, with Lewis Hamilton being quick to draw attention to the RB16B “curved” wing.
And so the box of worms was opened; Ferrari and Alfa Romeo have also admitted to introducing aeroelasticity into their rear fenders, and it seems entirely possible that there are more teams indulging in flexi-wing practice.
The situation now is that the FIA wants to introduce more rigorous testing at the French Grand Prix to make sure the wings don’t flex under load – even though the current wings already pass scrutineering.
As always in F1, this decision does not suit anyone; Mercedes and McLaren want revised flex tests ahead of Azerbaijani Grand Prix in Baku, while Red Bull, Ferrari, Alfa Romeo and anyone with a flexible wing say it will cost them more money to strengthen their designs.
On Sky Sports F1, Red Bull team boss Christian Horner – who experienced several scuffles on flexed wings during his tenure at the helm of the team – drew attention to the Mercedes front wing, who also seemed to sag down to the ground, and suggested The Silver Arrows scruples were rooted in hypocrisy.
As Hamilton’s disposable “curved back wing” comment was made, he pulled a thread that untied an important subplot for the 2021 season. Oh, what fun!
Carlos Sainz Jr., Ferrari SF21
Photo By: Andy Hone / Motorsport Images
What is a flexi-wing and why do F1 teams use it?
Flexible wings are … well, flexing wings. Strictly speaking, all the wings flex because it is impossible to achieve infinite stiffness, but some do more than others.
In Formula 1 terms, this usually manifests as tilting action. At high speeds, the front and rear fenders produce more drag as the car’s speed increases. In mathematical terms, the square of the speed determines the drag force, according to the following equation:
drag force = (drag coefficient * frontal area * air density * squared speed) / 2.
As the speed increases, the force that pulls the car backwards increases exponentially.
As such, you can’t use the full maximum power of the powertrain to develop straight-line speed. On circuits like Monza, teams use thin fenders to reduce drag, but on more conventional circuits you need the full size of the front and rear fenders to generate downforce when cornering.
By tilting them rearward at high speed, this can reduce the overall frontal area of the wing, and possibly its drag coefficient entirely. Using the above formula, the increasing square of the speed is slightly compensated by the reduced area and the drag coefficient.
The truth is, all teams would love to have infinitely flexible fenders on their F1 cars, as the front and rear fenders could theoretically straighten out and colossally reduce drag on the fastest sections of a circuit. But for security reasons, they just can’t do it.
The FIA has tests to ensure that the fenders do not flex during scrutineering, with the front fenders subjected to load tests and the rear fenders subjected to shrinkage tests, which are described in the technical regulations at l article 3.9.
Antonio Giovinazzi, Alfa Romeo Racing C41
Photo by: Zak Mauger / Motorsport Images
Why are flexi-wings not recommended for safety reasons?
The study of aerodynamics in F1 is often thought of as ‘aerospace, but turn it around’. Because many of the same principles exist between the two fields, they share many of the same issues.
Airplane wings flex very slightly, as the structure must be a compromise between stiffness and weight. Materials with high torsional strength are often heavy, and the same is true for an F1 car.
Today’s F1 fenders are made from carbon fiber and often use a low density core (like foam) to provide more rigidity – so they’re still light and stiff. But the same is true that the more weight you add, for example by using other plies of carbon fiber, the stiffer it becomes. Therefore, the compromise still exists.
But if a kite is too light, it will likely lose strength. Under load, this means that the wing could break, either by contact with another car or by effects developed by aeroelasticity.
Aeroelasticity is its own scientific field; although elasticity is desirable for some applications, it leaves a wing or structure exposed to phenomena such as flutter.
If an F1 wing floats, it means that it produces a very unpredictable level of downforce, which can fluctuate between extreme values.
Lewis Hamilton, Mercedes W12
Photo By: Steve Etherington / Motorsport Images
As such, if a driver drives a car with this unpredictability, there will undoubtedly be cases where they will have a very low level of downforce under braking when cornering. Naturally, it can lead to a particularly nasty accident if they cannot stop the car in time.
Flutter is harmonic motion and, if exposed to frequencies by an oncoming air flow that approach its natural frequencies, that can tear the wing in extreme cases. By increasing the stiffness, this can be avoided.
These reasons explain why the FIA performs technical checks to assess the structural integrity of the car to ensure that drivers stay safe in the cockpit.
What will happen next?
While more stringent tests are in place for the French Grand Prix, this should further reduce the wing flex used by the teams. There will undoubtedly be a cost to this, which will shake up teams operating near the cost cap, but it’s safe to say that safety is priceless.
This won’t prevent teams from trying to flex their wings to the maximum allowable level, but it will reduce the amount of performance derived from using flexible wing geometry.
In the future, as materials science continues to evolve, F1 may well allow the wings to change shape more blatantly during a race – but under current rules this is not allowed. .