The ‘flapping’ phenomenon behind F1’s latest flexi-wing intrigue

Formula 1 is as much an aero contest as it is a fight between drivers, so it’s no surprise that it has become the focus of the latest Red Bull versus Mercedes battleground.

The ‘flapping’ phenomenon behind F1’s latest flexi-wing intrigue

The subject become a hot talking point at the Spanish Grand Prix, when Lewis Hamilton suggested Red Bull had been running a ‘bendy’ rear wing to boost straightline speed performance.

In the wake of these allegations, and no doubt following some prompting from teams, the FIA has reviewed what some outfits are up to and agreed that action needs to be taken.

For while all the current rear wing designs are able to pass the static load and deformation tests, they appear to exhibit excessive deflections whilst the cars are in motion.

As a consequence, the FIA has invoked article 3.9.9 of the technical regulations that permits it to introduce further load/deflection tests on any part of the car it deems fit.

As such, new tests will be introduced from June 15 in an attempt to curb the practice whilst also giving the teams the necessary time to prepare designs that comply.

This gives the teams until the French Grand Prix to fall in line, although a 20% tolerance will be given during the first month of the new tests to aid in the transition.

The load and deformation tests that focus on the rear wing are designed to prevent the structure from being over flexible. Teams are well aware that the ability to lean the wing back as speed builds will result in drag being reduced, giving the driver a straight line speed boost.

Rear wing dimensions and load tests
Rear wing load test

There’s long been a battle between the teams and the FIA on this front, with the loads and amount of deflection applied during the tests regularly updated to prevent them being defeated during the static test.

However, the teams know that there’s still performance to be found if they can pass those tests but still find a way to have the wing lean back whilst out on track.

The current regulations focus on the uniform deflection of the entire structure with the checks focused on vertical and horizontal displacement.

However, the new checks will focus on the rotation of the wing around the cars centreplane, with just one degree of tolerance permitted as the loads are applied.

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The new rotational tests will prevent the wing from ‘steering’ around the centre plane, a trick that the FIA may be focusing on as being used to circumvent the symmetrical loading applied in the deflection tests.

This is a notable feature in the onboard footage from the rear facing T-camera of the Red Bull, for example.

Close examination of the moving images shows the top rear wing element ‘flapping’ laterally, moving side-to-side with the relative vibration of the endplates, which owing to their design also find themselves oscillating.

This could explain how the wing ‘bends’ rearwards under load, as the wing pivots around the central axis, with one side of the wing moving incrementally rearward before the other.

Red Bull Racing RB16B rear wing comparison

Red Bull Racing RB16B rear wing comparison

Photo by: Giorgio Piola

Interestingly, Red Bull had arrived in Spain with a new high downforce rear wing that it tested throughout Friday’s free practice sessions before making the switch back to it medium downforce arrangement for FP3, qualifying and the race in order to be quicker down the straights at the expense of a loss in the corners.

This new high downforce wing featured all of the usual architecture of its medium downforce counterpart, albeit with the flap arrangement adjusted.

The height and geometry of the top flap, its trailing edge Gurney flap and cutouts were all altered, whilst the most visually obvious alteration came in the form of a change to the shape of the mainplane’s leading edge, which features an upturn in the central portion of the wing. 

Meanwhile, the medium downforce wing features a gentle spoon-shaped spanwise curvature to the mainplane to offset the drag ordinarily created by the interaction of the outboard section of the wing and the endplate.

Red Bull Racing RB16B rear wing comparison

Red Bull Racing RB16B rear wing comparison

It appeared to be this change of wing concept that sparked the debate, with Hamilton making reference to it after qualifying and then again before the race.

“Yeah, considering the Red Bull’s are really fast, with that nice, erm, wing that they have” chuckled Lewis Hamilton in response to the line of questioning from Sky’s Rachel Brooks about the change in wind direction for race day.

In a post-qualifying interview, Hamilton made reference to it being a ‘bendy’ wing.

It’s certainly not the first, nor the last time, that flexible wings have been a topic of debate in Formula 1, with Jenson Button recalling on Sky the time when his BAR006 was first fitted with a flexible rear wing.

“Actually, BAR-Honda were the first people to do it back in 2004, we had that, I remember Hockenheim being the first race and it made a good difference,” he said.

Whilst BAR-Honda wasn’t actually the first to do it, it had taken the lessons of previous attempts and found a way to make it work under the prevailing regulations. 

During that period, a good many of the teams were pushing the regulations in interesting ways in an attempt to reduce drag.

BAR-Honda tried various solutions, including fins mounted to the mainplane (left image), paired with the slightly splayed leading edge to the endplate. This has become commonplace again as teams are no longer permitted to use louvres. 

BAR 006 2004 rear wing

BAR 006 2004 rear wing

Photo by: Giorgio Piola

It will be interesting to see if the new load/deformation tests have an impact on the competitive order when we head to the long straights at Paul Ricard.

Any team making changes to its wings, to ensure they comply to the rules, will also need to juggle the potential consequences that could have on them hitting the budget cap limit.

There could also be intrigue beforehand though, because teams could yet decide to lodge protests against their rivals should they believe they’re using a rear wing assembly that contravenes the current regulations, even before the new tests come in to force.

Red Bull Racing RB16B rear wing

Red Bull Racing RB16B rear wing

Photo by: Giorgio Piola

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