The full story of Mercedes' China front wing saga

It's now three races into the 2019 Formula 1 season, and each team is beginning to work out what makes its car tick. That said, we're still a couple of rounds away from the usual flurry of large upgrade packages arriving at Barcelona, and so most teams are keeping their powder relatively dry for the early flyaway events.

But there's still plenty to do at this time of the season. In China, the biggest technical talking point was Mercedes's brand new front wing - its legality immediately coming into question. As soon as it appeared in the paddock on Thursday, the new concept was straight away scooped up by FIA technical chief Nikolas Tombazis, who helped alert the team to changes that it needed to make before it could be run.

The device subsequently re-emerged with a reprofiled endplate - the rectangular cutout in the top trailing edge corner having been binned for a curved rear section, pairing up with a front wing that moves marginally closer to Ferrari's in configuration. This matches with an exposed section of wing, which is able to energise the flow coming off the front end of the car. Giorgio Piola's illustration shows how the Mercedes design was changed.

The footplate had been shortened, opening out earlier on to allow the rotational flow underneath to be carried out around the tyre by the endplate.

But the main sticking point with Mercedes' new wing was that exposed wing section, which was heavily visible from a side-on view, and the FIA's concern was that the sharp corner could result in punctures should the wing become damaged. But by the letter of the law, Mercedes had a case for the wing being completely legal.

The issue is, as ever, a little bit of a disparity in the regulations.

When the new aerodynamic formula came into play for 2019, the front wing endplates became more heavily policed by the FIA - as a result of the studies developed into generating closer racing produced by FOM's in-house technical research team. The new rule dictates that all endplates must fall into a bounding box, defining it as the "virtual endplate surface".

Mercedes was able to power to a one-two finish in the race on a dominant weekend - so it seems as if the hassle was worth the pay-off

Each wing element must be intersected by the virtual endplate surface, stopping teams from carrying any furniture to the outside of the endplate. But there's a regulation that also states that the real, physical endplate that the teams bring to the circuit must include at least 95% of that virtual endplate surface, meaning there's room available for small cutouts.

What that doesn't cover is exposed wing sections. As long as the exposed wing is bound by the virtual surface, it doesn't necessarily force it to be bound by the physical surface, especially if the cutout lays in the top corner where the wing meets the endplate.

That's something that Red Bull and Williams have already taken advantage of, with their designs featuring small square cutouts on the top trailing edge corner to expose those wing flaps.

This promotes a greater focus on shuttling airflow around the front wheel, recouping some of the effect lost to the new regulations.

But Red Bull and Williams were both forced to make changes, and remove those cutout sections for China following concerns outlined by an FIA technical directive. Mercedes, which had turned up with its own interpretation, therefore had to make changes too.

Ahead of Friday's practice, the corner of the uppermost flap on the Mercedes design was trimmed back slightly, as shown in Giorgio Piola's illustration, and the remaining overhang was covered up with a small triangular piece to placate the FIA.

Although a small change, it was still going to provide a knock-on effect to the aerodynamics of the Mercedes; front-end downforce is a little compromised as the top flap can't generate as much pressure on top of the surface, while that desired outwash effect is less pronounced.

While rumours suggested that the front of Mercedes' new endplates required a rethink too, the team revealed that no changes were made in this particular area - as it capably demonstrated the correct thickness and corner radius requirements to limit the potential to cause damage in the event of a collision.

Mercedes was able to power to a one-two finish in the race on a dominant weekend - so it seems as if the hassle was worth the pay-off.

Ferrari's issues exposed

At the rear of the floor, Ferrari's longitudinal slot immediately ahead of the rear tyre extends further inwards than other designs - sending as much airflow between the tyre and the foot of the diffuser as possible to mitigate the effect of tyre squirt.

This is the effect experienced where the rotational air created in front of the wheel bursts and squirts a mass of airflow into the diffuser, slashing the efficiency of the rear end aerodynamics.

The team needs to pin down more downforce in this area, as the Shanghai circuit exposed Ferrari's biggest weakness. While blessed with a power unit laden with grunt, the performance of the SF90 in the corners was severely lacking in comparison to Mercedes.

The team attempted to alleviate this by running more wing, but its shortfall seemed insurmountable - leading to a limp result in a less-than-thrilling race.

Alfa's new T-wing

Midway through pre-season testing Alfa Romeo had added a T-wing to the rear of the car, which drooped downwards to manage and move the tip vortices lower down.

But the team has made another change here, developing a new configuration more similar to that run by Ferrari and creating a coathanger-like double-wing.

In doing this, the design more or less eliminates the tip vortices, which create drag. The T-wing itself can now develop a bit more downforce, but doesn't have those vortices to create a little more suction underneath the rear wing. Clearly, that's a trade-off the team thought was worth having, finding the more reliable stream of downforce produced by the winglets more valuable for the long-radius corners in China.