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AERODYNAMICS, the war on winglets: a race against the wind

Why the new rule is wrong: once the genie has been released from the lamp, it is impossible to put him back in

AERODYNAMICS, the war on winglets: a race against the wind

Once you’ve released the genie from the lamp, it is impossible to put him back in.

This is the conclusion we came to after seeing what led to prohibiting the use of aerodynamic appendages in MotoGP.

With the excuse of being dangerous - not demonstrated - Dorna and FIM obtained the exact opposite of what they set out to do, forcing all the manufacturers on the playing field to invest large sums of money to recover the aerodynamic load that they lost.

The spoilers had two effects that were anything but minor: they improved grip during braking and allowed less traction control to be used in acceleration. This allowed wheelies to be limited, thereby letting the rider put more power on the ground with a clear increase in acceleration.

The winglets or spoilers or what have you were easy to design and the provided the best possible cost to benefit ratio.
With the new rules, however, protruding appendages are no longer permitted, so all the manufacturers had to invest hours in the wind tunnel to create profiles inside the fairings capable of recovering, albeit partially, the load that was lost.

In fact, the downforce produced by an internal winglet is inferior due to the loss of load that occurs in the conduit. The longer it is, the more load is lost. Usually you try to tighten the output of the conduit to increase the airflow speed, but at the cost of more losses.

In short, as one might easily guess, it is easier to design a spoiler on the outside of the fairing than to come up with one positioned inside. Without considering that the different shape of the fairing causes an increase in the aerodynamic resistance coefficient (Cx).

Sometimes called the aerodynamic penetration coefficient, it refers to the front section of the vehicle and clearly represents just one of the terms of resistance to forward motion. The other is the increase of the surface exposed to the air, the Cz or lift coefficient. Both of these determine a resistance to forward motion, also known as ‘drag’ which, even in the best case scenario, costs us speed on the straight, nullifying whatever benefits have been gained in terms of grip. What Aleix Espargarò shrewdly observed when he talked about the new fairing that Aprilia unveiled for his RS-GP.

At Phillip Island in Australia, besides the Venetian manufacturer, Suzuki also showed off a new fairing. More than anything, an exterior spoiler cover positioned higher than those, equally internal ones, seen on the Yamaha at Sepang.
But how much load do these solutions generate?

Very little when compared to what those on Formula 1 cars achieve: about 1,500 Kg.

Last year maybe about twenty could be achieved. Maybe Ducati, thanks to the proliferation of the spoiler profiles, had more. Not much? Maybe, but enough to counter the phenomenon of wheelies in acceleration, or at least to decrease it and definitely to provide more load to the front tyre in the first, extremely delicate initial phase of braking. The phase when the tyre is moving at top speed on the tarmac and the rider squeezes the brake lever.

After all, almost all the riders noticed that without the winglets and with the power of latest generation Brembo carbon brakes combined with double discs as big as frying pans, having the front end lock up and skid (thereby losing control) is business as usual.
The evolution of MotoGP bike aerodynamics is, in any case, still in the fledgling stages. And despite the rule that prohibits using more than two fairings during the season (in addition to the 2016 fairing without winglets), we expect to see further developments.

Very soon, in addition to internal spoilers, we will begin to talk about ‘nolders’: these are short and thin flaps placed at the ends of the spoiler output in a position roughly perpendicular to the flow. It is a small strip placed at its maximum inclination and it allows Cz to be significantly increased when the winglets have limited dimensions.

For the moment, also bearing in mind that the rider astride his bike significantly disrupts the airflow both on the straight and in turns, the time when aerodynamics will be able to create problems for the trailing rider with respect to the leading rider is still a long way off. In fact, unlike in F1 where slipstreaming a rival leads to a decrease in downforce with a consequent drop in grip, in modern motorcycle racing, the opposite is true.

When we see a decrease in overtaking even in the two-wheel world, then it will be time to call Aladdin to try to put the genie back into the lamp.

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