The underbody of a Formula 1 cars is the engineers’ biggest playground, especially now that the 2022 F1 cars achieve around 40 percent of their downforce as a result of the ducts under the car. The ground effect not only provides a lot of downforce but also efficient downforce. The ratio of downforce to drag is a healthy one, while it’s a different story for the front wing and rear wing, the other big downforce donors. Steeper flaps at the front and larger air deflectors at the rear increase drag disproportionately.
So if you make the best use of the ground effect, you can achieve high downforce values and at the same time drive with smaller wings. See Red Bull. And now Ferrari, too. The F1-75 has gained efficiency with a few upgrades. It is precisely these two teams that have come under the spotlight in the wake of Technical Directive TD039. It’s the nature of things in sports: the fastest ones attract the most attention. They are the ones that the competition looks at with suspicion. They are the ones who are first placed under general suspicion when inconsistencies occur.
With TD039, the FIA wants to limit bouncing and prevent excessive vertical forces on drivers. A complicated metric is designed to do this, as measurements are taken via an accelerometer, which must be located in a uniform place in the cars from the Belgian Grand Prix onwards.
The drivers’ complaints had become too loud after the Azerbaijan GP. About back and hip problems as well as a maltreated musculature. Since then, the races in Canada, Silverstone and Austria have passed. Since then, the debates about bouncing and bottoming have actually receded. Because virtually all teams have solved the phenomenon, even Mercedes, which was the worst affected. That’s why there are more than a few in the paddock who think that the new TD isn’t even necessary anymore.
The FIA disagrees. It states that bouncing varies from track to track. It had been expected that it would decrease in the last races and assumes that some tracks could cause it again strongly in the coming months. That’s why they’re pushing through the Technical Directive as a safety measure.
To briefly outline it again, bouncing describes an aerodynamic phenomenon. Englishmen also call the uncontrolled bouncing in and out of the car at higher speeds “porpoising”. It is a constant bobbing up and down of the car with low or high frequency. Bottoming describes the brutal touchdown of the cars on bumps and curbs. The 2022 race cars are lower and have much firmer suspension than their predecessors – to take full advantage of the ground effect.
Meanwhile, another issue is boiling up, also anchored in the Technical Directive. The FIA wants to monitor the wear of the floor panel more closely. There is a suspicion that some teams might be overdoing it with the interpretation of the underbody rules. That they can lower their cars in the front section by using special skid blocks. That they use a flexible plank as a protective shield against bottoming. The time saved by clever underbody design could amount to several tenths of a second. No one can put a precise figure on it.
Red Bull and Ferrari suspect Mercedes is behind the campaign to slow down the top teams of the season so far. In the Silver Arrows’ camp, they point to a meeting of the “Technical Advisory Committee” (after Canada), where the technical chiefs met, in which the possible trickery with the underbody is said to have been put on the table by the FIA itself. Mercedes team boss Toto Wolff then spoke of a “shock”.
In the sights are the plank and skid blocks, which protect the floor panel from excessive wear. The so-called plank is a central wooden board under the car. To get a better idea of it. It looks like the underbody is bolted to a beer bench. The plank is the lowest point of the car, so it is exposed to the impacts from the underbody. Article 3.5.9 e.) of the Technical Regulations prescribes a thickness of ten millimeters (+/- 0.2 mm). The base plate must be uniformly built when new.
The FIA allows a maximum wear of one millimeter. So at every check, the plank must be at least nine millimeters thick. Small holes are punched in the plank from front to back. Here, the FIA technicians can measure the thickness of the base plate. The so-called “skid blocks” made of titanium are there to protect the wooden plank. They are invisible to the spectators, and yet they become visible again – through the sparks produced by the cars. These occur when the titanium blocks come into contact with the asphalt.
The Red Bull cars had particularly many sparks in the past. This was due to the fact that Adrian Newey’s cars were heavily leaned from front to rear, meaning they were in constant contact with the ground with the front skid of the underbody. This year’s Red Bull also produced the most sparks. Which suggests that the RB18 is set low. And yet, unlike the competition, Red Bull didn’t struggle much with either aerodynamically generated bouncing or mechanical bottoming.
Ferrari did have bouncing, but the F1-75 didn’t seem to mind the bounce either on straights or in the corners. Aerodynamics remained stable. Bottoming was always a foreign word for the red car. It swallowed bumps seemingly effortlessly and climbed over curbs like no other.The trick that Ferrari and Red Bull are said to have, but which is not necessarily limited to the two top cars: They are said to have cleverly divided the skid blocks. As in individual pieces of cake around the holes. While driving, some of these pieces are said to miraculously disappear into the underbody on contact with the ground. When stationary, they return to their original position.
What is the purpose of this? Inspectors measure wear only in one spot, rather than around the entire hole. A practice that dates back to the days when Charlie Whiting was still Formula 1 race director. The trick is that the part of the skid block that disappears while the car is moving, the rear section, is protected. So the prescribed nine millimeters are always achieved during the check. Whether the front pieces of titanium have worn away by a few millimeters is irrelevant.
Flexible plank against bottoming
This trick has the advantage that the car can be driven lower, especially on the front axle. Every millimeter saves time. In order to stop this practice, the FIA is expanding its measurement method with the Technical Directive. Starting with the Belgian GP, thickness will no longer be measured at just one point, but at 75 percent of the periphery. And stiffer skids are prescribed in general.
The second clever idea concerns the flexibility of the wooden plank itself. A maximum bending of two millimeters is permitted. However, there could be teams that manage more under the ride. The idea is that the plank is practically “pressed” into the underbody. That would automatically enlarge the channels in the underbody. The air could expand and accelerate better. Downforce would increase. The bottom line is that these tricks would simulate a rearward-set car, according to German automobile magazine ‘Auto Motor und Sport’.
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Those who actually have some air between the floor and chassis to push the plank can enjoy a second advantage. Bottoming is reduced because the wooden plank absorbs the impacts better. At Mercedes, one suspects that this is precisely why Ferrari and Red Bull are so much better at dealing with undulating tracks.
Red Bull’s counterattack
It would be clever tricks to get around the underbody wear and stiffness rules. Red Bull team boss Christian Horner relegates the theories to the realm of fables. Word from the team is that they don’t really need to change much about the underbody, given the new measurement procedures starting in Belgium. Perhaps strengthen the connection of the rear floor panel to the engine. Red Bull points out that in the regulation process for 2022 it had itself advocated making the plank generally stiffer. There are rumors in the paddock that even before 2022 there were suspicions that some teams might be fishing in gray areas here.
In turn, Red Bull goes on the attack. The front wing of Mercedes bends far too much to the rear on the straights, which leads to a higher top speed. The constructors’ world champions speak of a targeted diversionary maneuver by Red Bull. Mercedes hopes that the TD from Belgium will weaken both its archrival and its Red rivals.
As usual, Ferrari is not letting its cards close to its chest. Team boss Mattia Binotto explained at the Austrian weekend that a few modifications to the underbody were necessary to meet the new design after the summer break, but the Ferrari team principal did not appear worried. Only the races starting in Belgium will show whether the TD039, which has been revised several times, will lead to shifts in the balance of power.
