Why do F1 Cars Have a Wooden Plank?
Being a Formula 1 fan, I’m sure you’ve noticed that every race car has a wooden plank, also known as a skid block, on the underside of the car. You can see it below.
But why do F1 cars have a wooden plank? Well, the purpose of the skid block (plank) is twofold:
- To enforce a minimum ride height by measuring the plank’s sustained damage during a race
- To ensure driver safety by limiting the amount of downforce acting on the car
Both of these reasons are tied to safety: the car’s safety and the driver’s safety. With the skid block, cars have their top speed limited.
There’s not enough downforce acting on the car to increase their top speed further. And this is caused by the increased car height, which is necessary to keep the plank’s sustained damage within legal parameters.
But why is more speed a problem? After all, F1 cars need a lot of speed to win races, right?
Well, yes. But the more speed you have, and the more downforce on your car, the riskier it gets.
Let’s see why!
Why Were Planks Introduced in F1?
Although F1 races were less restricted and thus less predictable before the plank, two major events took place that made the skid block necessary – the deaths of Roland Ratzenberger and Ayrton Senna during the 1994 San Marino Grand Prix.
Both drivers crashed into a wall and suffered severe injuries that resulted in their deaths shortly after the accidents.
Roland Ratzenberger swerved into a wall at 195.7 mph because his car’s front wing became lodged under the car, making him unable to swerve.
Ayrton Senna’s crash was caused by a badly-designed steering column. He crashed into a concrete barrier, which resulted in three fatal injuries.
Shortly after these incidents, the FIA introduced the skid blocks. Its purpose was to forcefully increase the car height and decrease the downforce acting on the car, especially in high-downforce curves.
This led to much fewer accidents and deaths, despite the race cars not being as impressively fast.
The cause of Senna’s accident was steeped in mystery for a good 13 years before it was determined that the steering column was to blame.
However, one notable aspect was that he had crashed while trying to take a corner. Corners are notoriously risky when tackling them at high speeds and with a high downforce pressing down on your car.
Without the skid blocksto restrict the minimum ride height, Senna’s car was generating too much downforce, therefore a lot of speed. Plus, there weren’t nearly as many safety mechanisms implemented back in the 90s as there are now.
Many are saying that the FIA had become complacent regarding safety during that period. No fatal accidents had taken place for approximately 15 years.
How Does the Plank Impact F1 Teams?
The existence of the skid blocks has more of an impact than you’d think. Like I said, its primary focus is to establish a minimal ride height.
This means that car engineers had to completely change the way they constructed the cars, down to the last component.
The car had to have a higher height in order for the skid block to remain relatively undamaged during a race. And as I mentioned in a previous article, serious damage to the skid blocks can lead to disqualification.
An increase in the car’s height leads to less downforce, thus less speed. However, since this was applied across the board to all cars, it isn’t an unfair disadvantage to anyone in particular.
Every single F1 car has become a tad slower overall after the skid blocks were introduced. But the speeds at which races are run is still ludicrous for spectators. And it’s much safer.
How Does the Plank Protect the Driver?
In a nutshell, the skid block helps protect the driver in two distinct ways:
- It prevents F1 cars from bottoming out too much and suddenly losing all the accumulated downforce, which leads to purpoising
- It forces a reduction in downforce pressing down on the car due to the higher ride height
Below, I’ll get into more details for each of these benefits:
Purpoising happens when the car bottoms out (the floor touches the asphalt completely) and the airflow under the car is halted, which leads to a bounce up.
When the airflow under the car is stopped, the aerodynamic state of the racing car is stalled, and through the nature of the ground effects (low pressure under the car), the car is pushed up in a bumping motion.
After the car is off the ground, downforce accumulates again, and the car eventually bottoms out. And again, it bumps back up.
This phenomenon is called “purpoising”, the continuous bumping of a car due to its suspensions, airflow stalling, or a bumpy track.
Purpoising is exceptionally bad both for the driver and the car. The car’s performance and reliability decrease, and the driver’s back and neck are affected.
2. Less Downforce
Downforce is an aerodynamic force that occurs when the air is moving on top of the race car. Gradually, as enough downforce builds up, it pushes the car down, working together with the ground effect to suck the car to the track surface.
More downforce leads to more grip, which enables drivers to drive faster without losing control of the car. So, downforce is good, right?
Well, yes and no.
The more downforce, the faster you can go. But the higher the downforce, the lower the car gets to the asphalt, as well.
And we’ve already seen what happens once the car bottoms out on the asphalt. Purpoising occurs, and you may lose control of the car when the airflow under it gets interrupted.
There’s also the matter of lateral force (acceleration), centrifugal forces, and G forces that apply when F1 drivers take corners.
The equation is roughly like this: lower ride height = more downforce = better grip = more speed = more G’s sustained by the driver and car = increased likelihood of purpoising.
There’s a fine line between harnessing as much downforce as possible without bottoming out and purpoising.
And the plank is designed to alleviate this issue by elevating the car height and reducing downforce. This means two things:
- Since the car is higher off the ground, it takes more downforce to bottom out the car completely
- Less speed, which leads to less downforce, which leads to a lesser bottoming out effect
While the plank helps with the purpoising, it doesn’t eliminate it completely. During the 2022 season, Lewis Hamilton famously complained about this issue and how it affects the drivers’ health:
“I have not spoken to a specialist on [spinal] discs but I can feel mine. I am a little bit shorter this week and my discs are not in the best shape right now. That’s not good for longevity. There is no need for us to have long-term injuries. […] I have had a lot more headaches in the past few months…”
Fortunately, the FIA issued a few technical changes, requiring teams to increase the floor edge heights by 15 mm for the 2023 season.
Teams and drivers alike are agreeing with this change and claiming that purpoising should all but disappear in the next season.
So, while the plank protects the driver from purpoising and a loss of control over the car, it also unintentionally decreases their performance due to a loss in downforce.
Technical Specifications of the F1 Plank
As per the FIA’s official specifications, here’s how the plank, or the skid block, needs to be assembled on the underside of F1 cars:
- The uniform thickness of the legality plank must be 10 mm ± 0.2mm
- The legality plank has to have four holes in specific positions
- The thickness of the legality plank (before and after the race) will be measured at these holes
- The plank can be made from any homogeneous material as long as it meets specific requirements
- The plank can be made from at most three pieces, and the forward piece has to be at least 900mm in length
- On the lower surface of the plank, the team can assemble metallic skids but only in place of the plank material
- The entire lower surface area of the skids needs to be visible from below
- The upper area surface of the titanium skid blocks needs to be at most 3mm below the reference plane
- The skids must be made from Titanium alloy
There are plenty of other requirements, very technical and complicated, that you can read on their official site, if you’re interested.
Let’s just say that the construction of F1 cars and the assembly of the skid block are extremely specific, down to the smallest details.
Plank Wear and Disqualification Issues
The most important thing about the plank/skid block is the 1mm wear limit allowed by the FIA.
To clarify, the FIA states that the plank must be:
- 10mm when installed on the car
- Not less than 9mm after wear (even excessive wear)
That 1mm of material is the wear and tear limit of the plank during a race. If the plank is deteriorated more than a millimeter, then the car is disqualified.
That’s because the plank’s thickness is calculated in such a way that wearing it beyond 1mm is considered to be too dangerous for the driver. More specifically, the car is driving too low, producing too much downforce, and is at risk of purpoising.
Michael Schumacher was once disqualified because the plank under his Benetton had an excessive wear beyond 1mm. The FIA ended up handing victory to Demon Hill.
However, teams have found a solution around the plank’s requirement of increasing the car height and thus lowering performance. They added titanium plates inside the plank, which send sparks flying when they touch the asphalt - this is the answer to your question: why do F1 cars spark?
They chose specific places on the plank that are more likely to touch the asphalt during a bottoming out. This leads to a slower degradation of the plank during races, which allows teams to lower the car height a bit and achieve more downforce.
This measure was accepted by the FIA, as shown above in their official specifications.
What Is the Plank Material Used in F1?
When the plank was initially introduced after Ayrton Senna’s death, it was made from a composite wood called Jabroc. It combined multiple wooden composites and beechwood.
The veneers were layered with high-strength resin to keep the plank strong and stable.
However, F1 engineers eventually found a better alternative that’s still in use today – Permaglass. It’s a homogeneous material made from glass-reinforced laminate that’s strong, durable, light, and non-flammable.
So, technically, the wooden planks are not made from wood anymore. It’s now a rectangular skid block material made from Permaglass that goes on the centre line of the car’s underside.
Inside the plank, there are internal fixing holes and titanium skid plates fixed symmetrically that help with post race scrutineering by FIA officials.
Permaglass degrades smoothly, even with excessive wear, so that it doesn’t pose a risk to drivers or spectators. The same goes for the flush mounted metal skids fixed on the plank.
The Rigid Plank and the Flexi Floor in F1
One last thing I should mention about the wooden plans on F1 cars is that they need to be rigid within certain parameters established by the FIA.
The FIA created these specific regulations to deal with purpoising.
However, F1 engineers got clever and managed to exploit some grey areas in the regulations. That’s how the “flexi floor” controversy was born.
Essentially, the engineers developed planks that would become flexible on the track, when enough downforce was pushing down on the cars. When the cars were checked while stationary, the skid block would be completely rigid, as per the regulations.
The extra plank flexibility lowered the car a bit, leading to more downforce and thus better performance.
This was eventually discovered by the FIA and new regulations appeared that took this factor into consideration.
However, that wasn’t the end of it.
Engineers exploited yet another loophole and split the plank into more than one piece. One of the sections moved around independently from the other one and effectively protected the portions of the plank (the holes) that the FIA checked for wear.
On the track, that section of the skid block moves up, disappearing “into the plank” and avoiding too much damage at any internal fixing hole.
The FIA found out about this and put a stop to it through new regulations, which Max Verstappen and the Red Bull team had criticized. For now, there haven’t been any more cheating attempts.
Closing the Chapter on Formula One Planks
Formula one wouldn’t be the same without its “wooden” plank. History tells us that the pre-plank period was a grim one. Drivers were fully aware that any race could be their last.
With modern car manufacturing technology and safety measures, that’s a reality long buried in the past. And the plank still plays an integral role in keeping F1 drivers safe.
I hope you’ve learned a thing of two about how the plank works in F1 and why it’s necessary. See you in the next guide!
- The Guardian – Lewis Hamilton Says Purpoising Injuries Are Unacceptable Before Canadian GP
- FIA – 2023 Formula 1 Technical Regulations
- Race Fans – Hill handed Win as Schumacher Is Thrown Out
- Formula Nerds – The Story and Conspiracy Surrounding the Death of Ayrton Senna: 27 Years On
- Motorsport – Roland Ratzenberger: The Inside Story of the Imola Weekend
- Planet F1 - Max Verstappen Declares 2023 Floor Changes Are ‘over the top’"