Are you following F1 this year and wondering what is porpoising? Here’s a quick explanation…
I’m no aero guy but here is my take on what is porpoising including some of the lesser known factors at play.
So at speed, the shape of floor of the Formula 1 car sucks the car down towards the ground. Porpoising happens when something interrupts this, with the effect abruptly stopping.
Video is a great medium to use to explain this so here is a video F1 shared of the Ferrari suffering porpoising:
Pretty uncomfortable looking right!
What is going on?
Introducing Ground Effect
Formula 1 cars use aerodynamics to increase the downwards pressure on their tyres, creating more grip in the corners. More grip in the corners allows them to go faster around the lap. It has a big effect and until 2022 was mainly created by two big wings – one at the front and one at the back.
The issue with using wings is that when you get close to another car, there is not enough air flow left for your front wing to work. When you get close to the car ahead, you loose grip so have to drop back. This makes close racing super difficult.
Called “ground effect” the aim with the shaped floor is to help the cars become less reliant on their wings for generating grip in corners. The goal is that the cars can then run closer together for better racing.
What is porpoising then?
The porpoising issue is that if the car gets too low, the ground effect abruptly stops in what my aero friends would call a stall.
No longer being sucked to the ground, the Formula 1 car will lift up. At which point the air flow un-stalls or “re-attaches”, and the car is sucked back down to the ground again … until it stalls again … etc.
This creates this very uncomfortable and unnerving looking effect people have labeled porpoising. It was also common last time F1 ran ground effect before it was banned…
You might wonder how and why the engineers missed this?
“Surely, their CAD tools would have predicted this effect? Maybe it was an assembly or setup problem. In any case, it’s amusing for the viewer and no doubt terrifying for the driver.”
A question from reader Doug
Porpoising is hard to predict. Here are some reasons why.
Even with all the great engineering tools, porpoising on a racing car is really hard to predict.
The reason ground effect was banned before was because if porpoising happened mid corner, your grip goes and you’re off!
I’m not an expert in aero – at all tbh – but you can imagine that there are a lot of variables, outside the designers control, that will need to be accounted for…
Variables Affecting Porpoising In A Racecar
Driving in a straight line, on a flat road is fairly easy to model in an engineering tool.
The variables which make things less predictable are things like:
- Side winds,
- Wind gusts,
- Road topology (i.e. hills, kerbs, road roughness),
- Other cars effecting the air,
- The effect of the front wheels when steered,
- The effect of “tyre squirt” i.e. the flexing of the tyre over bumps influencing the air presented to the floor.
On this last point regarding the tyres. The cars will be setup very stiff on their suspension so that they can run closer to the ground and generate more grip. This means there is little suspension travel to damp out the oscillations. The tyres do have a little damping but not a lot so they are not much help.
You’ve also got…
- air density,
- humidity and
- temperature…
… which all affect the viscosity of the air passing under the car too.
And on that point, it is likely you are going to get localised differences, as say the brakes heat the air before it passes through the floor.
Porpoising happens because of inconsistent behaviour
If all that wasn’t complicated enough … and remember … I think I’m really just scratching the surface (aero guys feel free to let me know what else I’m missing) … Another thing, which might not be so clear is that the loss of ground effect isn’t necessarily happening consistently along the car.
What I mean is you can have a car that is 99% ok, but then one area of the floor stalls – because of one of those variables – and then this sets off a chain reaction around the rest of the car.
A racecar that was previously fine is suddenly being asked to work outside of its intended operation window i.e. the front stalls a bit, causing the car to pitch up, which then stalls the otherwise happy rear end.
What is the solution to porpoising in a racecar?
The solution is always to be less aggressive with the amount of negative lift you are asking the floor of the car to give you.
But of course, that means giving away grip, performance and lap time.
It therefore becomes a trade off between how aggressive you can be trying to find lap time versus how consistent (and safe) you can make the car to drive should it encounter these air flow disruptions.
I’m sure we will be hearing a lot about “underfloor sensitivity” or similar phrases this year.
Looking forward to seeing how this pans out!
One last thing
I made the video play backwards as well as forwards on purpose. I’ve found you can often pick up different things when the same visual is mirrored. Take another look below:
For me forwards, I was looking at the drivers head moving. Backwards, I was drawn to the visible gap under the car.
What did you pick up?
Sign up below and maybe let me know.
