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McLaren was out early in Barcelona with an aero rake

Just when you’re expecting to finally glimpse the new season’s F1 cars, teams send them out covered in lightweight scaffolding.

The first day of testing almost always sees the appearance of fence-like structures hanging off the cars. Usually attached just behind the front axle or around the rear axle and diffuser, these fences are known as aerodynamic rakes and measure the air pressure over the car at any one point.

All of the teams will run an aero rake at some point during testing as they look to ensure there is correlation between their wind tunnel simulations and real on track running.

Ensuring that the correlation is as close to team’s simulations from their respective HQ’s as possible could determine whether it is going down the right development path or has developed an aerodynamic stall. If so, a trip back to the drawing board could be in order.

But what exactly is an aero rake and how do they work?

Made from special alloys such as titanium, the aero rakes used by F1 teams are capable of registering multiple readings in live time and feeding them back to engineers while the car is out on track.

Multiple Kiel probes are attached to the metal fence. These are capable of taking readings relating to air pressure from almost any angle of attack, so are resistant to changes in direction of airflow.

Mercedes testing its design with aero rake

Because of this, the readings are able to tell engineers how the air is reacting over the bodywork and other aerodynamic components and provide feedback that is as accurate as possible.

Rakes can vary from as little as 50mm all the way to 600mm in length.

The aero fence is comprised of Kiel probes that register the flow of air over each data point.

Each probe is shrouded by a protector shield with the probe itself registering the pressure of the air which is then fed back to teams and engineers live.

Williams ran a large aero rake on Day 1 in Barcelona

Kiel probes are useful for Formula 1 teams because they are less sensitive to changes in yaw angle, than pitot tubes, which measure air pressure on aircraft. This is handy when the cars in question are capable of pulling 5g through some corners before immediately flicking into the opposite direction for the next.

All of the captured data is the used to formulate a virtual map of the airflow travelling over the car while it’s in motion.

The accuracy of an aero rake is in the range of 10 microns, or 0.01mm.

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