A bold return to the past has Formula 1 fans buzzing with anticipation and controversy. Gary Anderson, a renowned F1 expert, has shed light on a design trend set to make a comeback in 2026, and it's a doozy!
The feature in question, once known as the 'mousehole', is making a comeback with a twist. Anderson suggests we now call it the 'rathole', and its potential impact on performance is nothing short of intriguing.
The mousehole, or rathole, is an opening in the rear of the car's floor, leading into the diffuser exit. It's believed to enhance airflow into the diffuser expansion area, similar to previous mousehole designs. But here's where it gets controversial: why would teams intentionally reduce diffuser performance with such a large opening?
As Anderson explains, it's not as simple as it seems. The slot is strategically positioned after the diffuser expansion area begins. The inner surface of the brake duct (marked with a green line) contains the airflow spilling off the inner corner of the tire, where the tread meets the sidewall (indicated by yellow arrows). Even the small duct in the lower section (highlighted in orange) plays a role, allowing more airflow to enter through another inlet route.
To further complicate matters, small louvres on the floor's top surface (shown with magenta arrows) pull airflow through, connecting it to the 'tyre squirt'. This effect, created by the squeezing of the tire tread against the track surface, can enhance the underfloor's performance if properly managed.
Anderson highlights the tyre squirt with purple and red arrows, indicating the airflow's direction. The longer red arrows represent the desired outward flow, or 'outwash', while the shorter purple arrows show the inward flow, or 'inwash'. By maximizing outwash and minimizing inwash, teams can improve the underfloor's sealing mechanism.
Mercedes has taken this concept a step further by adding a small wing section above the floor, increasing the power of the outward airflow (indicated by yellow arrows).
The positioning of the inlet duct is crucial. It sits behind the diffuser ramp's start and near the inner surface where the diffuser boat tail sweeps inwards around the gearbox. If the sweep is too dramatic, it can cause airflow separation, so optimizing inner diffuser wall airflow may necessitate this opening to reduce separation risk further outboard.
Most frontrunners, as seen in the pictures, have some form of opening in this area, along with a secondary turning vane mounted to the inner surface of the brake duct. McLaren, for now, is the exception, but Anderson predicts they may soon adopt a similar design.
But is it legal? Anderson suggests that, like many aspects of these new cars, the answer is not black and white. While the FIA will likely scrutinize this feature, the technical regulations, spanning 264 pages, may not explicitly define the height of the lower edge of the diffuser sidewall.
As long as it's a cutout and not a hole, Anderson doesn't foresee a problem.
This design trend's return promises to spark debates and discussions among F1 enthusiasts. What do you think? Will this feature revolutionize performance, or is it a risky move? Let us know your thoughts in the comments!
