Mercedes's secrecy about their car's floor triggered the interest of many ahead of winter testing. Though the team were perhaps most clear about it, others similarly tried to not reveal too much about the floors, as this area is where teams had to adapt their designs to comply with the modified regulations without losing too much downforce.
The reduced floor width towards the rear wheels meant teams had to redesign an aerodynamic area that is crucial for the efficiency of the diffuser and management of airflow around the rear wheels. Mercedes for instance have opted to curve the edge of the floor up just in front of the rear wheels, while a set of three covered vertical vanes attempt to guide air outboard. Red Bull Racing's RB16B on the other hand has a vertical standing element with a curved leading edge just ahead of the rear wheel.
Another interesting difference is a fairly large standing vane further upstream on the Red Bull, just ahead of the cutout in the floor that is therefore hidden in the image. Mercedes have a similar cutout, but without a vane in front of it.
Bigger differences are visible when we look a bit closer towards the car's centreline. The marked pull rod for instance has a completely different mounting on both cars. On the Mercedes, this rod is positioned so it's mostly within the car's bodywork, while Red Bull stuck with a rod that is completely exposed to airflow. Most teams are following Mercedes in that design, but Red Bull's layout has the rear damper sitting further forward, allowing to declutter the back of the car.
It's also interesting to see that underneath the lower wishbones - which Red Bull repositioned further backward for aerodynamic purposes, the height of the Mercedes diffuser does not appear maximized. Instead, it appears to taper off towards the rear wheels. That's a first, as teams typically maximise volume in the diffuser, while Mercedes now seem to find more performance with a different design route.
The car's sidepod bodywork is also very different. Mercedes has some bumps and an undercut in the sidepods' surface while at Red Bull they maintained the very elegant bulbous sidepods with extreme narrowing towards the back of the car. This, along with fairly high sidepod bodywork at the back created a very open rear end to optimise airflow over the diffuser on each side of the gearbox.
At Mercedes designers have opted for narrower outlets, a Y-lon to support the rear wing, a mid-wing and a clearly more compact rear part of the airbox.
Time will tell who did the best job this winter, but it's good we continue to see quite different design philosophies.