An increasingly common feature this year has been the choice of an exposed beam wing design. The beam wing is the single element wing that sits below the rear top wing. Normally this wing runs the full span of the allowable 800mm rear wing width, but often is split into two by the rear crash structure. In the rules the location of both the crash structure and beam wing are relatively fixed, the wing needs to sit between 300-400mm high and only sport one element, while the crash structure needs to be no higher than 400mm. Along the centre line of the car clearly they vie for the same space.
The beam wing acts both as a wing in its own right, as a device that turns the airflow upwards improving the scavenging from the diffuser and the flow under the top rear wing. Recently, the increasing use of pylons to take the loads from the top rear wing into the chassis (via the top of the gearbox case) means that the structural demands of the beam wing are reduced, as it no longer has transfer the loads from the top Rear wing via the endplates into the chassis. If you ever get to pick up a structural beam wing you;d be surprised at just how heavy it is. Certainly not the piece of feather weight F1 bodywork you’d expect.
But since 2009 when Toyota realised that the beam wing needn’t be compromised by the crash structure and shaped the structure to pass under the wing, allowing its more potent underside to be fully exposed to the airflow. In some respects Red bull followed this philosophy too, albeit the beam wing mounting was still a relatively obstructive section mounded into the crash structure. This year several teams have chosen to shape the crash structure to expose the beam wing. Although this does necessitate a more complicated shape which in turn affects the structures efficiency, in terms of meeting the crash test and adding extra weight.
In Renaults case the wing is supported by the same central strut that supports the rear wing, other teams use smaller mounts beneath the beam wing. Lastly Virgin took a cue from their Acura LMP car and used a swan neck mount that despite the tortuous load path, does provide less obstruction to the underside of the wing.