Ferrari’s big bodywork upgrade was introduced at the Spanish Grand Prix – and although the team suffered a very difficult weekend, that’s not necessarily to do with the upgrade. This was a point Carlos Sainz was keen to make after he’d faded to a fifth-place finish from a front row starting position.

    “I think the upgrades are working,” he said, “but we have introduced them at maybe our worst circuit.”

    This year’s Ferrari has suffered inconsistency from the rear of the car, with both drivers reporting sudden snappiness. The latest bodywork has been designed to address that, to give increased and more consistent aerodynamic loading to the rear of the car.

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    In chasing this aim, Ferrari have completely reshaped the sidepods and lower engine cover. The sidepods still feature a wide, bluff frontal shape (very much in contrast to the sharply undercut fronts used by most others) but they have increased the length of the wide section when viewed from above.

    They have also reduced its width – the ‘wide’ section, whilst still wide, is now narrower but longer. That, and the accompanying new floor, is the essence of the change.

    To understand why Ferrari believe these changes will give them what they are seeking, we need to look first at how the ‘fat’ sidepod fronts – introduced on last year’s F1-75 – work.

    That bluff front, without any undercut, is there to outwash the airflow away from the car’s surfaces before then being pulled back into the car at the rear, where the sidepods begin to merge into the coke bottle area leading to the area around the diffuser.

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    The lower pressure of that ‘coke bottle’ area is what pulls the airflow, which has been out-washed by the bluff front of the sidepods, back towards the car. The air is out-washed at the front, to then be in-washed at the rear, and will ideally follow a nicely consistent parabolic curve between those two points.

    Inducing that airflow to leave, and rejoin, the surfaces of the car is a very different way of accelerating the flow to that used by the Red Bull-style undercut sidepod, which has a channel cut into the front of the much narrower sidepods, following a line down to the bottom and along the lower edges.

    BARCELONA, SPAIN - JUNE 02: Charles Leclerc of Monaco driving the (16) Ferrari SF-23 on track
    Ferrari's big bodywork upgrade was brought in for the Spanish Grand Prix

    At the rear of the Red Bull sidepods, this line meets up with the airflow coming off the downward ramp of the sidepod top, the two flows merging to give extra energy as the air makes its way through the gap between the rear wheels and over the diffuser.

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    The airflow of the Red Bull-style ‘undercut and ramp’ combination stays largely in contact with the physical surfaces. That of the Ferrari ‘out-wash and in-wash’ leaves those surfaces between the two points of departure and re-entry.

    The two methods are seeking to do the same thing – maximise the speed and power of the airflow over the walls of the diffuser to enhance the pull of that airflow on that coming through the diffuser (thereby increasing the underbody’s suction effect on the car). But they are doing it in different ways.

    BARCELONA, SPAIN - JUNE 04: Carlos Sainz of Spain and Ferrari prepares to drive on the grid during
    Ferrari have completely reshaped the sidepods and lower engine cover

    Ferrari’s narrowing and lengthening of the ‘wide’ section of their sidepods suggests their belief is that the airflow designed to follow that curved parabola between the two points of contact is ‘detaching’ – i.e. breaking away from the intended path, dissipating the flow’s energy.

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    Airflow will detach when it is being asked to change direction too suddenly. Narrowing the pod will give that intended airflow curve a shallower curvature. Lengthening the wide section will make it even shallower.

    If airflow separation is indeed what has been at the root of the car’s rear-end snappiness, this change of sidepod geometry should help to add stability.

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