The use of upside-down aerofoils to provide an aerodynamic down-force on a racing car has been with us for a long time now, and the orthodox layout is to have small canard-fins on each side of the nose cowling, or a full-width aerofoil ahead of the nose, to assist the adhesion of the front wheels and a full-width aerofoil at the rear to assist the rear wheels. Looking at the rear aerofoil there is a diversity of opinion among designers and the variations make interesting study. Early beginnings were small aluminium sheets across the rear of the car, which later developed into driver-controlled, or automatically controlled aerofoils which eventually rose to absurd heights above the rear of the car, mounted on tall thin pillars; the aim being to get the aerofoil into “clean” air outside the cars turbulence. Legislation and commonsense eventually came to a compromise over the design of rear aerofoils, their height, width and distance behind the rear wheel centre line being fixed at certain maximum dimensions. This compromise, arrived at after consultation between the FIA technical committee and the Formula One car constructors, is accepted willingly by everyone.
There are two basic schools of thought among designers, the aerofoil mounted on a central pillar and the aerofoil supported at each end on a vertical plate. The single central pillar mounting is the most popular, for both aerodynamic and constructional reasons. With the driver’s head on the centre-line of the car and the inlet ports of V8 or V12 engine also close to the centre-line behind his head, it is reckoned that the air-flow along the centre-line is inevitably disturbed so a central-pillar mounting for the rear aerofoil could help to stabilise the air-flow out of the back of the car. Aerofoils must be fixed while the car is in motion, but can be adjustable by team members at the pits. In its simplest form the rear aerofoil provides more down-force at the expense of more drag and vice-versa, the settings being a compromise between down-force and drag to suit the circuit conditions. A central pillar mounting offers an easy solution to an adjustable hinge arrangement and can be mounted on the gearbox casing or from a framework incorporated in the rear suspension layout. Those Formula One designers who favour the central pillar mounting, either by an eliptical section fabricated pillar or by a pair of thin duralamin plates offering minimal frontal area, are Ferrari, Williams, Ligier, Brabham, McLaren, Shadow, Arrows, ATS and Ensign.
The opposing school of thought believes that the air across the top of a Formula One car should have as clear a run as possible off the back of the car. To achieve this the aerofoil is supported at each end on thin vertical plates so that there is an unobstructed area above the gearbox. Before total-enclosure of the rear of the car arrived on the scene the best system was to mount the vertical plates on the ends of a large-diameter thin-gauge cross-tube which was mounted on the gearbox housing. This large tube could also be used as a catch-tank, having all the breather pipes from engine, oil tank and gearbox fed into it. Adjustment of the aerofoil was done by pivotting the front on the side-plates, with graded holes and pins to locate the rear, the side-plates being fixed rigidly. Wolf and Fittipaldi used this system last year, and the 177 Alfa Romeo still uses it. With the advent of the ground-effects designs and their all-enveloping bodywork a better solution was to make the end plates as part of the bodywork. This system is used by Lotus, Wolf, Tyrrell and Merzario, the Lotus 80 having an adjustable trim-tab between the side-plates on a level with the rear bodywork, with an aerofoil across between the tops of the side-plates.
Renault favour the end plate mounting principle but have a system all their own which no-one has followed. The aerofoil is attached to the tops of side-plates, but these side-plates run down to the lower level of the gearbox and then turn inwards to form another aerofoil across the lower part of the car. This results in a rectangular shaped structure, with rounded corners, and it is attached to the gearbox at its lower central point. It is an end-plate design utilising a central mounting.
No two aerofoils are exactly the same, all the Formula One designers having their own aerodynamic ideas, some using a slotted aerofoil, others using single levels, others using double levels, but all are endeavouring to increase the down-force on the rear tyres for increased cornering power, without losing too much on the straights due to aerodynamic drag and tyre rolling resistance. — D.S.J.