Since the changes in the bodywork rules for 2009, teams have struggled to tune their cooling within the limits of what openings can be made in the cars sidepods. Tuning the cars cooling is always a compromise, between outlet area and drag. the more outlet area the greater heat that can be evacuated from within the sidepods. But this comes at the cost of drag, which will slow the cars lap times.
Heat is created by the engine, then ejected via convection through the radiators and radiation from the engine itself, especially the exhausts. Additionally cooling needs to be provided for the gearbox oil and hydraulics fluid (plus in 2009 the KERS hardware). The bodywork rules apply a no opening rules for three areas of the sidepods; 1) either side of the cockpit opening, either side of the fuel tank and then from their to a point near the rear wheels. Plus the teams can have a limited area to open around the rear suspension and an equally restricted single opening for the exhaust pipe outlet. (see the full rules at the bottom of the article).
Aside from the limited openings stated, the rules initially looked like the only area for cooling would be the exit at the rear of the coke bottle shape. To this end several teams created removable panels to tune the size of the exit, McLaren in particular created an effective solution to do this with the MP4-24. However the downside of solely using the coke bottle exit, was also the primary reason teams switched to chimneys and louvers in the years preceding the new rules. This makes the sidepods bulky as the air from the radiators needs to be ducted all the way along the cars length. Plus the exit being in between the rear wheels created drag and upsets the aerodynamics. Every team has oversized the apertures that the suspension passes through up to the maximum allowable area, this provides a useful exit as does the area the exhaust pipe which is oversized for the actual pipework the exhaust employs.
But closer reading of the rules shows there are other areas that can be exploited. Taking a wider view the rules allow room for unrestricted openings ahead of and behind the restricted sidepod areas. Additionally opening can be made inboard of these areas and an area up to ~50mm above the floor. We soon saw teams create openings near the cockpit, being just above the radiators they are particularly efficient, and with the raised cockpit sides being a add-on to the structure of the monocoque, quite easy to retrospectively apply to the car. Teams have employed both vents and louvers in this area, in extreme temperatures teams even have louvered and vented panels fitted to the same opening. Near this spot the very front of the sidepods extend beyond the controlled zone and Both Force India and McLaren have created openings across the front shoulder of the sidepod. Towards the rear, it was Red Bull that found that the upright engine cover could act as a vent, as the engine cover tapers towards its end open-able panels allow hot air to exit.
For local cooling rather than a major out many teams fit outlets along the lower edge of the sidepods, normally this is actually part of the floor, BMW Sauber in particular have fitted long runs of louvers to exploit this area.
Also Ferrari have exploited the rule on exhaust opening, while it demands a single opening of a maximum size, the rules do not state how narrow it can be at any point. Thus Ferrari created an exhaust pipe exit inline with the louvers, the four apertures joined by a small slot machined into the bodywork. The slot joins the apertures and effectively makes them one opening, extending the area allowed over a greater area. Critical for Ferrari who have a “U” bend in their exhaust pipe that would otherwise scorch the bodywork.
One other point on cooling opening is that teams sometimes have larger openings on one side of the car than the other. This is because the sidepods contain asymmetric cooler, one sidepod will also have an oil cooler, taking up some of the space of the water radiator. Thus this side has greater outlet area to maintain low oil temperatures.
COOLING RELATED BODYWORK RULES
3.8.4 Any vertical cross section of bodywork normal to the car centre line situated in the volumes defined below must form one tangent continuous curve on its external surface. This tangent continuous curve may not contain any radius less than 75mm :
a) the volume between 50mm forward of the rear wheel centre line and 300mm rearward of the rear face of the cockpit entry template, which is more than 25mm from the car centre line and more than 100mm above the reference plane ;
b) the volume between 300mm rearward of the rear face of the cockpit entry template and the rear face of the cockpit entry template, which is more than 125mm from the car centre line and more than 100mm above the reference plane ;
c) the volume between the rear face of the cockpit entry template and 450mm forward of the rear face of the cockpit entry template, which is more than 350mm from the car centre line and more than 100mm above the reference plane.
d) the volume between the rear face of the cockpit entry template and 450mm forward of the rear face of the cockpit entry template, which is more than 125mm from the car centre line and more than 675mm above the reference plane.
The surfaces lying within these volumes, which are situated more than 55mm forward of the rear wheel centre line, must not contain any apertures (other than those permitted by Article 3.8.5) or contain any vertical surfaces which lie normal to the car centre line.
3.8.5 Once the relevant bodywork surfaces are defined in accordance with Article 3.8.4, apertures, any of which may adjoin or overlap each other, may be added for the following purposes only :
– single apertures either side of the car centre line for the purpose of exhaust exits. These apertures may have a combined area of no more than 50,000mm when projected onto the surface itself. No point on an aperture may be more than 350mm from any other point on the aperture.
– apertures either side of the car centre line for the purpose of allowing suspension members and driveshafts to protrude through the bodywork. No such aperture may have an area greater than 12,000 mm when projected onto the surface itself. No point on an aperture may be more than 200mm from any other point on the aperture.