Mark Hughes on SF15-T
Instead of the conventional ‘A arm’ or wishbone arrangement, it instead had what in effect was just a single arm but with a forked end into the chassis. To get the equivalent strength of a conventional wishbone, this had to be much heavier but in eliminating the second arm it removed a key aerodynamic blockage in the creation of the vortices ahead of the sidepod. The Mercedes W05 therefore got to have its aerodynamic cake and eat it, with good front and rear downforce.
This suspension innovation has been copied by Ferrari on the new SF15-T. Although the car retains – uniquely among the 2015 field – pull-rod front suspension, it has Mercedes-like single lower arms with forked ends. The pull-rod layout already gives a clearer airflow passage (because the lower arms are higher, further out of the way of the airflow coming off the front wing) but with the single lower arms, it’s now clearer still. Ferrari’s aerodynamicists should have plenty of scope to place the vortices in just the right place to accelerate the overall front airflow. This should be vital in clawing back front downforce almost certainly lost to the very different nose layout.
Last year Ferrari had quite a narrow gap between the nose and wing. This restricted flow to the rear but helped the front. Although the siting of the oil tank within the gearbox casing (on all other cars the oil tank is in the gap between the cockpit and engine) allowed Ferrari to bring the engine further forwards to create a bigger diffuser area at the back, the nose layout was probably unable to feed that with sufficient airflow to maximise its potential. On the new SF15-T, when viewed from head-on the long nose being used for initial testing disguises the gap between nose underside and wing, making it look smaller than before. But when looked at in profile it can be seen that the gap is actually bigger than previously – feeding more flow to the rear of the car. This flow will be increased further when Ferrari makes its planned switch to a shorter nose (just as soon as it can pass the crash test). This is exactly what Mercedes did last year, when it introduced the shorter nose at the third race.
Ferrari’s rear downforce should be enhanced further with a tighter coke bottle section (though still nowhere near as tight as Red Bull’s or McLaren’s), a new rear wing family that James Allison reckons has been designed not for more peak downforce but more robust downforce that will stay attached better as the car turns or in windy conditions.
In essence Ferrari has surrendered some easy front downforce for more rear and McLaren has done the opposite. In terms of engine Ferrari is very bullish about significant power increase and better energy recovery. There is informed talk of an extra 80bhp. Last year’s motor was reckoned to be around 50bhp down on the Mercedes (though this year’s Merc is reckoned to have an additional 60bhp). If those figures are accurate, the Ferrari will begin the year 30bhp down on the Merc rather than 50 – and not be as limited as before on energy recovery from the ERS-H. In its initial form the 2015 Ferrari motor still has a rear-mounted compressor (and no longer split with the turbine to fit in the ERS-H) but it’s possible that the revised rules allowing engine development tokens to be used through the season will see Ferrari introduce the Mercedes and Honda layout of a front-mounted compressor later in the year.
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