Before the 2009 regulations revised the rules on F1 aerodynamics there were only four Grands Prix on the calendar for which teams built radically different car configurations: Montreal, Monza, Monaco and (sometimes) Spa.
Since the rules change, teams' rear wing development has been much more restricted by the FIA. Given the need for the front wing to balance rear downforce, many teams opt against bringing a new low-downforce configuration for the Canadian race.
However, unlike in other races the low downforce nature of the Giles Villeneuve track does give some leeway to designers to tweak rear wing design.
Last year Renault debuted its 'M' wing ' so-called because of its shape. This year the most obvious visual rear wing change was a concave design from Williams.
The first illustration shows Williams' rear wing from the start of the year. Apart from the colour it's little different from that of any other car in the pit lane.
The regulations require a two-element device and the only design considerations are the profile of the endplate (which don't diverge significantly) and the chord length of the two elements, which dictates the effectiveness of the DRS.
The shorter the cord length of the flap the more effective the DRS system is at shedding drag when opened as the gap between the two elements in maximised. This trade-off comes at the expense of total downforce when the rear wing is closed.
The second illustration shows Williams' concave rear wing developed for Montreal. Any deviation from a straight edge is going to reduce downforce simply because the area that the air can work with is less that it would be otherwise.
For the concave wing, the angle of attack of the wing is steeper towards the endplates, which means that less downforce is produced in the centre.
Therefore the total downforce produced by the rear wing is lower than the old configuration. Less downforce equals less drag and a higher-top speed.
Why this particular shape as opposed to say an 'M' profile? The engine cover alters the profile of the air flowing to the rear wing so by optimising the shape the rear wing elements designers can increase the efficiency of the device (as measured by the lift to drag ratio.
The objective is to ensure that the airflow is perpendicular to the wing on contact ' this allows to airflow to work the wing while giving up the least amount of drag.
In the coming races expect Williams to return to its more traditional wing ' the Montreal edition will probably return in a few months' time for Spa.
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Illustrations © John Beamer for F1 Fanatic. Image Williams/LAT
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