This weekend we are back in Canada after a one year absence. The track is quite different in character from the circuits we have visited so far this season and it is an interesting indication of how the cars perform in a lower downforce configuration.
Montreal is based on a series of chicanes and long straights without a fast corner to its name. As a result the cars run the second lowest level of downforce of the season, after Monza.
For Montreal they have lost the small upper winglet elements because they don’t need the extra downforce they bring and they don’t want the drag. The wing keeps the same basic philosophy, particularly with the elegant multiple channels on the endplate but it is a good illustration of the differences between a track like Istanbul and a track like Montreal.
It is noticeable, talking to engineers from other teams, how Renault seems to be making small but confident steps at every race. In Istanbul the car was faster than the Ferrari and this seems to be a team on the move. If Mercedes back off on development in the second half of the season, as has been suggested, then Renault may well finish ahead of them in the championship. After their humiliations last year both on track and over the Singapore crash scandal, Renault is an increasingly confident team.
A real brake killer
One of the problems with reducing the downforce on the cars is that the drag effect is not available to the cars when it comes to braking. Montreal is easily the hardest circuit on the calendar on brakes in terms of big, punishing stops. Monaco can be very hard on brakes because they are in use all the time and never get a chance to cool down, which can tip them over the edge.
But for big, brutal stops you cannot beat Montreal and this year the challenge is even greater in the race because the cars are carrying 160 kilos of fuel at the start. We can expect some teams to have brake problems, it’s just a question of how severe they are. The driver spends 16% of the lap time pressing the brake pedal here, which is quite high in addition to the severity of the stops.
According to Brembo, there are seven stops here of which the hardest is the final chicane, where the cars brake from 320km/h to 140km/h in just over 100 metres, which is a deceleration of almost 5g. But this isn’t the one that really kills the brakes, because they have had a chance to cool down on the long straight. It’s the stop at the hairpin which kills them.
For the hairpin the cars go from 290km/h to 60km/h but because the drivers have used the brakes twice relatively soon before, the brakes are already very hot when they are applied for the hairpin. Most of the teams have larger brake ducts here this weekend to help with this problem.
Red Bull F Duct The next talking point from a technical point of view is ironically, something which isn’t here this weekend; the Red Bull F Duct rear wing. The team tested it in practice in Istanbul, but did not use it for qualifying and the race. However our technical artist Paolo Filisetti, obtained some insights into what goes on beneath the skin, which you can see in this drawing.
The main channel is the top one and this puts the air flow out through the channel in the rear of the wing. The lower one has an exit (inset in the drawing) below the rear wing, which puts the air out underneath the wing. This helps to increase the stall, in other words to increase the effect by which the wing sheds drag. It is controlled by a fluidic switch, which is essentially a switch triggered by airflow.
However after trialling it in Turkey, they decided not to bring it to Montreal, where it would have been of great value with the long straights. The team wasn’t satisfied with the way it worked in Turkey, as it drained downforce away. This is something most teams are finding as they try to copy McLaren’s breakthrough.
The specific reason why they have chosen not to even bring it here is that the rear wings are not very high downforce in the first place. Also its likely that they have been focussed on getting it to work on the kind of wing they use for 70% of the races, rather than waste resources on getting it to work on a Canada wing.
There are some suggestions among engineers that taking this line of thinking to its conclusion, we might not see anyone using the F Duct in Monza. Although this sounds counter intuitive with straight line speed the order of the day, in fact the downforce levels are so minimal in the first place there is less need to shed drag.