Russian GP Tech: Renault, Toro Rosso and Sauber
F1 technical analysis from Russian Grand Prix
As predicted, the development race for 2017 has meant that significant upgrades are appearing at every race, with teams no longer being able to wait until the Spanish GP for major upgrades, while still remaining competitive. Renault used its Russian GP upgrade package, first tested in the post-Bahrain test, to good effect, securing its second points finish of the year. Modifications to the Toro Rosso and Sauber cars proved less successful, with these teams only securing one point between them.
Firstly, the upper flaps on the Renault R.S.17’s front wing have been completely re-profiled, with the upper two elements being split into three smaller ones in addition to featuring a new shape. The benefit from increasing the number of flaps is the same as that which Ferrari would have seen from the slotted mainplane it introduced in Bahrain, namely a gain in downforce consistency.
The squarer flaps now also span a larger area, which will offset a loss in absolute downforce from using more, smaller curved surfaces as opposed to fewer, larger ones. Further gains in front load will result from the movement of the front wing arch towards the endplate, raising the area of the wing dedicated to downforce production.
Reducing the gap between the arch and endplate will reduce the volume of air that the arch directs around the front tyre, but this will also be negated by the more outwardly shaped fin at the top of the endplate. The vortex this fin produces will have greater vorticity, due to the greater pressure differential either side of it, ensuring that more air is pulled around the front tyre. In this way, Renault has improved the downforce consistency of its front wing, while ensuring that other areas are not compromised, meaning its overall performance has improved.
Additionally, the taller, squarer nature of the flaps means that the wing tip vortices, shed as high pressure air from above the wing spills over to its underside, will span a greater height. This change was most likely made in order to maximise the performance of the bargeboards in directing front tyre wake away from the chassis and diverting airflow around the sidepods, to the rear of the car.
While the front wing, together with the blown front axle concept covered in my Chinese GP Tech post, was trialled in the Bahrain test, the R.S.17’s new turning vanes were not. The altered two-element design is a significant departure from the previous version, which featured a single vertical strake, and is much more in line with those of other teams.
Previously, the single element was being used to produce a high energy flow, in the form of a vortex, to help the bargeboards direct front tyre wake outboard of the rear of the car. As the front wing’s flaps now provide vortices that cover a larger vertical range, the focus of the turning vanes can be turned to assisting the bargeboards in another manner. Their new, outboard shape is similar to that of the bargeboards themselves, and the new vanes will serve a similar function in protecting the rear of the car from front tyre wake. Clearly, the new version of the part is less focused at vortex production with the footplate preventing this, and offering a drag saving.
Secondly, at the rear of the Toro Rosso STR12, asymmetric rear cooling outlets were used, with the outlet on the left side being the minimum size the team has used so far this season, while the other outlet is the middle outlet size, first used in Australia.
This asymmetry has been a feature of Toro Rosso cars for a number of years, yet other teams have been reluctant to follow suit. The benefits will be lower skin friction drag and less mass at the rear of the car, allowing more wing to be run, and greater ballast to be used for improved cornering stability. The weight distribution problem can be removed by placing more ballast on the left hand side of the car.
However, the aerodynamic effect is more difficult to understand, especially with the lower rear wings for 2017, which interact more with the top of the engine cover. It is likely that, as the vertical distance between the rear wing and engine cover is lower for the right side, air will accelerate through here more than on the left side, meaning there may be more downforce production on the right side. The difference will be small, but would have induced instability for the drivers.
Lastly, Sauber brought a new front wing to Russia for its C36, with the focus being on the innermost part of the flaps. Having already altered the flaps in this area during pre-season testing, the bottom two flaps were cut away further, forming a straight inner edge.
The purpose of this change is twofold; firstly, reducing the area of the wing will have lowered skin friction drag, partly making up for the straight-line speed deficit the team faces due to using last year’s Ferrari power unit. Secondly, the positioning of the vortices relative to the bargeboards may have been more amenable to better rearward aerodynamic performance, as discussed above with Renault. Ultimately, this new front wing was not used, with the team preferring the higher downforce version, with the longer flaps, in order to put the tyres in their operating window on the smooth Sochi surface.
During the weekend, Sauber also announced a power unit partnership with Honda, starting from 2017, which will also see the Swiss team use McLaren gearboxes. This is a sensible decision because the team’s Ferrari units have had poor reliability in recent years as the Scuderia has focused more on its partnership with Haas. Honda is expected to make significant progress in-season, which should allow Sauber to hit the ground running in 2018.
See more on www.formulaone21.wordpress.com