Guest writer John Beamer looks at the technical developments at the Italian Grand Prix.
The fine balance involved in setting up a Formula 1 car was a major talking point at Monza as never before.
It all revolved around the decisions teams had to make about whether to run their F-ducts or not – and the fascinating split strategies employed by McLaren.
To duct or not to duct
The question going into the race was whether to use an F-duct or not?
First, a quick recap on how the device works. There are many implementations but McLaren were the pioneers. Look at the nose of the MP4-25 and you?óÔé¼Ôäóll see a raised inlet by the ?óÔé¼?£F?óÔé¼Ôäó of Vodafone ?óÔé¼ÔÇ£ hence the moniker F-duct. Internally, McLaren calls the device the RW80.
Air enters the duct and routes thought a hole in the chassis where it exits into the cockpit. When the driver chooses he can close the cockpit exit, forcing air through the shark fin cover into a rear wing slot, which creates turbulent air and cuts downforce (disturbing air underneath the wing). Downforce induces drag, so this loss of downforce cuts drag allowing higher top speeds.
This comes at the cost of aerodynamic efficiency (measured as the ratio of downforce to drag). But that isn?óÔé¼Ôäót an important factor when flying down Monza’s 340kph straights.
Unfortunately for McLaren’s rivals chassis are homologated at the start of the season which means the neat solution seen on the MP4-25 is difficult to replicate. The most common and effective alternative is a ?óÔé¼?£fluid switch?óÔé¼Ôäó system, which is what Red Bull use.
Their inlet duct is fed from the airbox and splits in two ?óÔé¼ÔÇ£ the lower section blows harmlessly under the rear wing while the second (upper section), when activated, blows air at the rear wing causing stall. A third (control) duct routes into the cockpit that allows the driver to activate the switch.
When ?óÔé¼?£off?óÔé¼Ôäó air will blow into the cockpit through this third duct; when ?óÔé¼?£on?óÔé¼Ôäó the air pressure inside the switch changes forcing air into the upper section which stalls the rear wing.
The McLaren conundrum
McLaren offered their drivers two striking different aerodynamic options. Surprisingly, they each chose differently: Button preferred the higher downforce wing with F-duct and Hamilton opted for a traditional Monza-style super-skinny rear wing.
Button?óÔé¼Ôäós car wasn?óÔé¼Ôäót much different from what was raced at Spa – the rear wing was identical. Hamilton?óÔé¼Ôäós car had no F-duct or shark fin. This confirms McLaren?óÔé¼Ôäós view is that the fin is aerodynamically marginal – its only purpose on the MP4-25 is to carry the F-duct to the rear wing.
A closer look at Hamilton?óÔé¼Ôäós rear wing shows that McLaren simply updated last year?óÔé¼Ôäós design. It was a slimline two-piece wing with the flap attached to the end plate with three raised gills which increase its efficiency.
The difference in top speed between the two set-ups was massive. Hamilton clocked 345kph (214.3mph) through the speed trap to Button?óÔé¼Ôäós 330kph. However, Button could carry more speed through the corners, particularly the Lesmo bends, to reduce the deficit and arrive at an almost identical lap time.
One reason why Button opted to carry more downforce was that it was easier on his tyres. Graining, which is when the rubber forms balls on the tyre surface reducing grip (think of it as having a film of fluid between tyre and tarmac), is less likely if a car has more downforce, as the tyres slide less. However the additional drag meant Button had to carry more fuel causing him to brake fractionally earlier into the corners and making acceleration slightly slower.
Hamilton mooted that Button had chosen the better set-up after being out-qualified by his team mate. His first-lap crash meant we didn’t get to compare the two solutions over a race distance.
Hamilton?óÔé¼Ôäós final qualifying lap was compromised because he got too close to Webber not because of car set-up. Yes, the car slides around more but Lewis had shown all weekend there wasn?óÔé¼Ôäót a hair?óÔé¼Ôäós breadth between the two set-ups.
And in the race having an extra 15kph of top line speed, coupled with less fuel, would have been pretty handy to bag an overtake or two.
Through the speed trap the F10 topped out at 338kph – the same as the F60 managed the year before. The difference in lap time was half a second, which shows the benefit of the F-duct (although part of that lap gain is due to increased aerodynamic efficiency as part of normal development).
Ferrari bought two rear wings to Monza: the version that Massa ran at Spa and one with lower downforce ?óÔé¼ÔÇ£ both cars raced the latter.
This featured a smaller main element and had no endplate gills in addition to a smaller F-duct channel. The slimmer wing required a lower volume of air to stall, hence the smaller F-duct outlet.
The Scuderia also introduced a new front wing featuring an almost flat main plane and a shallower flap/cascade combination. Together these produce a more aerodynamically efficient device ?óÔé¼ÔÇ£ perfect for Monza.
A close look at the Ferrari endplates shows a lack of slot gaps like on the McLaren or Red Bull.
The slot gap is to allow air to bleed from outer part of the endplate underneath the plane and flap. This air carries more energy so keeps flow underneath the rear wing attached for more downforce. When running a shallow wing, like Ferrari did, the slot gaps hurt performance because airflow generally remains attached anyway and the slots just add drag.
After the success of Spa, where the team successfully introduced its F-duct, it was no surprise the device was retained for Monza.
For Monza Renault introduced another version of its much-developed front wing. The fiendishly complex endplate was simplified, but still had more detail than most other teams?óÔé¼Ôäó. And although the wing retained the usual double flap (three elements in total) the cascade on the inner part of the endplate was deleted.
The upper flap had a ?óÔé¼?£V?óÔé¼Ôäó etched into it. Air flowing over the front wing would be pulled under at the ?óÔé¼?£V?óÔé¼Ôäó creating a vortex. This vortex has rotational energy that is directed towards the tyres (possibly the brakes) or floor to improve either brake cooling or downstream aero performance.
The remaining teams
Among the big teams Red Bull were notable for an absence of major aerodynamic upgrades. The Milton Keynes-based outfit ran a medium/low downforce package similar to what it raced at Spa, but it was almost as if the team passed on Monza in the knowledge it would be quick at the remaining circuits.
Toro Rosso bought its most significant upgrade of the year to Monza and debuted both an F-duct and a blown floor.
The blown floor was very similar to other teams?óÔé¼Ôäó versions with exhausts exiting from low down below the back of the sidepod undercut. The gas blows inside the rear tyre over the diffuser and does not blow into the diffuser ?óÔé¼ÔÇ£ that will likely come later, maybe next year for Toro Rosso.
The blown floor was raced but F-duct proved far more problematic. Point blank it didn?óÔé¼Ôäót work ?óÔé¼ÔÇ£ the device was effective at shedding drag but couldn?óÔé¼Ôäót retain downforce when it was ?óÔé¼?£off?óÔé¼Ôäó. The design is similar to that of sister outfit Red Bull.
Force India and Mercedes both opted to race without F-ducts – an indication that their respective devices aren?óÔé¼Ôäót as effective as other teams?óÔé¼Ôäó.
Mercedes first introduced a passive system and is the only established team that doesn?óÔé¼Ôäót run a shark fin to pipe stall the rear wing. Instead the system routes through the rear wing endplate. In recent races Mercedes has introduced an active driver-controlled device but it wasn?óÔé¼Ôäót raced at Monza.
HRT seldom get a mention in the technical review but it was the only team not to bring a lower downforce package to Monza ?óÔé¼ÔÇ£ both Virgin and Lotus brought different specification wings. It gives an indication just how much the team is struggling for funds.
The team ratcheted the wings down to the lowest permissible angle and made do. In one sense if you?óÔé¼Ôäóre at the back of the grid it doesn?óÔé¼Ôäót matter what wings are raced.
Monza saw the advent of the more stringent splitter deflection test. A 100kg weight can now be placed at any point along the front splitter rather than just at the central section (which is allowed to deflect by 5mm). This stops any lateral flex that may allow the front of the car to sink especially when cornering.
In addition articulated joints are outlawed and teams must use a 1m plank leading up to the splitter. This is to prevent a dual splitter which may be hinged with an articulated joint.
Before the introduction of the new tests most teams had a central stay attached to the chassis to ensure compliance. The stricter test saw teams employ a variety of solutions. Red Bull were publicly keen to show that the changes didn?óÔé¼Ôäót affect them and their splitter fixing was visually unchanged. However, Red Bull failed the load test on Friday by a small margin, then passed the following day.
Counter-intuitively McLaren deleted its central fixing opting to strengthen the splitter. This suggests that the MP4-25?óÔé¼Ôäós splitter may have had some lateral flex. Monza isn?óÔé¼Ôäót a circuit where a hinged splitter will have a massive effect of performance.
Mercedes produced the most visually robust solution with an inverted ?óÔé¼?£V-style?óÔé¼Ôäó joint to prevent any part of the splitter flexing. Although adding strength this disrupts airflow over the splitter to the floor and sidepods ?óÔé¼ÔÇ£ Mercedes will likely adopt a neater solution for future races.
The European season has now finished and there are now only five fly-away races left. Singapore is next up and we can expect it to be the race where most teams bring their last major upgrade before dedicating most of their resources to the upcoming season. Red Bull, McLaren and Ferrari are all due significant upgrades.
After two low downforce tracks (Spa and Monza) designers have had plenty of time in the wind tunnel to perfect their latest upgrades. However, given the closeness of the championship don?óÔé¼Ôäót be surprised to see the top constructors continue to develop aggressively up to Brazil, which will likely compromise the beginning part of their 2011 campaigns. Ferrari, for instance, have reallocated resource back to the F10 after Alonso?óÔé¼Ôäós victory last weekend.
Singapore is a classic street track ?óÔé¼ÔÇ£ it?óÔé¼Ôäós tight and bumpy and requires oodles of downforce. It should play to the strength of the RB6. The McLaren is uneven over the bumps and doesn?óÔé¼Ôäót relish ?óÔé¼?£point and squirt?óÔé¼Ôäó corners as much as its rivals. However, McLaren will have upgrades to the blown diffuser and we should see whether the new front wing and deflection tests have curbed Red Bull?óÔé¼Ôäós speed.
Ferrari will be in the hunt too. The F10 rides the bumps well and performs exceptionally well under braking, which is important for Singapore where there are 23 medium/low speed corners. Come the end of the race we?óÔé¼Ôäóll have a good idea whether the five-horse race will continue to Abu Dhabi or whether Red Bull still has a comfortable performance margin on high-downforce tracks.
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Images ?é?® www.mclaren.com (1-3), Ferrari spa (4-5), Renault/LAT (6), Red Bull/Gett Images (7), Bridgestone/Ercole Colombo (8)