Tech analysis: McLaren MP4-21

Released to almost no fanfare from the team, McLaren rolled out their all-new car in the pitlane at Barcelona back in January. The car is a clear development of the MP4-20 - a car that failed to win either championships but was clearly the fastest for the much of the 2005 season.

Last year the team delayed the design of the new car to better accommodate the then-new one-race tyre rule and revised aero regulations. This move clearly gained McLaren the pace over their rivals, but the car's season was blighted early on by over-conservatism on their tyre use and latterly over optimistic designs costing reliability. These two issues allowed Renault to build and maintain an advantage they were never to lose.

In preparation for 2006, McLaren ran the Mercedes V8 in a car as early as the September test at Silverstone, having first run the engine on the dyno only three months earlier. They also ran this revised MP4-20 throughout early winter testing. Meanwhile, the design and build of the new car continued. The only disruptions to their winter programme were a limited supply of the interim V8 engines - which prevented further running in the MP4-20 - and question marks over the new engine's power output.

In detail

As the car carries over a lot of the design concepts of the MP4-20, the primary changes are simply to accommodate the shorter V8 engine and tidy up aerodynamics at the front.

No confirmation has come from McLaren on the revised layout of the car, but as most Michelin runners opted to lengthen the gearbox, this is most likely the case for McLaren as well, since it shifts weight forwards to make the wide square-shouldered front tyres work better.

It was said that the MP4-20 carried the penalty of the pre-season redesign all year, in particular with the packaging of the keel-less set-up. On the new car, the revised rules concerning the ground clearance of the turning vanes between the front wheels has led to a lot of tidying around the nose.

At the front there is a much narrower nose (over the unusually wide nose-cone on the 2005 car), and it has a pronounced droop over the front wing. This makes a large part of the nose-cone below the bulkhead it mounts to, making the frontal impact test particularly difficult to pass without an unduly heavy nose cone. Again, a familiar triple element front wing hangs from the nose with similar endplates to those used in 2005.

It is the detail around the front suspension and lower bargeboards that has seen the more influential change. McLaren's favoured format of the "keel" area being blended into the turning vanes is retained. This year the design is tidier and the wishbone and vane are much thinner, while the keel itself is slightly offset from the bottom of the chassis. This leaves the front bulkhead very high, which is in turn mated to a higher dashboard bulkhead, resulting in the distinctive step ahead of the cockpit opening.

Such a high nose section brings the aerodynamic benefit of the space it clears under the nose; this has allowed McLaren to further streamline the join between the chassis and sidepods.

There is now a clear path from the V shape above the splitter to the undercut around the front of the sidepods. This is perhaps the most extreme treatment of this area, with the sidepod inlet now merely a bulge at the very top of the sidepods' face. This, along with the higher placed flip-up along the sidepods' flank, accentuates McLaren's work in this area.

Another small alteration on the side of the monocoque is the loss of the small niche to the side of the cockpit, used for the various electronic control units. One additional use for this recess was to mount the tyre temperature's cameras, used in testing. These infrared cameras mount to the access cover and detect tyre temperatures around the lap. McLaren will have to find an alternative location to mount these cameras for future tyre testing.

From there on, the sidepods are a development of the MP4-20's. The design detail is much tidier - such as the exhaust ducts and the mounting of the rear shelf wing, which are now part of the main engine cover moulding.

With less cooling demands from the V8 engine, the outlet duct format at first appeared to be purely a chimney and exhaust fairing. Worryingly, though, during running at the recent Valencia test with the new engine, the car did appear with a heavily louvered exhaust panel and sections cut out of the sidepod to improve cooling.

Attached to the roll structure are revised Viking wings. These are altered in layout for this year; they now have smaller vertical end plates and are mounted by more angled plates.

These unusual devices have yet to be adopted by other teams - their new format also defies understanding, and they may have uses for either converging the airflow back towards the rear wing, or resisting yawing motions. The new, smaller format wings would be less effective at either, but the former explanation still sounds the most likely.

At the rear, the airflow over the final section of the car has been much improved. The gearbox fairing is now in three major parts: the upper section is attached to the main sidepod/engine cover, so it removes easily for access to the torsion bars and dampers.

Then, left and right sections merge the sidepod flanks around the gearbox, leaving the drive shafts to exit through an aerofoil shaped opening. Within this fairing McLaren have a new development of the carbon fibre cased gearbox. Again unconfirmed, the gearbox features a seamless shift mechanism believed to have been raced throughout 2005.

The rear impact structure follows on from the shape of the gearbox fairing. Even though the impact test to the rear of the car has been doubled this year, McLaren have been able to radically reshape the structure. These impact structures are usually a deep rectangular section with perhaps a slight "V" to the base. What McLaren have done is to make the cross section more accurately reflect the airflow in that area.

As the structure passes through the central diffuser tunnel, the majority of the flow actually passes upwards over the spar, hence McLaren have evolved an aerofoil section ending in an almost fin-like tail. This leaves only the accommodating of the light, which itself is tacked on the very rearmost part of the structure in a teardrop shaped pod. I doubt this is a major gain aerodynamically, but the attention to details is impressive.

With that in mind, it is strange to see no strut supporting the rear wing. McLaren have still managed to retain a very shapely lower beam wing, but this shaping must come at the cost of weight to keep the loads of the upper wing passing through the ends of the beam.

Like with some other teams, the rear suspension does not use deep fairings around the drive shafts. Instead, the rear toe links are mounted slightly higher than the drive shaft. While the rear brake ducts follow the 2005 car with a deeply dished format, making them as exposed as the rules will allow.

While the drivers report the chassis as "mega", the engine has been pointed to as the weak point of the package. Mercedes started work on the engine back in October 2004, the resulting FO108S engine was worked on with close co-operation between the German and English ends of the Mercedes-Ilmor operation, as well as input from McLaren on its packaging and installation.

The first engine running in the MP4-21 is already due for a major revamp, bringing more power than it has been reported to lack. At such an early stage, to see their engine programme falling behind the opposition must be a worry for the team, but if the new spec engine is able to match its competitors on both power and reliability, then the impact may not affect the season's outcome.

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- The Autosport.com Team

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