How the F1 rules changes for 2009 are meant to improve racing (part 3/3)

Posted on | Author John Beamer

Felipe Massa tests the Ferrari F60 at Mugello
Felipe Massa tests the Ferrari F60 at Mugello

F1 Fanatic guest writer John Beamer concludes his review of changes in the 2009 F1 rules designed to allow cars to follow each other more closely and encourage overtaking.

Rear bodywork

Changes: In the 2008 rules there were few limitations on the placement of bodywork between the front and rear wheels. In the last section we discussed the onerous restrictions on the barge board zone. Now we examine what designers have to contend with in the mid-part of the car (between the rear wheels and the front of the sidepods).

The short answer is that for 2009 chimneys, flip-ups and winglets are mostly excluded. As ever the wording is convoluted: it stipulates that any vertical cross section must form one continuous tangent curve on its external surface with a minimum radius of 75mm. In practice any sharp corners (i.e., with radii less than 75mm) are banned, which means an end to the detailed flow conditioners we see in this region today. Apertures are prohibited except to accommodate the suspension and exhausts, which prevent louvers and any opening of the bodywork for cooling.

The continuous tangent curve condition covers bodywork spanning from the rear wheel centre line to a point 450mm forward of the rear edge of the cockpit entry template. Ahead of this point there is some latitude to introduce simple wings and fins provided they are integrated into the sidepod structure (as discussed in the barge board section).

Finally, it?s worth noting that shark fin engine covers are still permitted.

Performance implications: Chimneys, winglets and flip-ups create a huge amount of turbulence so their removal will reduce the car?s wake. Also banning apertures should cut drag and associated turbulence.

Air management in this zone is largely to the benefit of rear downforce. Raising the rear wing by 150mm actually goes some way to negating the need for complex bodywork, although no doubt teams would have appropriately adapted flow conditioners to better interact with the rear wing. A consequence of these changes is that rear downforce falls slightly and centre of pressure shifts forward.

Retaining the shark fin cover probably wasn?t a difficult decision. For a start team bosses like the extra advertising space it yields. In addition it is designed to help redirect air more efficiently over the rear wing and encourage air to stay attached behind the airbox, both of which reduce turbulence.

Marks 9/10: As with the changes to the barge boards, the restrictions on mid-region bodywork support both of the FIA?s objectives by simultaneously reducing the sensitivity of the car and the size of its wake. Armchair aerodynamicists lose out as this region has been a frequent source of innovation and has contributed immensely to our understanding of how to use vortices to create downforce and manage airflow.

Also the banning of apertures in the bodywork could cause teams cooling issues particularly at hot, engine intensive circuits ?ǣ anything that helps lift someone other than Ferrari or McLaren to the top of the podium is welcome.


Interim diffuser on BMW's 2009 F1 prototype (image brightened to enhance detail)
Interim diffuser on BMW's 2009 F1 prototype (image brightened to enhance detail)

Changes: The rules governing the location and geometry of the diffuser for 2009 are, once more, opaque. Compared to the 2008 diffuser, the 2009 diffuser is moved to the rear wheel centre line (from 330m forward of this point) and its outer section is slightly longer and higher ?ǣ allowable height has increased from 125mm to 175mm and can extend 350mm behind the rear axle, an increase of 20mm.

The central section has also changed. Whereas in 2008 it was up to 400mm high, 300mm wide and 830mm long, for 2009 it is shorter and narrower. Length is reduced to 500mm ?ǣ by virtue of the whole diffuser moving back ?ǣ and permissible width has halved to 150mm. Actually rear bodywork can overhang to a point 600mm behind the rear axle and this could be used to extend the central section, but in practice is for the crash structure and brake light, as it was in 2008.

Interestingly during the recent Jerez test, Williams? prototype 2009 diffuser did not have a separate central section ?ǣ it retained the same profile across its width. This may be because the presence of the plank limits the utility of the central section, or that undesirable separation occurs at the point where the central section extends aft of the rest of the diffuser. However, I?d be surprised if teams aren?t deploying some sort of central section when they take the grid for the Australian Grand Prix.

Finally, overall diffuser width is unchanged from 2008. It can extend up to 500mm from the car centre line ?ǣ and while the inner 250mm section is allowed to touch the reference place the outer 250mm must be at least 50mm above the reference plane.

Performance implications: The net volume of the diffuser in 2009 is less than in 2008, with a consequential effect on performance. Although the outer sections are a little more powerful, it is in the central section where performance will dip causing overall power to drop. Some of this loss might be clawed back by virtue of the diffuser being steeper, allowing better pressure recovery. One other possible benefit of running a steeper diffuser is to lift upwash over a trailing car?s rear wing ?ǣ that the rear wing is also raised negates this effect somewhat.

However, moving the device back reduces coupling with the beam wing (and upper elements too) as the wing is above the diffuser rather than behind it. It will also cause balance to shift rearwards. Perhaps the rationale is to counteract the possible downforce loss from the shorter and taller rear wing or the loss of flow conditioners in the mid-region.

Marks 4/10: The change to the diffuser is the most unwelcome part of the 2009 regulations for me. The diffuser and floor generate downforce but create little turbulence. Given that the FIA?s aim is to reduce the size of the wake then a powerful diffuser in conjunction with, say, a less cambered and more shallow rear wing is a must.

Making the diffuser steeper is, I believe, contradictory to the goal of reducing upwash, but perhaps the wind tunnel data tell a different story. The decision to move the diffuser back is also questionable because balance will fluctuate more when the car is in dirty air making it harder to drive. The only silver lining is that the reduction in power should help tidy the wake.

Closing thoughts

The 2009 regulations are a reasonable attempt to address the obvious overtaking issues that plague F1 today. By substituting aerodynamic grip for mechanical grip (largely through the introduction of slick tyres) races should be closer and passing more frequent.

Any revision to the rules draws criticism and these regulations certainly do. Three stand out. First is the huge cost associated with implementing the changes, which is ironic given F1?s cost cutting drive.

Second is the belief that the FIA hasn?t gone far enough in addressing overtaking. These rule changes will help but more radical solutions (for example, a more powerful diffuser with shallower front and rear wings) are needed to bring back the passing fans so crave. Indeed the FIA has already set out proposed changes for 2011 to encourage yet closer racing.

Finally there is the needling thought that by being ever more specific about what is and isn?t permitted F1 is slowly becoming a spec series by stealth. Aero restriction coupled with engine homologation are two major steps in that direction.

Perhaps the one group of people who are worse off are readers of this site. F1 has been the pinnacle of aerodynamic innovation and a source of inspirational ideas for other motor racing categories for many years ?ǣ look at how other categories mimic F1?s design lead. As the 2009 regulations come into force there could be less to talk about!

Although the words feel very restrictive, if there is one lesson from the past 20 years is that you can never keep a good aerodynamicist down. Every time the FIA has challenged teams to cut downforce aerodynamicists have hit back. Barring the imposition of a spec series expect the next 20 years to be no different.

This series continues tomorrow with a look at the rear wing and barge boards. This is a guest article by John Beamer. If you want to write a guest article for F1 Fanatic you can find all the information you need here.

How the F1 rules changes for 2009 are meant to improve racing

More on the 2009 F1 rules

Images copyright: Ferrari spa (1), BMW ag (2)