I joined Peter Windsor on the www.theflyinglap.com, to discuss the upcoming Canadian GP and Red Bulls diffuser developments in Monaco (see also http://scarbsf1.wordpress.com/2011/06/08/red-bull-monaco-floor-analysis/)
Monaco is a unique venue, not just for the layout of the circuit, but also the pit lane facilities provided to the teams. With no space for a conventional paddock and pit building, the teams park their transporters away from the small pit garages. Thus parts have to be ferried in-between the trucks and the pit, as well as parts being stored in the upper floor of the pit facility. Luckily for F1s technical observers, this presents an opportunity to see parts not normally exhibited in front of fans. Just such an opportunity presented itself to Jean Baptiste (@jeanbaptiste76) who saw Mark Webbers floor being lifted up to the mezzanine, through the crowd he was able to a quick photo of the entire assembly. From a single picture we have been to gather a lot of info on the design of Red Bulls floor. We’ve confirmed where the exhaust blows, how the trailing edge forms a flap and exclusively how the starter motor hole is blown by ducts in the upper floor. There also a wealth of detail not normally visible, although not unique to Red bull, seeing this detail is a rare treat.
Firstly we can see that this is a floor that has been run on the car, evident by the burns and dirt generated to what would otherwise be pristine black and silver floor. I suspect this is a floor assembly used for free practice, as the floor ahead of the rear tyres still sports the tyre temperature sensors. These are not typically run from qualifying onwards.
We can also see that the floor is in one complete piece, which is unusual. Normally the front t-tray splitter section is removable. Perhaps with the front splitter being lighter this season, it no longer formed of a large piece of ballast, making having a one piece floor more convenient. Plus the new more stringent splitter deflection tests are probably easier overcome with a single structural assembly, rather than two assemblies bolted to the car. Plus we can see the front bargeboards are a permanent fitment to the floor, whilst the sidepod fins are unbolted from the floor and remain attached to the sidepod fronts.
Exhaust routing
Silver coating (zircotech) and gold film provide heat shielding
We’ve seen many pictures of the Red bull exhaust system, how it curls down to pass the exhaust along the floor towards the outer 5cm of floor aside the rear tyres. Obviously no exhausts are fitted to the floor, but the general heat protection within the engine bay appears a coating applied to the carbon floor (most likely Zircotech). Additional local heat protection is provided with separate heat shields and gold reflective sheet, under the exhaust area. The exhausts then run out of the engine bay and along the floor. Again reflective coating is used on the bare floor beneath.
The exhausts route along the floor and blow beneath the diffuser
We can then see the exhaust exits to the edge of the tyre decks 9the small section of floor between the tyre and diffuser. This area is extensively cut away and the edge of the floor is a metallic part which curls up to encourage the exhaust to pass beneath the floor and into the diffuser. We have seen from pre-season (http://scarbsf1.wordpress.com/2011/02/02/red-bull-rb7-open-fronted-exhaust-blown-diffuser/) that the exhaust curls up into the outer top half of the diffuser, further proven by the additional heat protective coating applied in this area. Recent pictures of the Ferrari being craned away in Spain, show that Ferrari do not shape the floor to encourage as exhaust flow to pass under the floor, McLaren are also more similar to Ferrari than Red bull in this regard. As of Monaco 2011, Red Bull were the only team to passing the exhaust flow under the outer edges of the floor towards the diffuser.
Trailing edge flap
On the diffusers trailing edge a flap aids downforce
Red Bull switched to a revised diffuser at the Chinese GP, this exploited a new treatment to the top trailing edge of the diffuser. Rather than a simple Gurney, the team formed a flap above the trailing edge in-between the rear wing endplates. This was not a new feature in F1, Toro Rosso launched their car with just such a flap and historically many cars have sported the detached gurneys of flaps. The Arrows cars in the 2000s sported just such devices. Completely legal, these simple aerofoil sections of bodywork, sit within the allowable area for bodywork at the rear of the car. Much like the gurney, these devices aim to use the high pressure air moving over the diffuser to create a low pressure region above the diffuser exit, to drive more flow out of the diffuser beneath. Effectively making the diffusers exit area larger than a simple exit.
Blown starter hole
Two inlets lead to ducts (yellow) that feed the Starter Motor Hole with airflow
What’s most interesting from Jean Baptistes picture are the two ducts set into the floor ahead of the diffuser. Looking closer we can see these two inlets, lead to ducts that pass inside the engine bay and either side of the starter motor tube. The starter motor hole in the boat-tail of the diffuser is a wide slot, so I believe these ducts blow the starter motor slot. Until other teams cottoned on to Newey’s exploitation of the outer 5cm of floor, most teams pointed their exhausts towards the Starter Motor Hole (SMH), as a way of using the high velocity exhaust gas, to drive more flow through the diffuser and thus create lower pressure for more downforce. With Newey’s outer blown diffuser he could not exploit the large SMH with his exhausts, so this solution allows him to exhaust-blow the diffuser and passively-blow the SMH. By passive-blowing, I mean the exhaust is not used to blow the SMH, but simply the normal airflow over the car. Of course the effect of this passive blowing is dependant on the airflow approaching the ducts inlets. The RB7 has all enclosing bodywork around the gearbox and floor. So airflow could not directly lead to the SMH. So Newey has had to duct flow to this area. It’s unlikely that the flow arriving at these ducts is that powerful, having had to pass around the sidepods and over the fairings covering the exhausts. This is likely to be a small aero gain, albeit one that other teams with similar gearbox fairings could employ. Should the engine mapping ban make the outer blown diffuser solution too sensitive to throttle position, then this duct could receive the exhaust flow to still provide a degree of blown diffuser.
Other details
The T-Tray is formed with the floor and has an opening normally covering by the plank
Away from the unique Red Bull features, the floor exhibits a lot of standard practice for contemporary F1 floors. In Red Bulls case the floor completely encloses the underneath of the car, only a small open section in the t-tray splitter is open. This opening will be enclosed when the plank is fitted to the car. There’s probably a matching section of ballast attached under the chassis that fits in the hole, allowing the ballast to sit a precious few millimetres closer the ground.
An older Red Bull floor (this floor can be purchased via F1-247.com)
With other teams more sections of the floor above the plank are open, and in some cases the base of the monocoque also forms the floor, so the removable floor section has even larger openings.
Enclosed Lower Leading: note the ECU inside the hollow section
The area forming the front lower leading edge of the floor also has to house the Side Impact Tubes (SITs). Clearly with a one piece floor like this, the floor cannot be removed with the SITs still attached to the monocoque. Many teams have the SITs removed with the floor, by unbolting them at the side of the monocoque. This would appear to be the case the RB7 floor. Although not visible in this photo, presumably the removed SITs remain with the car, so possibly this floor is being changed, rather than stored temporarily for refitting.
Such is the tight packaging of the area within the sidepods; space for electronic boxes is limited. We can see a small black box and loom within the enclosed section of floor. Just to the rear of this there appears to be a blue-grey square set into the floor. This is probably a transparent window for sensors to project through, most likely the ride height sensors. Normally three are fitted, one to the left one the right and another at the front or rear, these three ride heights can be extrapolated to provide the engineer with the cars attitude to the track.
Note the wiring for sensors passing around the floor
There is also a reasonable amount of wiring loomed around different areas of the floor. When wiring was seen dangling from Vettels front wing mounts earlier this year, people were quick to assume, this related to wing flex. But instead a lot of the car is instrumented, both for data acquisition but also troubleshooting during the race. In the case of the floor, two measurements are commonly taken, pressure and temperature. Pressure sensors log the pressure beneath the floor, should a car suffer damage in the race, the team can tell from the telemetry if a change in pressure readings are likely to cause handling problems. Equally teams have been known to fit temperature sensors the titanium fasteners holding the plank to the chassis. If these skid blocks, ground too frequently they will heat up. This delta in temperature will alert the team that the plank might be suffering undue wear and cause legality problems in scrutineering.
More pictures from @Jeanbaptiste76
Teams have been adopting exhaust blown diffusers (EBD) since last year and in 2011 every team has exploited the exhaust to some extent to help drive airflow through the diffuser. As I have explained in previous posts on the subject (http://scarbsf1.wordpress.com/category/exhaust-driven-diffuser/), the problem with EBDs is that they create downforce dependant on throttle position, so as the driver lifts off the throttle pedal going into a turn, the exhaust flow slows down and reduced the downforce effect, just at the point the driver needs it for cornering.
If a team want to really exploit the benefits of an EBD then they need to resolve this off-throttle problem. Last year Red Bull exploited a different mapping of the engine when off throttle (see http://scarbsf1.wordpress.com/2010/07/10/red-bull-map-q-the-secret-to-the-teams-q3-pace/ ). By retarding the ignition when the driver lifts off, the fuel is no longer burnt inside a closed combustion chamber, but instead the fuel and air burn in the exhaust pipe, the expandign gasses blow out of the exhaust exit as though the engine is running . This creates a more constant flow of exhaust gasses between on and off throttle. The problem here is that the mapping uses more fuel and creates excessive heat in the exhaust pipe and at the exhaust valve. Renault reported that both Red Bull and Renault used 10% more fuel in Melbourne compared to last year, most likely due to these off-throttle mappings.
With these off throttle mappings the fuel burns in the exhaust pipe, not the cylinder
As the engine suppliers have become increasingly comfortable with the heating effect of these off throttle mappings, teams have been able to use more of this effect in the race. One of Red Bulls advantages this year according to McLaren is their use of aggressive engine maps for downforce. At the Turkish GP several people pointed out the engine note on the overrun on Alonso’s Ferrari during FP2. Teams have clearly started to drive the engine quite hard when off throttle, to keep the diffuser fed with a constant exhaust flow.
Now the FIA have stepped in to limit this effect. Although initially scheduled to be in effect from this weekends Spanish GP the change will now take effect after Canada. This clarification is based on Charlie Whitings changing opinion of how these mappings are used. At first some mapping was allowed, but these increasingly aggressive and fuel hungry mappings are changing the engines primary purpose. Effectively when off throttle the engine is being used purely to drive the aerodynamics, this contradicts the regulation on movable aerodynamic devices. Although this is a vague interpretation it can be justified.
What is now required is that the engines throttles (at the inlet manifold) must be closed to 10% of their maximum opening when the driver lifts off the throttle pedal. Unlike in most road cars, in an F1 car the engines throttles are not under the direct control of the driver via the pedal. The throttle pedal is instead the drivers method to request powertorque, the cars SECU then controls the level of throttle required to meet the drivers request. So as the driver lifts off the throttle pedal, he is no longer requesting powertorque and therefore the throttles should close. what happens with these EBD mappings is that the throttles remain open, Fuel continues to flow then the delayed spark from the plugs sends the burning charge down the exhaust pipe.
Now with the throttle closed to 10%, the amount of fuel that can be burnt will be limited and thus the blown effect will be reduced. so drivers see will a bigger variation in downforce as they modulate the throttle pedal, making the car less predictable to drive.
Blowing the exhaust under the 5cm of outer floor (yellow) will be most penalised by the ban
All teams will be affected to some extent, however the more aggressive that teams have been with the exhaust position relative to the floor, then the greater they will be affected. From the start of the season Red Bull, Ferrari and McLaren have blown the exhaust at the outer 5cm of diffuser. this area is allowed to to be open and bow the exhaust gas under the diffuser for greater downforce. these designs will be most greatly affected by the clarification. Renaults Front Exit exhaust is also likely to be a victim of the change. Many teams have been developing Red Bull Style outer-5cm EBDs, such as: Williams, Lotus, Virgin, Sauber, While Mercedes are rumoured to be adopting a front exit exhaust. These may to need be shelved after Canada, in order to employ a less aggressive EBD.
Copyright Sutton Images via Formula1.com
Although we almost didn’t believe it when the rumours emerged at the launch of the Renault R31, The car does indeed have exhausts that exit at the front of the sidepods. We (@f1fanatic.co.uk and I) managed to see, understand and get the first pictures of the unique set up (http://scarbsf1.wordpress.com/2011/02/01/renault-r31-front-exit-exhausts-fee-explained/). Now the car can be seen stripped in the pit garage, we can see exactly how the Renault packages the exhaust.
The exhaust system routes the four pipes into a collector which then continues to point forwards and direct the secondary pipe low underneath the radiator to the front of the sidepods. As the exhaust routes gasses at up to 1000-degrees C, it needs insulating to protect the other equipment housed in the sidepods. Renault appear to have fitted an insulated jacket around the main length of pipe in the sidepods. What is clear from the set up is that Renault had to raise the radiators to allow the pipe to ass underneath. The R31 has unusually large sidepod inlets and this might to cope with the ducting of the cooling airflow to the laid down radiator.
Copyright: Andrew Robertson (@JarZ)
From these pictures via Andrew Robertson (@Jarz) we can see the front detail around the sidepods. Although the exhaust outlets are not seen here, the problem of the final routing is apparent. Teams need to fit beams to the side of the monocoque for side impact protection. Known as Side Impact Tubes (SITs) there are two pairs to share the load, with one upper pair and a lower pair. As these SITs are heavy, the majority of the work is down by the lower pair, to keep the weight low in the car. Correspondingly the lower SITs are larger and the exhaust needs to pass over these and down to exit sideways.
Copyright: Andrew Robertson (@JarZ)
Renault has packaged these lower SITs into a narrow front and wider rear Tube. The exhaust will angle down along the front tube to blow still pointing downwards across the lower leading edge of the floor. We can see the metallic heat protection on the SITs.
Copyright: Andrew Robertson (@JarZ)
More info on Front Exit Exhausts and how they work – http://scarbsf1.wordpress.com/2011/03/22/trends-2011-exhausts-and-diffusers/
A ScarbsF1 follower in the Melbourne pit lane sent me these exclusive pics. We can see the McLaren stripped in the garage. There’s a huge amount of detail to take in, The key details are the missing exhaust heat shielding, cooling ducts and suspension detail.
We can see the exhaust system is missing in the picture. However there’s a lot of grey heat shielding around the floor giving us some clue to where the flow is going. Notably at the side of the engine where the main exhausts will sit and beyond exit to the sidepod. I can also see heat shielding above the starter motor hole, which is a rounded profile further suggesting this will be subject to fast exhaust gas flow. There’s a curious bulge in the tail of the coke bottle shape. This would be next to the exhaust collector and unlikely to be a good place for sensors, so it’s a mystery why this shape is there. So we can see potentially an exhaust route blowing out of the back of the sidepods, some of this flow passing under the gearbox to the starter motor hole. This seems innocuous enough, as long as the gas finds its own way to these areas. Continued rumours around the pitlane suggest bodywork is used to duct flow to these areas, which would be a contraversial solution. Only when the car is fully built and scrutineered will we fully know what the solution is.
As already explained in this blog (http://scarbsf1.wordpress.com/2011/02/16/mclaren-roll-hoop-and-cooling-arrangement/) the roll hoop fulfils several function for engine air feed and cooling. We can see the main airbox, beneath it the KERS cooler and its exit duct wrapping around the airbox. At the rear of the airbox is the gearbox oil cooler. The oval exit duct for this cooler isn’t fitted in this picture.
Lastly the pullrod suspension can be seen, the rocker and some of the springdamping set up is down low on the gearbox. A small detail is the shaft and rocker merging vertically from the gearbox, (beneath the silver pipe with blue connector). This might either be the heave damper or inerter, placed higher up for better access, or it might be the pre-load adjuster for the torsion bar (if torsion bars are fitted).
A ScarbsF1 follower in the Melbourne pit lane sent me these exclusive pics. We can see the Ferrari stripped in the garage. There’s a huge amount of detail to take, but the key things are the exhaust routing for the EBD, the rear suspension and Rear Wing mechanism.
The exhaust loops forwards before turning back on itself to route towards the diffuser. This set up is used as it keep the exhaust well forwards within the sidepod, which helps to keep the sidepods tight and slim. We cant see the final section of floor, this might need to be removed in order to take the floor off.
Ferrari retained the pushrod rear suspension set up for the F150. To keep it competitive in aero packaging in comparison to the recently favoured pullrod, they have pushed the entire rocker and damper assembly to the front of the gearbox. In doing so they have placed the rockers nearly flat with their pivots pointing down. This keeps the assembly in the aerodynamic shadow of the engine and airbox, so effectively they don’t add any volume to the rear ends aerodynamics.
Lastly the “Drag Reduction System” mechanism can be seen sticking out of the gearbox. This is a hydraulic system and needs to be powerful in order to move the rear wing flap at quickly at speed. As both the flap will be heavily loaded by airflow and designers want the switch from closed to open to be in a matter of milliseconds.
This year the technical talk has largely been about exhausts. How teams have adapted to the ban on double diffusers and the added restriction on Exhaust blown diffusers. Just to aid understanding going into the new season, I have explained how these solutions work and how they look from beneath.
Double Diffusers
Force India 2010 Double Deck Diffuser (DDD)
Since 2009 the regulations regarding the floor have been interpreted in a literal sense to allow the double deck diffuser (DDD). Indeed the very same rules were exploited to a lesser extent under the previous rules, but this only produced small extra channels in between the outer and middle diffuser tunnels. With the major cut in aerodynamic aids for 2009, several teams sought to find a way to gain more expansion ratio from the smaller diffusers. In essence the loophole exploited the definition of surfaces formed between the step and reference planes. Multiple surfaces allowed fully enclosed holes, which fed the upper diffuser deck that sat above the 175mm lower diffuser. This allowed diffuser to be significantly larger in order to create more downforce. Notably Brawn, Williams and Toyota launched 2009 cars with DDDs. Other teams soon followed suit in 2009 and last year every car exploited the same loophole. Over the winter the FIA acted to close the loophole, by enforcing a single continuous surface across a 90cm span under the floor. In a stroke this banned the double diffuser, there being no scope to create any openings in the floor to feed the upper deck.
Single Diffuser
Double Diffuser
Exhaust Blown Diffusers
Another approach to regain lost downforce was the re-invention in 2010 of the exhaust blown diffuser (EBD). This used high energy exhaust gasses to blow the diffuser, the faster throughput of flow under the floor increased downforce. Two methods of EBDs were used in 2010, one blowing over the diffuser and the second blowing inside the diffuser. This latter solution was more effective at driving flow through the diffuser and created more downforce. However this necessitated a hole made into the diffuser to allow the exhaust gas to enter, I‘ve termed this method an ‘open fronted diffuser‘.
2011: No openings allowed in the yellow 90cm zone, outside certain holes are permitted
A by product of the 2011 rules intended to ban the DDD, also stopped this open fronted diffuser solution. However the rules enforced the continuous surface only across a 90cm width of floor and the diffuser is allowed to be 100cm wide. Thus a 5cm window was allowed each side of the diffuser.
Outer Blown Diffuser – Solution
Red Bull Diffuser: Flow passes under the outer 5cm of floor into the diffuser
Red Bull and Ferrari appear to have found this loophole simultaneously. Recently Sam Michael pointed out this was probably the most efficient way to blow the diffuser under the new rules. As Red Bull appeared with this set up first, its often termed the Red Bull Blown diffuser.
What these teams have done is to open up the floor 5cm either side of the diffuser, then route the exhaust towards this opening. The exhaust gas gets collected by the coved section of floor and this directs the high energy gasses under the diffuser, to recover some of the losses from the more open diffuser allowed last year.
Front Exit Exhaust
Renault Front Exit Exhaust: Flow passes wide around the floor before entering the diffuser
Renault meanwhile turned the problem on its head. As the aim of the EBD is to increase flow under the car, they pointed their exhaust at the front of the floor. I’ve had it confirmed to me by two ex-Renault sources that the exhaust does indeed mainly flow under the floor.
The exhaust pipe outlet sits above the step plane just ahead of the leading edge of the floor. This is not simply blowing out horizontally and across the floor, but is ducted slightly to blow downwards and backwards, this is roughly in line the with the flow trailing off the “V” shape above the splitter. Along with the strong vortices set up by the splitter, vanes and bargeboards, this makes the floor appear wider than it is. The flow will go out beyond the floor and then curl back in and under the floor. Some flow will inevitably pass over the floor, but the most of the energy will be driving more flow under the floor to the diffuser.
McLarens Slit Exhaust
The slit above the floor is visible. Copyright: Liubomir Asenov
No conversation about exhausts this year, would be complete without some speculation about McLaren. Amongst the several exhaust systems run by McLaren over the pre-season tests was a “slit” exhaust. This appeared at the first Barcelona test, but did not seem to appear for the second Cataluña test. The exhaust collector could be seen to duct towards a double thickness section of floor ahead of the rear wheels. This section was also interesting for its longitudinal slot, this slot was not large enough to be the actual exhaust outlet, This might be a cooling slot, or to improve the flow from above to beneath the floor. I beleive the Exhaust is actually below the floor. As when the car ran the same floor with a conventional exhaust outlet, there appeared to be a removable section of floor ahead of the rear wheels. Being just outside of the 90mm opening rule, the floor ‘could’ be opened to allow an exhaust to blow through to underneath. If sculpted correctly, the exhaust could be ducted back inboard and blow towards the diffuser from under the floor. It’s possible that this could be in interpretation of a legal opening, assuming it met the maximum fillet radius rules.
I’d expect the resulting exhaust outlets to be a long wide slot, this wider outlet would be needed to meet the maximum radius rules and also reduce the back pressure from the tight curve of the exhaust outlet. As the exhaust would have a tortuous bend, to curl back under itself to direct the flow inboard, rather than out wide around the rear tyre.
Mac Slit: The exhaust might exit beneath the floor in a long narrow outlet
An F1 car is a complex vehicle, a lot of emphasis is placed on the things we can see, the wings and bodywork. Sometimes we can talk about less visible items such as engine, gearboxes, suspension or even electronics. But perhaps the least visible and detailed part of the car is the underbody. The floor and diffuser, that together create nearly half the cars downforce, for almost no drag. Underbody aerodynamics have been the key to F1 car’s ever faster laptimes. All we ever see of the underbody is the exit of the diffuser and sometimes, if seen from a low angle, the step under the cars floor. To aid explanations in my other articles on underbodies, I have summarised and simplified what the underbody consists of.
Reference plane
Reference plane: Red
This is the datum for the cars dimensions and is effectively the lowest part of the cars floor. When the old flat bottom regulations, dating back to the banning of ground effects in 1983 were revised in the wake of Senna’s 1994 crash, the floor has had to have a step along its length. So we see the stepped shape of the car in frontal profile, with the reference plane sitting lowest in the middle of the car. This step cannot be wider than 50cm or narrower than 30cm, the reference plane must by flat and run continuously from behind the front wheels to the rear axle line. The Reference planes leading portion, also forms the splitter, also known as the T-Tray or Bib.
Step plane
Step Plane: Yellow
Above the reference plane is the step plane, this is effectively the underside of the sidepods. This must sit 5cm above the reference plane. Again the surface must be flat and run from the complex regulated bodywork zone around the front of the sidepods to the rear axle line. A large clearance is mandated around the rear wheel to prevent teams sealing off the floor against the rear tyres.
Step or Transition
Step: Orange
In between the reference plane and step plane, is the step itself or transition. Simplistically there must be a vertical surface in between these two planes. Any intersections of these surfaces are allowed to have a simple radius to be applied, with a 2.5cm radius on the step plane and a 5cm radius on the reference plane.
Plank
Plank: Brown
Not considered part of the floor for measurement purposes, the plank is a strip of wood placed under the car to enforce a minimum ride height. The FIA technical term for this part is the skid block, although this term is rarely applied. Holes in the plank allow the cars reference plane to sit directly on the FIA scrutineering jig, for legality checks over the course of a GP weekend. Titanium skid blocks are allowed to be fitted in certain places in the plank and their wear is measured to ensure a car is not grounding from excessively low ride heights.
The plank can be made in two parts to make removing the floor easier, bit the front section must be at least 1m long. This must be made of a material with a specific density, to prevent excessivley heavy or hard planks producing a performance benefit. Typically the plank is wood based, eiterh jabroc a laminate of beechwood, although more exotic blends of woods and resins not unlike MDF have been used. The plank is 30cm and 5mm thick, any holes made into it must conform to a FIA template.
Diffuser
Diffuser: Yellow
A purely flat floor would probably produce lift rather downforce, so the rules have allowed a diffuser to be fitted to the rear of the underbody since 1983. Before that date there were no rules demanding floor dimensions and diffusers were the full length ground effect tunnels that typified the wing cars of the late seventies and early eighties.
A diffuser creates downforce by creating a pressure differential, with low pressure beneath and higher pressure above. The larger a diffuser is, the more expansion ratio is has, thus more potential to create downforce. Diffusers were limited to a simple 100cm width, 35cm length and 17.5cm height from 2009. Then for this year the height further reduced to just 12.5cm. This massively reduces the potential of the diffuser to create downforce compared to the previous rules. Diffusers are allowed to have fences, but the fences and the diffuser itself must not form undercuts when viewed from below. Which is why we see the simple vertical fences and jelly mould curvature.
Other rules around floors
Overriding all of the above rules are broader regulations covering holes and flexibility. No unsprung part of the car can be visible from below the floor. Typically this means anything, but the suspension and additionally the wing mirrors. This means that no holes can be made into the floor to let flow in or out. The underbodies surfaces are termed bodywork within the rules, there is no term ‘diffuser’ or ‘wing’ mentioned in the rules. Just as with any bodywork in the rules, these parts are not allowed to move or flex. For the floor in comparison the wings, there are few deflection tests commonly carried out, the main one being the splitter deflection test.
Exploitation
Double Diffuser
Over the past two year these rules have been exploited by teams. Firstly the interpretation of holes in the floor and continuous surfaces. This lead to the openings that allowed double diffuser. Effectively the step formed two separate, but individually continuous surfaces, allowing airflow to pass up above the step plane into the upper deck of the diffuser. This rule has been clarified for this year and a single continuous surface must be formed under the floor.
Additionally the flexibility of the splitter has been brought into question, teams were believed to be flexing the splitter upwards, new more stringent tests were introduced in 2010 to stop this.
After a slow start to the 2011 campaign Mercedes GP brought along the long expected changes to the W02 at the last Barcelona test. We have already covered the front wing (http://scarbsf1.wordpress.com/2011/03/11/mercedes-w02-new-front-wing-analysis/). But more crucially was the revised sidepod and exhaust package. Mercedes have gone their own way with the design of the W02, with its short wheelbase set up and the resultingly bulbous mid section. Contrary to my expectations the new sidepodexhaust package was not as unconventional as expected. Which still leaves some questions over some design choices on the car or the permanence of the solution shown in Barcelona.
Firstly the new sidepods are formed of a completely new moulding, common to several other teams the sidepod bodywork is one piece and is not formed by add-on sections to the monocoque. Even though the general shape appears the same as the launch format, the overhead view shows the sidepod inlets are angled inboard slightly. Although the bigger visual change is the exhaust and cooling arrangement. Uniquely the exhausts are sited halfway along the sidepods, exiting where the sidepod is nearly at its widest and starts to taper in to the coke bottle shape. Unlike Red Bull and Ferrari Mercedes have not extended the exhaust towards the diffuser, instead the exhaust blows over a long length of open floor. A small vane redirects the flow inboard of the rear wheels and into a coved section that sends the exhaust flow under the diffuser to be more effective at creating downforce. To keep the bodywork safe from its close proximity the exhaust pipes numerous grilles are moulded into the sidepod. The rearmost of these are outside the exclusion zone for cooling outlets, but the larger removable grille appears to be at odds with the bodywork rules. Perhaps the low exhaust position (below the 100mm above the reference plane) allows the grille to be regarded as the opening for the exhaust. Equally these could have been precautionary fitments for overheating (which blighted the cars earlier tests) and might removed for the Australian race.
Having the exhaust so far forward does not make the exhaust act like Renaults Front-Exit-Exhaust, nor like Red Bulls ducted set up. The exhaust gas will lose energy as its merges with the freestream airflow before it reaches the diffuser. Its exactly this energy that teams want to exploit to drive more flow through the diffuser for more downforce. So why is the set up a less efficient solution? Potentially there are several reasons, last year Mercedes struggled with overheating bodywork, unable to get enough supply of the permitted Glass Ceramic Composite (GCC) material used to protect the phenolic composite of the cars floor and bodywork. When they ran their blown floor, the heat, simply melted and warped the bodywork. Its unlikely supply of the material is still an issue, but keeping the bodywork cool and the nature of the exhausts might be the problem.
All three Mercedes teams (McLaren, Mercedes GP and Force India) all had issues with sensitivity of the car when run with EBDs in 2010. McLaren found the cars balance changed significantly on and off throttle, while Mercedes found that the exhaust plume would touch differing parts of the bodywork in different sessions and even differed between cars. This suggests that the exhaust plume was less than predictable. Where-as CFD and wind tunnel tests use a simulation of the exhaust blowing, perhaps the knowledge of what the exhaust flow is actually like is missing. Strangely this seems to be a very Mercedes engine specific problem. Being too aggressive with the exhaust blowing and too specific with the heat shielding makes the car throttle-sensitive and prone to overheating bodywork. McLaren have more problems with their EBDs in pre-season testing and Force India have yet to truly shine, with an otherwise good looking design. If this is the case, then the teams either have to lose potential downforce by having to use a less aggressive EBD solution or suffer the sensitivity problem. Its hard to be clear how easy an unpredictable exhaust plume might be to solve, its not likely to be a solution teams and engine suppliers have had to look at before.
Elsewhere on the sidepods the cars pod vanes have been enlarged from the truncated versions seen in the cars early tests. Why the team would be run stunted versions of long standing designs is again part of the confusion around the W02 debut. The pod vane features an unusual outwards bulged lower section. This mimics the shape of the short launch spec vane. I presume this is mated to the sidepods undercut to feed more flow around the sidepod and over the diffuser. Along with the new undercut the car sports new serrated bargeboards and the complex shaped under nose vanes from late last year have been revised with the more common nose cone mounted vanes.
One last unsolved conundrum is the side impact protection on the sidepods. Normally teams pass the side impact tests with two pairs of crash beams, one upper pair above the sidepod inlet and a lower pair in line with the floor. Each of these pairs are formed of one larger carbon beam and a smaller one to spread the load over a wider area of the chassis. Rules demand these parts are not exposed to the exterior airflow and must be covered by bodywork. These structures are quite heavy and unavoidably raise the cars Centre of Gravity (CofG). This years car sports something appearing very much like a side impact structure passing horizontally across the middle of the sidepod inlet. This would be beneficial as the weight is that much lower down and better for a low CofG, a high CofG was a problem that afflicted the 2010 W02. Meanwhile at floor level the structure is unusually slim, which is better for aerodynamics.
But this mid placed structure appears to be in contravention of the rules as its exposed to the airflow. The FIA have started to be stricter with teams interpretation of these structures, so its hard to understand why this set up has been accepted. Possibly the structure is covered by vestigial bodywork to bypass the rules, but this detail did again promote some of my ideas that the sidepods were to be more unconventional. If allowed this year, we can expect the FIA to stamp out this set up for future years. Of course teams cannot copy this, as crash structures are homologated for the year, and cannot be changed.
For the final test at Barcelona, Ferrari brought the long awaited revisions to the F150 (although the cars name has frequently changed, I’ll continue to use this title). This consisted of a revised wings, new sidepods and new exhausts. It was Ferraris assertion at its launch that the car would have evolved aero and specifically different exhausts before the first race. So despite some people suggesting the changes are copying their rivals, it’s more likely that different teams have converged on the same ideas.
The front wing pylons have been lengthened to form turning vanes
At the front the main changes are to the front wing and its supporting pylons. These pylons have been extended in a similar manner to Renaults ideas from 2009-2010. Since 2009 the rules on vanes and bargeboards around the front of the car have been severely restricted. The rules mandate a limit on the cross sectional area for the front wing mounts, Ferrari have therefore extended their wing mounts, but also narrowed them. Thus meeting the rules and still providing the car with some aero advantage.
3.7.2 Any horizontal section taken through bodywork located forward of a point lying 450mm forward of the front wheel centre line, less than 250mm from the car centre line, and between 125mm and 200mm above the reference plane, may only contain two closed symmetrical sections with a maximum total area of 5000mm2. The thickness of each section may not exceed 25mm when measured perpendicular to the car centre line.
A shapelier endplate has been added to the cascade
Details of the front wing have also changed, in particular the endplates, these now feature a more sculpted vane on the footplate. As well as the endplate fro the main front wing, the inner endplate for the small cascade mounted to it is also now shapelier. The small endplate now having a distinctly flared shape, aimed at redirecting flow inside the front wing.
New sidepod inlets and a blown diffuser are the main changes to the F150
Along the middle section of car, Ferrari have produced a new sidepod, initially similar to the launch specification. But the main radiator inlet is now reshaped, being much more of a “U” shape and smaller with it. The sidepod inlet retains the distinctive protruding upper lip. I was told by Nick Tombasis that this was an aero feature and not a structural one (i.e. side impact crash protection). Curiously this lip features a removable panel to allow for cooling. Being so far forward of the radiators its hard to understand how heated radiator flow could be ducted into the small exit, or perhaps some electronics of KERS components are sited within this hollow section.
Further back along the sidepods, the new exhaust system is routed along the floor and into an open section of floor in the outboard 5cm section of diffuser. This is the same solution as Red Bull has come up with, as already explained this was an obvious area in the 2011 rules for exploitation, as I even proposed this location in my pre-season trends and solutions article. Ferrari route the flattened exhaust inside heat shielding along the floor. The blowing effect of the exhaust passes under the floor for a more effective method of blowing the diffuser. Ferrari wanted to produce the exhaust in glass ceramic composite (such as Pyrosic), but this request was denied by Charlie whiting who clarified the exhaust must be made of materials on the permitted materials list. Such composites, while allowed to be used in some exceptions, are not allowed to be the actual material of the exhaust pipe.
Also the middle of the car gained revised wing mirror pods. these appear to be split into upper and lower mouldings. Presumably to allow sensors or electronics to be fitted inside the pods during testing or free practice.
Lastly the rear wing has also been modified with a smaller flap. Several teams have switched their rear wing to smaller flaps, at first this is counter intuitive to the exploitation of the Drag reduction system (DRS) also termed the adjustable rear wing. As one would initially deduce that adjusting a larger flap would reduce drag by a greater amount. However, shallower flaps effectively flatten out when the leading edge is moved 50mm from the trailing edge of the main plane (50mm is the maximum slot gap allowed for the DRS). Thus they produce very little load and therefore little drag.
