China: Ferrari introduce a blown rear wing

In the first practice in China, Ferrari unveiled their new rear wing, which features a blown flap in a similar manner to McLaren.  Mclaren have infamously produced the F-Duct which uses a duct controlled by the driver to alter airflow around the rear wing to stall it at high speed to gain more top speed.  Is this an F-Duct as used by McLaren, may be not.

Unlike the McLaren and Saubers set ups, the Ferrari solution does not appear to have the driver interacting with the duct.  Instead the wing is fed with airflow coming from an inlet high up on the engine cover, well away from the drivers reach.  It is possible that the there is additional ducting inside the car that does allow the driver to control airflow through the duct.  But so far no signs of a driver controlled inlet around the cockpit are evident.  It could be Ferraris set up uses pure aerodynamics to affect the duct, by choking at high speed (safely well above the maximum corner speed). 

Latest: Alonso to Autosport.com  “I had nothing inside the cockpit because the system is not complete. We tested the engine cover to compare it with the standard one. I didn’t notice anything. I guess there will some new numbers from an aero point of view.”

We will update this post as more info emerges over the weekend.

Sauber: F-Duct detail

The duct on the sidepod runs through the slot in the rear wing and possibly the cockpit too

Having declared they had rushed through their own version of the F-duct, we can speculate how it might work.  We know that the McLaren duct is vented into the cockpit around the drivers legs.  Then it is their leg that closes the duct to feed the rear wing.  This alters; the flow through the slot in the rear wing flap, stalling the wing, reducing drag and increasing top speed.

Sauber have already run with a vented rear wing, theirs uses the inlet on the front of the wing, to blow through a slot underneath the wing.  This allows the rear wing to be steeper without stalling, for more downforce.  Their new shark fin bulging with the duct moulded inside it, feeds into this same slot.  they could be aiming to blow even more airflow through the slot or like McLaren alter the flow to stall the wing. 

But the flow through McLarens slot is driver controlled, so Sauber need to find a way to ‘switch’ the flow on and off.  This could be done purely by the airflow being overcome by the drag creating inside the tortuous duct and hence cutting off the flow above a certain airspeed.  Or they have found a way to vent the duct into the cockpit. 

the hollow side impact spar coud lead into the cockpit to allow the vent to closed

In Saubers case the duct does not pass through the footwell of the cockpit as in McLarens case, so how might they enable the driver to seal the duct?  The placement of the duct may be gives us a clue.  It is possible that an opening exists within the side ofthe moncoque.  Sited near both the ducts inlet and running accross the frotn of the sidepod to the side of the tub is the impact spar, this could lead to an opening into the cockpit and allow the drivers elbow to seal the duct and redirect the airflow.  Its not normal for teams to want to create any opening in the side of the chassis to improve stiffness and crash protection.  But it is possible.

Therefore the driver presses his elbow against the opening at high speed to achieve the same stall as McLarens drivers get with their leg.

Sauber to trial an F-Duct

As we can see in these pictures Sauber have indeed prepared an F-Duct for testing in Australia. More details from the team are on Autosport.com (http://bit.ly/cSXnjh ). It seems the team are now more agile once again since they have shed the BMW ownership & management. Perhaps ex-McLaren test driver Pedro De La Rosa brought some ideas to the team

from the limited pcitures we have, we can see that the lefthand sidepod shoulder has an inlet mouded into it. this presumably feeds back through the sidepod and around theairbox to run int the shark fin. The ducting inside the sharkfin is quite evident and ends by connecting to the rear wing. it appears to attach to the mainplane (not the flap as with McLarens set up) somewhere behind the exisitng blown slot inlet.

From what we can see, it cannot becontrolled by the driver, so the duct may not be trying to do the same thing as the McLaren. Either the team rely on a a puely aerodynamic way to control the rear wing stalling, such as the duct choking at high speed and cutting off the flow the slot. Or the duct merely adds mass flow to the exisiting blown slot (raced in Bahrain) to allow the wing to be run even steeper and create yet more downforce. We will need mor eimages to be sure what Sauber are trying here.

McLaren Snorkel: How it works

MP4-25 - The infamous snorkel

http://www.autosport.com/news/report.php/id/82001

It has now emerged from comments by Martin Whitmarsh to Autosport.com that McLaren do indeed have a link between their rear wing and the snorkel on the top of the chassis.  While a link between the two parts emerged during testing as they were both fitted with the same aero testing set up, it is only now that the full picture has emerged.  Using the driver to interact with the snorkel feeding the rear wing and its attendant slot, the wing can ‘stall’ increasing straightline speed when the driver needs it.

How its done…

The snorkel on the top of the chassis feeds a duct passing down inside the footwell, its position is some where around the pedals, most probably it runs down alongside the brake pedal\footrest so as to avoid the mandatory padding inside the cockpit.  This duct has a ‘hole’ in it to ‘cool’ the driver inside the cockpit.  However the duct continues inside the chassis, past the fuel tank and up and over the airbox (probably passing by the hatch fitted high up on the engine cover), then through the shark fin and into the rear wing flap. 

When the driver places his foot\leg over the ‘hole’ the flow is diverted into the rest of the duct and this feeds the slot on the rear wing flap.  There is enough airflow through the convoluted duct to disrupt the airflow under the rear of the wing, effectively breaking up the flow around the wing.  This is what F1 aerodynamicists term a ‘stalled’ condition, although this is different to the term ‘stall’ used in aeronautical aerodynamics.  In this ‘stalled’ state, the strong spiralling flows coming off the wing, that lead to the huge drag penalty a highly loaded F1 wing incurs, break up.  With out these flows and their resulting drag penalty, the car is able to get to a higher top speed, by around 3-4kph.

When the driver is ready to brake for the next corner, he releases foot\leg and the airflow passes back into the cockpit and the rear wing flow reattaches, creating downforce and its attendant drag.  In this format the car can lap normally with its wings delivering maximum downforce.

This set up is legal as the rear wing slot in itself is legal (used by McLaren, BMW Sauber last year).  There is no specific working to prevent wing stalling in the rules.  There are no moving aerodynamic parts, except perhaps for the drivers foot\leg.   It’s a piece of interpretive genius, but perhaps as far removed from the spirit of the rules as you can get. 

What now

Of course now its deemed legal, teams can either formally protest it or adopt it themselves.  Doing the the latter is possible for most teams, as they have apertures in the footwell area to fit a snorkel, while the shark fin and rear wing are easily created.  But, finding a route for the duct out of the tub might prove the headache, as the monocoque may not have any openings sufficiently large enough.  This year the monocoque is also is subject to homologation and hence cannot be altered until the 2011 season.  Of course ‘where there’s a will, there’s a way’, teams will not want to lose a straight line speed advantage.

McLaren: Legality and Bahrain spec

MP4-25 - Rear wing scrutineered and declared

Correction the diffuser has again appeared in its full guise in FP1, we all make mistakes…!

Incidentally McLaren arrived with major revisions around the rear of their car. firstly the diffuser shown in the pitlane for scrutineering was devoid of the upper deck bodywork that extended to the beam wing. this slotted panel effectively stretched the diffuser into a longer and higher device for more dowforce. While the diffuser below this panel is the same version as McLaren ran late in their testing programme. above the diffuser the crash structure and slotted beam wing remain the same, but the added duct to vent the oil cooler has gone.

McLaren Developments: Snorkel rumour

NOTE: Update on McLarens Snorkel\Rear wing here http://wp.me/sNdA9-235 

As McLaren continue to use testing rigs to map their cars aerodynamics, the importance of the snorkel on the top of the chassis is becoming apparent.  On Friday The car lapped with an array of sensors attached to the rear wing.  However, there was an additional sensor mounted inside the snorkel.  Raising the question why would you want to test rear wing and driver cooling simultaneously?

This Snorkel, is an apparently innocuous looking part, which was at first believed to be solely an inlet to cool the cockpit.  Several teams add similar inlets in this area to supplement the inlet in the tip of the nose.  The cockpit houses the power steering rack, hydraulic lines and electronics boxes, so cooling is often required.  However the initially simple inlet has been superceded by at least two more shapely snorkel-like derivatives each with an apparently unnecessarily complex double wall construction creating smooth narrow inlet and a streamlined outer surface.  This snorkel has been present ont he car through out all the cold and wet testing sessions, suggestion its purpose goes beyond a simple primary purpose of cooling.

One rumour around the internet suggests the inlet is linked by a duct to the shark fin\blown rear wing.  At first appearing to be simply a wild rumour, that the snorkel is blocked by the drivers knee to alter the rear wing airflow.  However the presence of the airflow sensor along with the rear wing test rig, suggests there might be a link after all.  The rumours suggest the drivers left  braking leg, which sits unused on long straights could be used to alter the flow from the snorkel to the rear wing duct, where a valve alters flow through the blown slot to stall the rear wing.  This would reduce downforce and also drag, which would allow a higher top speed.  Then the driver moves his leg to start to brake for the next turn the valve switches airflow back to normal, the wings airflow reattaches and provides the downforce needed for the turns.  This sounds both feasible and far-fetched at the same time.

It would be hard to link the rear wing and snorkel with any certainty, but any input from the driver that would alter the cars aerodynamics as the rumours suggest would certainly be an area of greyness in the rules and liable to protest come Bahrain.