Toro Rosso STR06 – Double Floor

Scuderia Toro Rosso (STR) launched their car on the first day of the Valencia test. It’s significance has been somewhat lost amongst the fanfare of the front running teams cars and the innovation of the midfield runners. However the new STR06 deserves more attention, as it has some unique aerodynamic concepts that are drawing praise from other teams engineers. STR have been able to reduce the cooling and packaging demands placed on the sidepods. Thus with a smaller sidepod envelope, the team have revived an old concept from Ferrari, the double floor. This separates the sidepod from the flat floor of the car to improve airflow towards the rear. Pioneered by the Jean Claude Migeot while at Ferrari, the twin floor concept came about in 1992 for the teams F92A. Although not a success, mainly due to mechanical reasons, the car did exploit clever sidepods to improve flow over the diffuser.

Diffusers are limited in length and exit height, as such there is little that can be done with their internal geometry to create a greater volume for more expansion-ratio and hence more downforce. Teams realise that driving more airflow over the diffuser not only creates higher pressure above, but can also drive airflow within the diffuser with aids such as gurneys on the trailing edge of the diffuser opening. The problem is getting airflow with enough energy to pass over the diffuser. To reach the diffuser, the air has a tortuous journey. Starting with passing over the front wing, under the nose and raised chassis, then over the splitter and around the sidepods, before sweeping in between the rear wheels and through the rear suspension. We’ve seen other solutions aimed at improving this path, such as the extreme raised nose, tight coke bottle shape and recently the undercut sidepod. It is the sidepods that create the biggest obstacle to the airflow, sidepods span some 30-40cm beyond the sides of the chassis and in order to package large enough radiators they tend to need the full width across a significant height, making the sidepods effectively a rectangular block to the airflow. If you could remove some of this blockage, especially low down then the airflow can head unimpeded to the diffuser. This is exactly what Migeot did with the Ferrari F92A and Ascanelli has done with the STR06. The Toro Rosso’s sidepods curl in backwards towards the monocoque along their full length, this space is evidenced by the large area of flat floor beneath the sidepods. Air passes under the sidepods directly to the diffuser with little to sap energy from the airflow.
With any advantage comes compromises, as it is the case with the double floor. These compromises being the space available within the sidepod and centre of gravity height. Space within the sidepod is already taken up by extra wide fuel tanks and various electronic boxes, not to mention in STRs case the rounded sidepod profile which further robs space. STR must have somehow been able to package large enough radiators to meet the Ferrari engine and KERS heat rejection requirements. Indeed at the first test the team soon blocked up the sidepod openings with moulded panels to reduce the inlet size.
Centre of Gravity height is clearly compromised, as the sidepods sit some 10-15cm higher than normal, This weight needs to be offset with ballast placed low down in the car. The increased minimum weight limit this year (640kg) will help, but conversely running KERS will not help in this regard. As with many of this years concepts, the double floor can be copied. As it does not impact on the homologated monocoque, although the teams side impact crash structures may not be optimised for this sidepod shape. Just as with McLarens “L” shape sidepod, any switch to this format would be a major undertaking. Which would also only be possible if the engine can cope with the downsized radiators.

Other details on the STR06 were the ducted exhaust outlets. On the cars initial runs the exhausts exited low and along the floor, contained within box like covers and blowing through long rectangular outlets. In later tests the car was tried with conventional periscope style exhausts, protruding through the upper part of the sidepod exit.

At the rear, the diffuser in interesting, STR have created a slotted gurney flap, air passes under and over the gurney for a greater effect in drawing air from within the sidepod. Perhaps a sign of the more powerful airflow now reaching the top of the diffuser. They have also exploited the middle 15cm behind the diffuser, this area does allow extra channels to be created, so STR have added a simple “U shaped diffuser trailing the main underbody.

20 thoughts on “Toro Rosso STR06 – Double Floor

  1. I’ve been waiting for someone, anyone to pick up on the STR since the “double floor” was mentioned in passing all over the place. As usual, if it’s not on a frontrunning team, the mainstream press seem to ignore it completely. “Double floor” made this sound completely different to what it is, I have to say. As usual, excellent article Craig, thanks.

  2. Pingback: Tweets that mention Toro Rosso STR06 – Double Floor « Scarbsf1's Blog --

  3. I really love reading your articles Craig, your attention to detail is fantastic for someone interested in the technology.
    But on this report there is a mistake, because as far as I’m aware ToroRosso does use KERS (Ferrari/MME) in their STR6.

    • You’re right, I made a mistake, I have edited the article to take the no-KERS references away. I should have been at Ascanellis press conf, but I was busy looking at the Renault exhausts instead!

  4. Nice analysis as always

    The F92A is making a spiritual comeback with the McLaren Moosepods and Toro Rosso’s double floor, although I still think of it more as very heavily undercut sidepods rather than a double floor in that sense

    • No i saw it with my own eyes, it is a double floor. The undercut goes all the way back to the chassis, for the whole of the sidepods length and is well clear of the floor.

  5. Thanks Craig – Pleased to read after all this time that the problem with the 92A was mechanical and not it’s previously unique aero treatment.

    It’s got to be an interesting flow problem to manage high speed airflow through a 10-15 cm gap. It presents similar challenges to designing an engine airbox. A bad harmonic could stall the air, a good one might be worth some tenths.

    A lot to worry about in an F1 car …

  6. Thanks for this and all the other great technical articles, the detailed looks at technical decisions is really eye opening and interesting

  7. Could this have been Newey’s back-up idea? He could’ve shared it with the TR guys to see how it works out for them and to possibly think about adding to the RBR’s for 2012 or a later 2011 update.

  8. Have just recently found your blog, Craig, and it is a fantastic read! I’ve enjoyed this launch season even more than before with all of your in-depth technical coverage (I’m a car nerd, so all of this stuff is 100% up my alley), which I didn’t even think was possible. Even better, this year we’ve got a spiritual successor to the F92A, one of my all-time favorite F1 cars, even though it was pretty awful in its results.

    Anyway, many thanks for all that you’re doing here.

  9. Just one point of clarification: won’t the increased weight limit in 2011 make it easier, not harder, to get ballast down towards the bottom of the car? The KERS weight is carried high up, yes, but the higher the minimum weight limit, the more of the mass of a given car can be concentrated into ballast. Imagine the minimum weight were raised to 700kg: you could immediately put 50kg of ballast wherever you had the structural ability to do so. Imagine the minimum weight were lowered to 600kg: you’d look very carefully at every piece of ballast to see if it gained you more time than just being lighter.

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  11. I was just wondering: maybe this double floor concept from STR is still cleverer, because it

    could exploit some gray area of the rules about bodywork bending.

    Such a flat surface is easy to model with fem (because of flatness and easy-to-model

    constraints to the center of the car), easy to build precisely (no fibre distortion) and lends

    itself to be tailor made to comply with rules and still allow for a certain deflection which

    would help dowforce.

    Waht do you think?

  12. Pingback: F1 Constructor: Scuderia Toro Rosso | Georgegumm's Blog

  13. Pingback: F1 Constructor: Scuderia Toro Rosso | Georgegumm's Blog

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  15. Pingback: Toro Rosso STR6 Launch pictures ( 1st of February) « Indy/F1 Racing

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