the mean time we've sent a back and forth via email to Delta
Motorsport's Nick Carpenter. Delta had been tasked by the ACO/FIA with
coming up with a solution to further reduce sudden high-speed yaw
induced blow overs. The result was the rather large vertical
centerline fin that the cars will have to have starting from 2011.|
Mulsanne's Corner: We're
curious about the origins of the vertical fin concept. We also undertand that
Porsche approached the FIA with this solution about 18 months ago?
Is this correct? Could you lay out a time line of Delta
Nick Carpenter, Delta Motorsport: Timing
broadly as follows:
First meeting of the Sportscar Technical Working Group to discuss the
high-yaw issue. At this meeting it was decided that the constructors
should (a) consider possible solutions, and (b) get together to see
if they could agree on a common approach to analysing the problem,
and also that we would put in a proposal to the FIA for an
Second meeting of the TWG. The constructors had begun to investigate
the problem (and it may even have been this early that Porsche first
proposed the fin, but I don’t think it was till a bit later), but
it became clear that they weren’t going to share enough (VERY
sensitive) data between them to allow comparisons of the various
different cars and particularly to compare their different
methodologies (from CFD to full-scale testing in a tunnel with a
in October: we
were asked by the FIA to carry out a CFD and multi-body analysis of
the characteristics of the cars while spinning at high speed, and we
delivered this in early January. Epsilon and KWMotorsport very kindly
shared their CAD data with us (or specifically with Totalsim) to
allow a full aero map of the two cars (one open, one closed) at a
wide range of roll, yaw and pitch angles, and these results were fed
into the multi-body sim to ensure that the numerical model behaved in
the same way as the real cars, which it seemed to do.
Further TWG group meeting to discuss the results of the study and to
see whether there were any ideas that could be implemented in time
for the start of the 2009 season. The curved plank was discussed as a
comparatively minor change that might help at low risk of making the
problem work (the law of unintended consequences was always in our
minds but as a group, everyone felt we should try to implement
something if at all possible). We fed the results back to the FIA at
the start of February and it was decided that the plank change was
“doable” in time for the Sebring race.
then embarked on a program of analysis of a wide range of devices
(including the fin) in May ’09 after further discussions
about which devices tested by the constructors showed promise (and we
came up with a few of our own too!). As usual, some of the devices
worked on the open car and some on the closed car but the consistency
of their effect was unpredictable. We shared these initial results
with the group and iterated the various shapes, then carrying out
the to-ing and fro-ing to constructors, as well as giving the
constructors time to test alternatives and validate our results, we
submitted our final proposals in mid-September (2009).
then attended an ACO meeting in Paris at the start of October to
allow discussion of the results that had been circulated in our
report. The constructors gradually fed back their thoughts, concerns,
comments etc between this meeting and the end of 2009, and we held
another TWG meeting towards the end of January this year, at which it
was decided that the fin should be put before the next FIA World
the program we were all very aware of the need to do something as
fast as possible, but this was always tempered by the knowledge that
we shouldn’t rush into anything with a device that might make the
problem worse or introduce a different one.
Mulsanne's Corner: What
were the parameters the FIA/ACO set in place for the solution?
Presumably they outlined parameters and said, "how ever you get
Nick Carpenter, Delta Motorsport: The
parameters were pretty broad really. Having made the mods to the
underfloor shape in 2002/3, we were left with working on the upper
body (because a wholesale re-think of what a Sportscar should be was
deemed unfeasible). The constructors came up with ideas (including
the fin from Porsche), we came up with some, and we tested – and
iterated – them all until we found a device that made a significant
reduction to the problem.
Mulsanne's Corner: What
you can tell us about the methodology Delta Motorsport used to come
to the conclusion that vertical fins will eliminate the possibility
of LMPs taking off in sudden high speed yaw situations? Were
any other solutions considered?
Nick Carpenter, Delta Motorsport: There
are two main areas of concern. Lift (a vertical force that physically
lifts the whole car up) and overturning moment (“OM”). OM is a
moment that will tend to roll a car backwards, against the direction
of travel, and is made up of contributions from lift and drag, both
resolved around the rearmost contact patch (the leeward wheels when
sliding sideways). The early simulations (as well as videos of the
accidents in 2008) showed that OM was the main culprit.
looked at many devices such as louvres, cut-outs in the inner when
arches, longitudinal strakes, changes to sidepod geometry, RWEP
geometry changes and many different sizes and shapes of fin. Quite a
few showed promising results on one car but not the other, and we
were obviously looking for something that could be applied to both
open and closed cars in a consistent and fair fashion.
don’t think anyone would assert that we’ve “eliminated the
possibility of LMPs taking off” – there are just too many
variables to give that unequivocal an answer. As you no doubt saw
from Mark Webber’s recent accident, motorsport is a dangerous
pastime, but what we’ve tried to do with the fin is (a) minimise
the chances of getting into a potentially dangerous attitude, and (b)
reduce the risk of take off if a driver does find himself there.
Mulsanne's Corner: How
does the fin effect airflow to the rear wing in normal yaw
(cornering) situations? We understand the fin generates an
overturning moment of its own though presumably its ability to
eliminate the lift generated by the leading side rear fender makes
this easily overlooked? Is there any situation where the fin's
overturning moment would be cause for concern?
Nick Carpenter, Delta Motorsport: One
of the constructors shared the results of their low-yaw work with the
Technical Working Group (in broad terms at least), and this showed no adverse effects.
All the fins tested showed some degree of improvement, with the
bigger fins producing the largest benefit. The tests we ran didn’t
show any vehicle attitudes where the fin had an adverse effect.
Mulsanne's Corner: What
was Delta's role with Totalsim and Intec Dynamics handling the CFD
Nick Carpenter, Delta Motorsport: Delta
ran the program, sub-contracting the CFD and multi-body elements of
the work. The FIA needed a “one stop shop” for the whole program,
which is what we offered. We defined the programs of work, carried
out the CAD design work, coordinated all the CFD and multi-body work,
interpreted the results and wrote/presented the reports.