rec.autos.simulators

by **Dave Henri** » Mon, 07 Jan 2002 13:56:06

I've been watching replays of last summers FIA prototype racing on
Speedvision(going out with a bang, DTM, Aussie, and FIA racing) But I have
a question. Some of the cars like the Ferrari 333sp and the Reynard 2kq
have rear wings that are approximentally level with the driver's helmet.
While other cars like the Ascari and Courage & Dome have rear wings that
barely rise above the rear body work. Is there an advantage to having the
rear wing set so low? I'm old school, I guess, the cars like the Riley &
Scott and Ferrari with the higher mounted wing looks 'better' to me. The
flatter cars with wings not sticking up look odd.
But..with the Prototype cars passing Porche 911's, it's amazing how LOW
they are.
dave henrie

by **Haqsa** » Mon, 07 Jan 2002 14:15:52

I'm guessing here, because even though I have done a lot of passenger
car aero I have only a little experience with race cars, and none with
winged cars. A higher wing is going to get cleaner, faster airflow
normally, making it more effective, however also raising the drag. You
also get added drag from the supports. If you could get clean enough
air coming off of the vehicle, and you put the wing back behind the car
so that the low pressure on its underside did not communicate to the
vehicle body (thus cancelling much of its effectiveness), then it could
be nearly as effective, but with less of a drag penalty. The problem
that I would think this would create though is a very high pitch moment,
IOW you would need one hell of a good air dam in the front to balance it
out or you would push very badly at high speeds. Also that kind of
design is risky over tracks where you can get airborne: losing front
downforce without losing rear is the reason heavily ground effected cars
used to flip at Mosport, Lime Rock, etc. Just my thoughts, I'm no
expert. ;o)

by **Haqsa** » Mon, 07 Jan 2002 14:19:20

Almost forgot - this link has some good overhead pictures of LMP's,
showing that low mounted wings are indeed behind the bodywork.

http://www.totalmotorsport.com/Championships/display.asp?ID=253

> I'm guessing here, because even though I have done a lot of passenger
> car aero I have only a little experience with race cars, and none with
> winged cars. A higher wing is going to get cleaner, faster airflow
> normally, making it more effective, however also raising the drag.
You
> also get added drag from the supports. If you could get clean enough
> air coming off of the vehicle, and you put the wing back behind the
car
> so that the low pressure on its underside did not communicate to the
> vehicle body (thus cancelling much of its effectiveness), then it
could
> be nearly as effective, but with less of a drag penalty. The problem
> that I would think this would create though is a very high pitch
moment,
> IOW you would need one hell of a good air dam in the front to balance
it
> out or you would push very badly at high speeds. Also that kind of
> design is risky over tracks where you can get airborne: losing front
> downforce without losing rear is the reason heavily ground effected
cars
> used to flip at Mosport, Lime Rock, etc. Just my thoughts, I'm no
> expert. ;o)

> > I've been watching replays of last summers FIA prototype racing on
> > Speedvision(going out with a bang, DTM, Aussie, and FIA racing) But
I
> have
> > a question. Some of the cars like the Ferrari 333sp and the Reynard
> 2kq
> > have rear wings that are approximentally level with the driver's
> helmet.
> > While other cars like the Ascari and Courage & Dome have rear wings
> that
> > barely rise above the rear body work. Is there an advantage to
having
> the
> > rear wing set so low? I'm old school, I guess, the cars like the
> Riley &
> > Scott and Ferrari with the higher mounted wing looks 'better' to me.
> The
> > flatter cars with wings not sticking up look odd.
> > But..with the Prototype cars passing Porche 911's, it's amazing
how
> LOW
> > they are.
> > dave henrie

by **Jonny Hodgso** » Mon, 07 Jan 2002 22:15:31

> I've been watching replays of last summers FIA prototype racing on
> Speedvision(going out with a bang, DTM, Aussie, and FIA racing) But I have
> a question. Some of the cars like the Ferrari 333sp and the Reynard 2kq
> have rear wings that are approximentally level with the driver's helmet.
> While other cars like the Ascari and Courage & Dome have rear wings that
> barely rise above the rear body work. Is there an advantage to having the
> rear wing set so low? I'm old school, I guess, the cars like the Riley &
> Scott and Ferrari with the higher mounted wing looks 'better' to me. The
> flatter cars with wings not sticking up look odd.

To the best of my knowledge:

The rear wing on an enclosed-wheel racing car produces the
majority of its downforce by encouraging airflow through
the 'underwing', i.e. under the floor of the car.

LMPs, even more than F1s, rely on ground effects (even with
a flat floor) and the lower down you place the rear wing, the
more it acts like an extension of the diffuser. It does create
less downforce in its own right, but the overall effect is to
create more downforce (and closer to the centre of the car).

Following up Haqsau's post, I suspect that it might be the
other way around: you move the wing upwards when you can't
generate enough rear downforce to balance the front. My
understanding is that front downforce is *not* a problem,
especially with mandatory front wheel arch louvres.

Jonny

by **Haqsa** » Tue, 08 Jan 2002 01:54:51

That makes sense, the rear wing and body become in a sense a single
large slotted wing. Additionally, you have more effective planform area
this way.

by **Dave Henri** » Tue, 08 Jan 2002 05:14:26

Still effective or not....I 'LIKE' the looks of a wing that is at least
poking up from the body work. Probably, cuz I still remember the
Chapparalls and McClarens that had those wings several feet above the car,
and...of course the old Daytona & Superbird aerocars from 70's Nascar.
Wings should be seen doncha think?
Next somebody will tell me looks don't matter, only speed does...and they
will be right...but....
dave henrie

> > To the best of my knowledge:

> > The rear wing on an enclosed-wheel racing car produces the
> > majority of its downforce by encouraging airflow through
> > the 'underwing', i.e. under the floor of the car.

> > LMPs, even more than F1s, rely on ground effects (even with
> > a flat floor) and the lower down you place the rear wing, the
> > more it acts like an extension of the diffuser. It does create
> > less downforce in its own right, but the overall effect is to
> > create more downforce (and closer to the centre of the car).

> That makes sense, the rear wing and body become in a sense a single
> large slotted wing. Additionally, you have more effective planform area
> this way.

by **Ed Solhei** » Tue, 08 Jan 2002 14:37:48

I'm not sure the reasons for the "low slung wing" are as important today as
they used to be back in the "good 'ol" Group C. days.. Back then when they
were still running real ground-effects cars with huge venturi-tunnels, the
low mounted wing served numerous proposes..

First of all... a low-mounted will usually create less drag - and higher
top-speeds - than high mounted wings. Whilch is one of the reason so many of
the manufactures that "aim" to bring their car to Le Mans opt. for
low-mounted wings... All the long straights means high top speed is vital
there.

A low-mounted wing will also create more downforce than a high mounted
wing... The closer the wing is relative to the ground the more higher it it
will be able to accellerate the wind running under it [relative to that
running over it] and the more downforce you get.
Which inturn mean that you can run with less angle of attack on the wing -
compared to a high mounted one - and still achive the the same downforce
levels.. This is one of the reasons the F1-teams have been creating some
wicked looking front wings these last few years.... Even though the
regulations say 100mm (?) of clearance they will read - and re-read the
regulations to find loop-holes that allow them to run them closer to the
ground - even if it's just for 50-100 mm. or so...

In the Group C. days though, they had a - possibly - even more important
purpose... The huge tunnels during the ground-effects days meant that the
car would get bags of mor edownforce from the venturi tunnels than they
would be able to get from the wings - so they wing were used to aid the air
out of the tunnels instead... By extracting (i.e accelerating) the air out
of the tunnels, they created a higher air velocity, more downforce and less
drag (by "delaying" the boundary layer separation) - as seen on the glorious
Jaguar XJR-9LM that won the race in 1988

I'm not quite sure the air-extraction factor is *that* imporant today - the
rules calls for flat-bottom cars and thus the venturies have been replaced
by small diffusers..
In the end tho - it's the complete package that matters.... weither you
should run a low or high-mounted wing really depends upon the whole
aerodynamics-package and design of the car - as the wing need free air to
work anyway...

--
ed_

> I've been watching replays of last summers FIA prototype racing on
> Speedvision(going out with a bang, DTM, Aussie, and FIA racing) But I
have
> a question. Some of the cars like the Ferrari 333sp and the Reynard 2kq
> have rear wings that are approximentally level with the driver's helmet.
> While other cars like the Ascari and Courage & Dome have rear wings that
> barely rise above the rear body work. Is there an advantage to having the
> rear wing set so low? I'm old school, I guess, the cars like the Riley &
> Scott and Ferrari with the higher mounted wing looks 'better' to me. The
> flatter cars with wings not sticking up look odd.
> But..with the Prototype cars passing Porche 911's, it's amazing how LOW
> they are.
> dave henrie

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