[DeTomaso] Jr. Wilson Pantera wing

[Paul A Rimov]

And that's why a Countash is slower with a wing. 

Sent from my iPhone

On Aug 11, 2015, at 12:47 PM, Daniel C Jones <daniel.c.jones2 at gmail.com> wrote:

>> How well versed are the those who opine in aero?A
>   I was awarded "Outstanding Aerospace Engineeer" in 1986 at the
>   University of Cincinnati.A  I still remember some of it.A  Does that
>   count? :-)
>> A properly shaped wing will generate downforce with the top side of
>   the wing parallel to the ground.A
>> The cord angle will still be angled down giving you the downforce
>   desired.
>   I think you mean the airfoil camber line, not the wing chord (wing
>   chord is just the imaginary straight line joining the airfoil leading
>   and trailing edges).A  Camber can provide lift (or downforce) at zero
>   angle-of-attack.A
>> While tipping the nose of the wing down will increase downforce, it
>   increases drag as well limiting top speed.
>   Lift generated by either camber or angle-of-attack comes at the expense
>   of induced drag.
>   Dan Jones
>   P.S. Here's a segment of an earlier post I made on automobile
>   aerodynamics that covers camber:
>   Also, the path the air actually travels may be quite different from the
>   contour of the vehicle.A  For instance, a flat shape with equal
>   distances over
>   and under can produce a lot of lift.A  If you don't believe me, try
>   this
>   experiment at home (just don't sue me if you do).A  Step into the bed
>   of a
>   pick-up truck and lift a 4'x8' sheet of plywood over your head.A  Be
>   careful
>   to hold the sheet of plywood parallel to the ground, while the driver
>   slowly
>   accelerates to 60 mph or so.A  Now comes the fun part.A  Grip tightly
>   to the
>   sides of the plywood and quickly tilt the leading edge upward.A  What
>   happens?
>   Instant lift (and an impressive, if short lived, Peter Pan imitation).
>   What you've just experienced is the influence angle-of-attack has on
>   lift.
>   Take a symmetric (top-to-bottom) airfoil shape that does not produce
>   lift
>   when it is aligned parallel to the air flow (i.e. is at zero angle of
>   attack)
>   and point it up.A  It produces lift.A  Point it down and it produces
>   downforce.
>   While the physical distance over the top and bottom of the plywood are
>   the
>   same, the distance the airflow travels is not.A  Likewise, you don't
>   need
>   angle of attack or even thickness to produce lift/downforce.A  A thin
>   curved
>   shape like a Venetian blind slat will also produce lift.A  This is an
>   extreme
>   example of wing camber.
>   A little wing theory and several definitions are in order here.A  This
>   would
>   be easier to explain with illustrations, but I'll give it a shot with
>   words.
>   An airfoil is the 2-dimensional cross-sectional shape obtained by the
>   intersection of a wing and a perpendicular plane.A  The mean camber
>   line of an
>   airfoil is the locus of points halfway between the upper and lower
>   surfaces
>   (measured perpendicular to the mean camber line itself).A  The chord of
>   an
>   airfoil is the straight line connecting its leading edge to its
>   trailing
>   edge.A  Camber is the maximum distance between the mean camber line and
>   the
>   chord line, measured perpendicular to the chord line.
>   An airfoil's angle of attack is the angle between the relative wind
>   (the
>   local airflow direction) and the airfoil's chord line.A  Drag is the
>   component
>   of aerodynamic force parallel to the relative wind and lift is the
>   perpendicular component.
>   If an airfoil is symmetric (top-to-bottom), it has no camber.A  A sheet
>   of
>   plywood has no camber.A  A Venetian blind slat is a shape that has
>   camber but
>   (practically) no thickness.A  The camber, the shape of the mean camber
>   line,
>   and the thickness distribution of an airfoil determine its lift and
>   moment
>   characteristics.A  Surface roughness also plays a roll but is usually
>   treated
>   as a separate design issue.
>   Because of camber, wings can have lift at zero degrees angle of attack
>   and
>   because of angle of attack, wings (and sheets of plywood) with no
>   camber can
>   still produce lift.A  To separate these effects, aerodynamicists break
>   an
>   airfoil's lift into two components:
>   A A A  Cl = Clo + (Cla * alpha)
>   A  where:
>   A A A  Cl = coefficient of lift
>   A A A  Clo = coefficient of lift at zero angle of attack
>   A A A  Cla = lift curve slope (the slope of Cl versus alpha)
>   A A A  alpha = angle of attack
>   On low speed circuits where downforce is very important, Formula 1 race
>   cars
>   will have multiple, highly cambered, wings, oriented at a relatively
>   large
>   negative angle of attack.A  All of this is done in an attempt to
>   generate
>   downforce.A  Since this approach is a relatively high drag method of
>   generating lift, you won't see similar set-ups on aircraft (they are
>   not
>   limited by wing size rules).
>   Wings are not drag reducing devices, they are lift (negative lift or
>   downforce, in the case of automobiles) producing devices and will
>   generate
>   substantial drag if they are effective.A  Wings produce drag as a
>   direct
>   consequence of generating lift/downforce.A  This drag is in addition to
>   the
>   wing's basic profile drag (the drag at zero lift) and is termed induced
>   drag.A  Induced drag is proportional to the square of the
>   lift/downforce
>   produced:
>   A A  Cdi = Cl**2/(pi*e*AR)
>   A where:
>   A A  Cdi = induced drag coefficient
>   A A  ClA  = coefficient of lift
>   A A  ARA  = the aspect ratio (wing span squared/wing area) of the wing
>   A A  piA  = mathematical constant (approximately 3.14159)
>   A A  eA A  = wing efficiency factor (1 for an elliptical wing planform
>   like
>   A A A A A A A A  that used on the WWII Spitfire fighter planes, less
>   than 1 for
>   A A A A A A A A  other planforms)
>   When they are not strictly cosmetic, wings are added to cars for
>   stability
>   and downforce reasons.A  The wings on a Formula 1 race car generate
>   incredible amounts of drag because they generate equally incredible
>   amounts
>   of downforce (4 to 5 times the weight of the vehicle - the primary
>   reason
>   these cars are able to pull 4 to 5 lateral g's on high speed corners).
>   Obviously, F1 cars are willing to trade a lot of top speed for
>   increased
>   corner speeds.
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