5 replies to this topic

[oleksa]

Hello all!
Can anybody tell me about dihedral wings,which were used at racing cars.
Who first used them? What are the fors and againsts of those wings? How do they work?
And maybe some pictures?

[BRIAN GLOVER]

Let me take a poke at that if you don't mind, Oleksa?

A low wing airplane uses 'Di- hedral', and a high wing airplane uses an 'An-Hedral' wing for directional stability.
Lift acts perpendicular to the surface of the wing, so any deviation from horizontal, the vertical component of the lift vector is reduced. The converging or diverging vectors oppose one another on a di/an hedral wing in level flight and keeps the aircraft going straight with a slight loss of lift efficiency. Banking the plane to the di-hedral angle, will cause a further loss of total lift. That is why when you bank an airplane you must deflect the elevator and add thrust to maintain altitude.

In the case of race cars, di-hedral is not there for stability. The centre part of the wing is in ground effects and a gradual angle from that point to the end of the wing reduces frontal area (drag). Without di hedral, youwould need 2 vertical sections on either side of the wing centre wing section that is in GE to support the horizontal part of the wing that is not in GE as seen in some designs.
With di -hedral, the wing may have an extended section of the wing in GE when the car is in a roll. With end plates, the loss of lift efficiency is reduced on the inside section but a huge gain in lift takes place at the part of the wing that is in GE. A wing of uniform cord that is within 10% of it's span above the surface that it is traversing over, gains 35% in lift coefficient, which more than offsets the inside sections loss.
Don't quote me.
I cant say who used them first and I am only guessing as to their proper function.
b.

Originally posted by oleksa
Hello all!
Can anybody tell me about dihedral wings,which were used at racing cars.
Who first used them? What are the fors and againsts of those wings? How do they work?
And maybe some pictures?

[Paolo]

An isolated wing with dihedral or anhedral is always less efficient than a straight wing of the same span.
A nice theory explains this with the interaction of bound vortexes at mid span ; when they meet at an angle, an additional downwash is created and the wing behaves as one of a smaller aspect ratio.
In more plain words, the wing will have more drag for a given downforce.
When the wing is not isolated, other factors come into play.
For example, a F1 wing will have endplates.
Although benefical, end plates develop a boundary layer that causes separation on the outermost part of the wing. Separation is more marked when the angle included between wing and plate is decreased.
A F1 wing with its extremities bent downwards will suffer less separation on the lower side, although having more problems on the upper.
Since the lower side is more critical, being more prone to separation and more important than the upper side in providing downforce, the net balance of angling the tips downwards will probably be positive.

Another reason for giving dihedral or anhedral can be a will to partially deflect air inwards or outwards and have stronger vortexes in certain zones, to play around with the airflow.

[Christiaan]

I am having difficulty understanding the two of you, especally where end plates come into play. I know with planes dihedrals are to counter rolling. the end plates are to reduce the edge effects and eliminate the trailing vortex at the edge of the wing. Without them the downforce at the at the edge is effectively zero, but with them it is significantly increased. If you plot a curve of the of the downforce along the wing it looks like a half ellipsoid. I'm guessing that if you ben the wing the ellipsoid flattens out so you get a more even districution of lift.

[RDV]

...sorry to interrupt , but consider racing car wings not only work (in the case of the front wings) in ground effect , but also that just behind it you have a rotating wheel.. thus most classical wing aerodynamics not applicable... the effect of ft wing endplates has a lot more to do with guiding the wing tip vortex and its interaction with wheel and elements dowstream than classic circulation theory..... and Paolo , check out some CFD representations of ground level flow, you will see that extremely 3 dimensional.......as to original question , probably most extreme case was on the Vels Parnelli Jones indy car...... nice try anyway , even if no cigar...

[Henri Greuter]

The only dihedral wings used on a racing car I can recall right now is during May at Indy '72.

The Vel-Parnellli Jones team used the Parnelli chassic that year and its side pods were a bit like the Brabham BT44's, pyramid sloping down with the bottom part the widest. In practice the cars ran with wings, set under an angle of 90 degrees with these sidepod. Not used in the race however.
Interesting that the car can be mentioned here. because one of the drivers of these cars was Al Unser Sr. And if he had won the race he would have achieved what Castroneves is shooting for this year: a threepeat!.

Sorry, no scanner available but the Carl Hungness 1969-1972 yearbook has some pics of the cars.

Henri Greuter