Is it the wing test that's at fault?

02/09/2010
FEATURE BY GUEST AUTHORS

The ongoing controversy regarding the Red Bull, and to a lesser extent Ferrari, front wings, caused me to wait with baited breath as to how the teams would cope with the 'beefed up' testing procedures at Spa. I have to say that I believe Christian Horner when he says the wing is identical to that run in Hungary. Red Bull has a wing that passes the FIA test procedure.

So I have two thoughts on the subject the second of which is more important. The first is my hunch, why the wing behaves as it does. The behaviour of materials is loosely encompassed in the world of engineering as the "Mechanics of Materials" which, for undergraduate engineers a foundation course to study how steel and other engineering materials deflect under load. Quite a useful course.

However, there is a caveat right at the beginning of it that says "what you are about to be learn applies to isotropic materials" which in all reality flies under the radar of most students. What it means is that the material exhibits similar properties in all directions e.g. steel. The opposite of isotropic is anisotropic, which means exactly the opposite, i.e. not the same in all directions e.g. wood, because it has a grain, which also happens to make it nature's composite… Formula one cars, constructed of composites - a mixture of carbon/polymer thread and epoxy - are potentially anisotropic structures, in that their behaviour can depend on the direction in which the loads are applied. An example being that wood is very good when loaded along the grain, but relatively fragile when loaded across it.

Why is this important? Well a wing, constructed of a composite, a potentially anisotropic material, could behave differently depending on how it is loaded. The FIA 'replicate' working loads by loading the tip of the wing with a 100 kg mass, and this is a nice and simple test. The trouble is that this is only half the story; Red Bull has designed a front wing to pass this test.

The issue is that a front wing not only produces a lift force, but also a drag force, and this is the force that the FIA test currently does not replicate.

By introducing drag, the direction (and magnitude) of the force applied to the wing changes, and as has been discussed, an anisotropic structure's behaviour can differ significantly as a result. The proof of this hypothesis would appear to be the Darren Heath photographs in Hungary and the onboard footage in Spa.

I am therefore left to wonder if it is the type of test the FIA uses which is the issue, not the size of the mass used in the test.

Oh, and I haven't even mentioned the rotational forces that could be imparted along the wings longitudinal axis via the endplate elements…

James Saunders
PhD Candidate
Clean Energy Research Centre
Dept. Mechanical Engineering
University of British Columbia
Vancouver

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Published: 02/09/2010
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