Quote:
Originally Posted by SuperTrooper
How do you know for sure it doesn't generate any lift? The profile resembles a wing shape to me. Anyway, the problem here is the perspective of the photo. It's shot from ground level giving the appearance that the spoiler tilts up. The rear edge actually winds up horizontal, or parallel to the road surface; which is what you want when breaking airflow away from the body to reduce drag.
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I'm given to understand that van and wagon style bodies do not generate the kind of lift that would be found in a fastback or notchback body style.The explanation given, is that the way the air mass is distributed for vans and wagons,yields essentially the same air velocity above the body,as it is alongside.Without the velocity differential,there cannot exist a pressure differential which would induce the lift.Sure,the matrix does have some roof camber,and it occurs directly over the driver's head,and there is some lift associated with deformation of the streamlines,but at normal highway speeds,this would present no challenge to stability,especially something which could be cured by something at the far end of the roof.And actually,if the air could continue rearward,at its defined slope,it would achieve atmospheric pressure at a distance,1.78 times the body height,behind the point of maximum camber.If the hatch wing tilts up,it blasts the airstream into turbulence which cannot recover it's kinetic energy into static pressure,and you're left with higher drag.Air needs about 3.5 more time to decelelerate without separation,than the time it can withstand during acceleration from rest.The long progressively increasing curvature roofline,with no interruptions,provides that gentle deceleration ramp the air needs to reach equilibrium pressure.