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Old 10-14-2013, 06:34 PM   #15 (permalink)
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Cd 0.22

Originally Posted by Cd View Post
I was thinking over how that the Mercedes C111 seemed to be the 'perfect' shape aerodynamically, yet the numbers are rather unimpressive when compared to the new Mercedes passenger cars, and even some new cars from Mazda.

Or perhaps, I am looking at it wrong. The Cds on the new cars are so much more impressive when you compare them to this ideal car.

Just look at the car from all angles and it should be perfect aerodynamically.
A low front end sloping upwards to a windshield curved which tapers back in plan form to a tear drop shape. No wipers or external protrusions. A tiny almost nonexistent grille. Full covered wheels - both front and back, and a curve which matches the aero template perfectly.

By looks alone, this car is a streamlined bullet with all of the right aero tricks. Perfect in fact.

Yet we see that the short tailed version of the car has a Cd of .237 .

By comparison, the new Mercedes has a Cd of .22 despite looking dumpy in comparison.

Does this make anyone else feel as though air is so unpredictable as to make modifying our cars nearly fruitless ?

Not that it would stop me all that much, but it is frustrating never the less.

Imagine taking a car and modifying it by lowering it, removing the mirrors, adding front and rear wheel covers, a blocked grille, a curved windshield, a full belly pan, as well as a tapered template matching shape, and all the other aero tricks, only to find out that your car has more drag than a car like the CLA with its gaping grille and side scoops, uncovered wheels and profile that is completely out of line with the template curve.
So the new M-B has caught up to the 1983 Ford 'Sierra' concept car.Or a little better than R.G.S.White's MIRA recipe car of 1968.
The C-111 III was a 'track' car and there were concessions to down-force to protect Hans Liebert and his driver team.
The nose was changed the very next year to the 'flachbau' blunt nose.
Hucho has criticized the C-111 III for its misuse of fineness ratio.
The plan-view reveals a lot about lost potential.
Kamm and Koenig -Fachsenfeld were only able to get Cd 0.21 out of the 'Template' when they ignored edge radii and body side camber integrating into the boat tail 'early' on the body,like the streamline half-bodies have.
When they did all the proper contours they got Cd 0.12 just like Walter Lay in 1933.
The C-111 looks good only in side elevation.It is not a proper 'Kombinationform'.The whole thing is a compromise.I drooled all over the thing in Stuttgart.I love it.But we can do better.Which is born out with the more 'modern' cars.
Blunt the nose,round those edges,narrow the rear axle and pull the body sides in to match the side contour of the greenhouse and you'll have a real 'hotty.'Or cold-rod,if you prefer.
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