IML: Reply

Keith,

Ideal aerodynamic stability in a cross wind occurs when the Center of Pressure (COP) on the side of the car is in line with the Center of Gravity (COG). Adding quarter panel fins would move the COP aft but the amount would not be significant. I base this judgment on the development of the Dodge Charger Daytona. I was Chief Engineer of Dodge in 1968 when we set out to design and build the ultimate aerodynamic NASCAR "stock" car. We had to add very high airplane rudder type tail fins to move the COP aft a significant amount and to offset the Front Overhang (FOH) that we had added to get a lower drag coefficient. The answer I think is that the fins on the Exner designed 1957 - 1961 cars theoretically helped stability in a cross wind - but not much.

If you wanted to pursue this subject further I recommend that you read a Society of Automotive Engineer technical paper #700036, titled "Aerodynamic Development of the Charger Daytona" and written by Bob Marcell and Gary Romberg.

Were we successful? The Dodge Daytona debuted at Talladega on 9/14/69 and qualified on the pole at 199 MPH. Over the next year and a half Chrysler won 45 out of the 59 NASCAR races. In 1971 the Daytona's and Roadrunner's (Plymouth version) were parked because the NASCAR rules were changed to limit these aerodynamic models to a maximum engine displacement of 305 cu. in. With a 28% reduction in engine size they could not be competitive.

Burt Bouwkamp

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Sent: Tuesday, January 15, 2008 1:09 PM

Subject: IML: Virgil Exner Biography

For all of you interested in the "Fin Era" of American car design, I encourage you to read a recently published book VIRGIL EXNER:VISIONEER. This is, I think, the first biography of Virgil Exner and contains many previously unpublished photographs and drawings that are in the collection of Exner's family. The book covers his entire life, but concentrates on his years as the design chief at Chrysler. Exner oversaw the design of all Chrysler products during his years with the company, but according to his son (still living) he was most closely involved with Imperial and "practically lived" in the Imperial design studio when the 57s were being conceived. Also, Exner always maintained the tall fins helped provide stability at high speeds. I'm not sure that has ever been proved though.

Keith, 58 Southampton 4dr

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