Kamm tails and drag

[C M Smith <cmsmith@xxxxxxxxxxxxxxx>]

I thought the Kamm tail effect resulted from the fact that the Kamm tail 
caused the tail to drag a blob of turbulent air behind the tail that 
approximated the airflow of the long tailed tear drop shape previously 
thought to be ideal, which reduced skin drag due to air to air friction 
being lower than air to bodywork friction. The increase in efficiency is 
due to the reduction in skin drag resulting from the chopped tail and the 
fact that air to air friction is lower than air to bodywork friction of the 
long tail version. Certainly Porsche experimented successfully with the 
long tail Le Mans design that also had a Kamm tail but further back along 
the ideal teardrop shape. I do not think that turbulence associated with 
tear drop shape could be a factor since the tear drop has very little 
turbulence associated with it. Skin drag is a huge factor at high speeds. 
Turbulence drag is a problem at low speeds also, hence the amount of money 
devoted to reducing turbulence drag from door mirrors and rain gutters to 
cite two mundane examples.

cheers etc
Michael Smith
White 1991 164L
Original owner
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