Re: Kamm tails and drag

[George Graves <gmgraves@xxxxxxxxxxx>]

 Mea Culpa. I used the word turbulence, but it is obviously NOT the 
word I wanted. Perhaps "skin drag" is the proper term.

George Graves
'86 GTV-6 3.0S




On Sunday, April 13, 2003, at 06:45 AM, alfa-digest wrote:


> Date: Sat, 12 Apr 2003 20:56:04 -0600
> From: C M Smith <cmsmith@domain.elided>
> Subject: Kamm tails and drag
>
> 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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