Re: Kamm tails and drag

["Jim Steck" <4sfed@xxxxxxxxx>]

Contrary to popular belief, the long teardrop tail does not maintain smooth
laminar flow its entire length.  The boundary layer progressively thickens to a
point where it cannot stay attached.  Kamm's (Professor W.I.E. Kamm) method of
reducing drag was to cut the bodywork off sharply at the point where the optimum
flow separated, providing the smallest possible interrupted cross-section for
the wake behind the vehicle while minimizing friction drag.

Regards,
Jim Steck
AutoComponenti

> ----------------------- snip -----------------------------------
> 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.

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