Re: Aero rule of thumb (was: RE: More three wheeler stuff)

[jerry dycus <jerry5335@yahoo.com>]

   Hi Chris and All,
      The 17deg is to the centerline of the airflow
which is close to the body centerline if the body is
going straight into it.
      The reason I like 15deg is at 17deg the air
breaks off. By using less angle the air stays attached
better when air gusts and cross winds hit it keeping
it in the lower drag region longer. Beware of trying
to get the last 5% of anything. It usually costs as
much as the other 95%.  
              jerry dycus  
--- Chris Tromley <chris_t@microtrac.com> wrote:
> Peter Vanderwal wrote:
> 
> > There was a fellow (can't remember his name) who
> discovered
> > that if your
> > back end is too close to taper all the way to a
> point (at no
> > more than 17
> > degrees), you are better off tapering at 17
> degrees as far as
> > possible and
> > then sharply cutting it off (flat back end).  This
> actually
> > works well for
> > vehicles because it gives you a place to put tail
> lights and
> > license plates,
> > etc.
> 
> The fellow's name was Kamm, I believe.
> 
> I've seen this 17 degree rule of thumb before, and
> I'm curious where it
> comes from.  I'm not challenging it, I'd just be
> more comfortable with a
> source before using it to design a body.  To what
> range of road speeds does
> the rule apply?  And just to clarify, do you mean 17
> degrees included
> (between upper and lower, or right and left sides of
> the body) or 17 degrees
> to the centerline (i.e. between the roof and the
> ground)?
> 
> Chris
> 


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