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Old August 20th 07, 01:25 AM posted to rec.aviation.piloting,rec.aviation.homebuilt,rec.aviation.ultralight,rec.aviation.soaring
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Default Electrically Powered Ultralight Aircraft

In rec.aviation.piloting Montblack wrote:
wrote)
The coefficient of drag for motorcycles is usually pretty bad unless they
are faired, and it still ain't great.
The power required to overcome drag is 1/2(p*v^3*A*C)

p is the densitity of the fluid
v is the airspeed
A is the area
C is the coefficient of drag



80-ft length of the semi
(vs.)
8-ft length of the motorcycle


Does this play (much) of a role here?


Is that role expressed (adequately/sufficiently) in the above formula,
through "C" ...drag?


The C is the catchall variable that is determinded by the object's
overall shape and for all but the most simple shapes (i.e. flat plate,
sphere, etc.) determined by measurement.

As to what length does specifically, it depends.

Smooth sides are going to be less "draggy" than lumpy sides.

A flat back end is going to be more "draggy" than a tapered back end.


--
Jim Pennino

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