REFLECTOR: MODIFICATIONS

[Tom Martino]

I don't profess to be a genius, but I do have extensive education in
physics and related sciences ... and what I am reading on this forum
about "Center of Gravity" (CG) and "Center of Mass" (CM) is not
accurate.
 
The following statement is inaccurate:  "When the center of mass gets
too far away from the center of gravity, it makes the object unstable".
 
I think what people mean to say is:  "When the CM gets too far astray
from the CG envelope, the object become unstable".
 
Physics dictates that the CG must be the same as CM when weights and
moments are factored by their distances from a common reference point.
They are one and the same ... also referred to as the "Centroid".
 
A CG Envelope is determined by the Mean Aerodynamic Cord (which is the
average distance from the leading and trailing edge of the air foil).
The middle of this is the center of lift.  
 
If you picture the plane being lifted on a string at its center of lift
... the CG takes on simple meaning.  If forward ... the object will lean
forward, if aft, it will lean aft.
 
Heavy weight on one end or the other has nothing to do with it, so long
as the CG has been calculated properly and falls within the safe
envelope.  That is why it is called "Center of Gravity".
 
Sudden, jerky movements can disrupt the stability but does not make it
inherently unstable.  However, when you are close to the ground, you may
need more time to recover than the ground will allow!
 
In other words ... as you get farther away from the center of the
envelope, the recovery becomes more difficult but it is almost never
dangerous unless close to the ground or "out of balance".
 
As far as ground handling, the center of rotation is the only thing that
matters at lower speeds.  As speed increases you shift over to center of
lift and ascend.  When the CG is aft in the envelope, the transition
could cause a prop strike if not rotated properly.
 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.tvbf.org/mailman/private/reflector/attachments/20050104/2270e87d/attachment.html