*** Posted by Robert ***
Hi,
A great resource for theory on line is the "see how it flies" site, the address I see when viewing it is
www.monmouth.com/~jsd/how/htm/how.html#contents

As I understand it, as cg shifts rearward, the moment of the rudder is reduced, reducing the force available at a given speed. If you want to maintain a specified force provided by the rudder, the airflow past it must increase. For a constant speed, the force will diminish as the cg moves rear, increase as the cg shifts forward.
For an example, consider;
Airflow is the working medium of the rudder, and cg affects the needed rudder power. Aircraft speed will equal available rudder power, higher speed means more rudder power.
Think of trying to lever a boulder out of the garden, with a short stick you need lots of power, and if you have a longer stick, the power needed is reduced. The "moment" of the rudder is the length of the stick, and vmc corresponds to the power. Rear cg equals a short stick, so more power is needed, meaning a higher airspeed.
Probably a poor explaination, but the "see how it flies " site will do much better. Hope this helps.


[I'm curious to know what factors affect Vmc and how they do. I know that C of G affects Vmc but I'm not clear on how. If anyone knows or has a web address where I can get this information please let me know.]