How to Determine the Tail Volume Coefficient
09-15-2002, 05:19 PM
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How to Determine the Tail Volume Coefficient
I read with interest the discussion on "Tail Volume Coefficient" as a means of determining the CG. I have a problem when it comes to determining the tail moment arm length since the tail plane on my aircraft is a triangle not a standard trapazoid. I am building a model of the Antionette and am trying to determine where the CG should be. If I use the 25% of MAC then the CG ends up on the spar and I have to add a lot of nose weight. If I can move the CG back then I can reduce the amount of additional weight. 
Anybody have any ideas?
Anybody have any ideas?
09-15-2002, 06:43 PM
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How to Determine the Tail Volume Coefficient
The tail moment arm is from 25% of the MAC of the wing to 25%of the MAC of the tail. You can use the same method to find the MAC of the tail as the method you use for the wing. Just plug in tail numbers instead oe wing numbers. BTW the tip chord of a triangular plan form is zero.
Start out with the nose weight to give a conservative CG at 25% of the MAC of the wing. Then, between test flights, remove a little weight at a time until you have the handling characteristics you are looking for. Start out with plenty of control throw and gradually reduce it as needed. There is no such thing as a "correct" CG. The desired CG varies with the purpose of the model, the flying style and skill of the pilot. There is a range of CG locations for a particular model that starts at a conservative forward location with excess stability and ends with neutral stability on the aft end where the controls are sensitive, the plane goes where it is pointed with no tendency to return to normal level flight. Then if the CG is moved much aft of neutral stability the plane becomes uncontrollable.
Start out with the nose weight to give a conservative CG at 25% of the MAC of the wing. Then, between test flights, remove a little weight at a time until you have the handling characteristics you are looking for. Start out with plenty of control throw and gradually reduce it as needed. There is no such thing as a "correct" CG. The desired CG varies with the purpose of the model, the flying style and skill of the pilot. There is a range of CG locations for a particular model that starts at a conservative forward location with excess stability and ends with neutral stability on the aft end where the controls are sensitive, the plane goes where it is pointed with no tendency to return to normal level flight. Then if the CG is moved much aft of neutral stability the plane becomes uncontrollable.
