CG Location

[Carl Cisneros]

Folks;

Doing up a Greenaway/ Tom Dixon (CAD by Pat Johnson) Time Machine and on the plans there is no mention of the CG location.

I was thinking around 2 to 21/2" back from the LE at the root.

Any help would be greatful.

thanks in advance.

Carl

[Jim Svitko]

Is the plane in question the 60 size version?  The last example of that plane that I built, and still flying it at times, balances 4 inches aft of the leading edge at the root, which is about an inch aft of the wing high point.  That might seem tail heavy but it is not.  I have no problems with the CG that far back.

I made some changes to the stab/elevator area so maybe this allows me to move the CG that far aft without control issues.

A starting point of 2 to 2.5 is quite safe but might produce sluggish turns.

I have been incorporating a tail weight box in my latest builds.  I needed it only once, but it is a nice feature to have when needed.

[john e. holliday]

From day one reading the publications at the time the CG should be 25% of the average wing chord.  If nose heavy don't worry as you will be able to add weight after the first flight.  Even when I joined a club I was given the same advice.  remember a tail heavy may be a hand full.

[Carl Cisneros]

thanks ever so much guys.

yes, 60 size plane

Carl

[pat king]

I show the C.G. at 20% MAC (Mean Aerodynamic Chord) on my kits. If you start there the airplane will not be aerodynamically unstable. Move the C.G. aft slowly until the response is what you want or the airplane starts to become unstable. An airplane with the C.G. too far aft will be uncontrollable. On some airplanes 25% of MAC is nearing the limit.

Pat