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C of G problem
Galaxy Mustang
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              Hi folks.   Has anyone built a galaxy large mustang and flown it!   please,  please could you tell me where the C of G is , as galaxy have told me 3  different positions.   HELP!

                                                     Dave Gombar.

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I don't know this particular model, but a good starting point is at one third of the AVERAGE chord, or where the spars are, as that is usually the thickest point of the wing. Forward of that is ok, but you might find that you lack elevators at low speed. Behind that, and you will need bicycle clips!
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David - where have they told you? Have you flown the model successfully?
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            Hi folks.

                             No i still havent flown the model yet, The guy at Galaxy told me to forget the 6.5" on the plan ,and put a straight edge on the leading edge and make a mark where that line meets the centre of the wing. do the same on the other leading edge and do the same. Measure to the trailing edge, and divide that measurement  x 4 and that will give you the forward c.o.g  Divide the same measurement by 3 and that will give you the rear c.o.g.     Is it right or wrong !.  who knows.

                                                                    Dave.

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Best go on their advice David, you'd expect them to know at the end of the day....

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Centre of gravity should be near centre of lift.

Centre of lift as I have it is: 1/3 span (from centre-line) and 1/3 chord (from front)

So, your COG should be near there, but as others have said, please, please, from bitter experience, head for COG 1/4 chord rather than 1/3 chord as a nose-heavy plane is user-friendly whereas a tail-heavy plane is a "nightmare on steroids". It just keeps "rolling off the top" - like a plane flying too slowly - it just can't keep stable.

Regards, Rob

Edited: 16/10/08 00:07
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The balance point on any conventional model is always in the same place, around 25 to 30% MAC. For your Mustang with its simple tapered wing the simplest method is to measure half way out along the wing from the fuselage side to the tip, then dividing the chord at this point into four. At the 1/4 point on this line from the leading edge, project this point to the fuselage side. This will be, as near as dammit, 25% MAC, and a safe place to start. Flight testing determine you preferred positon after that.

Evan.

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If you can find it, or if Timbo can patch a link in, there is a discussion on this, possibly in 'All Things', complete with a drawing of how to find the approximate c/g on an unknown design.

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