3D CG Balancing

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3D CG Balancing

Postby DonEmmel » Mon Feb 06, 2012 1:51 pm

I bought the 48" MXS-EXP from Extreme Flight RC near the end of last season. This plane is designed for crazy 3D but it also supposed to perform well doing pattern flying. The recommended CG was between 3.5" to 4.0". I set my CG to 3.75" figuring somewhere in the middle would give me a balanced feel to the plane. The maiden flight was a near disaster. Even though I was in the mid-range of the recommended CG the plane felt extremely tail heavy. I feel pretty lucky that I was able to land it w/o crashing. After numerous flights of moving the battery more and more forward with each flight I was finally able to fly w/o feeling like it was tail heavy (and elevator sensitive). The CG is now slightly less than 3" and the battery is nearly completely inside of the cowl area. Wing incidence is fine and thrust seems fine as well. So, I guess my question is are 3D planes supposed to feel this tail heavy?
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Re: 3D CG Balancing

Postby DOUG NOVAK » Wed Feb 08, 2012 10:39 pm

True 3D's are trimmed with slightly tail heavy which make them snappy but be prepaired. They are not trimmed to be rock solid Pattern Planes so you need to understand the difference between 3D and Pattern. I think a Pattern plane trimmed slightly nose heavy and with a slight amount of down trim is capable of a wider range of aerobatics from slow roles to flat splins, flat turns, inverted flight, Snaps, etc. The slight down trim helps to keep you in touch with the plane because you must continually imput slight up to fly level. Also with Ballance you need to consider too much of too little down thrusts and how it can confuse its effects with ballance. Frankly the other thing is the size of the plane. A 90" wing 3D verses a 48" 3D is a matter of scale and speed. The larger the plane the slower the movements occur and as size decreases things speed up in scale terms. IMO
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