View Full Version : VMAR Harvard II/ PC9 45-60 electric conversion, suggestions for CG?

10-02-2007, 03:15 AM

I'm just about finished fighting with an electric conversion for this plane. The instructions (assuming glow) say to have the CG 3" to 3.5" from wing leading edge with the tank empty. Then, with the tank full (8 oz?, about 6" ahead of the wing leading edge) it will be considerably further forward, but they don't actually say where it should be. I don't know how the glow guys deal with stuff like changing CG in flight!!

Any ideas or guesses about where I should try to get the CG for the maiden?

It will have a tower pro 2915 750KV with 4 cells, apc 12x6 approx 450W @ 8000 rpm static on the test bench.

10-10-2007, 02:19 AM
gave it a go with CG 2 5/8" from leading edge. This worked well, no bad habits.

flies very fast and very stable. this is the first large model i've flown, except for the high speed it is easier than a typical park flyer. Take off and landing requires considerable real estate. power system is adequate with 4s2p 2200, i will guess level circuits require about 200W. 12" prop is good, larger might be better but clearance issues on rough surface.

The only concerns I have are the elevator horn protrudes a lot and could get caught on landing, and the landing gear are too stiff for the weight of the plane, very bouncy.

10-10-2007, 04:27 AM
CG should be about 30% of MAC or there abouts on pretty much all planes (3D aside), with glow always balance with an empty tank.