by Chappy » Mon Jun 13, 2005 10:15 am
Art,
The discussions on center of gravity that you dug up are obviously for Lazairs with the original axel placements - Series I and II. The series III had the gear pushed forward a couple inches, so the above scale method of checking CG would be much too little. On the Elite, for instance, when you weigh the tail (pilot seated normally, full tank, and boom horizontal) you should get around 30-35 pounds on the scale to be in the safe CG zone according to my Elite Builder's manual, page 7-15.
The statement also contained there (in the Elite manual) should apply to all Lazair's: "Note that for weight and balance calculations, the C of G limits are 12 to 15 inches aft of the leading edge."
Make sure you KNOW what is the proper spec for the model you are concerned with. I don't think you should have to add weight to the tail to correct for C of G if your plane is in a stock configuration. If you have a modified aircraft, be careful of adding weight at the tail. It can adversely affect the dynamic stability of an aircraft by moving to center of mass. I've read reports where doing this has made some planes that previously had good spin recovery characteristics become difficult or impossible to recover. I don't think this would be applicable to a Lazair, but it might. No one likely knows. I would suggest making slight adjustments to the seats position rather than resorting to adding weight out on the end of the boom at the tail.
As always, IMHO,
Chappy
