Measuring CG on a symmetrical wing.
#1
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Join Date: Mar 2007
Location: tipp city,
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Measuring CG on a symmetrical wing.
Hey there, got a basic question about locating CG. If you have a flat or nearly flat bottom wing, measuring CG from the leading edge is easy. If you have a symmetrical wing and say the plans call for a CG of 2" from the LE, is there a good way to measure and mark the wing? A person can try eyeballing the edge of a ruler to the LE but that doesn't seem to accurate depending on how good your eyes are. If you try a sewing (cloth) tape measure or piece of paper to follow the wing contour from the LE center, then you'll end up a little forward of the specified CG (because the CG is based along the chord). If you use a sewing tape to follow the contour, I guess you'll be a little nose heavy, which is safer than tail heavy. I tried marking my wing using a straight ruler and eyeballing it then did it with a sewing tape measure and the marks were over a 1/4" off.
Anyone here have a better way to mark off the CG on a symmetrical or non-flat wing?
Thanks,
Gary
Anyone here have a better way to mark off the CG on a symmetrical or non-flat wing?
Thanks,
Gary
#4
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Yep, a square makes it easy. But it's not a real crucial measurement. The real setting is found by flight testing, so if you are a percent or two off it won't really matter. Precise CG measurements are really only relevant when you are resetting a known good configuration after a recover or repairs.
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Thanks everyone for your suggestions. I went out and got a carpenters square. Still have to eyeball it a little to get the LE perpendicular to the square, but it works and gets me in the ball park.