ORIGINAL: Tom Antlfinger
Hi Craig:
I always wondered why BV chose to use a distance along the leading edge on the F-4 and that little hole near the leading edge on the F-100D/F. With a swept wing, if you extend the C.G. point with a perpendicular line from the C.G at the root, out to the absolute front of the leading edge, you will get one measurement vs if you measure along that same perpendicular 1.5" more aft like the holes on the F-100. Why not do the measurement at the root like he does for most of his other models?
I notice on my Phantom that a perpendicular from the C.G. at the root measured about 1" back from the leading edge passes thru both the 12 3/4 point, as well as thru the center of the box at the front of the leading edge, if that makes any sense.
So when you do your C.G, how do you suspend the model.......right along the leading edge with a device like Tom Cook uses on the Firebird, or with your finger or some some sort of rocker device and inch or so back from the front of the leading edge?
Tom
Hello Tom,
I agree that it would be much simpler for BV to just provide a distance back from the leading edge for the c.g. In reply to your second paragraph, no, it doesn't make sense! I just measured down the L.E. 12-3/4" (photo) and made a mark on both wings. I connected the marks with a string or straight edge and put a small piece of tape on the bottom on each side near the fus (two blue pieces of tape representing the 12-1/4" and 12-3/4" positions in photo). Not sure what "box" you guys are talking about or where the 1" behind the LE comes in to play.
I just use my flimsy wire Great Planes balancer to suspend the plane. It's too imprecise and awkward to try and balance it along the leading edge with your fingers. For my bigger planes I've got a contraption I made out of 2 X 4's to balance my planes but it takes at least 3 people. I think in the future I will use the JPO method of weighing each wheel and using their spreadsheet to calculate c.g., but of course you still need a longitudinal datum reference for the c.g.
Craig