Thought I'd bring this back to life instead of starting a new one, because it's in line with something we discussed earlier in the thread.

Call it an "alternative use" of the Vanessa, and the sort of thing that makes the machine, for me at least, an invaluable tool. Rather than using it to FIND the CURRENT CG, we're going to use it to help GET the airplane TO the CG we want.

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I'm currently assembling WildHare's 102.5" Edge. At that wingspan, weighing in the 25 lb range, as you can imagine, this isn't an "easy" model to set/locate/experiment with the CG on. It's getting to be time to put the gear in. Batteries, Rx, Regulators, Smoke system gear, etc. The question this raises, of course, is WHERE to put this stuff? Sure...there's plenty of room...but do i need to be thinking "toward the rear", or "as much up front as possible" or what?

Enter the Vanessa, which, when used creatively, not only gives me "an idea", but can downright pinpoint where I need to be looking to put all this stuff, to within just a couple inches.

Here's how:

First, the airplane is hoisted off the table in the machine. A level is set on the foredeck astride the CG we're after (center of the wing tube in this case). Obviously, the level can go anywhere you wish, but astride the CG means it, itself, won't impact the balance of the model. Certainly, the level should be placed somewhere with a 0 degree incidence angle. This is true (or at least 'close enough") of the foredeck on most airplanes.


Next, we rotate the shaft of the Vanessa to bring the airplane to such an angle that the plumb bob is pointing at the INTENDED CG. Note, we don't care at this point if the airplane is level while indicating that CG. We just want the machine pointing at that location. Indeed, in the 2nd picture below, you'll see that the airplane is quite tail high, or "nose heavy".



At this point, it gets pretty simple. We just start stacking our gear on various locations on the airplane. What we're after is to bring the airplane to level. Note that the indicated CG won't change...just the balance of the airplane will. In short, when we bring the airplane to level, the ACTUAL CG will be right where we INDICATED we wanted it before.


All you need to do is move batteries, or smoke pump, or whatever you're working with, around on the airplane. Nose needs to come up? Move a battery back a bit, check the level. Nose needs to come down? Move the smoke pump forward a tad. Whatever works.

At this point, once the airplane is level, and indicating the desired CG, just take a picture or make a few notes.

VIOLA! Now you can begin installing gear with a high degree of confidence that, once everything's in there, the airplane will be at, or very near (well within a bit of wiggle room) your desired CG.

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Certainly, I agree with MinnFlyer's basic assertion...that CG is often more "worried about" than it need be. Anything within the usually conservative range provided by manufacturers will almost certainly fly acceptably well initially...and from there it's most definitely a subjective "feel" thing. You certainly need to decide what traits YOU like in an aircraft, and then experiment with weight and balance to achieve those...and your final CG may well be a good bit outside of the suggested range, or considerably different from what another modeler may like.

And, indeed, each of us will think about changing the CG in different ways. You may fly an airplane and think "Huh...that 'feels' like it might need an oz of weight in the tail" while another may think "that 'feels' like the CG should go back half an inch". Again, it's a subjective issue, and largely modeler dependent.

I did, however, want to revisit this topic, and give a "real world" example of how the Vanessa can be used in 'creative" ways to do more than simply determine where a particular airplane balances at a given point in time.

Hope someone somewhere gets some benefit from the idea.