Balance Stands

[stangflyer]

Rob here is one example

I have never seen it done like this, but have seen it hung by the wing tube, and using a plumb bob. Here is more of the one I seen. http://www.rcuniverse.com/forum/tips-techniques-180/708060-vanessa-c-g-rig-how.html
There are a few more examples out there, but I don't promote or provide links to azzhat's site.

This one kinda neat also

Hey that's kinda cool. I do like the idea of hanging for balance. Still, the balance stands still seem to be the best option.

 

[Terryscustom]

The hangy thing is pretty darn cool, but I would not put that force of a rope on the trailing edge of the wings on a 100cc+ plane. Maybe make some type of wide strap to distribute the force a bit. Even on an ARF I normally draw out the wing in CAD and find the actual neutral CG which is typically 32-33% of MAC. It is funny how many ARF's out there vary in their "safety zone" for CG setup. I set my planes up like that and very very few times do I do any post maiden CG changes. But, I do like my planes very neutral to just a slight touch towards the nose.....never tail heavy of neutral. I normally pick up the plane from the top at that measured point with the canopy removed.

 

[Phil.Griffin]

I just been using my fingers. There is such a wide range of CG on these planes, get her close, fly, move batteries around till you get her where you like.

Pretty much what I do as well.

 

[Phil.Griffin]

What's the advantage of a balance stand versus weighing all three wheels of a leveled airframe as full scale aircraft are done?

Perhaps because c.g. needs to be close before fine tuning is done after actual flights?

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To me, it's just easier, quicker, cheaper to just hang it from the tube or get a buddy to help pick it up..

 

[ChickenBalls]

To me, it's just easier, quicker, cheaper to just hang it from the tube or get a buddy to help pick it up..

I've seen it hung on the wing tube also, just can't seem to find it. I'm like Terry, don't think I would be using the rope as in the video, on larger/heavier aircraft.

 

[Terryscustom]

To me, it's just easier, quicker, cheaper to just hang it from the tube or get a buddy to help pick it up..

The tube is not always on the CG though, so that is not always a good indicator. I think most mfg's try to get it there to make it easy but it's not always the ideal structural place for it.

 

[Dennis9412]

The hangy thing is pretty darn cool, but I would not put that force of a rope on the trailing edge of the wings on a 100cc+ plane. Maybe make some type of wide strap to distribute the force a bit. Even on an ARF I normally draw out the wing in CAD and find the actual neutral CG which is typically 32-33% of MAC. It is funny how many ARF's out there vary in their "safety zone" for CG setup. I set my planes up like that and very very few times do I do any post maiden CG changes. But, I do like my planes very neutral to just a slight touch towards the nose.....never tail heavy of neutral. I normally pick up the plane from the top at that measured point with the canopy removed.

There are 2 ways the Vanessa rig can be used. One is the way shown in the video, and the other is to put the rope in front of and behind the wing around the fuse, hanging the airframe from the fuse rather than the wings. Works great!

 

[Phil.Griffin]

The tube is not always on the CG though, so that is not always a good indicator. I think most mfg's try to get it there to make it easy but it's not always the ideal structural place for it.

I agree. I tend to fly similar stuff, and most of it seems to balance close enough on the tube for a safe maiden.. But my experience is limited, and I'm certain not all airframes would tolerate this well.

 

[CatalinaWOW]

The three scale method is a perfectly general way to balance an airframe, but if the airframe is fairly well laterally balanced (basically if it doesn't twist noticeably while sitting on its wheels) it can be simplified a lot, and requires only one scale to implement. You need to know the total weight of the airframe (which could be tricky with one scale before you balance it.). For the normal taildragger aerobat you then put your scale under the tail wheel. You need to put the scale on a platform so the airframe is at the desired flight angle of attack. You measure the distance (parallel to the ground) from the front wheel axle to the tail wheel point of contact, and the weight on the tail wheel. Call the total weight of the airframe W, the weight on the tail wheel w, and the distance between gear and tails d. The distance from the axle center to the cg is then:

cg=w*d/W.

For trike gears you do the same thing with the scale under the nose wheel, and the distance is now the distance in front of the main gear axle.

Pretty simple, but I still like the Vanessa approach. Scales up and down in airframe size, and stores in a small box. Big balance machines like the one shown in the OP take up a lot of shop space.

 

[stangflyer]

The three scale method is a perfectly general way to balance an airframe, but if the airframe is fairly well laterally balanced (basically if it doesn't twist noticeably while sitting on its wheels) it can be simplified a lot, and requires only one scale to implement. You need to know the total weight of the airframe (which could be tricky with one scale before you balance it.). For the normal taildragger aerobat you then put your scale under the tail wheel. You need to put the scale on a platform so the airframe is at the desired flight angle of attack. You measure the distance (parallel to the ground) from the front wheel axle to the tail wheel point of contact, and the weight on the tail wheel. Call the total weight of the airframe W, the weight on the tail wheel w, and the distance between gear and tails d. The distance from the axle center to the cg is then:

cg=w*d/W.

For trike gears you do the same thing with the scale under the nose wheel, and the distance is now the distance in front of the main gear axle.

Pretty simple, but I still like the Vanessa approach. Scales up and down in airframe size, and stores in a small box. Big balance machines like the one shown in the OP take up a lot of shop space.

Not really..... they fit nicely in the corner of the closet with no problem at all.