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Old Apr 26, 2015, 10:59 AM
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Balance ?

On a f3 V Tail or x Tail do you Balanece the plane right side UP or Upside Down, I noticed that when I balanced right side up on cg. When I turned plane over it needed a few grams of weight for the same angle. Ian
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Old Apr 26, 2015, 11:04 AM
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Right way up on multiplex cg device.

It's hard to get an exact balance when the model is fully loaded (e.g f3b/f model). So upside down might work.
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Old Apr 26, 2015, 01:28 PM
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Thanks
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Old Apr 26, 2015, 02:29 PM
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Technically it shouldn't matter. I measure my CG's upside down because I can balance them on a single point, establishing both longitudinal and lateral CG positions. The subtle point that might be impacting your measurements is vertical CG. Measuring Z-CG is very sensitive to pitch angle when you take the measurement. It can have an effect on the longitudinal (X-CG) if your model isn't perfectly level. I would guess that is probably why you are experiencing a difference in measured CG.
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Old Apr 29, 2015, 07:29 AM
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What it does in flight will be way more accurate than a millimeter one way or another in the shop.

Curtis
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Old May 03, 2015, 08:23 AM
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I like the idea of the balance point in the center, I would really like to see a picture of how you do it, this way I can replicate it. Thanks for the input. Ian
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Old May 10, 2015, 02:24 PM
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I have over the years experienced similar problems. I found out that I didn't have a good enough CG device...until recently. Very accurate and simple to use...should have gotten one 15 years ago!

/Jonas Ekman
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Old May 11, 2015, 10:39 AM
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Interesting looking CG measurement device. Who makes it?
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Old May 11, 2015, 12:45 PM
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Martin sells them.

http://www.weberschock-development.de/enfmb/
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Old Feb 09, 2016, 04:03 PM
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I just purchased this balance. It is very well made - unlike anything else out there. That said, the distance between the beams is 3" = making it barely usable for anything but the smallest airplanes. The horizontal support is a machined rod with M3 thread into which thumbscrews thread into it - so I am going to get some M3 threaded rod and spacers and make a few horizontal supports of different lengths. Hopefully it will work.
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Old Feb 09, 2016, 04:29 PM
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What's wrong with heavy?
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You need to have the CG underneath. the point that you are measuring from. As long as the CG is above the plane will teeter. Usually the vertical CG is very close to the lower wing surface and it gets difficult to measure.

Moving the suspension points out and away from the roots will move the CG below the suspension points making reading easier.
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Old Feb 09, 2016, 05:14 PM
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All types

I have bought just about every balancer there is. I find the Great Planes one pretty unsuitable for gliders. The one made by Sig (I think) which is wood and you put together yourself is quite good if you make a good job of assembly. The Greek ones are not bad but not the best. The Multiplex (I thought they were out of production but I got one recently) is very good but not as blingy as The Weberschock balancer. The both produce very similar measurements, within a range of 1mm. The Multiplex is easier to use because the arms only pivot in one plane. The Weberschock is potentially more accurate but only suitable for gliders, for which it was intended in any case. Looks great on the bench, Typically German design and engineering. Mind the points of the pivot though, they can bite !
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Old Feb 09, 2016, 08:03 PM
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I'm old school. I generally do not care about the down to the millimeter setting. Get it in the ballpark and fly. Tune to taste. Don't get hung up if you are at 101 or 100.4 mm from the LE.
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Old Feb 10, 2016, 07:12 AM
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Thanks for the comments, gents. Sounds like I need to sell the balance to a glider guy.
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Old Feb 11, 2016, 02:02 PM
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FYI
No don't sell your devise , its a good tool to get you into the ball park.
As someone previously mentioned , get it into the Air ..
Do your tuning . Check out some threads from Mike Smith on CG tunning..
he always explains things very simply and easy to understand.
The "Dive Test" will always get you very very close to what you need.
Remenber to re-trim your plane for hands off, level flight after you add or remove weight .. then re test it..

See some of Mike's posts or others too ..
Dyno Don


QUOTE=Halifax1;33965722]Thanks for the comments, gents. Sounds like I need to sell the balance to a glider guy.[/QUOTE]
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