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Old Dec 21, 2012, 03:56 PM
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Originally Posted by campbellj View Post
I measured with a metric ruler, from the leading edge at the fuse. But I totally think I'm measuring from the wrong spot because my t-28 always measured tail heavy. I got fed up with trying to make it right and just shoved the battery as far forward as it would go and put it in the air. Flew great!
Well, a nose heavy plane will fly good. a tail heavy plane will be more sensitive (extreme cases are called squirrelly) to stab movements and will indicate lift/thermals better. You will need less throw the further back you move the CG

Another thing that people don't think about is that you need to move your control rods on the horns/servo arms when you reduce your throws and not just dial it back in the radio. The full travel of the servo has a number of discrete steps (256, 512 or 1024 depending on the radio - this is a function of the D to A converter used in the electronics) and if you set your rates/travel adjustment to 50%, you use half of them. This means that as you move the stick the control jumps a step at a time to move. If you are set up with miniscule travel ranges (extreme case example here) such as 10% and you have a 256 step radio, you only have 25 positions for the control surface and this makes errors for the slop in your linkage and the centering of your servo much worse over the range of the movement (amplifies the error) When setting up a 3D plane, it is recommended that you set your radio to the maximum travel, 150% on some, and then adjust the hole on the servo arm and control horn to get the movement desired so even if you only have 10% of the possible motion, you get (in the example above) 256 discrete positions of the control surface and much more precise control. This can also sometimes be seen when using trims and one click is wrong in a direction but a click the other way is in the other direction because (in the example above) your 25 step surface travels 10 steps for the click versus one by one in the 256 (150%) step case. This is also why more expensive radios tend to have higher resolution (more bits in the D to A converter)
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