I was wondering what's the strategy on choosing the arms length. is it just prop size?
let's assume i already have my motors and props, say 10". and i'm building a quad.
is it enough to have arms enough long so the props don't touch, say leaving 2 inches gap, or is better go to much much more larger?
the other question could be: given same config, same motors and prop size.
does it fly better a frame with short or longer arms?
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Also with much longer arms you tend to run the risk of more flex and twist in the arms. The longer the arms, the more pronounced the flex and twist will be, obviously depending on the material the arms are made of.
Adding 2cm to an arm lengh, you should not notice this effect that much either.
Well, by changing the arm length you change the characteristics of the system. The PID controller regulates that system.
The difference is that you increase the length of the path that a prop needs to travel in order to change the rotation of the vehicle, which slightly increases the latency for attitiude adjustments. That increase in latency has an impact on how much P, I and D settings you can apply before it oscillates.
I think for the sizes we're talking, it doesn't have an impact on the ability to hover and move around (they'll both fly), but the ones with shorter arms will be more agile and acrobatic and has stiffer gains. I don't think you'll notice much with 2cm extra, but if you double the length for example I'm pretty sure you'd notice something.