Took some reading for me to understand what this was all about, then I stumbled on this image and it helped: http://www.tirevan.com/tire-installation-technology.aspx Bergen RC Dynamic Balance Video: http://www.youtube.com/watch?v=XGI6BzVzNrY This would be the case with shaft runout and maybe some slop in the bearings, I think the tape is acting as a preload device to counter the effect of the runout.
So why balance the propellers in the first place if only to unbalance them again? Wouldn't the un-balanced propeller offer the theoretical preload?
That video didn't tell the whole story. I'm guessing it was made in support of some other written explanation. You need both dynamic and static balance. In the video the size and placement of the tape looked pretty arbitrary, but it's not. There was more to the story that wasn't shown in the video. You basically can't do what it looked like he did and expect good results. ...Tiger
FYI that video was Chris Bergen himself of Bergen RC: http://bergenrc.com/ he has just started making multirotors and I bet that video was probably the result of some discussion with someone somewhere about something
