Hello All,
First let me start by saying that I may know the answer to this one but I'd like to get your opinions and other thoughts. Sorry for the length.
A couple weeks ago I had my first crash while learning to hover (I'm still on training gear). I only had to replace the see-saw arms, head links, and the main blades. I installed the new parts, balanced the blades and setup the pitch. In order to get a head start on tracking, I measured the pitch on both blades and adjusted the links so that both were as close as possible so when I fired it up at the field, I would not have to adjust too much. Well, at the field I could not seem to get the tracking correct, the "marked" blade (I colored the tip with a marking pen) was always higher than the other. I tried 3 times to adjust the link but it made no difference. Then someone explained that my rotor speed was too low and tracking cannot be done w/o proper speed first. He made some adjustments to the carb and measured my speed at 1650. AOK. He also made one linkage adjustment and blades appeared to track almost perfectly. Everything OK right ? Well, out of curiosity I just sat down and re-measured the pitch of both blades. Turns out the "unmarked" blade was zero (low stick) as I wanted it, while the "marked" blade was -5 !!! WOW
I then proceeded to measure the pitch at the root and tip of both blades (I usually only measure pitch at the root). The "unmarked" blade is 0 at the root and -2 at the tip while the "marked" blade is -5 at the root and +2 at the tip !!! Son of a b*^#@ !!!
My eyeball could not see the warp in the "unmarked" blade but the "marked" blade that had 7 degrees difference was definitely noticeable.
Here is my summary: The average pitch of the "unmarked" blade is -1 and the average of the "marked" blade is -1.5, close enough (measuring pitch is not quite an exact science) so the blades appeared to track descently while in the air.
Here is my solution: Send them back and get some glass or carbons.
The blades are 550 Revolution CP woodies from Heliproz.
Any comments ?
Thanks.