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I was thinking about something that most of us know but never think to mention. Are your blades balanced? Not do they weigh the same, are they balanced?

Recently I was helping another pilot try and find a vibration in his model. I asked him if the had balanced his blades. He looked surprised and said “No, I just bolted them on.” Now commercially produced blades tend to be very good but it never hurts to check. We pulled off the blades and I weighed them, really good, within a 1/10 of a gram.

I said, just to be safe, lets check the CG (center of gravity).. I pulled out my trusty old Koll RotorPro, and checked the spanwise CGs of the blades. I was shocked that the CGs were about 3/4 of an inch off. The other flyer asked how do you balance blades that weigh the same? Answer, you put weight in both blades, one at the tip, the other at the root. These were off so far, I had to drill a shallow hole and epoxy in a lead shot, positions determined by the RotorPro. After the epoxy cured, the weight was still identical in each blade, but the CG was only about 1/16 inch off. We bolted the blades onto his model and, SURPRISE!, the shake was gone and the model was dead smooth. To say he was pleased was an understatement.

What about Tail Rotor blades? They are small and light, so they should be no problem, right? When you think about it, the TR is turning really fast and, even a small difference in weight makes a difference. It generates a high speed buzz that will drive a gyro crazy. Always check new stuff right out of the package. Most of the time it will be good, BUT if it’s not, fix it.

~ Gordie Meade, ARCCHS Facebook