After the first test, he determined that the prop was "within spec" at 0.20 IPS, but there's still a ton of room to improve beyond that. It took three iterations of adding and relocating tiny weights (on the order of a few grams) to the prop hub, and in the end he got it down to 0.01 IPS! The result is definitely noticeable.
Here's the printout of the data taken before adding the weights. This was taken at 2000 RPM, so the "orders" on the left represent frequencies relative to 2000...i.e. 4.0 order is 8000 Hz (I believe). You can see the vibration isn't bad per se, but it's not perfect.
Check out the same data taken after the tiny bit of weight was added. The key is up in that 4th-6th order range.
As I mentioned, he got it down from 0.20 IPS to 0.01 IPS. That's about as close to zero as you can get. You can really feel it. Even just running the RPM up you can sense the absence of the vibration that used to be there. I went flying tonight and found the plane to be much, much smoother in flight. Varying the RPM is one area where it really shines. Previously, you'd hear and feel resonance when changing RPM and when setting it at various RPM. Now it's smooth throughout. I tried power settings from 2250 up to 2650 and you can barely tell anything's changing as you cycle through. Beautiful! I highly recommend Jim if you're in the southern CA area. He's definitely a professional who knows his stuff. Much of the dynamic balancing process is cerebral, not just mechanical, and Jim is definitely an expert.
Here's something I've been messing around with for days now. I may have mentioned that in cruise, the ball was about 1/2 out to the left. My theory is that the left offset of the VS leading edge was a little overshot...but the good thing is that when the required left rudder is applied, the rudder is centered. So I've been playing around with wedges on the rudder to center the ball. Basically I've been shrinking it bit by bit. I started with a section about 8" long and way overshot it. It needed 1/2 ball of right rudder after that. So I've been cutting the wedge down 1/2" at a time or so. Tonight I got it really close (ball out to the right by maybe 1/8 ball), but I cut another 3/8" off. Let's see how this ends up...I think this will be it. When I get it where I want it, I'll just fiberglass it permanently to the rudder. For now it's just aluminum taped in place.
This is the balsa trailing edge stock that I used. It's like a buck at any hobby store.
