Today I fine tuned the tail drive shaft alignment since the last time I did it I didn't have the tail fins or tail rotor on and I realized that the weight of those components hanging on the tail affects the alignment so I left it as was until everything was installed.
I pulled a tight fishing line over my two 29/32" wood blocks at each end of the drive shaft and was pleased to see that my readings at the two carrier bearings were the same as I'd left them last time which means that my checking procedure is consistent. The rear carrier was 1/16" high and the front one was 1/32" high. I loosened the bolt on one side of the bearing holder, stuck a piece of tape to the mount for reference, gapped about 1/16" from the bearing holder then tapped the holder down until it touched the tape then re checked the measurement. I had to do this a couple times until I got the reading to 29/32". Since I was only moving one side of the holder I had to move it further than if I'd moved both sides down. Moving just one side with the other bolt still tight made it easier to control the adjustment and I chose the side that was higher to begin with.
The side to side alignment was within 1/64" so I didn't try to improve it as I'd likely have made it worse or messed up the vertical alignment again. Also, since the drive shaft is 1/64" to the right at the two carrier bearings and considering that the tail rotor will be pushing the tail to the right with about 20 lbs force, the alignment will be better under load than if I had it aligned perfectly with no load.
Next, I tried to determine the empty CG as best I could by placing 1/4" thick, 1/2" wide strips of wood under the skids at the points where the helicopter would best balance on them. This turned out to be 9" behind the main shaft (109" behind the Datum). I'll use this info to better fine tune my weight and balance form, which is only academic since the real balance will be done with a hang test and me in the seat.
