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I installed the horizontal stabilizer, saddle piece, and connected the elevator control cables on my 601 XL B. I immediately noticed a couple things. The effort to raise the elevator to full up position was excessive, to me. It took about 4.6 lbs pressure on the "Y" control stick. Also, the elevator cables tightened considerably as the stick was moved back. The cable tightening happened mostly because the nylon fairlead holes aren't aligned with the cables very well at up elevator position. I enlarged the holes and had to move one of the nylon pieces to get it so the cable didn't rub whether the elevator was down or up. That took care of the change in cable tension. Next, I figured out a spring arrangement to balance out the weight of the elevator when it is in neutral. That reduced the up elevator stick pressure to about 2.5 lbs and it took 0.5 lbs to move from neutral to down position. It was simpler to do than I thought it would be. I used a piece of 3/8" OD aluminum rod 0.437" long and drilled a 3/16" hole through it. I turned a groove 3/16" in from on end to locate the loop on one end of the spring. I drilled a 3/16" hole through the control stick about an inch below the upper cable attach point. I fastened the spring attach "spool" to the stick with a AN3-7A bolt, washer and stop nut. The other end of the spring is secured to piece 6-B-16-2 below the hole for the elevator cable far enough so the spring doesn't interfere with the cable. I used a piece of 1/8" x 3/4" angle that was left over from the center spar upgrade. I figure this should help make the up elevator trim more effective since the trim tab won't have to lift the weight of the elevator which weighs 3 lbs at the trailing edge. Less trim tab for neutral in cruise will mean less drag = more speed. :-)
Here is a couple pictures of the balance spring. The spring is 8.5" overall length unextended, OD 0.625" and wire diameter 0.063". I bought it at a 2nd hand store, but the spring was new. Unknown lineage.
Hmmm. I can't figure out how to attach the pictures.