This is pretty cool if you can see it. There is a small jack screw on each side that fattens the rib. It was covered up on the last fabric job. The plane flew fine so maybe a factory adjustment?
I'm not perfectly clear on how it works though. Does the fat side cause more deflection?
Michael, the 10A had the same setup with the adjustment screw. Ours was covered too so we could never adjust it. We could have used some adjustment with the Lyc 135 up front. Quoting from the 10A Service Manual:
"In the event that airplane tends to fly to the right, the adjustment screw on the left side of the rudder should be turned to the left (unscrewed), and the screw in the right side is tightened an equal amount. If the airplane tends to fly to the left, the reverse procedure should be followed." Stinson 10A Voyager Service Manual, p. 12.
I would want to leave that screw uncovered if it was my airplane. You must not have a service manual for your airplane?
No I don't have the service manual. I turned each screw all the way in so I will start from zero. I should probably turn each one out, so there is some adjustment for the other side. If I remember, probably the side that gives you left rudder.
Those 10A service manuals pop up on eBay every now and then. I'll keep an eye out for one for you...
Our 10A with the Lyc 135 required constant right rudder pressure to keep the ball centered. I expect when the rudder was recovered the trim screws were never re-adjusted when going from the original 90 hp Franklin to the Lyc. The Stinson 10 was originally powered with the Conti A-80, so I expect you're going to experience the same thing moving up to the increased hp of the O-235. According to the above, for right rudder trim you're going to need to screw the right side trim screw OUT and the left side trim screw IN from an intermediate position. I would screw both screws all the way out and count the turns; and then screw them half way back in and start from there. Then you have enough threads to go out on one side and in on the other. Just my thoughts.