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Rudder throw question


Aug 9, 2009
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Seems like no matter how often I've tried to picture everything in my mind before building, something gets missed. I'm puzzled over the rudder post fit. I searched the forum and no one else seems to have mentioned this and so I must be missing something obvious. I just can't figure out what. Any help will be appreciated.
A have my long-a-building Acro-II ready to build the rudder. The stabs and vertical fin are in place. I am building the rudder post/spar as the last piece of the tail. The hinges are slid on the rudder spar but nothing is welded yet.
I have plan #1521 printed 3/1993. Tail wheel mount is built according to B2 on sheet 3. The tail wheel bracket is according to D1 on sheet 3. The tail group is built according to sheet 10. I am using a Piper J-3 spring with a Scott 3200 tailwheel and the geometry looks right for the tailwheel. I think that the tail construction is as per the plans.
Note in the following picture the triangle of .090 4130 stabilizing the tailwheel mounting bracket. I think I did everything in this area according to the plans, but this seems to be the problem area.

I have built the tail wheel steering fork according to A4 sheet 11. I have thought about the advice to use a Piper J-3 fork, but I have the plans-built fork for now. I think if I bolted on a Piper fork instead of welding on the per-plans fork I would have the same problem. I test fit the hinges on the vertical fin post to see how the rudder spar and tailwheel fork fit. Nothing is welded to the post yet, and I want to see how things fit and move. The steering fork will get welded to the bottom of the rudder post (or if the Piper part is used, bolted) so they all will move as one piece.

when I try to turn the rudder, the tailwheel fork hits the tail wheel bracket limiting travel to about 8 degrees left or right. The rudder needs to travel 32 degrees!
I can't lower the post to miss the bracket because the tailwheel spring is in the way. You can see a roughly 1/2" block holding the post up above the spring. Even scraping on the spring, the arm still hits the .090 bracket on the back of the fin post.
If I lift the rudder so that its bottom is about 2 inches up the tailwheel steering fork misses the flat bracket and hits the post at just a bit over 32 degrees travel. But everything is way too high given what the plans call out. That can't be right.
The hinges give a gap between the rudder post and the vertical fin post of about 1/4" which seems about right. If the hinge gap were a bit over 1/2" there would be sufficient travel, but that large a gap doesn't seem right and doesn't match the plans.
I can't find anyone else complaining about rudder travel. I must be missing something obvious, but I can't see what it is.
What have I missed???

Thanks in advance


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