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N strut question

K

kodiakcub

MEMBER
I'm in the process of rebuilding my PA11 wings. I have them partially assembled and am at the point of trammelling them. When done with this process I have a slight bow in the spar between the number 3 compression strut and the N strut. It is visible when sighting down the spar and the string line confirms it. After much head scratching and triple checking all the trammelling points and measurements I didn't find any errors. I finally disassembled the diagonal on the N strut and now have perfectly straight and parallel spars. The hole on the N strut diagonal is now about 3/16 of an inch out of alignment. I was wondering if anyone has had this experience and if so how the problem was dealt with.
Thanks
Dan
 
kodiakcub said:
I'm in the process of rebuilding my PA11 wings. I have them partially assembled and am at the point of trammelling them. When done with this process I have a slight bow in the spar between the number 3 compression strut and the N strut. It is visible when sighting down the spar and the string line confirms it. After much head scratching and triple checking all the trammelling points and measurements I didn't find any errors. I finally disassembled the diagonal on the N strut and now have perfectly straight and parallel spars. The hole on the N strut diagonal is now about 3/16 of an inch out of alignment. I was wondering if anyone has had this experience and if so how the problem was dealt with.

Try flipping the N strut over it looks like it can be installed either way but it has to be installed the one way.

Bryan
Click to expand...
 
I had an identical problem - bowed spars when trammelling - after much head scratching I found the lower member of the N strut was 1/8" too long. It had been replaced at some time in a former life with an upper member. the lower one allows for the drag wire fittings.
 
One leg of the N strut is longer than the other. The short leg goes between the two wire pulls. Had a Super Cub out of Mexico that was assembled that way.
 
I also found one like that on John Meades S. cub some years ago during an annual. It was corrected when they covered the wings not long after. That one had a cable rubbing so wasn't hard to find.
 
I've checked the N strut installation and it all seems good. The strut is installed correctly by the wing drawing 10625 and I have the short leg on top between the wire pulls. Would anyone have the dimensions for the diagonal tube hole centers? This wing had some hidden damage I found when disassembling and I am not sure if this N strut is correct.
Thanks
Dan
 
20230118_160716.jpg Im having alot of fit issues for basically a new wing. First the N strut now the center aileron hinge doesn't seem to fit. It is hitting the wing attach fitting before the spar. Am I missing something in this installation? After doing some quick measurements I don't see any real differences between the old spar and the new.
Thanks
Dan
 

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