R

RyanM

Well Known Member
Hello,

I'm in the process of fluting the leading edge ribs for the wings, and I'm running into an issue where I can get the rib pretty straight, but once I pick it up from my flat surface, I notice that there is some twist diagonally. It seems to get worse the more I flute the areas closer to the tip of the rib. But then if I un-flute the area, I can sometimes lessen the twist, but then the rib isn't as straight.

Is this acceptable? I can lay the rib on a flat surface, and apply light pressure and it lays flat. If not, what is the best way to get rid of the diagonal warp?


Advice needed,
Ryan
 
If you can get it to lay flat with light pressure, don't worry, as the clecoes will hold it straight when assembling. The point is the line of holes need to be straight without force. I recall the same problem, and it was a non-event with assembly.
 
Tip Ribs

Agree with the other comments above-don't get too wrapped up in the fluting process...see this thread:

http://www.vansairforce.com/community/showthread.php?t=28076&highlight=fluting

Having said that...I learned during the rib fluting process that I could get mine to lay completely flat by double-checking the fluting at the aft end of the top and bottom flanges.

Sounds kind of backward since you're working at the end opposite where you see the problem (twist), but if the top and bottom flanges aren't fluted in balance it will twist the tip of the rib....

Good luck,
Mike
 
I found the worst ribs to be the fuel tank ribs (especially the end ribs), as there are few or no lightening holes to take up any change in geometry...if the flanges aren't *perfectly* done, you get this twist of about 1/4" end to end, and the rib will actually "pop" back and forth between being twisted one way and twisted the other. Took me forever, it seemed, to get rid of it (or very nearly so). As others have said, of course, what matters is that the line of holes is perfectly straight when the thing is assembled. Add to that the match-drilling and dimpling process, and I'm not sure just how accurately you have to "flatten" the ribs given the tolerances in the process, anyway, but I got mine as flat as I possibly could (laid on a slab of granite from a countertop to check flatness).
 
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