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Old 02-22-2012, 04:46 AM   #1
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Tonight I was working on the cleanup of the other lower wing to prep for the new aileron install. I was (carefully) using a japanese pull saw to help remove some parts that wouldn't be needed or would be replaced as things went back together. I was trying to separate a piece of quarter inch ply from a rib on one end, when the saw hit a void and dug into the top of the rear spar.

As I regained my composure and the cursing died down, I finished cleaning up the area so that I could see how much damage I had done. The saw cut a neat little slot right next to the rib that is about 1/16" deep on the front and 1/8" deep on the rear of the spar. It's just inside of the inboard rib on the I-strut bay. Bad place to mess with the spar.

You can see the detail in the pictures below (not talking about the cracked corner block).

So here's the question of the hour. Is there a way to repair this without replacing the rear spar from here to the tip? If I need to, I can remove about half the spar and have plenty of room to do a nice scarf inboard of the damage. I'm hoping that isn't necessary, but sometimes that's just the way goes. Let me know if that is overkill.


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Old 02-22-2012, 05:31 AM   #2
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See Figure 1-10 in the 43.13-1B.

I'd consider that "Local Damage" and go from there. Looks like it'll be some work, but better than splicing a new spar section.


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Old 02-22-2012, 05:45 AM   #3
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Old 02-22-2012, 05:46 AM   #4
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Look at AC 43-13. Fig 1-10. Looks as if you can make new hinge reinforcement plates go past the rib to the strut reinforcement should work.
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Old 02-22-2012, 06:19 AM   #5
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Thanks. That is what I was looking for. It applies directly to my problem. The spar is 2.375" tall, so it could be considered local damage up to almost a 1/4" (2.375"/10 = .2375"). So I'm ok there. The spar is 11/16" thick (B), so the overlap on each side needs to be 2.4375". That brings the doublers up close to, but not past the ply doubler for the I-strut.

Unless that is too close to the landing wire and I-strut attachments, it will work.

Thanks for the link Beej. I was still digging around my office for my hard copy.


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Old 02-22-2012, 11:02 PM   #6
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If you measured from the bottom of the saw cut to the bottom of the spar with a caliper, compare to the plan tolerance - it may be ok just to "dress out" the cut mark and fill with sawdust/ epoxy. The spars that I had had tolerances of +1/16/-0, so the spar cutter tends to cut ++ on the spar.... you might have been lucky. I would also consult with Kevin Kimball on his opinion if the measurement comes slightly short of perfect.

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