----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----Hi Byron; Sorry to hear about the corrosion. I think this is why the FAA issued the AD.
The easiest way to fix it is to remove the bottom skin. The top skin has the wing walk corrugation riveted to it with angles for support, so it is a little tougher to remove it than the bottom one.
Yes, you will need the -L parts. I think the service assembly drawing on page 42 of the parts catalog shows it the best. When removing the bottom skin, if it has not been removed before, there will be two flush rivets under the overlap of the center section bottom skin that hold the wing walk bottom skin to the inner rib. These rivets are located near the front spar and apparently were put in during assembly of the walk box assembly. In any case, after you have drilled out all of the rivets holding the bottom skin to the ribs, you will find that it does not want to slide out because of these two flush rivets you do not see. If you gently pry the center bottom skin away from the stub wing bottom skin and clean the lap joint, you will find the two flush rivets that are preventing the stub wing bottom skin from being pulled out of its position. Once you have the heads drilled off the flush rivets, the bottom wing skin will slide out from under the front spar cap and the center section bottom skin.
With the bottom skin off, you will get a clear picture of what needs to be done to repair your corrosion damage. I would recommend removing the bottom skin and getting a good look before you order any of the parts. You may find corrosion damage to the rear portion of the rear spar where those two corroded ribs attach. You may want to take a real good look at the RH side in the same area. It is a little easier to see the RH side because the pitot and static lines are not on that side.
I have removed the bottom skin on a couple of stub wings in order to repair corrosion damage.
Good Luck
Lynn Nelsen
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