Taper of wing walk doubler at rear spar?

The plans call for scarffing the wing skins where they overlap and are coincident with the main spar flange, but what are people doing with the wing walk doubler at the rear spar. It appears that if the doubler is left with a square edge, the outer skin will form a crease when the rivets are set. Does anyone taper the doubler in this area?

Brice, It won't form a crease.

It will transition from the thicker stack of sheets to the thinner, single sheet smoothly.

CJ

Both the main skin and doubler overhang the spar. As a consequence, there's no reason for the doubler to push up on main skin and hence no reason to taper it. I suppose tapering it a little wouldn't hurt, but I just got done riveting my flap gap fairings and there doesn't seem to be any tendency for the aft edge of the doubler to show up on the main skin at all. Hope this helps. Good luck.

Thanks,

Thanks for the tips. With all the other tapering on the elevators and wing skins, it seemed like it might help. I'll probably take a little of the edge off but not go too far here. It is going to be a riveting week!

BJohnson said:

Thanks for the tips. With all the other tapering on the elevators and wing skins, it seemed like it might help. I'll probably take a little of the edge off but not go too far here. It is going to be a riveting week!

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Brice--Since you're about ready to rivet those skins, I'll just pass along what I found. Following other's warnings to me, I found the rivet callouts occassionally questionable. I found that I had to go a half size bigger in some cases. If you have a good bucker and can keep the bucking bar square, the extra half size did not seem to cause a problem but gave me more "wiggle room" in terms of finished shop head size. If you stick with the smaller rivet you really have to time the shooting perfectly. Other than that, the skins were a breeze. FYI--It took me and a good riveting partner about 14 hours to rivet both skins and stringers, if that is of any planning use.

Have fun and good luck. It sure is nice to see those skins on for good!

Steve - Thanks. Tomorrow is the day for the first wing. The instructions say to start at the center rib and work outwards. I was thinking about riveting the skins to the spar flang first and then starting from the center rib and work out. I looks like the skin will sit flatter on the flange with it just hanging from the top spar holes possibly giving a better fit behing the LE and tank. Any thoughts anyone?

Also is it better to work from the center of the center rib and work outwards, or is it best to start from the front of the center rib and work outwards and aft?

BJohnson said:

Steve - Thanks. Tomorrow is the day for the first wing. The instructions say to start at the center rib and work outwards. I was thinking about riveting the skins to the spar flang first and then starting from the center rib and work out. I looks like the skin will sit flatter on the flange with it just hanging from the top spar holes possibly giving a better fit behing the LE and tank. Any thoughts anyone?

Also is it better to work from the center of the center rib and work outwards, or is it best to start from the front of the center rib and work outwards and aft?

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Hi Brice--IN case you haven't already started... I did exactly as you describe planning to do. I never did understand what Van's was trying to describe in terms of order. I did inboard skin first: started from center at spar and rivet the entire spar first. Then I went down on the center rib and riveted the top two holes on all ribs moving from center out. Then worked the next two holes starting from center, etc. Thus, the rear spar was the last to be riveted and I also did that from center of each skin outward in both direction. Then I did the outboard skin the same way, starting up and riveting the entire main spar first and rear spar last. FWIW my skins are almost drum tight with no oil canning--they should get even tighter once the bottom skins go on. Also, my gaps between the leading edge/tank and main skins almost disappeared entirely doing it this way. Originally I had 1/32' on tanks and 1/64" on the LE when they were match drilled. Now I have probably 1/128" on both. Hope this helps--good luck.