Step 5.5 Wing walk doubler

Yes indeed, the wing walk doubler.  These are exciting times aren't they.  Well, it all has to get done and wining about it doesn't pay very well, so on we go!   The wing walk doubler, in case its purpose is not obvious, is a reinforcement of the wing walk. Which of course is the foot wide section at the wing root (closest to fuselage).  It is actually a 9-3/8" x 26" piece of aluminum sheet that is riveted to the back side of the wing skin "doubling" its thickness.

The wing walk is the only place on the wing where we are allowed to step while entering or exiting the aircraft.  Stepping on any other section will almost certainly result in a dent in the wing.  So no dancing on the aircraft except on the wing walk, and please, no high heels.

The location of the wing walk doubler is at the right of the photo above where the first four ribs are located close together.  It's really important to make sure that the wing frames are sitting level and square, and that there is no twist in the wing.

As far as the squareness goes, the skin's pre-punched holes will pretty much take care of that. Squareness in this case is that the ribs are exactly perpendicular to the spar.  For the twist, we measure from a point at the top of the main spar to the top of the rear spar using a plumb line.  Using digital calipers to measure to the center of the string gives sufficient accuracy to insure a straight wing.  The wing frame is then adjusted such that the measurement is the same at both ends of the wing.  Assuming nothing moves during the match drilling or riveting, the wings should be within a 1/32" of straight.

While I was getting the frames straight, Carol scuffs the right leading edge skin prior to priming.

And the dogs were entertaining themselves...

Removing the blue plastic from the inside of the wing walk skin.  On the outside only the rivet lines are removed.

So the wing walk doubler is cut to length from a piece of sheet aluminum that has already been cut to width by Van's.  All that has to be done here is to snip it off at 26" and debur the edges.  The doubler is then lined up underneath the wing walk skin and offset 9/16" at the forward edge because the doubler does not rest on the main spar.  The skin and the doubler are then match drilled and clecoed together to the wing frame.

And finally, the right wing walk doubler skin on the frame ready for match drilling.

And the left skin in place.