Left Wing 3

Next comes the arduous task of prepping all the skins for final assembly.  This is another monotonous task to deburr and dimple all of the skins:

When doing the leading edge joint plate, you need to install the platenuts that attach to the fuel tank.  One tool that is invaluable for doing this activity is a nutplate jig.  I found it was difficult to accurately line up all three holes with just a pilot nutplate, so I purchased the jig at the yardstore for $17 (it works much better).  You will note that the instructions have you dimple all three holes.  Normally you would c-sink the rivet holes, as the dimples overlap in this scenario.  I went ahead and dimpled (per the instructions) and everything came out fine.

One other oddity I noted in the plans was dimpling the rear rib flange.  Since the instructions have long since instructed you to rivet the main ribs to both spars, you can't really dimple the rear spar flange or the rib at the intersection.  Given that the spar flange is .040" thick, it is acceptable to c-sink that area.  I suppose it is possible that that was Van's plan altogether (but not called out in the instructions.  When c-sinking, the hole in the rib holds the c-sink pilot.

While the rear spar is being finished, it is important to remember to c-sink the dimpled holes slightly.  Since the .040 is pretty thick to dimple, Vans has you run a quick c-sink in the holes to ensure a flush fit.

Last metal prep step (before priming) is to make the scarf joint.  The purpose of this is to thin the skin thickness where the skins overlap, so that there will not be a bulge in that area.  I have used my mouse sander to do this in the past, and I feel it works pretty well.  Don't be shy when doing this, as it takes some doing to thin the skin.