Kit Airplane: Wing Part 5 (Leading Edge)

And now on to the most nerve-racking part of the construction so far (possibly for the whole build) - drilling the leading edges onto the wings. The 12' long wings must have their spars at 81 degrees, level between the front spar and rear channel, all the ribs lined up with the predrilled holes of the skin, the leading edge skin centered over the nose ribs, held in tight to conform to the shape of the ribs, and drilled into the flanges of the spar. There is no undo; it has to fit. And significant mistakes have cascading detrimental effects on every part of the wing made so far. If it's bad's enough, I can't use any of the wing.

Marks were made on the ribs and skins to verify alignment...

Marking the leading tip of each of the nose ribs...

Using a piece of paper with marked distances to find the center of the skin... 

Drawing a line down the center...

The leading skin edge has predrilled holes for every nose rib except for the one for the fuel tank as there are 2 different tank sizes available. I needed to measure its location offset from adjacent ribs and then mark down where to add pilot holes.

The leading edge bottom clamped (and taped) into place. I use the predrilled holes (and the pilot holes I added for the fuel tank rib) to line up the ribs underneath the skin.

There is a line drawn along the edge of the leading edge skin to position it along the spar and lines drawn on every rib. I need to ensure those lines are visible through the predrilled holes in the wing skins and the leading edge skin.

And drill down the shape of the leading edge...

After all of the holes have been drilled (including along the spar), I flip over the wing to get the top side complete..

And here was the stressful part. The skin is a fixed precut size. It must reach around the ribs and underneath the skin on the top side of the airplane (with its predrilled holes). Those wing skin predrilled holes go through the flanges of the wing spar. This can't be misaligned.

I used ratchet straps to pull over the wing skin, and I was so relieved to see my marking line through the predrilled holes of the skin. That means I'm able to successfully drill through the wing skin, through the leading edge skin, and though the spar.

I used a strip of wood to apply pressure through the span as I was drilling...

Going down through the shape of the airfoil...

Once all the holes were drilled with a #40 bit, I flipped the leading edge skin to be at the top / above the rear skin. 

Then went through all the holes and drilled to final size...

The same process was repeated for the other wing. The bottom...

And drilling the top... Again I was thankfully able to line up the edge marking through the predrilled holes.

Continuing to drill the top side with the #40 bit...

Then I flipped the leading edge skin to be on top again and drilled to final size...