Now we install the Wing Root Doubler (6-ZU-1-2) to the front side of the spar root:

The Wing Root Doubler is a flanged piece that sits in front of the spar:

We decided to drill out the existing inboard noserib and replace it so that we could drill the Wing Root Doubler flange well into the noserib flange (the replacement noserib will be supplied as part of the Upgrade Package kit):

The new noserib and Wing Root Doubler drilled and clecoed together:

We use a punch to position the main spar bolt holes (without redrilling the the existing spar bolt holes):

The punched hole positions ready for drilling:

The repositioned Wing Root Doubler after having drilled the main spar bolt holes, ready for riveting:

The repositioned Wing Root Doubler after having drilled the main spar bolt holes, ready for riveting:

After riveting the noserib back in, and riveting the Wing Root Doubler flange into the noserib::

We install the AN4 and AN3 bolts (one each on the top and bottom) through the Wing Root Doubler and the Extrusion, as shown:

And finally, we position the Cap Spacer 6-ZU-1-6. The spaces fits btween the main spar web and the wing root doubler, and will be drilled and bolted:

Here's the video clip: Installing the Spar Wing Root Doubler: