After having positioned, drilled, and clecoed the upgrades to the center wing spar assembly, we now rivet the parts back together and bolt the two halves of the center spar assembly back together to reinstall it into the fuselage.

Here we begin to rivet the center wing spar assemblies back together using the "conventional" bucked rivets:

We use a 3X pneumatic riveter and flat bucking bar here...

Since we have the equipment, we also use our pneumatic squeezer:

(Of course, this squeezer is not required equipment)

See the video clip below for good views of the riveting...

Once the two halves (front and back of the center spar assembly) have been riveted, we can position and install the Spar Uprights (6-ZU-2-4) with the required shims:

And we now join the front and rear halves of the center spar assembly together...

...separated by the spacers:

View of the center spar assembly (upside down):

Positioning and drilling the spar uprights through both sections (front and rear) of the assembly:

Drilling the spar uprights through both the front and rear sections of the assembly:

...and bolting the assembly together:

Drilling the top doubler:

Two lines of rivets in the top doubler:

After drilling, we deburr the assemblies and join them together once again, separated by the web spacers:

We bolt the center spar assembly assembly together:

The completed center wing spar assembly (viewed from the front):

Now we slide the center spar assembly back into the fuselage:

The center spar back in position (viewed from the right seat):

Here's the video clip of riveting and re-assembling the center spar assembly. I'll add more photos and text shortly: