Thanks Mark for all your help. Charlie T, Burlington, Ia

Mark, you are correct, ZAC did "work the center section from the back uprights and back bottom to the front when reassembling". Remember that ZAC was making this up as they went along, they didn't have the advantage of hindsight. Would it be easier if I did it this way? Could we do this outside the a/c on a workbench? The answer is yes, it can be done on a workbench.

After I had Upgraded the Center Spar, all the holes were drilled, then it was time to install. I realized that the Bottom Doubler could also act as an install template since we use the existing rear Center Spar rivet line and the Bottom Doubler uses the same holes. This meant that after setting the rear rivet line, I could then set the front Center Spar rivet line making sure that I used spacers to maintain the wing spar gap before drilling. ZAC does the same thing while the Center Spar is in the a/c. Finally, the front rivet line on the Bottom Doubler is just a matter of measuring back 10mm and using the holes on the front and back of the Center Spar that go through the longeron for the edge reference line. The existing longeron holes can be drilled later.

The back uprights (Rear Attachment Uprights, the ZAC Drawing names to avoid confusion) are attached to the Center Spar via a top and bottom Spar bolt hole, so we have exact alignment, the Center Spar doesn't have to be in the a/c. My blog details setting the Front Upright using the Center Spar as the template.

So, you end up with a pre-drilled Bottom Doubler Template. Install using the existing Rear Center Spar holes and then back drill up through the fuselage without the Center Spar installed. Then you drop in the Center Spar and it all lines up :-)

Like you, I work alone. Unlike ZAC, I don't have 3-4 guys laying around, so I had to get creative based on my skill set to accomplish the task. The Center Spar and Uprights mate to my fuselage perfectly, not saying my fuselage is perfect, since I used the original components as a template.

jake

Hello Mark,

My 601XL is flying regularly. I have almost 1,500 hours on it.  I am on my second engine.  The first one died at about 900 hours with camshaft/lifter failure which also destroyed the crankshaft.  I am still using the Bing carb but have added the HACman mixture control.

Steve