Initial Prep (Debur, Trim, Drill, and Cut) 3/3/24 – 1.1h This is the first of two steps to prepare the aft-center and forward-center bulkheads. Eventally, these two bulkheads will sandwich the wing spar to attach the wings to the fuselage. The two bulkheads are prepared (alodined and critical/large rivets set) and delivered just like the wing spar. This step is focused on the aft-center section bulkhead. There aren't many parts for this step, so initial prep goes pretty quickly. [Hole and Edge Deburring Tools] Final Prep (Dimple, Countersink, and Shape) 3/6/24 – 0.8h 3/8/24 – 0.3h 3/9/24 – 0.2h 3/23/24 – 0.4h Every part in this step has holes to countersink. I hung the bulkhead from the edge of the work bench and secured it with clamps to countersink the flanges. This technique kept the work at bench level, and was more secure than clamping the bulkhead to the top of the bench. I countersunk the top flange holes for flush rivets to attach nut plates, and flipped the bulkhead over to countersink the bottom holes for the bottom fuselage skin dimples. The guideline to go 0.007” (seven clicks) deeper for the dimpled skin countersinks than the flush rivet countersinks worked well for me. Each side angle gets two countersunk holes in the web of the angle. Take time to study the drawings to identify the correct two holes. The other parts in this step are the bearing bracket assemblies. There are two bearing bracket assembly drawings on the sheet for this step. At first glance, I didn't notice a difference, but upon closer inspection the drawings are mirror images of each other - one is for the right assembly and one is for the left. I started with the #40 holes, and had some problems countersinking the forward-most holes in the bearing brackets. The holes are very close to some irregular shaped edges, and there wasn't enough surface to hold the countersink cage square to the hole. The result was a couple of bad countersinks and a trip to the Vans webstore to purchase some more. The bearing brackets will eventually carry loads from the control sticks, so it's worth it to make sure these are prepared and assembled correctly to preserve their strength. After I sorted out the #40 holes in the bearing brackets, I moved on to the #30 holes. This is where the left and right assembly drawings matter. The exterior sides of the #40 holes are countersunk in both the inboard and outboard parts for double-flush riveting. The #30 holes are only countersunk in the outboard part of the assembly. Countersinking the #30 holes went smoothly - no issues like I had with the #40 holes. The bearing brackets also have two #19 holes that are countersunk for the head of AN509-8R12 screws. Like the #30 holes, the #19 holes are only countersunk on the outboard side of the assembly. I countersunk the #19 holes by hand using a hole deburring handle with the #19 countersink cutter attached, and inserting the deburring tool into a 5/8” drill guide to keep it square with the part. The bench setup for this technique took a little thought, but ultimately worked out well. I deburred each hole slowly, regularly checking the depth with a screw head. A little care and patience resulted in really good countersunk holes. [#30 Countersink Cutter, #40 Countersink Cutter; Microstop Countersink Cage; Electric Drill, #19 Countersink Cutter; Deburring Tool, Drill Guide] Prime 3/8/24 – 0.2h 3/9/24 – 0.9h 3/12/24 – 0.3h 3/23/24 – 0.1h Priming followed my standard process of scuffing, cleaning, degreasing, and priming parts after they are fully prepped and ready for assembly. In addition, I used a Q-Tip to prime the holes that had been countersunk in the aft-center bulkhead flanges. [Grey Scotchbrite Pads, Bon-Ami Cleanser, Dupli-Color Degreaser, Rust-Oleum Automotive Self Etching Primer (Green – Rattle Can)] Assemble 3/17/24 – 0.5h 3/24/24 – 2.4h 4/5/24 – 1.1h The first assembly step was installing the nutplates to the top flange of the aft-center bulkhead. Once again, I hung the spar from the edge of the workbench and clamped it securely in place. I then used the pneumatic squeezer with flat sets to set the rivets for the nutplates. Attaching the side angles came next. The instructions specify inserting 4 AN-6 temporary bolts through the side angle and spar webs. I decided to get some 5/8” bolts at the hardware store for this, so I wouldn't damage the AN-6 bots and nuts that will be used for final assembly. I started riveting with the 2 flush AN426 rivets. That allowed me to back-rivet with a small back-rivet plate before the universal head rivets were in the way. From there I switched to the C-Frame for the universal head rivets using the same technique as the previous step. The bearing bracket assemblies, which had counter-sinking issues earlier, also had some riveting problems that led to yet another trip to the Vans webstore for replacement parts. The first issue is the AN426AD3-7 rivets specified for the bearing brackets are too long to double-flush rivet. The shop head complete fills the countersink and leaves a significant tail that has to be filed flush with the bracket. I used 3-6 rivets during my second attempt, which worked much better. The 3-6 rivet still leaves a tail, but it is much shorter and easier to file flush. The other gotcha is the riveting method. I chose back-riveting with the part securely clamped to a small back-rivet plate. This method works well as long as you account for the actual bearing that sits just proud of the bracket. In other words, the assembly has to be clamped to the back-rivet plate in a way that allows complete back-riveting without affecting the bearing. I didn't account for that correctly the first time and the result was a very stiff bearing sandwiched inside the bearing bracket assembly. I ended up removing the rivets to pull the assembly apart and inspect the bearing. The bearing was fine, and moved freely and smoothly outside the bearing assembly. I was more careful with the bearing placement relative the back-rivet plate for the second attempt, and the bearing now moves freely in the assembly. [Pneumatic Squeezer, 1” Yoke, 3X Rivet Gun, Back Rivet Plate, Back Rivet Set, C-Frame, Cupped Set]