NOTE: This step contains several laser-cut parts that Van's determined should be replaced. Therefore, I will only be able to prep the punched parts in this step for now. I will finish the parts prep and assemblies when Van's sends the replacement parts to me.
The laser-cut replacement parts arrived on 3/28/24! I got quite a bit done in several steps while waiting for them, and the shipment of replacement parts timed out well to keep the build sequence on track. I'm back into full-on build mode :).
Initial Prep (Debur, Trim, Drill, and Cut)
2/26/24 – 0.8h
2/27/24 – 1.0h
3/2/24 – 1.1h
3/3/24 – 0.3h
3/29/24 – 1.9h
A few parts in this section, including the bulkhead bars for this step, are manufactured from a single piece of aluminum and have to be separated. I set up the bandsaw and separated all of the parts for the mid-fuselage bulkhead section. After the standard hole and edge deburring of all the parts for this step, I skipped forward a bit to complete the bulkhead bar assemblies. I bought a handful of 3/8” bolts and nuts at the hardware store, and used those to temporarily bolt the bulkhead bars together, I then inserted a 3/8” bolt with 1/4" worth of nylon and metal washers into the outboard-most hole of the bulkhead bars to prepare for double-flush riveting later in this step.
[Band Saw, Flat File, Hole and Edge Deburring Tools]
Final Prep (Dimple, Countersink, and Shape)
3/3/24 – 0.4h
3/22/24 – 0.1h
3/31/24 – 0.4h
The two pairs of F-01405B Bulkhead Bars are assembled by double-flush riveting them together before they are bolted to the Bulkhead Bottom Channel and eventually bolted to the rear spar of each wing. The plans make it very clear that the bars are to be double-flush riveted, but the plans omitted the step to countersink the holes for the rivets flush on the exterior surface of each of the bulkhead bars. It's been awhile since I've done any countersinking, but the eight countersinks (two on the exterior face of each bar) went well.
After the bulkhead bar assemblies are riveted together, the outboard hole that attaches to the bulkhead bottom channel is reamed to final size with a .311” reamer. The plans recommend using a drill press at low speed for reaming whenever possible. That is certainly an option for this hole, but is more problematic as the bulkhead assembly comes together and is more difficult to position and secure for drilling. I decided to use an electric hand drill and drill guide with a 5/16” guide hole to ream all of the holes in this step. I found that to be a really good technique to keep the drill square with the holes, while maintaining flexibility to reposition for other holes relatively quickly.
The other final prep operation in this step is dimpling the outboard holes on the side channels and the bottom flange holes in the bulkhead bottom channel. The drawings for this step clearly outline the #40 holes in the side channel that are not dimpled as well as the 3 #30 holes in the side channel that are dimpled. The pneumatic squeezer clamed to the work bench with standard diameter dimple dies did a nice job with the dimples.
[#30 Countersink Cutter; Micro-stop Countersink Cage; Electric Drill; 0.311 Straight Flute Reamer; Drill Guide; Pneumatic Squeezer, #30 and #40 Standard Diameter Dimple Dies]
Prime
3/3/24 – 0.3h
3/12/24 – 0.2h
3/31/24 – 0.6h
Priming followed my standard process of scuffing, cleaning, degreasing, and priming parts after they are fully prepped and ready for assembly.
[Grey Scotchbrite Pads, Bon-Ami Cleanser, Dupli-Color Degreaser, Rust-Oleum Automotive Self Etching Primer (Green – Rattle Can)]
Assemble
3/16/24 – 0.9h
4/3/24 – 2.4h
4/4/24 – 1.5h
I started the assembly step with double-flush riveting the bulkhead bars to make bulkhead bar assemblies for the port and starboard sides of the bulkhead. As mentioned above, I prepared the bulkhead bars by countersinking the exterior face of the rivet holes. I used a small back-rivet plate and back-rivet set in the rivet gun to do the double-flush riveting. I found that the shop-head side of the rivet was not quite flush when the rivet was set, so I filed the shop-head side down flush with the face of the bulkhead bar and reprimed that area. The result was flush and tight rivets on both sides of the bulkhead bar assemblies.
The remainder of the riveting for this step used AN470 rivets, so back-riveting on a plate was not an option. Most rivets are also out of reach for a squeezer, so this became an opportunity to try a different riveting technique. I've primarily used my 22” C-Frame for dimpling, but it can also be used to set rivets. For this step, I inserted a 1/8” cupped set in the base of the C-Frame and a flat set in the C-Frame ram/arbor, which was attached to the 3X rivet gun. I used some scrap lumber to level the parts with the cupped set in the C-Frame, inserted the rivet, aligned it with the C-Frame cupped set, and set the rivet. This technique worked really, really well. All the rivets were set successfully with no re-dos and no “smiles”. I definitely recommend this technique to everyone who has access to a C-Frame. There are a couple of things to consider, though. First, my cupped set, which I also use with the pneumatic squeezer, is now a permanent attachment to the C-Frame die holder. All of the rivet hits and pressure on the set and holder made it impossible to separate the tools, and I had to buy a new cupped set for my squeezer and a new die holder for the C-Frame. The flat set in the C-Frame arbor also needed to be replaced. The stem of the flat set broke off inside the arbor, and there is no way to get it out. The flat set still works with the arbor, but nothing else will fit. Once again, a quick visit to the aviation tool supplier was needed for a new arbor and flat set. Even with the tool issues, riveting with the C-Frame was totally worth it!
The final task in this step is to ream the bolt holes in the bulkhead and bulkhead bars, and install the bolts that attach the bulkhead bar assemblies to the bulkhead. The directions on the order to ream the holes makes a lot of sense when you're actually completing this step. First you ream the outboard holes in insert that bolt, then secure the bulkhead bars in place with a cleco (a bit difficult since the cleco hole in the bars and the bulkhead didn't align very well), ream and bolt the inboard holes, then finish by reaming and bolting the two center holes. Once again I used the electric drill on low speed and the 5/16” drill guide to keep things aligned during the reaming process. The AN5 bolts, washers, and nuts are installed with a torque wrench set to 100 – 140 in-lbs (I used 130 in-lbs based on a 15 in-lb drag measurement). Pay attention to the drawings in the plans – the inboard bolts use three washers, and the outboard bolts only use two.
[Pneumatic Squeezer, 1” Yoke, 3X Rivet Gun, Back-Rivet Set, Back-Rivet Plate, 22” C-Frame, Cupped Set, Flat Set, Torque Wrench, 1/2” socket]