I haven’t made much progress on the fuselage recently due to work on the wings, but now it’s back to work on the bulkheads – specifically the F-705 rear spar carrythrough bulkhead. Here’s the 2024-T4 strap that forms the primary carrythrough load path. It gets match-drilled to the lower bulkhead channel…

…and here’s the doubler that forms the other half of a clevis with the strap (above) that retains the wing rear spar ends. This part was match-drilled in assembly with the strap and lower bulkhead channel. Nothing particularly tough here.

Here’s the entire lower channel and spar carrythrough structure clecoed together after match-drilling.

One gotcha when doing final assembly on the bulkheads…I found that when I drilled the spacer bolt holes out to 0.25″, there must have been some chips generated by the drill that scored the sides of the hole. This is in the heavy bar that forms part of the rear wing carrythrough bulkhead, so I was somewhat concerned – don’t want any crack initiators in a part of primary structure.

I spoke with my Tech Counselor, and sent pictures to Vans tech support and engineeirng (note from the future – I also talked with Ken Kruger, Vans Chief Engineer, at Oshkosh 2010) – all said that there are no issues because there are essentially no loads on these spacer bolts. They’re there only to hold the spacer in place.

See the larger picture here.

No, I haven’t been doing nothing since August. Surf on over to the Wings page and you’ll see that we’ve been working on the wings when I’ve had someone to help with riveting.

Meanwhile, I’ve been doing final deburring, priming and assembly of the wing bulkheads. Nothing too stressful here.

There are some additional cover support ribs and web stiffeners that require fabrication and/or match-drilling to the wing bulkhead. No problems here, but no pictures either…sorry!

Here are the control column mounts bolted in place after the lightening cutouts have been made. The prefabricated control column weldment is bolted in place. I had a few issues with the control column, some of the predrilled holes didn’t line up quite right.

I had a few issues with the control column, some of the predrilled holes didn’t line up quite right. I called Vans, they assured me that there’s enough play in the column mount bearings that I won’t have problems when permanently installing the column.

This is starting to look like an airplane!

Now the close-tolerance bolts are installed – a couple of them took a little persuasion with a small hammer, but that’s why they’re close-tolerance bolts, right? With the bolts and clecos installed, I match-drilled all four of these assemblies with no problems.

The next step is fitting the control column mounts. These beefy angles come with bearings already press-fitted into them, and the only prep required is to measure and drill one mounting hole. That mounting hole is used to bolt the column to the bulkhead, and the existing bulkhead hole is used to match drill the other hole in the mount.

No problems, everything worked well. There are some optional cutouts on the mounts to lighten them a bit, they’ll require a little filing and sanding.

No updates for the last three weeks, I was at Oshkosh for the entire week of the show. Lots of fun and very motivational, as always. I came back and started working on the F-704 center fuselage bulkhead assembly. There are a lot of small things that must be done to these bulkheads for them to be ready for installation. First step was drilling holes for the electrical conduits; not a hard task, but I double-checked the measurements before starting in with the Unibit. Came out fine!

The next step was to fit the left and right center section side angles to the bulkheads for match-drilling. Here they’re clecoed in place, but the close-tolerance bolts that will eventually hold the wing spars, muts be inserted so that the corresponding holes in the side angles are closely aligned.

More random parts prep on the firewall…dimpling the brake doubler and firewall itself. For some reason, I take a lot of satisfaction in a simple thing like fitting that little plate.

Dimpling the firewall…gotta make sure that the dimples go the right direction. I wouldn’t be the first builder to screw this up.

Dimpling done…looks good!

I also finished countersinking all the stiffeners on the firewall’s back side. No problems, but no pictures.

The firewall is disassembled and I’m deburring parts. I’ve said it before…if you have a Dremel tool, you gotta have a #500 abrasive wheel for it. It’s a 1″ Scotchbrite 7A Medium wheel, and is the absolute berries for deburring in close quarters. Can’t always find ’em in the big box hardware stores, I find mine in the local neighborhood hardware stores. I’m sure you can order them online, too.

The next task for the firewall is fitting the recess that accommodates stuff hanging off the back. To put it bluntly, the fit of this part sucks – especially around the top. Apparently this is a common problem, some builders use a little “manual adjustment” with hammers and wood to improve the fit, others just do the best they can and accept a couple of sloppy holes at the top of the recess. I tried the manual adjustment route and had no success so I just drilled it in assembly with the firewall, making sure to drill from the side with the stiffeners so that those structural stiffener holes would remain unmolested. The result is a couple of slightly-egged holes in the recess, but it’s not structural – so I’m not gonna worry about it.

That finishes up, for now, the match-drilling required on the firewall.