Over the last few days I’ve started working again on fitting the F-711 and -712 bulkheads to the F-779 tailcone skin. It’s still turning out to be a pain in the ass. I also pulled out the tailwheel mount weldment and spring, and cleaned a little rist off the weldment – nothing too serious.

After spending hours and hours trying to get the skin and bulkheads sufficiently lined up to get clecoes in holes, I did some research and found out that Vans is apparently shipping a new F-779 skin that fits better than the old ones that were shipped a couple of years ago.

So after evalating the monetary value of the time I was spending and the frustration I was experiencing, I ordered a new skin. Hey…I buy really expensive things for the Air Force, so I’m used to throwing money at problems. It’s just not usually my money!

With the firewall riveted, I started in yesterday on the F-705 rear spar carrythrough bulkhead. First order of bidness was to hit some of the previously-primed parts with a coat of the interior color – Sherwin Willams JetFlex WR “Pepperdust”. The only parts I painted were the bulkhead top and seat stops, since it’ll be difficult to paint under some of those parts once they’re assembled. JetFlex WR (water reducible) goes on kinda rough, but smooths out nicely when dry. And it’s a whiz to clean up after painting – just use water!

Here’s the bulkhead top with seat stops riveted on after painting…

…and here’s the whole bulkhead with most of the rest of the rivets set. I’ll have a few rivets remaining to do, but I can get those in between other work.

Over the last few days I did just about all the riveting on the firewall. As is sometimes the case, some of Vans rivet callouts were quite short – especially on the steel gussets at the firewall corners. Rivets of the correct length were easy enough to squeeze, but I wasn’t always able to maneuver the squeezer to get every rivet. That left me with back-riveting some of the tough-to-reach rivets. Sometimes a little “english” was required with the back-riveting set, but everything turned out ok.

Here’s the completed firewall, with all rivets done except a couple I’ll have to buck by hand with Ellen’s help.

Got the firewall clecoed together for riveting. Sorry, no pictures.

With all the longeron hassle behind me, I got back to finishing up prep and priming of the firewall angles and F-705 rear spar attach bulkhead parts. I decided to try a new primer on these parts, since they’ll be top-coated with interior paint. The new primer is chromate-free, which makes it a little easier to handle. It’s also available locally, which is a bonus. It’s not as durable as the fluid-resistant primer I’ve used, but it’s a lot safer.

The rear spar bulkhead also serves as an attach point for the seatbelt anchors. The anchors come pre-fabricated, but they need to be match-drilled to the spar carrythrough/bulkhead channel assembly. This gets done by laying out a mounting hole on one bracket, bolting it to the spar carrythrough, then bolting on the mating seat belt bracket clamped around a 3/16″ spacer. The entire assembly gets aligned at right angles to the carrythrough and clamped in place. The mating bracket then gets match-drilled to the bulkhead.

One picture is worth a thousand words…

Here are all the seatbelt anchors in place.

One last hurdle to tackle on the longerons. Each one has to have a slight downward bend forward of the canopy deck in order to mate correctly with steel attach angles on the firewall. Compared to the “big bends”, these are easy – just a single downard bend to put the forward end of the longeron a specified distance below the canopy deck. Got ’em both done, and the longerons are complete – for now…

I’ve been laid up with a cold for the last week or so, but managed to get the canopy decks match-drilled to the longerons. This is a nice little test of whether the longerons are bent correctly, as the curves cut into the decks have to match the longerons to fit correctly. Here’s one deck fitted to the longeron…the bend matches nicely!

The decks actually overhang the longeron by 0.032″, so I clamped a piece of 0.032″ sheet stock to the longeron as a reference. Where necessary, I also clamped some scrap angle to hold the longeron flush to the deck during drilling.

Here’s one longeron and deck match-drilled…the other one looks the same.

Another big day of progress, I finished trimming the aft ends of the longerons. There are two cuts to be made on each longeron – one to allow the VS vertical spar to fit flush against the F-712, and one to accomodate the F-711’s HS attach bars. First step is to trim the longeron aft end to accomodate the VS spar. Here’s one cut completed on the right longeorn

I used the F-714 aft deck to make sure that the side cutouts were properly aligned.

Here are the HS bar cutouts marked, and drilling/cutting is in progress on the left longeron.

After a lot of cutting, filing and sanding, the cuts are complete…

As often happens on any project, the second part takes less time than the first…and that’s what happened with the left longeron. Trying to follow my own don’t-do-it-all-at-once gudance, I was working very slowly over the course of a Saturday. But everything was working out, and before I knew it I had a correctly-bent left longeron.

Just to make sure I wasn’t imagining things, I clamped the left longeron to the right. They match each other within 1/16″, so I think I’m in good shape here.

With both “big bends” made, I flipped the clamped longerons around and measured/marked their aft ends for some trimming that needs to be done so they fit in and around the tail bulkheads. These cuts made me a little nervous since they’re being made on parts that I just spent a lot of time on while bending.