Started working on F-704 bulkhead^5h

Finally, started working on the central bulkhead.

First, I drilled the holes for the SB625-7 bushing. There are 12 of them. 4 are the holes for the rudder cable and 8 for the electrical wiring.

I marked the estimated location of the holes and carefully drilled them with the unibit. Well, it turns out the two electrical holes are somewhat misplaced: they interfere with F-704C/D parts once upsized to 5/8". On top of that, it seems like the wires going through these holes might interfere with the wing spar web.

All in all, it is not a big issue as there are a few other places holes could be drilled through the F-704 bulkhead if needed. I will estimate the wires I need and decide if I want to drill more holes.

The positive thing, however, is that two (four, if you count both front and aft) holes for the electrical wiring in the center were drilled already. And they are sized 3/4", which is even better.

After that, I worked a bit on the control column. I used my mill to locate the holes on the column mounts and drilled them. The plans suggest match-drill the remaining holes through the bulkhead. However, I don't really want to put a drill through the holes in the bulkhead bars. Instead, I used my transfer punch to mark the hole center on the column mount.

Then I used a wiggler tool on my mill to locate the hole, and drill it. The wiggle is surprisingly accurate, with some patience and a lot of light, you can position the mill spindle very precisely.

After that, I worked on control column parts for a bit. I machined the bushing in the lathe.

And I filed the control sticks with the file. I got parts to fit, but the bushings are very tight in the control sticks. I ordered a reamer to clean the hole in the control sticks. Another recommendation I saw on VAF was to sand the middle of the bushing a bit (to make it the form of an hourglass). Either way, I will work on that later once I get the reamer.

I also need to fiddle with shims a bit. I used regular AN960-10 and AN960-10L washers, but I cannot get the exact dimension I need. I will try to sand a washer a bit to make it a perfect match for the gap I have.

The assembled control column.

Finally, I installed the nutplates. Which was uneventful, except that I managed to screw up the outermost countersink on the front bulkhead (because of poor support of the countersinking cage). However, since I use NAS1097 rivets for nutplates, I simply upsized the countersink for the regular AN426AD3 rivet.