I started working on the longerons tonight. First up is to cut them to length. This is a critical cut because replacing these 15′ long angles would be very expensive (both in material cost and in shipping). These need to be cut to precisely 173 7/16″. Since the ends of tape measures can have some slop in them, a trick to get more precise measurements is to position the tape measure at the 1″ mark. You do have to be sure to add 1″ to your measurement to account for this though.
The bulkheads have a bunch of separate flanges because of the tight radius of some of the curves. Some emery cloth cut into 1/4″ wide strips works pretty sell when used like dental floss.
After a lot of sanding, cleaning and priming, the bulkheads are starting to go together. Here, the F-705 bulkhead is clecoed together. Double check that this bulkhead is square before riveting since the clecos allow some play in these pieces. I could change the diagonal measurement as much as 1/4″ by racking these pieces from side to side. After assuring that everything is square, this can be riveted together. The blue tape signifies the holes that need to be left open right now since they will be riveted together with other parts of the structure at a later time.
Here is the F-705 bulkhead riveted together. The clecos near the top are there because these pieces are riveted in conjunction with other parts.
This rivet needs to be a flush head since the seat belt attach anchor extends past this point.
Here is a closeup of the upper left portion of the F-705 bulkhead showing how many holes need to be left open for later riveting.
The upper seat adjustment pieces can also be riveted on now. I used some rattle can primer on these so that I can easily remove it later when I’m ready for final paint.
The rear bulkheads are primed with epoxy primer and just need a few rivets each to join the two halves together.
The F-706 bulkhead is riveted along the bottom, but the top is left clecoed since it is riveted in conjunction with a top skin rib.
The F-711 bulkhead is riveted through the bars and around the lower curved section. The upper and lower hole in each bar is left unriveted for now.
The F-712 bulkhead is riveted together using flush rivets on the aft side since the vertical stabilizer rear spar attaches here.
The F-728 and F-729 ribs that support the elevator bellcrank are attached and everything except for F-728 is riveted in place.
For fun, I clecoed the F-706, F-707 and F-708 bulkheads to the bottom skin to see how everything fits together. The hole alignment is pretty poor. The bulkheads will definitely need some fluting before everything aligns.
I drilled the upper seat back adjustment pieces. None of these pieces have any layout holes, so everything has to be measured and drilled.
No pictures today. I spent several hours deburring fuselage bulkheads. I still have a fair amount to do before priming.
I had the day off work, so my buddy Andre dropped by and we got started on the F-706 bulkhead. First up is to drill some 0.063″ angle to a couple of support ribs. Here is the rib that goes from the back of F-706 back to F-707.
I used some self-fusing silicone tape to keep the two fittings on the pitot tube from rubbing against each other or the inside of the pitot tube mount.
I drilled the flap blocks to the sides of the F-705 bulkhead. These won’t be bolted on until much later in the construction, but it’s easiest to drill them now.
I also drilled the four holes in the top of the two F-705G angles.
…as well as drilled and filed the elongated holes for the canopy latches.
I managed to get all of the holes in the F-705 bulkhead deburred. I still need to finish the upper seat back adjustment parts, then this will be ready to prime and rivet together.
I cut all of the pieces that form the upper seat adjustment. I started to layout the holes, but I realized that my rivet fan won’t adjust wide enough. Instead of doing this old-school, I’ll borrow a large rivet fan from a friend.
The lower bulkhead needs a couple of 5/8″ holes for snap bushings to run wires through this area. Edge distance to the adjacent holes is right at the recommended amount.
The F-705D uprights need 5/8″ holes as well for the rudder cable snap bushings as well as a couple of K1000-08 nutplates each. I installed these before priming because I’m only going to prime parts now that won’t get a top coat of the interior color. I’ll also probably use self-etching primer for all of the cabin components so that I can easily wipe off the primer at some point in the future if I need to paint an area.
My buddy Andre stopped by today to give me a hand with the rear spar carry-through bulkhead. First up is to shoot the two rivets I couldn’t do easily yesterday. I didn’t get a picture of it yesterday, but I also riveted on the main spar uprights. A few of these rivets could be squeezed, but most needed to be shot and bucked. I’m definitely getting the hang of doing that solo.
The rear spar bulkhead starts with a could of beefy pieces of 2024-T4 bar stock. The lower one in this picture runs all the way across the bulkhead and carries the major portion of the load. Shorter pieces of bar stock with a couple of bends in them are riveted to these to create a socket which will receive the rear wing spar.
The lower seat belt attach points are drilled and bolted to the rear spar carry through structure. The technique here is to mark and drill one side that then clamp the other side in place with a 3/16″ spacer. An AN3 bolt is exactly 3/16″ thick, so clamping one of these between the anchors creates the perfect spacing. The holes in the top of the anchors (off the top of the picture) are held in alignment with an AN4 bolt. The other anchor can then be back drilled through the spar. You can also see here the outboard seatbelt attach points require the anchors to be cut to clear adjacent rivets. Here, the left anchor has been cut, but the right one is still full size.
Here are all four seat belt attach points match drilled to the spar.
The shorter spar bars are tapered for weight reduction. You need to make sure that the last rivet has 1/4″ edge distance all around the radius. By positioning this end first, I could easily ensure that.
Then the other end can be cut flush with the long spar bar.
While I was working on the rear spar, Andre fabricated the upper angles that will receive the canopy latch pins.
The angles fit behind the upper portion of this bulkhead. I drilled the four corner holes so that I could use rivets to keep the three prepunched pieces in alignment. The angle could then be clamped in position and the holes match drilled. I’ve said it before, but these self-adjusting clamps absolutely rock.