More riveting the aft fuse (bottom skin) - 2.5 hours

I putzed at riveting the Aft fuse tonight. Admittedly I am not enjoying this very much. I riveting by myself and its not very easy. I'm staring by riveting the bottom skin and then will work my way up, alternating sides as I go. The difficulty is trying to hold the gun in one hand and the bar in the other at such an awkward  position. After a bit of head scratching, I finally figured out to put the back rivet set on the gun, and use my 3"x 1" tungsten bucking bar as a backing bar. I have to admit the results are extremely good. It still feels odd and sometimes its tough to get the bar nice and tight when your arms start getting further away from your body. But at lease the adjacent cleco gives your fingers/bar something to reference to ensure proper placement.

Started Riveting the Aft Fuse - 2 hours

Spend a very small amount of time on the build. I started the riveting process. I'm dreading this as I have not really riveted in quite some time.

Began assembly of the aft fuselage - 5 hours

Nice big day in the garage today. I started the fuselage assembly with riveting both the F-729B angle and the autopilot servo mounting bracket on the F-729 rib. Rather than squeeze the rivets, I opted to start the set with hand bucking them and then finish with the squeezer. I find that the result is much better and consistent set rivets as the AN470 rivets tend to slump if your not careful about being perfectly centred on the rivet head. The setup for clamping takes some time.


Next I began the long tedious process of cleco'ing the aft fuselage together...Again.


much of the time is taken on trying to get the fuselage perfectly straight.

Primed the exterior mating surfaces onf the Aft Fuselage Skins - 2 hours

Spent a little bit of time priming the mating surfaces on the outside of the fuselage skins. To determine how much to prime, I temporarly clecoed the two pieces together and marked the piece with a sharpie. Then I knew where to mask off. A wipe with MEK, then scuff with maroon scotchbrite and wipe with MEK and then prime.
Only the bottom skins get a little TLC. There is no extra exterior priming on the side skins.

Some closeups for reference.

Debur, Prep, Dimple and Prime Aft Fuselage - 6 hours

Not much in the way of pictures, It’s taken me a couple of evenings to disassemble, debur all the holes (This took some time as a few of the holes gave me some trouble...The F-711 bulkhead holes that were extremely difficult to cleco and a few holes had some nasty burrs) it takes a little extra care to debur. A few holes I buffed with some maroon scotchbrite. Next I broke all the edges with a file and smoothed them with the 3m wheel. I worked the edges that overlap other skins with the edge forming tool. After that I dimpled all the holes with the exception of the F-706 bulkhead holes and the two holes for the rudder stop.

Lastly everything was scrubbed with maroon scotchbrite. Degrease wipe, MEK wipe, Acid wash with Cleanbrite, another MEK wipe and finally prime.

Dimpled and Primed Aft Fuselage Bulkheads - 2 hours

Small day, I deburred and dimpled the bulkheads. Then I touched up the primer after dimpling.

Installed the Autopilot Pitch Servo - 5 hours

One last thing I needed to do before disassembling the aft fuselage was to install the autopilot pitch servo. Unfortunately for me, this is a long a tedious process as I have not drilled the F-728B and F-729B angles yet. (When I drilled the angles on my first attempt the holes did not appear to line up properly, hence when I reordered pieces for me second attempt, I left them undrilled so I could drill them one I can confirm proper alignment).



First order of business was to cleco the top skins to the aft fuselage, this will ensure that the F-706 pieces are all in proper alignment. I could then check alignment of the bellcrank bolt. Alignment looks very good compared to the first attempt.



Oddly enough the factory holes in the channels/webs were spot on. This lead me to believe that on my first attempt there was something up not factory related that caused my alignment to be out. Perhaps the assembly I had originally made was ok, just it not being cleco'ed into proper positions made the alignment way off. Oh well... i'm good now.

I then managed to drill the bellcrank bolt holes F-728B and F-729B angles using pieces from my first attempt as a guide. I set up the drill press and used a 1/4" bit and drilled the holes, then reassembled in the aft fuselage.

Next I needed to locate the autopilot mounting plate 3.43" measured from the center of the bellcrank bolt to the front face of the mounting plate flange. Not as easy to measure as you would think as the angle of the mounting plate is not perpendicular with the top or bottom of the F-729 channel. I figured the best way was to measure and mark a plywood spacer to help.


Once the mounting plate is positioned, its easy to drill the #30 holes at the top. The holes along the bottom flange take a bit of head scratching. The installation manual states the bottom flange can be removed, but I decided to keep it as it will provide a more solid mounting point. I marked out on the bottom of the flange where the mounting holes for the adjacent channel line up and choose to drill new holes in between, like this. 

I figure it's most advantageous to stagger the rivet holes rather than keep then aligned. Also, figuring out the distance from the edge to drill the #40 holes was a bit of a head scratcher. Since the mouning plate is 0.050" thick I will countersink for the rivets. The MIL-Spec states minimum edge distance for 3.32" countersunk rivets is 0.219". I opted to use 0.240" from the edge of the flange. Once the holes were drilled in the flange, I used the long #40 drill bit to drill to the bottom of the aft fuselage.