Bulkhead Bottom Channel
First of all the Bulkhead Side Channels and doublers are riveted onto the Bulkhead Bottom Channel.
The manual gets you to temporarily cleco the Mid Fuselage Brace to the side channels to help with correct alignment. I also checked with a set square to make sure … I found a slight tweak was needed to make it spot on.
I managed to squeeze all the rivets …
… the ones near the Bottom Channel flange needed the Longeron Yoke.
The rivets on the outside edges are not set at this stage.
The Bulkhead Bars are clecoed together and alignment is ensured by a temporary 3/8″ bolt, with a 1/4″ spacer between the tongues. I had a piece of 1/8″ Aluminium scrap, so I sandwiched two plates together.
I couldn’t find a 3/8″ bolt in the kit, so I had to lash out and buy one!
I found that the edges of the bars were not brilliantly aligned, but relaxed once I realised that the holes were exactly matched.
The bars are double-flush riveted, & the manual suggests AN426AD4-6’s, but I found they were just a bit too long for the shop head to fit flat in the countersinks. On the second bar I trimmed the -6 rivets down to about -5.5, and they fitted better.
I’ve read ahead to try and work out why they are flush both sides, but not worked it out yet. Anyway, I decided to put the manufactured heads next to the channel web. I think it’s maybe to help with clearance when the bars are removed and re-inserted later in the build.
Holes are now rearmed in a fixed order to ensure perfect alignment.
As advised I used the drill press on the lowest speed to ream the 0.311″ holes, from the forward side.
As holes are reamed, temporary bolts are inserted. I checked the reamer was exactly perpendicular with a navigation protractor!
Once the drill press and supports had been set up, it was a quick job to ream and attach the bars.