March 10, 2016 - Fit and Tack Weld Aft Fuselage

With the forward end tack-welded, I was able to rotate the structure on its side.  I immediately noticed that there was too much space between tubes in some of the joints, so I had to cut the tacks and adjust the fit, then re-tack.
The two sides ultimately come together at the tail end and I had really worried a lot about how I was going to do that.
It turns out that I was able to pull the two sides together with hardly any effort at all!  I was amazed at how easily the steel tubing bent.
View from the front.

I used the Dremel tool to cut the longerons at the tail end.

I've discovered that steel wire and turnbuckles are extremely useful things when building a steel tube fuselage.

A turnbuckle in action.  Available at the aviation aisle in your local hardware store.
It's important to have the tail straight and aligned.  I used the 1 1/8" steel tube to do this.  This is the steel tube that will actually be welded in later.
I cut the aft cross-members tubes.
I hung a plumb-bob to make sure the fuselage is straight from nose to tail.
To hold the tail area in the correct position, I built a jig out of perforated steel tubing.
Doing so reminded me greatly of the Erector Set kit I had as a kid.
A good look at the tail jig.
You may notice something is missing in this picture.  Initially, I thought instead of using wire and turnbuckles for cross-bracing per the plans, I would use 5/8" tubing as some builders have done.  The primary reason was cost, as the aviation-quality turnbuckles are expensive.  So I tack-welded diagonal 5/8" tubing into my fuse sides.  But I found notching the diagonals and getting a good fit was a nightmare, and the cross-member diagonals would be even worse.  So I decided to go back to the wire and turnbuckles.  It was easy to cut the tacks and remove the diagonals from the fuse sides.
Tack-welding the aft cross-members.
From another angle.