I made the uprights that connect to the center section out of 2x2 1/8 6160 24 inches long. The center section had some nice wood blocks already bolted into them, so I used that for my interface.
With a way to connect the center section to my jig, I started welding up a T structure that would support the wheels. The main structure of the jig was a 64" long 2x2 1/8" square tube that falls directly under the center section and connects to the main wheels and the 24" center section up-rights. The structure heading aft is 1x1 1/8" 6 feet long.
After I had the main T structure built up I ended up going back and re-inforcing all of the 1x1 connections with 1x2 angle. The jig was going to have two front wheels directly under the center section and one rear wheel under the tail, so there shouldn't be that many torquing forces on these joints, but with that said, I had this bad vision in my head of this connection failing sending 1x1 up through my fuselage.
The main structure complete:
This was really an after-thought, but I ended up really liking it. I was not exactly sure where I was going to need support under the belly of the fuselage. I was going to start putting cross braces in the main section heading aft, but I had some 5/4"x10" boards around and it just so happened that I built my structure ~9" wide. So I lag bolted the 10" board to the aluminum structure and everything stiffened up really nicely.
From there, I slide the jig under the fuselage and lifted everything into place. After that I added a couple more bolts to secure the uprights to the jig.
Done! I used a lot of material that was just around the shop and I when with a lot of the lengths that I already had sitting around. The height ended up being perfect and if I were to do it again from drawings, I would dimension everything the same way.
