Center Section/Seat Substructure Done

Time: 8 Hours

Another great day in the Hangar today. We had beautiful weather here in Chicago which made for a nice day with the door open. After doing some research last night and consulting with my buddy Glen I increased the space between the center section to 1.440″ to give that extra little bit of room for the eventual wing spar attachment. I also abandoned the PVC spacer idea in favor of using the bolts and several nuts to maintain the space. I did this as it was just going to be easier to get the space just right as I adjusted things.

Once I had all 8 bolts in I riveted the flange and the flange nutplates. I taped off the ones that don’t get riveted now so I would have to drill out rivets later.

That basically completes the center section, the only step left was to install the snap bushings to protect items that will travel through the section.

I set the center section as side to start the assembly of the seat substructure. When I ordered the fuselage kit I forgot to order the electric trim option so I made that order this week and it arrived on Friday. That was the first task at hand with this section. It’s funny that Van’s has this kit that has instructions and plan drawings from 1998 and now have totally different parts for the seat ribs. Back then you have to measure and use a template to cut holes for this trim kit. Now the ribs come pre-cut for it, so you have to do a little interpretation to figure things out. Once I did just that I had the 2 brackets, one for holding the trim servo and the other a pin guide, in place I match drilled all the holes.

A little time cleaning up all the edges and holes and off to the primer table.

While the primer was drying I moved on the the assembly and riveting. First up was the bulkhead and the 2 rear spar attach doublers along with the seatbelt attach point and corner gussets.

I riveted the nutplate’s on the rib angles next.

At this point you rivet all the parts for the 2 forward inboard ribs. They get the rib angle, the seat belt side attach points and a small bracket.

At this point the plans have you systematically add all the parts and rivet as you go. I was able to get some with the squeezer but moved to the double offset head for the rivet gun and my tungsten bucking bar.

I didn’t have to drill out any rivets in this section. I did however have the gun bounce off the rivet head and make a mark on the rib when I was riveting the servo bracket but not too bad and a little touch up on the primer and all was good.

So I was on a roll even though I had 6 hours of solid work in. The next step is to flip the section over and put the two bottom skins on.

I used a sharpie to mark the holes that get skipped now for later riveting. I then started the riveting working as deep as my arms would reach.

I was able to reach all but about 19 rivets with it laying on its back.

I tried to back rivet the rest but only had access to a couple as the bulkhead was to tight. I left the back rivet tape on to hold the rivets in place and stood the whole structure in its aft end. That gave me access to the rivets and it would stand on its end to give me time to get the gun and bucking bar in place. Not the easiest task but it worked. I found that the rivet that was dead center in the bulkhead, on the skins, didn’t actually have a hole in the bulkhead flange but rather a slot cut into the flange. When I dimpled the skins that dimple now sat up a little as the slot wasn’t as wide as it needed to be. I didn’t catch this when the skins were match drill since the dimples were not done. So I drilled out that center rivet and went to a flush blind rivet. This allowed me to put a lot of pressure on the skin and rivet at the same time to get the skin to sit more flush. You don’t rivet the outboard ribs at this time so that’s as am far as I could go on the skins. I only had to drill out 2 rivets as the skins were a little bouncy causing the gun to slip a little.