Scott & Tanya Card RV9A build log (N4822C)

I got back to work on the center bulkhead by installing all of the nutplates on the top flange. I installed all of these with NAS1097AD3 rivets which are 3/32 rivets with a small head (like what Vans calls an oops rivet in AD4 sizes). The deal is that the machine countersink doesn’t have to be nearly as deep and can be done with just a few turns of a deburring bit. This is the deal for nutplate installation in thin material where the surface has to be flush (nearly always). I used the same method for the nutplates in the cover brackets too.

I then started riveting the uprights to the bulkhead ends. I have seen that many people do all kinds of gyrations for driving these rivets with the C-frame. I tried it, yes it worked quite well, but was a very slow and unnecessary operation. I quickly abandoned the C-frame and jigged the bulkhead upright on the end of the bench (clamped rigid) and shot all of the rivets normally. This was much easier for me. After all of the rivets were in, I popped in the snap bushings and did some preliminary control stick assembly fitting.

I had been fretting about how I was going to make the spar blocks that are required to be exactly 1 and 7/16″ thick. I couldn’t think of anybody that I knew that had a planer. I ended up going around the garage measuring every piece of ply wood that I had (it takes an awful lot of wood to build a metal airplane). The key was finding the thinnest piece of 3/4″ ply that I could find. I found a piece that was almost exactly 1/32″ short of 3/4″. Two of these laminated together with a very thin layer of glue came out perfect with very little effort. After the glue dried, I match drilled blocks for the spar bolts and this assembly is done.

 

  

  

  

  

  

  

  

  

 

Next up is the center section bulkhead. I spent a little time digging out parts that came with the wing kit for the center spar section that makes up the backbone of the airplane. These parts are match drilled at the factory with the spars in the wings. I started out with opening up some pre-punched holes for snap bushings with a unibit. It is a bit of a scary operation to go after this beautifully anodized assembly that is matched to the wing spars (no easy replacement) with a unibit to 5/8″. Don’t just measure twice and cut once, but think three times and drill once here.

Then I assembled the uprights (fore and aft) using the close tolerance bolts to line things up. I measured the bolts and found one that was .0005 smaller than the rest. I used that one and one other to line up the parts. Match drill after everything is lined up. Next up was the shear blocks. I aligned these with close tolerance bolts and back drilled them by hand. Looking back, I probably would have just marked them with the back drilling process and then transferred the drilling process to the drill press. i.e. my by-hand drilling wasn’t perfectly square, but will be just fine.

I also match drilled the control pivot brackets (pictured) via the above concept. Then the brackets were trimmed per the plans on the band saw. Oh, yeah, don’t forget deburring both sides of any holes that are drilled. Next is to prepare and assemble nutplates on the top edges of the center section…

 

  

  

 

With everything ready to go, I setup to rivet the firewall stiffeners and brackets. I squeezed most of the rivets along the bottom and side stiffeners, then back riveted the rest. This was kind of a slow process as I back riveted just a few (4-6) rivets at a time. It also took some jigging with 4×4 blocks. Two to support the firewall and one with the back rivet plate on it. I didn’t put any rivets in that will eventually secure the recess hole in the middle. There are certainly a bunch of little thinking parts inbetween. We’re now definately building from drawings and not so much from instructions. Firewall is done.

 

  

  

  

 

While I dimpled the stainless firewall with the C-frame and a hammer, Tanya was gracious enough to wash parts in prep for primer. Then she was there the next day to even mix the primer! Am I lucky or what? The only priming process that I haven’t been able to convince Tanya to try is actually shooting the material with the gun. She doesn’t like too much responsibility in this whole thing. If the primer comes out crappy, it is my fault. She has done the rest of the entire process more than once. That is just cool.
Firewall parts are dimpled, countersunk, and primed.

 

  

  

  

 

I continued my work on the firewall with fabricating the recess cover plate. I don’t need the center recess with my engine so I just made a flat cover with some 26ga. stainless steel from Vans. This stuff isn’t fun to work with and will dull any tool that comes near it if you aren’t careful. I got to looking at the plans and noticed a rivet callout for an An436AD4-6! This is obviously a mistake on the plans and should be an AN426. I then moved on to deburring, machine countersinking, dimpling, and preparing all of the firewall parts (except for the stainless firewall itself) for primer. With a little primer, I’ll be ready to rivet things together.