Z Bracket Nutplates, Drilling and Countersinking

Time: 6 Hours

Today started with riveting the K1000-3 nutplates on the z brackets. There are three per bracket and 12 brackets that need them. I set up the squeezer and went at it. It didn’t take too long once I had the setup all done.

You can see one bracket is missing a nutplate! I ran short since I used 4 of them when I was drilling the brackets and used the nutplate as a jig. The drilling process started enlarging the holes of the nutplate after a a couple of brackets so I had to use several. I also used 2 extra when riveting them to the main spars and had to drill out a rivet causing damage to those nutplates. I placed an order with Aircraft Spruce for some more and will finish when they arrive. Next up was to match drill the tank skins to the ribs and baffle. I set up the drill with my #40 reamer and hit every hole, and there are a bunch! On each of the ribs there is on hole that needs to be drilled using the skin as a guide so I did that as well.

After those holes are drilled I opened up the lower half of the tank to get access to where the stiffeners go. I clecko’d those and reamed them as well.

I then removed the stiffeners and closed up the skin and repeated everything on the other tank. The plans call for countersinking all the holes that run spanwise and connect the tank skin to the baffle. This is done rather than dimple so that the installation of the baffle, durning tank sealing, is easier as it would just slide in and not fight with the dimples. The skin is only .032″ thick and the thinnest that you can do countersinking on. You do the countersinking with the skin clecko’d to the baffle so that the holes in the baffle will act as a guide for the pilot on the countersink bit. After removing a strip of the blue film, I set up the bit/cage for the right depth and started on the lower side of the right tank skin.

I was a little nervous about countersinking the skin but it went well and I had no problems on the lower skin. My shoulder was a little tired from all the drilling and decided that this was a good time to call it a day and watch some football. So next time in the Hangar I will finishing the countersinking on the right tank and both sides of the left tank.

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