Month: October 2019

I finished up the Spar and stringer countersinking work tonight, everything went quite well. The only issue I had was when I tried to use the drill press for the stringers. After a lot of setup time, and lots of clamping, the piece moved slightly and I ended up with a lopsided hole. I switched back to using the drill after that mistake, as it’s easier to feel what’s happening and stop or adjust if needed. The enlarged hole will need to be drilled out to fit a larger rivet, which shouldn’t be a problem. Given that I countersunk over 400 holes, I’m ok with one error.

Then I riveted the inboard inspar ribs to the stringer web, and clecoed the stringers to the stringer web. I decided to stop there, as it’s getting late.

More countersinking on the Horizontal Stabilizer spars tonight. I finished the rear spar, and got about half way through one side of the forward spar. It’s getting faster, given how much practice I’m getting, but I think I still have another hour to go to finish this step.

I finished deburring and dimpling the HS skins this weekend, and started countersinking the spar flanges where they will accept the dimples. It’s challenging getting a perfect countersink. The goal is to have the top of a rivet be 0.007 inches below flush. Even with a well calibrated countersink, just the slightest hand pressure difference can result in a different amount. I contemplated setting up the drill press, but opted for the hand drill where I can more easily feel what’s happening. The drill press would also be a little awkward given how long the spars are (10 feet). Everything came out ok so far, I’ve finished around 50 of ~400 holes. Once I’m done countersinking I’ll also prime the inside of these holes, as they will be contacting the skins.

The last couple of nights I’ve spent time deburring and dimpling the HS skins. I peeled off the vinyl inside the skins, and on the outside to expose the holes. Deburring is fairly easy, the edges don’t take much to smoothen out, and the holes are all pre-punched to final size. For the holes, a quick debur with the tool is all I’m doing. For edges, I’m using my vixen file to remove bumps, then an edge deburrer, and then a small file. The combination of tools gives a good outcome. I was only able to finish dimpling one side of one skin tonight, I just can’t stay awake any longer.

Tonight I started by addressing an over-sunk hole on the spar. I reamed the hole out to #30 size, then countersunk for a 1/8th rivet. Then I trimmed a 4-5 rivet to 4-4.5, and riveted it in place. This is the very middle rivet on the top of the spar, so it even looks symmetrical.

Then I used a beam-style torque wrench to torque the rear spar nuts to 28 inch pounds. The tool is easy to use for these low torque settings, and apparently sufficiently accurate.

Then I match drilled some holes for the inboard most ribs, then dimpled all the ribs, except for the specific holes that will take screws for the fairings etc.

Here is the forward spar with the inboard ribs clecoed on for match drilling. They are set at a 10 degree angle:

I used the squeezer to dimple the ribs. It was fast and easy.

Stack of dimpled ribs:

I finished up the riveting for the forward spar doubler and caps tonight. A variety of rivets are required due to the various combination of materials getting riveted. Everything came out nicely. I will have to fix one rivet hole that was over counter sunk, probably drilling it out to the next larger size rivet (1/8).