June 24, 2007

Fabricating the Tie-Down Assembly - 5.5 hrs.

Today I got a lot done. I started on the fabrication of the tie-down assembly by marking and pilot-drilling the aluminum bar used to make the spacers that go underneath the tie-down bars.

As you can see above, I thought it would be easier to drill out the lightening holes first, then cut each spacer from the bar. One big piece is easier than four little pieces to work with and clamp into place in my drill press.

I do not have a fly-cutter. So I considered whether I should wait and buy one, or try another method. In the end, I decided to try my 1-inch hole saw so I could keep going on the project. It worked beautifully. I went slow and cut halfway through, then moved on to the next one.

Then I flipped the bar over and cut through from the other side to finish the cuts. This worked out very well. It produced nice clean holes with very little clean-up or deburring required.

Here you can see all four holes cut according to the plans, with the plugs that were removed in the process. I highly recommend doing it this way before cutting the individual spacers apart. It's so much easier to handle and work with one large piece rather than four smaller ones. Next, I used my die-grinder with a 1-inch scotchbrite wheel, to deburr and smooth the inside of each hole. Now it's finally time to cut them apart.

I'm so glad I have this little bandsaw. With a metal-cutting blade installed (18 t.p.i.) it cuts through it like butter. I was done with this in no time.

All cleaned up! Each spacer was run on the scotchbrite wheel to deburr the edges and surfaces. Here they are, laying on the spar, ready for drilling to the tie-down bars.

Here are the tie-down bars, after being polished and deburred on the scotchbrite wheels. They are ready for drilling to the spars with the spacers.

I didn't get a shot of them clecoed and drilled to the spars, but here they are immediately after drilling. They are deburred and ready for a shot of primer. I just used the rattle-can for this small batch of parts.


Here they are primed, riveted together, nutplates installed, and ready to be tapped for the tie-down bolts. Then they 're ready to install on the spars. I'm going to quit here for the night and let this primer dry completely. It's been quite a night!

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