Prime time — Getting a serious start on the rear fuselage

When I left off on Wednesday, I had basically finished priming the small parts of the rear fuselage.

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The next step is to deburr and prime (yes more priming) the j-stiffeners, the longerons, the rear bulkhead, and the tiedown block.

The longerons are about 8 feet long and very roughly cut.  In the first steps of the section, I had to cut two small tabs off with the bandsaw (very thick stock).  I cut them a bit long and decided to file them down to smooth.  I also smoothed all the small tags left from the CNC cutting process.  The longerons are a bit longer than one of my work tables, but I just ran it across both and clamped it down.  Making more magic pixie dust before heading over to the scotchbrite wheel.  The only downside was that due to the position of the table with the wheel, I had to open the garage door and let in the 36 degree air!

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I similarly filed and deburred the j-stiffeners while I was at it.

I looked ahead at the next step and figured that I could prime the first rear bulkhead at the same time as the longerons and stiffeners.  To do that, I had to do some match and final drilling through the bulkheads, the vertical stabilizer, and the steel rudder hinges.  The instructions note that you need to drill these holes carefully and keep them perpendicular to the surface.  It seemed hard to get the whole stabilizer into my drill press, so I made some drilling blocks with #30 and #40 holes as needed.   I didn’t even have to pull the vertical stabilizer down from the wall!

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I had to modify the block as I went along to reach around some clecos and to twist down to get at the tiedown attachment, but it worked pretty well.

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I added some Boelube to the drill bit for the cutting and had to turn up the air pressure in the drill.  The holes came out nicely.  The picture below is the tiedown block.  You pull the clecos, drill a #12 hole, and slide in a AN3 bolt to keep the alignment straight.

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I dimpled and countersunk the parts to get ready for riveting tomorrow.  Then I deburred and prepped the parts for priming.

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There was a lot of stock to scuff.  The j-stiffeners were a pain because all the curves made it hard to reach the surface for cleaning.  In the end my hands were pretty blue-grey from the aluminum dust (at least it is better than argyria which turns you blue permanently!).

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I had some long pieces of paper left from uncrating the wings, so I used that to keep my tables clean.  Its a lot of priming work.

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It was pretty cold in the garage, so I warmed the primer with a hot water bottle before spraying it.  I also used a heat gun to warm the parts before spraying.  The propane heater is working pretty well.  I ran the temperature from sub 40 degrees up to almost 70 degrees.  It took about two hours to cool back down to 50 degrees.

In the end, I  had a huge pile of primed parts.


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Tomorrow, I’ll rivet the rear bulkhead and tiedown and start prepping the rest of the bulkheads.

This goes a lot faster when you work on it every day!


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