The spar is finally done….

The work on the spar really dragged on.  Section 13 is another one of those nasty little sections that just drag on and on…  It is only 3 pages of instructions, but oh, there are so many holes!

I had a long break in the work as I was off in Houston helping my brother out.  He was starting a new job (actually returning to an old one after a few years of trying a startup). He needed some help watching his family while he went to Chicago (in the midst of the Polar Vortex) and followed that with a week in frosty Delaware.  The long and the short of it is that I lost 3 weeks in the aircraft factory (but earned the love of my brother).

It was pretty cold in the shop, a pretty hash 18 degrees.  My torpedo heater brought the temperature up to almost 60, but with the high roof it just kept sliding back to freezing.

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I finally got to the point where I could install the 120 some odd nut plates.  This went pretty smoothly.

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I did mess one up when I didn’t have the squeezer set when I hit the trigger.  I managed to drill it out (with a small bit of my finger).   This is a plane building right of passage, apparently, glad to get that out of the way.

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While I was doing that, I put my son to work deburring and smoothing the lightening holes in the many, many ribs.  I had a little Scotch-brite flap wheel installed on the drill press.  It made pretty quick work of the task.

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He did some nice work!

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I was still in nut plate hell, so I let him head home to warm up. I kept plugging away at the nut plates.  Eventually, you do get to the end of it.  Yay!  All the flange nut plates are in place.  The blue tape is there to (1) keep the aluminum chips out of the gap between the flange and spar web and (2) mask it off when I spot prime all the countersinks.

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With the nut plates in place, it is time to countersink the fuel tank screw holes and the inspection plate screw holes.   There’s a couple hundred of those to do as well.  Van’s provides specs for the max hole size.  The bottom of the spar went really great.  My holes were all smooth and consistent.

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A quick hit of primer, and I wrapped up for the day.

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The top countersinks did not go as well.  I chipped my countersink bit which made very rough holes.  I ordered new ones Sunday night from Brown Aviation.  They were delayed a day (FedEx wouldn’t deliver in the blizzard), I still got them Friday.  Saturday, I finished the top screw countersinks (much easier with a good, sharp bit) and spot primed the spar as well.  With that, I finally finished the first two pages (it took a full month of build sessions, sigh).  The last page covered another dozen nut plates on the spar face, 10 final AN470 4-6 rivets at the end of the spar, and the aileron bellcrank bracket.  The hardest part of the bellcrank bracket was finding all the parts.  The W823-1 brackets were hard to dig up (they are in one of the small parts bags).

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I had to mentally put myself back into part prep mode — I really hadn’t done any deburring and priming since before Christmas. It was nice to install some green parts on the spar.

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At last, Section 13 is done!

I got started on Section 14.  It begins with some part prep.  I had to replace my bandsaw blade since some of the teeth had gotten bent and were messing with the cut.  This meant a trip to the aviation department of my local Home Depot (I was breaking for lunch and ice skating lessons anyway).  I deburred and primed the parts for the whole section.  You have to be careful because some of the left and right parts are nearly indistinguishable.  There are many cautionary notes in the instructions and the blogs to mark them before separating them.  I added the markings to drop paper so that I could keep them all straight (important since the acetone wipes off all the marks).    I put them far apart on the paper (left parts on the left side, right parts on the right side naturally!).

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The parts were rough from the bandsaw cuts, so they needed some filing before moving to finish on the Scotch-brite wheel.  The aileron brackets are very hefty chunks of aluminum.  They appear to be cut with a water jet and are very rough.  They needed some serious work in the vice with the bastard file.

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I made a lot of magic pixie dust!  They polished up very nicely though.

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That gave me a nice pile of parts to end a solid day at the shop.  I’ve got all the parts for Section 14 ready to go (including the two bearings).

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Sunday was a lot warmer than Saturday —  The mid-40’s seemed almost tropical.  It was the first day in months that I could work in the shop without running the heater.  I even left my jacket in the car!  I did have to shovel a foot and a half of snow to make a path to the shop door though 😦

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The first real step in Section 14 is to square the rib flanges.  I made a little tool from the end of a paint stir stick to check them.  Most were pretty square and didn’t need any adjustment.  My seaming pliers fixed the rest. Not hard, but there are 28 ribs to check!

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The ribs also needed fluting.  They look pretty straight, but if you lay them along a straight edge you’ll see a pronounced bow.  Three or four flutes on each side of each rib took care of that.  But with 28 ribs, that’s 150 flutes!

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Lastly, I reamed the #40 skin holes, deburred them with some Scotch-brite, and dimpled them.  I now have two piles of ribs.  After I dress the flange edges and prime, they’ll be ready for assembly.

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