Rear spar finally done… Wing skins on for the first time

I had 192 rivets left in the rear wing spar…. I finally got them all!  I did most of them while the spar was still loosely attached to the ribs.  This gave me a nice clamping surface to hold the spar steady for the riveting.  Most of the double plates were easy to get at with my longeron yoke (switching sides as needed).  My pneumatic squeezer is pretty wimpy on the 1/8″ rivets, so all of these were hand squeezed.  I picked one rivet size and got all the rivets that matched that size.  Here, I get the AN470AD-4.5 rivets to hold the aileron bracket in place.

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The inner doubler plate is really thick.  It uses AN470-AD-6’s on the fork part…

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… and massively long AN470-AD-8’s on the second doubler plate.  I switched to my basic yoke for those to get more reach.

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That finished the spar riveting.   Here it is with the orange tape I used to keep from riveting the rib attached points still in place.

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There is one more step left before attaching the spar to the ribs.  There is a rather dire looking note in step 6 that warns that the spar attach hole must be reamed on a drill press.

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I moved my tabletop drill press over on to my work bench and propped the spar up to make it level.  The hole was already at 11/32″, so reaming it to 3/8″ did not remove a lot of meta. (NOTE: a reamer would work better here than a bit.  I thought I ordered a new reamer but, in fact got a bit…. You should order a .311 and .375 reamer. You’ll need then for the fuselage anyway)

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I still had to rivet the spars to the ribs.  Since I could not push individual ribs out of the way anymore, it was harder to get the yoke into the tight corners.  I ended up bucking two of the AD426 rivets here.  Not a big deal.  It settled down very flush.

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I was able to reach the rest of the ribs with my 4″ flat nose yoke.2015-08-01 13.09.47 2015-08-01 15.18.32

Just like that!  I had some wing skeletons!  Section 15 done!.  They were a lot less floppy once I got everything riveted, but they didn’t seem very strong.  That was about to change.

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Time to start section 16.  The Top Wing Skins! I dug down to the very bottom of the crate and pulled out the inboard and outboard top skins.  My son and a couple of his friends stopped by.  They had a lot of fun clecoing the right wing!  Once the skins went on, the wings tightened up right away.  They feel very solid (and are getting heavy!).  I’m sure they will really pull it tight once I rivet.

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My son and his friends got bored and left after a while.  I did the left wing on my own.  I used a pin punch to help me line up the ribs (or used a step ladder to reach down inside and move the rib into position).

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The prepunched holes are amazing.  Every hole in the skin lined right up with a rib flange. My father-in-law told me horrifying tales of rivet fan spacing lines on skins and carefully blue lining the rib flanges.  Then, the ribs where nudged into place until the blue showed through the hole and drilled.  It was quite tedious!

The whole cleco action on this kit took me about an hour, tops.  Most of the holes are already final drilled to size.  I just need to dimple.  Very happy to be doing it this way.

Well, most of the holes are final.  You need to final drill through the doubler plates.  I snuck over to the workshop early Sunday morning and reamed them out before church!

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You also need to match drill and final drill some of the nut plate holes.  That went pretty fast as well.  The blue mark is to remind me where the #19 holes for the nut plate go.  My wings were upside down relative to the plans, so I was extra careful

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Where the skin hangs out past the rear spar (out where the gap farings go), you need to dimple one hole for a #8 screw head.  Again, the plans have dire warnings urging caution.

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I carefully smoothed the hole with a deburring bit, a hole deburring tool, and a rolled up piece of sandpaper.  They were very smooth by that point.  I carefully squeezed the dimple.  They both came out very clean.

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The next step is to gently countersink the wing skin over the doubler skins.  The skins are pretty thin for countersinking, but with the doubler plate underneath and the undimpled rib flanges below, that’s what the plans call for.  There is yet another dire note telling you it is better to be shallow than to be deep on the countersinks (up to 0.005″ shallow).  I wanted to start on that task fresh next week, so I just stripped off some of the blue plastic to get good access to the holes I need to countersink.

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Next week, I’ll countersink the wing walk holes, do some skin fitting (the corner where the inboard and outboard skins meet the tank skins gets shaped to make a smooth edge), and get some dimpling done.  I’ll probably get to riveting in two weeks.   There are a lot of rivets!  I’ll do it with my back rivet bucking bar and a 12″ back rivet tool.  This should give me a very clean top surface.

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