Zipping Up the Impossible Rivet Seam

2-18-18 and 2-19-18 – 5 hours

So this session is mostly about closing the impossible back seam on my modified aileron – although my son and I spent also dimpled the second aileron.

He clecos and dimples.  A 13 year old assistant is good news every now and again!  Thanks Jason!  Look carefully, and you can see the laptop playing Pandora tunes in the background.  Also, notice the two flaps and the rudder on the wall.  We’ll be adding to that wall in this post.

Its not a red carpet, but it is a big help.  Here we are assembling the trim tab.

And so we ended up with a dimpled aileron, ready for riveting.

And here is the trim tab, mostly riveted in place on the aileron.

And we ended the day by spraying zinc chromate on the second aileron structure.  KW already got the skin.

And for this act, I will rivet together not one but two impossible rivet seams.  First I have to rivet the trailing rib inboard of the flap.  THer are 7 of these little boogers.  The rib faces into the aileron, so NONE of the rivets are reachable without “going deep” from the other side.  I had a piece of 1″ square aluminum in the shop, and I taped my smallest bucking bar onto a short scrap aluminum.  This will just reach the right area if I can just attach it properly.  It has to be flexible to get into the right spot.

And this, boys and girls, is where to use pop rivets when building an airplane.  Actually, these are worse than pop rivets – they are harbor freight imitation pop rivets.  Think of them as tiny single use clecos.  At a penny each, the cost is right.  These will hold the bucking bar in position, but allow some side to side movement and control.

An here is the jig in use.  I C-clamped the aluminum bar over a 2×4, so it can be shoved into the aileron.

Its hard to see in the photo, but the bucking bar is in there, and in position.  I got 3 rivets without moving the rig.  Riveting like this, you carefully raise the aileron with one hand while you use the gun with the other.  Like any other technique, it takes practice.

Moving up the seam, I withdrew the bucking bar and reattached it – this time in a notch I cut in the aluminum arm.  Electric tape worked well.  This got the last four rivets of the first seam.  Seven rivets in 1.5 hours!  This is why Vans suggests just pulling the back rivets.  About now, I am wishing I had!

Now I’ve switched bucking bars to reach the other (long) seam.  Too bad this arrangement didn’t quite fit due to the height of the stiffeners inside the aileron.

And now I am on to my 4th cantilever bucking bar arrangement for the day.  It looks kind of like a prehistoric spear.  This arrangement worked well.  You can also see the unzipped seam in this photo.

With the right arrangement, it only took a few minutes to zip up the aileron.  I did the previous seam while I was alone in the shop, as I needed to concentrate.  By the time I got to the second seam, class was back in session.  You can see my students busy working on their projects in the background.  This pic shows the seam about 1/4 zipped up.  I kept this bucking bar arrangement taped together, because I’ll use this on the normal aileron tomorrow, DV.

And now I have an aileron to join the “long term storage” wall of parts!  On to the next aileron, which I anticipate will be done MUCH more quickly.

This also is a major milestone.  I have now completed the preliminary structural mods to add my trim tabs.  They say to count on 100 hours per departure from the plans.  I have made two significant departures, and am coming in way under budget on hours according to that math.  Of course, I haven’t added the servos yet, nor have I wired them in to the autopilot, so I still get lots of hours to spend…

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