Wings: Ailerons. Complete and an important lesson learned.

Completed the ailerons today. 

A bit of a story here though.

Last week, I attempted completing the trailing edge of the left aileron only.  I very carefully calibrated the countersinks in the wedge to allow the skins to sit flush.  About ten fully-driven rivets in, I gave up as the same problem I was having with the flaps was presenting itself to an even worse degree.  Specifically, the dimples on the bottom (shop head) side were collapsing into the wedge countersinks, providing a very poor finish.  I tried a) classic backriveting, b) the mushroom set and c) even using the mushroom set itself banging on a steel plate, thinking I could avoid the dimple collapse.  No joy.  Time to remove the wedge and try something else.

With pliers, I easily pulled out all the rivets that I lightly tapped in with the backrivet set.  But the other ten fully-driven ones required more deliberate removal, causing some messed up holes (since there are three separate pieces each with their own independent planarity, it's not an easy task, plus any force applied to the trailing edge can bend the constituents).  Oh well, at least they're messed up on the bottom rather than the top (poor quality image below).  A chip chaser let me separate the wedge from the skins given they were taped in.

In an attempt to solve the issue I consulted a very knowledgeable tech counselor.  It was the first time he'd seen the issue.  He thought the countersinks might be too deep.  I consulted an A&P friend of mine.  He thought the same thing.  But I didn't think that could be it since I calibrated the countersinks against a scrap piece of wedge to make sure the skins sat flush.  And if they were too deep, why was I getting a large gap between the wedge and skins?  That didn't make sense to me.  

Concurrent to all of this, I had shot an email to Van's about the flaps issue and Sterling replied that he thought the countersinks might be too deep and that my edge break might not be aggressive enough...Wait, edge break?  Uh oh.  I didn't do that.  The plans don't call for that on the flaps (yet, they should), but they do for the ailerons.  In the case of the latter, I was too concerned that, without a metal brake, I would really jack up the aileron trailing edges (these aren't nose skins or skins sitting underneath other skins like elsewhere).  Besides, wouldn't the riveting process compress everything together rendering that step moot?  

Making an edge break was not an option now that the dimples were in place on the skins and the skins were on the spar.  So, for the wedges (replacement on the left aileron, first try on the right) I reduced the depth of the countersinks:  7 clicks beyond a flush rivet for the left aileron and only 5 for the right.  The dimples still compressed into the countersinks (I redid the left first, hence the shallower depth on the right). 

And I do have ridiculously large gaps between the skins and wedge.  Not much to do about it now, other than to reduce the countersink depth on the empennage surfaces and actually make the edge breaks.  I believe it was the riveting process that caused the skin edge to lift away from the wedge and introduce the unsightly gap.  The edge break would have eliminated, if not mitigated, that problem.

Here's a comparison of the countersink depths used on the wedges.  The bottom wedge shows the original depth I had on my first attempt after calibrating to skin flushness.  The top shows 7 clicks beyond a flush rivet.  Big difference.  Yet both depths permitted the skins to sit flush against the wedge, so clearly I went too deep initially. 

The edges of the ailerons are reasonably, though not acceptably, straight.  The right side has a distinct curve to it that I'll have to bend out.  The left side is mostly fine but there are a few places I could fiddle with to straighten it out better.

Be careful using a backrivet set.  It's very easy to dent the skin.  See below:  Upper left of lightly tapped rivet has a dent from the backrivet set's collar.  And when using a mushroom set, it's very easy to mash the wedge out of true.  Just can't win!

Other issues:  Significant oil-canning on the bottom skins.  It's probably related to there being stiffeners rather than ribs.  Also, many of the top rivets on the left aileron aren't fully flush.  Since the right side is fine and my technique was the same, I suspect it might be related to the tape residue that remained when I pulled out the first wedge on the left aileron.  Example of the worst rivet on the left is below.

So, lesson learned.  Edge break trailing edges and be cautious on the countersink depth.  I'm not at all pleased with how the aileron trailing edges turned out.  But it's time to get over it and move on.  Perfection, whilst an admirable goal, isn't going to be realized on this build.  How to feel like an idiot:  Build an airplane.