Today, the real work on the wing kit begins.  Van's has you starting the wing kit by preparing the main spar(s).  I was going to work on one spar at a time, however, after I started countersinking, I decided to prepare both wing spars before moving on.

You begin countersinking the spar to accept a #8 screws that attach the wing tanks.  In order to obtain the correct countersink depth, I took a scrap piece 0.032" aluminum left over from the empennage kit.  I drilled, deburred, and dimpled the hole.  Use this scrap to set up your countersink so that this scrap will sit flush on the spar flange.

Prior to beginning the countersinking marathon, I masked off the cracks between the upper (W706D-L) and lower (W706B-L) spar bars and the spar doubler (W-706C) of the front spar assemblies.  There was a TON of aluminum shavings while countersinking and I MEAN A TON.  The goal was to keep the shavings out of any cracks where they could result in rubbing causing stressors on the spar assembly.  I used this "expensive" sensitive materials masking tape.  Don't spend the money on that junk!!  It splintered when taking it off and took forever to get it all off.  There was also a bit of tape adhesive residue that I had to remove.  From now on, I will use vinyl electrical tape (Scotch 33+).  The vinyl won't splinter and pulls off very easily.  It isn't that much more expensive than this high dollar masking tape.

When countersinking, these holes are pretty deep.  What this means to the countersink cutter, is that there will be no material to hold the countersink pilot in position to make a nicely machined countersink hole.  Fortunately, for me, there are other builders out there that published their mistakes so others can learn from them.  Without having something to guide the countersink cutter pilot, this is what you are likely to end up with (picture below).  This is from a fellow builder, Tom Wruble.  This is his "ugly.jpg" as he calls it on his web site.  Click on the link below and scroll to the bottom of the page, you can't miss it.  Thanks for publishing this Tom, because of this, I did not have one countersink that looked like this.  This freed me up to make my own, unique mistakes.

http://mywebpages.comcast.net/thomaswruble/Progress.htm

The method I used to prevent this was a derivation I took from Dan Checkoway's web site.  My technique was as follows:

• Obtained some scrap aluminum angle from Home Desperate or Menards.
• Drill a #30 pilot hole (actually several, I'll explain later).
• Center the #30 pilot hole in the aluminum angle in the hole to be countersunk and cleco it in place.

I recommend reading Dan Checkoway's web site to review is method.  His is a little more precise than mine.  Check out his method at: http://www.rvproject.com/20020502.html  I guess the big difference between Dan's method and mine is that I "eyeball'd" placement of the pilot hole in the center of hole to be countersunk.  I have to admit, all my plate nut holes look excellent with the exception of two.  Those other two....  are good but not great.

When determining the depth of the countersink, I struggled a little bit at this point because it seemed like after a certain point, there was no additional benefit of continuing to set the countersink deeper.  When I set the scrap piece of aluminum with the #8 hole on the spar it seemed to set off of the spar flange by a couple of thousandths of an inch (heck, that could be the my sample dimple to).  Going deeper with the countersink cutter did not help any.  Once the upper edge of the countersink cutter goes past the top edge of the spar flange, you won't get any noticeable improvement in the fit.  Once I figured that out, I backed the countersink cutter off so that I did not get those "lips" on the countersunk hole.

Also, because the countersink goes so deep into the spar, the scrap aluminum I was using also started being cut by the countersink cutter (See the picture above).  After one or two holes in the same pilot hole, I began to get "ugly holes" like Tom's above.  Therefore, I just drilled a series of holes in a row on the scrap and when the countersink cutter began to chatter, I used a new hole.  Hey, it worked for me.

The rivet holes for each plate nut are pretty straight forward.  I didn't need anything to hold the countersink cutter in place and that dramatically increased the speed of countersinking.  However, those holes are slightly undersized and will need to be drilled to a #40 prior to countersinking.  I then used a rivet to set my countersink depth and began countersinking. 

Van's instructions state to prime spar parts where the anodized finish has been removed.  In the picture below, you can see that the prepared holes on the left have a similar look to the original spar color while the right is un-touched after countersinking.  All I did here was take a Q-tip and dab a drop or two of Alodine 1201 in until I got adequate conversion (color).  Then I blew the holes out with low pressure air (carefully not to splatter Alodine all over) and wiped dry with a rag.  All the holes looked great when I got done!!!

There are some 60 plate nuts to countersink per spar (just to attach the fuel tanks), multiply that by two and you have 120 plate nuts.  That is a ton of holes....  On average, each plate nut hole took me 5 minutes.  That doesn't sound like very long, but that is roughly 10 hours of drilling.  That doesn't count the riveting time this will take or the 48 plate nuts you countersink for the inspection plates.  This was a very long and monotonous day.  I was dang tired of drilling!!!