Initial Fuel tank Fit and more on the revised joiner plate fabrication

Only one thing to say about a modification from the original plans - it is HARD! More on that in a bit. Here are some lingering pics I tool to show the initial fit of the left fuel tank, top wing skin, and LE. Looks pretty close even without cinching anything down with the straps:

And I marked the inboard rear tank rib flange hole locations just to see where they lined upon the flange:
NOte the severely out of alignment rib to rear baffle holes on the right - not sure why these are so off but will have to check ribs and straighten flanges again for resorting to anything else.

Then I marked the basic location of the holes for the #8 screws that will attach the tank skin to the joiner plate. I am not going to use the stock joiner plate, but wanted to see where the holes ended up being positioned out of curiosity.

Some how the spacing on the top of the joiner was reduced from the 11/16th of an inch, so the hole location for the screw and nut plate is very close to the edge. Not sure if a dimple can be applied with it that close to the edge. Enough about the fuel tanks. The rest of my final weekend while on vacation was spent working very hard on the modified joiner plate.

I began by removing the fuel tank and putting it back in the cradle. I then removed the left wing LE and placed it on my work table, after removing all the skin to rib clecoes for the first inboard W709 rib. SO the two most inboard ribs are not attached to the LE skin:

Then I took some measurements on the main wing spar to verify that the center holes of the 408 rib and the 709 rib are in deed in the same place. This was painful, as there was no easy way to find a reference on the main wing spar for the W709 rib holes. I don't even remember exactly how I did it, but I did confirm that the center holes of each rib are in fact aligned with each other, so that was good news. This means that I could use the center hole of the 709 rib and the one I drilled in the second 408 rib as a starting point for marking and drilling holes.
Here is the 709 rib on the left and the 408 rib on the right, flipped so that the tops and bottom LE skin flanges of each rib are matched up with the correct top/bottom orientation.Note the difference in the length of the rear flanges of both ribs:

As shown in this next photo, I marked the location of the pre-drilled hole in the 709 rib on either side of the center hole onto the rear flange of the 408 rib:

You can also see the two outboard holes in the 709 rib that will not be usable on the 408 rib because they are outside of the rear flange of the 408 rib. The two most outboard holes were drilled by me to match the hole pattern in the wing spar. Instructions said to drill new holes using the hole pattern in the wing spar,which is what I did. The two holes inboard of those holes are the original factory holes which Vans says to "abandon." Easier to view in the pic than explain. I did decide to go ahead and use the two marked holes on either side of the center hole for the 408 rib, but I have some questions for a tech counselor about where exactly to drill the remaining holes - I meet with him tomorrow after work to discuss.

Next is the hole spacing of the first 408 rib in the main wing spar. I needed to compare this hole spacing to that of the 709 rib to try to determine how the rivet holes would line up (or not). IF anyone i interested, the casual observer might say that these holes are spaced about 1 inch apart. My more exacting measurements revealed that these holes are actually 31/32nds of an inch apart. Consider it useless info, as is most of this post if you are building the stock wing. You can also see my intended center line and the one that I actually mistakenly marked and drilled. We shall see how this works out.

Oh yeah, NOw I remember how I checked the center of each hole pattern cuz I took a pic of it. I used a flat wood block held along the spar flange and ran my ruler up against the wood block. GENIUS!

Next I took the original 408 rib and clecoed it to the new 408 rib to mark the existing holes in that rear flange so I could compare spacing with the 709 holes I marked previously. Why is this so important? Too many holes can weaken the part, and not enough holes can created stress points in other parts of the rib during flight. This needs to be done correctly.

And here are all the holes marked on the rear flange of the new 408 rib:

And now for the infamous hole drilling exercise of the rear flange of the new 408 rib. I had to remove the LE skin to do this, and I also had to reverse the orientation of the rib on the spar so that I could afix my square to the wing spar to ensure that all holes drilled in the rear flange of the rib are straight, and therefore the skin flanges of the rib should also be straight. THe tie down bracket gets in the way for this rib so you have to squaer it from the other side. Since the center hole was drilled correctly it did not matter how you positioned the rib on the spar. I'll just run these as a series of pics since they pretty well show the procedure I use. The only trick was that I had to use a different approach to clamping the square to the wing spar, since there is no spar bar to keep the square from sliding off the rounded edge of the wing spar flange and web. I was able to figure this out but it took some serious time to get it all secured properly before I back drilled the two additional holes into the rear flange of the rib.

And two new holes successfully back-drilled:

WOW! I never even got to the part about forming the new joiner plate/subskin for the LE! I will have to get to that tomorrow as it is past my bed time. I will just say that I spent most of my day today and part of yesterday trying to form this part. It was real bitch and I used a large number of techniques that I will detail tomorrow.