More Custom Leading Edge Rib Work

Who would have thought that modifying a rib would be such an enormous task? Truth is its not really all that bad, but there are moments.....

Anyway, wanted to post a pic of the graduation cake from the party we had back on the 23rd of May.

4 more years!!!

Now back to the latest on the build. With both upper and lower rear rib flange extensions fabricated, now it was time to fit them to the rib and match drill them. I decided (rather stupidly as it turns out) to drill the holes with the rib still clecoed to the main wing spar and the extensions clamped into place against the rib web. One small problem that I ran into was that I needed to match drill the holes from the inboard side of the rib. I forgot that the wing tie down bracket and fuel tank z bracket would be in the way of the drill, so I had no choice but to use the 12 inch #30 drill bit extension so that the drill chuck would clear the brackets (just barely). I should have removed the rib and match drilled the holes on the bench, but I was concerned about the rear flanges of each fabricated flange extension sitting flush with the main wing spar, so that is why I wanted to drill the holes with the rib attached to the main wing spar.

Here the drilling has begun:

The trick was to get the flanges of each part flush with the main wing spar, and I also needed to provide about a 1/32 inch gap between the edge of each part the edge of the original rear flange of the rib sothey would not rub against each other, as shown in the next pic:

Also, trying to get all those clecos to fit next to each other was a chore. I needed to get creative about the order in which I drilled the holes. As shown above I tried to drill the first two holes to secure the part in position by drilling one hole on top and the opposite side hole on the bottom.

Next are the tools used:

After drilling the holes I deburred them and basically All I need to do now is prep the parts for primer and prime them. I am wiating to drill the final two holes in the new rear flange extensions until the LE is all primed, and the underskin mod is final trimmed to size. I need to mount the LE with all ribs in place and the entire assembly clecoed into position before I drill those two holes in the new rear flanges.

So that then led me to tonight's activity. With the flange extensions pretty much completed I unfortunately have one more rib modification to make. As shown in the pics below, which I switched the W709 rib out for the W408-1 LE rib, the missing rear flange extensions were one thing that I had to resolve. The other thing has to do with the last LE skin rivet hole that attaches the LE skin to the LE rib flanges on the top and bottom of the LE rib. Since the rear flanges are cut out of the W 408 rib, the top and bottom rib flanges are also shorter than the ones for the original W709 rib that I am replacing. SO, when I match drilled the LE skin to the 408 replacement rib, the rivet holes ended up at the very edge of the rib flange as shown in the next two pics:

SO I obviously have to do something about this to ensure that the last rivet hole at the base of the LE skin for this rib location has enough edge material to provide proper support for the rivet and the stresses that may occur in that area of the LE skin. My solution is to cut part of the existing flange away, and fabricate a small strip of metal almost as wide the rib flange that I can fit underneath the rib flange and create a kind of extension of the upper and lower rib flanges. its kind of weird but in order to do this I actually have to trim away part of the existing flange so I can fabricate a new flange and attach it so that it has the proper edge material for that final rivet hole.

For reference, here is what the W709 rib flange looks like for that final rivet hole. Note that there is at least an additional 1/4 inch of material beyond that last hole. This is what I have to create for the 408 rib.

I am going to accomplish this by fabricating a strip of .032 aluminum and then putting a joggle in it to serve as an extension of the existing rib flange.A joggle is simply a small rise at the end of a part that allows it to slide over the top of another part and fit seamlessly next to the other part.I'll start with what it looks like after the joggle is formed.

The joggle is formed by determining the location where the joggle is needed, drawing a reference line,and then position the part between two pieces of metal of the same thickness or the desired thickness for the joggle that is needed. One piece goes on one side of the part and the other piece goes on the other side of the part. You then tape everything together and there are a couple of different methods to create the joggle. You can either pound the part with a hammer, or you can place the taped up assembly in a bench vise and let it form the joggle as you apply extreme clamping force with the vise. I tried both methods just to see how each would work, and the vise method definitely comes out better.

I used two pieces of .032 scrap metal and taped them to the part, which is simply another strip of .032 metal about a half inch wide and several inches long. This was a practice piece so I was not too concerned about actual measurements.

Then you put in the vise so that the jaws will apply pressure to the joint created by all three pieces of metal:

ONce that's done,you remove it from the vise and fit the newly joggled part to the other part that it will be attached to. Here you can see the basic idea and how it will allow me to extend the length of the flange just enough for the final LE skin rivet hole.

Of course, as with everything else about this project, it is a bit more complicated, because I have some precise measurements to make to determine the exact amount of material to remove the from the existing flange so that I can create a part that is long enough to accept two flush rivets to secure it to the existing flange and then provide enough length to accept the hole for the last LE rivet hole. I wish I did not have to do this, and there is an alternative, which would involve drilling holes in the skin and the rib flange, which I am trying to avoid at this point. So the joggle is the next best option and that is what I am going to do.

"NUff" for now......