The forward center ribs needed to be trimmed because the front spar's angles protrude. Here you can kind of see what I'm talking about...the rib has already been trimmed and I'm fitting it.
A critical step in this whole ordeal is making sure the ribs are perfectly flat and straight. Often they come slightly concave or convex, and you need to "flute" the edges in order to straighten them. Here you can see the fluting position guide drawing, which shows you where rivets go and where you can flute. I use Avery's vise grip fluting pliers. It only takes a second to make a few fluted edges, and the parts straighten right out. You also have to make sure that the flanges are perfectly perpendicular to the web face. This ensures that the skins lie flat against the riveting surface and also that they don't bulge on the ribs.
Here's a view of jigging up the end rib between the rear and front HS spars. What you do is cut up a handful of 1.25"-wide aluminum strips, and you clamp it all together. Basically the strips ensure that the spars and ribs are aligned with each other skin-surface-wise. This makes sure that the skin will lie flat against both the rib and spar at the joint. Otherwise the skin would have to curve up or down to meet one or the other. You want a nice, flat surface (duh...).
Once this crap is all jigged up (one rib at a time) you drill the rib and cleco it. Here you can see the right end rib clecoed to the rear spar, getting drilled to the front spar.
Getting there...both end ribs are basically on.
Next you move to the middle interior ribs. This one's done. In the background you can see the Bass Ale that kept me going through this...I hit a point when I first started jigging everything together where I got really nervous about committing to drill those first few holes. I was way too paranoid about the front spar lining up perfectly, everything being square, etc. To other builders out there, don't sweat it. It doesn't have to be square until it goes in the jig. Just follow the measurements in the plans and it'll work out FINE. And refer to that picture above with the C-clamps. That was partly what I had trouble understanding in the totally unclear diagrams. The Bass helped me get through without pulling all my hair out...
Here's the finished product...this is really starting to look like airplane parts!
Another view of the HS, clecoed together.
I took everything apart and deburred all those holes I drilled. Tomorrow I'll be priming these ribs and riveting this sucker together. Then it'll go into the jig for skinning! I feel like I'm making great progress here...very encouraging to be moving along so quickly. Pretty empowering.