There are 27 ribs on each wing for a total of 54 ribs, each of which needs to be prepared for assembly. Preparation involves deburring all of the edges so they are not sharp or jagged, then squaring the flanges so they are at a right angle to the web, and finally fluting the curved parts of the flange to bring the rivet holes in the flange into alignment. When the ribs are stamped out of sheet metal, the flanged curves tend to warp the shape of the part. Fluting puts small indentations into the flange that pull the warp back into alignment.
I’ve found that squaring the the flanges is difficult with the tools I have. I found a very clever design for a flange-squaring tool on Lynn Dixon’s RV-7 website (http://theskunkwerx.com). I decided to build a similar set of tools to aid in the prep of all of my ribs. I bought an oak baluster from Home Depot and other miscellaneous hardware costing about $16 total. Here are some pictures of the finished tools:
I’ve found that these tools work very well for getting good flanges. The angles of the end of the tool bases were cut at a hair over 10 degrees to cause just the right amount of over-bend. Here’s how it is applied to a rib:
And here’s a close-up of a fluted flange in the curved section of one of the forward ribs:
The front sections of the forward ribs have a bunch of nooks and crannies that need to be smoothed out. I use thin strips of 400 sandpaper to clean up the hard-to-reach edges.
I will be working on the ribs for a couple more days before I get them all completed.