Tue Oct 13 2020

Fabricating sub panel ribs

My friend Greg recently completed his Sportsman 2+2 and is now in phase 1 flight testing. Since he's no longer building, he sent me an extremely generous selection of excess aircraft hardware and tooling. Thanks, Greg!

As I'll be fitting the ribs to the sub panel and firewall, I made up some .040 thick spacers to between the sub panel and the plywood jig. These are made from two pieces of scrap .020 thick material and, as with spacers I added the other day, will offset the sub panel from the jig by the same thickness as the flanges of the triangle supports that are riveted to the longeron.

Okay...bent the forward and aft flanges of this rib and clamped it in place.

The rib cannot yet be seated fully down into place, so I used a straightedge to draw a reference line on the rib web that matches the loft line from the firweall to the canopy frame weldment bow.

Offsetting this reference line to the top edge of the rib, showed that I needed to trim this edge at a very slight angle...around .100" over the full length of the rib.

Since the top flange of this rib needs to be bent slightly more than 90 degrees, when it was installed, I used the firewall as a guide to transfer the angle to the forward flange of the rib. Then used my little machinists protractor to determine the angle.

97 degrees.

Bending the top flange required moving around some of the fingers on this brake.

...which then required my forming guides to be cut.

Ready to bend.

So, yeah...I worked a (more or less) entire day and managed to make three bends. Sigh.