Rib attachment

Not much work today, mostly experimenting with the rib attachment and leading edge shells. 

I attached only the outermost two ribs and used the method as described in the drawings.  I first pulled the fiberglass tape around dry, situated the fabric, and lightly marked the edges with a thin sharpie.  After removing the dry glass, a quick rough using 220 grit sandpaper within the lines gave some tooth for the epoxy to grab.  When I mentioned sanding aluminum to a colleague, he warned about removing the oxide protective layer and inviting corrosion.  With the epoxy sealing out the surface scratches, hopefully surface corrosion is no longer an issue.  Anyway, a good wipe with alcohol cleaned the surface and prepped for epoxy.  After adding the epoxy and clamping the fiberglass tape to hold it all in place, it cured for a few hours in the warm sun.

Several leading edge shells were added temporarily just to take another look at this process.  The outermost one had to be cut down an inch or so to fit the reduced width spacing, which was easy enough with a new, sharp Exacto blade.  After it was in place, here's a look at a few of the leading edge shells held in place with masking tape.

I'm considering to put a layer of fiberglass on the back of the foam prior to bonding it in place.  If I also add a layer on the front (after sanding), that will stiffen the foam tremendously, providing some ding resistance and hopefully keeping the foam from getting cracked from any poor handling.  Sandlin calls out for a layer of epoxy seal coat for the foam. The Stewart Systems process I'm using to cover does not eat foam like Polyfiber adhesives, but it is a good idea anyway.  I have a bunch of 2.75oz/yd2 cloth that is probably a bit light.  4oz unidirectional fiber seems about right.

Remaining covering is the right aileron, the cabanes, the nose, and then the wings!  I'll be stopping for a load test prior to beginning the wing covering.