Right Wing - Rib Prep

Today was all about prepping the wing ribs to get ready for priming.  I'm hoping that the temperatures get back to around 50 tomorrow.  I think that's enough to heat up the garage a bit and get the priming done without too much downtime for drying.

Just like in the left wing ribs, I drilled a 3/4" hole in the bottom portion of each rib web for the wiring conduit.

I've tried every flavor of aluminum prep for priming.  The bottom line is the aluminum has to be cleaned and etched (well, it actually doesn't HAVE to be etched, but my testing has shown that the primer does indeed stick better with the etching, so I think it's normally worth the effort).  How the metal is etched is the question.  In the past I've mostly used the EkoEtch as an acid etch/cleaner.  This stuff works great, but it requires the metal to be rinsed with water afterwards.  When the temp is 30-40 degrees, that adds at least a day of priming since the water doesn't dry quickly.  Instead of using the acid etch, this time I just manually scuffed with Scotch Brite.  That still takes forever on ribs because of all the bumps, especially the fluted spots on the flanges.  Once done with that, I cleaned with acetone until the rag didn't pick up any aluminum.  It took a few hours, but now I'm ready for priming tomorrow. 

Once I'm done with the wing ribs (still have to do the leading edge ribs as well as flaps/ailerons), primer prep should get considerably easier for the rest of the plane.  The wing ribs are just very awkward to do, and the fact that there are so many of them to do is what's killer.  I'm very glad I had already deburred all edges last summer while I was waiting to get the tail.  Having to do that at the same time as the rest of this would have been rough.  Scuffing the big surfaces like skins should be pretty quick, so not that big of a deal.  I've found that for flat surfaces, just putting a Scotch Brite pad onto a random orbital sander makes very quick work of it.