Time: 8 Hours
Today I spent around 8 hours in the Hangar working on the HS. Items for today were to drill the forward flange of the middle rib, HS-405. I found that many builders have edge distance problems with this part of the build. The problem lies with the center two holes that you drill and how they match up with the forward rib, HS-404. The plans call for the measurements for all 4 holes which is fairly easy to understand. The errors occur when you match drill the aft flange of HS-404, that’s the flange that you trim so it clears the spar stiffeners. The issue is the remaining flange that you trimmed does not leave a lot of space for error when drilling. I decided to not drill the two center holes in question until I mate up the ribs with the spar and then drill from forward to aft ensuring that I make my edge distance. Seams like an easy option however that took me almost 3 hours of measuring, marking, consulting the plans and Internet, re measuring, marking and so on! So many builders end up with errors on this step I was really worried about doing the same.
Once I decided on my game plan I started by drilling the 2 outboard holes on the left and right middle ribs. The next step was to divide all the ribs into a left set and a right set. I did that and marked them as such. Now was the boring task if deburring, the process of removing the little edge on cut or drilled aluminum. You can do this with several different tools, my favorite is a Scotch-Brite wheel in my bench grinder. It is a very dense wheel of the same stuff as in you kitchen Scotch-Brite pads. This makes quick work deburring and scratch removal. A deburring bit is a cordless drill makes easy work of the drilled holes. Every hole needs this treatment on both sides! I then prepped all the surfaces with a Scotch-Brite pad to prepare them for priming.