bulkhead work
Ok, where are we… Oh, yeah, bulkheads, bulkheads, bulkheads. I fabricated all of the parts and pieces that are made of various stock. I’ll admit that there was a fair amount of head scratching trying to figure out some of the assembly details, but no rocket science involved. I got a cheap little 6″ cutoff saw to cut the longer lengths of angle. It is a pretty aggressive little tool that seems to melt the metal just as much as it cuts it.
With all of the bulkhead parts roughly stuck together, I got out the bottom skin for some more pre-assembly and adjustments. There were two things that I wanted to get accomplished by putting things together with the bottom skin. First, it seems that every -7 and -9 kit that I have heard of has fit issues between the forward most bulkhead, the bottom bellcrank rib, and the bottom skin. The problem is that with all these parts put together, the holes in the bottom skin don’t match up with the bellcrank rib at all. This seems to be a clear kit issue that everybody encounters. My solution was to do some creative minor part reshaping. A little here, a little there, and the holes come into alignment. First I made a little jog in the lower (forward facing) bulkhead that essentially pushed it forward about 1/16″-3/32″. I used some wood blocks, clamps, and a mallet to accomplish this. I jigged it up very carefully so as to only effect the section above the flange and not get the whole thing all bent out of shape. I gave the doubler plate a little bend at the bottom to accommodate the new shape. I also made a small adjustment in the forward flange of the bellcrank rib. I pounded it down and over kind of in the direction of the arrow in the picture. I only moved it about 3/64″. Now all of the holes all line up! This adjustment sequence took about an hour an a half.
The second thing I wanted to accomplish with all the bulkheads arranged on the bottom skin was to try to roughly work on the flange alignments on each bulkhead. Usually most parts require the flanges to be adjusted to exactly 90 degrees. The bulkheads are different in that the skins are not perpendicular to the bulkheads, so the flanges have to be bent at an angle. I used a piece of aluminum angle as a long straight edge along all of the bulkheads to gauge the angle to bend the flanges to. I did this around each bulkhead. Also included in this process is a little fluting here and there. It took me about two hours of this to get the flanges roughly in shape. I know that they will have to be tweaked when it comes time to really aligning things with the skins, but at least it will be close.
While we have things setup, I thought I might as well prepare the bracket for the TruTrack autopilot pitch servo. Just a heads up for the next guy, the TruTrack drawing is incorrect (pictured) in the way that it depicts the flange on the bottom of the bellcrank rib. I just improvised and put a few more rivets in the bracket web.
Then it all gets taken apart for hole and edge deburring and scuffing for primer.
