We've been prepping more parts for the tail cone and most of the work has been very tedious. There have been more hours of deburring than I care to think about. Occasionally we get to figure out some new skill, like how to remove the bow from some very thick pieces of aluminum. There are two heavy aluminum bars that will eventually attach the horizontal stabilizer to the tail cone. At least, that's my educated guess based on the fact that the pieces are called "horizontal stabilizer attachment bars." They are pretty badly bowed from the manufacturing process and we had to straighten them out. You can really see how much room there is between the left side of the piece and the workbench. It's not as noticeable on the right side, but the whole thing is curved like a dish at this point. The instructions make the process sound much more technical than it really is. To remove the bow, we "pre load the free end of the attachment bar in the direction required to straighten it and, using a rubber mallet, firmly strike the bar one time near the vice." In laymen's terms, you put the bar in a vice, push against the end (that's what they mean by "preload") and whack it with a rubber hammer. You do that over and over again, moving the bar as you go, until it is straight. Here is a comparison between the bar that has been straightened (on the right) and the one that hasn't (on the left). Mike has also been cutting varying lengths of J-channel, which is a long stick of aluminum with a profile that's roughly shaped like the letter "j". These pieces of J-channel will run the length of the tail cone and act as stiffeners. Mike cuts the 90° angles on the bandsaw and smoothes the edges with a bench grinder. Some of these stiffeners have be cut on a 45° angle. Because of the orientation of the 45° cut, the bandsaw won't work for these pieces. We don't have many saw blades that will cut aluminum and instead of buying a $50 saw blade, Mike came up with an inexpensive solution. (I know, I'm as shocked as you are! Mike actually resisted buying a new tool!) He built a mitre box out of some scrap lumber and bought some $10 metal blades for his hacksaw. He smoothed the ends of the shorter lengths using the bench grinder, but some pieces are nearly 8 feet long and he used a pneumatic hand grinder for those. While Mike was manufacturing various parts, I deburred my little heart out. We are almost ready to get out some tail cone skins and start fitting things together. I can't believe how quickly things have gone so far...but that could be because I skipped several work sessions at the hangar while Mike either worked alone or got help from his buddy, Keith. It's always amazing how fast work gets done when you're not the one doing it. I've still put in about 6 hours of deburring but easily missed out on just as much. Here is a portion of the parts that have been assembled so far.
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After a week of basking in the euphoria of finishing the horizontal stabilizer, it was time to move on to the next portion of the build - the tail cone. But first, we had to move the horizontal stabilizer into storage. That task wasn't as easy as expected because 1) the hangar where we are working is packed full of stuff and 2) the horizontal stabilizer is nearly 12 feet long. It's not especially heavy, but it's very awkward to move. After moving a LOT of stuff out of the way, we made a clear path and got the horizontal stab all settled into storage. With the horizontal stabilizer out of the way, we were confronted with a view that we haven't seen in a really long time. That, my friends, is an empty workbench! Don't worry, it didn't stay empty for long. While we were stowing the horizontal stab, we grabbed the parts that we will need for the first stage of the tail cone. It's been 10 months since we started a new section of the build and I had forgotten what the early stages are like...peeling vinyl, marking pieces, and deburring! Deburring is one of those tasks that just never seems to end and these tail cone pieces are full of lightening holes, nooks and crannies. It also seems like every piece is curved and has a million flanges. I did manage to get a pretty good picture of why we have to deburr every single edge. You can really see how rough the edges are on the flange. While I spent hours deburring, Mike started work on the first pieces of the tail cone. The first few pages of the tail cone instructions also require us to fabricate quite a few pieces. Mostly, they instruct us to cut a short length off of a long piece of metal and drill some holes. Mike likes to cut the pieces a little bit long and then finish the ends using the bench grinder. The holes always need to be drilled a very odd, very precise distance from the edges. I thought Mike used a very clever system to get the holes in the right spot. He laid down a solid layer of black sharpie and then used a scribe to make a line the appropriate distance from each edge. Where the scribed lines make an "x" is where he needed to drill. The holes that go into this particular piece are absolutely enormous (compared to every other hole we've drilled so far). When Mike got out the drill bit I made him double check the size a couple of times before I would let him make a hole. When we were done, we realized that the holes weren't in the right place. They were each off by about a quarter of an inch, so we started over and did the whole thing again. Even when building airplanes you should measure twice.
These big holes then needed two smaller holes drilled on each side. We will eventually rivet on a nut plate that does...something. I'm going to admit right now that I have absolutely no idea what any of this stuff is. When we worked on each of the stabilizers I got pretty comfortable with the types of pieces we were preparing and using. On the tail cone we seem to be prepping a whole bunch of parts that then get set aside. I honestly have no idea what's going on, which makes it very hard to explain. As this part of the build progresses, we will just have to figure out what is going on together. Anyway, here are some pictures of drilling the holes for the mysterious nut plate. |
AuthorThe supportive spouse's guide to building an airplane. Archives
May 2017
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