Horizontal Stabilizer Update

Over the last week I’ve spent 4.7 hours working on the front spar of the horizontal stabilizer. This required cutting a couple spar caps to shape (just like the vertical stabilizer) and drilling a bunch of holes in them, the spar, and the spar doubler. The toughest part of this though was the step where I had to fabricate a couple brackets. I’ve been putting this step off for a while because it seems like it’s kind of an important step. These brackets help position the horizontal stabilizer on the rest of the airframe so I was worried about doing a bad job and causing the HS to sit at an angle an causing the plane to not fly well or something.

I actually started to do this step several weeks ago but it didn’t start off as well as I wanted so I decided to order another piece of the aluminum angle and give it a second try. Also, the first time I tried to make them I learned that my cheap band saw really wasn’t up to the task of cutting through the 1/8 inch aluminum or maybe I just already need to replace the band saw blade. Either way, I decided that for my second attempt I would use a hack saw.

I started by marking up the part with all of the lines that I needed to cut, like this:

IMG_20170311_125235

Then after about an hour and a half using the hack saw to cut them out and the scotchbrite wheel to get them closer to the right dimensions they looked like this:

IMG_20170430_103220

I’m pretty happy with how they turned out. Like everything else so far, they’re not perfect but I’m confident they will do what they need to.

The next hard part was drilling the holes in the brackets. You drill one in each of the brackets on the larger side of the bracket. This is where the plans tell you to be very accurate because this hole positions the brackets on the HS spar. I measured, triple and quadruple checked, and then since I wanted to make sure the hole went through as perpendicular to the part as I could get it, I used my drill press to drill the holes. Then you drill two holes in the smaller side of the brackets that are used when you position the HS onto the tail cone.

Later, I got to the point where I needed to cleco the brackets onto the rest of the spar assembly and drill the other 8 holes in the brackets that will be used to attach them to the spar. The plans tell you to clamp the bottoms of the brackets to a flat surface to make sure they are perfectly aligned. The best thing I could find to use was my 4 foot level:

IMG_20170430_154239

Once the parts were in place with the level clamped to them I stared at them for a while. Then I had my wife come out and stare at them too. I wasn’t sure if the level was perfectly parallel to the spar not, which would be the case if I did a poor job positioning the holes in the brackets. After 20 minutes or so (ok maybe longer) I was convinced that  if they were off, then they were only off by a very small amount. If I understand the plans correctly in the later sections, then these brackets are used to make sure that the HS sits square to the rest of the airplane and so I don’t think a very small difference in their position will make a huge difference anyway. So I went ahead and drilled the rest of the holes in the brackets.

Everything is disassembled and deburred now just waiting until I have a good chance to get some priming done.

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