Horizontal Stabilizer ribs dimpled and countersinking trouble

I’ve finished dimpling all of the HS ribs. I started using the 1-inch Scotch-Brite light deburring wheel in a cordless drill to finish off the deburring of the holes in the ribs. Compared to the tools I have been using to debur holes I like this method a lot better. Unless someone tells me this is a terrible idea I think I”ll stick with it.

I also started to countersink the stringers and ran into a couple issues. Some of the holes got countersunk way too far because the countersink cage adjustment came loose without me realizing it. I’ll make sure I tighten it better from now on and will also recheck it regularly while I use it.

The other problem I encountered was the countersink bit cutting it’s way through the part, starting to turn the hole into a line. I think this happened because the part is thin enough that the ends of the cutting parts of the countersink bit extend just far enough down the pilot of the bit to cut into the side of the hole. Here is a picture of the back side of one of the holes I messed up when I was countersinking it.

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I decided to spend some time practicing on scrap parts of the same thickness and found that I’m not very good at stopping the bit from moving sideways through the part. Typically I use a 3-flute countersink bit but I do have one single flute bit from the tools I am borrowing from a friend. I decided to give this one a try to see if I had the same trouble with it, and I was happy to find out that it didn’t seem to want to start cutting sideways at all. Even pushing directly on the side of the tool while it was cutting didn’t cause it to cut sideways through the hole so I ordered one of these in the size I need.

I can still use the 3-flute bits that I have but I’ll need to back up the part with a block of wood or something with a hole for the pilot bit to extend into and clamp it in place so that the bit can’t move sideways at all. Or I could just put it in my drill press.

Horizontal Stabilizer Deburring

I’ve been slowly deburring the holes I final drilled in all of the horizontal stabilizer parts over the last week and a half or so. I haven’t spent too much time working on it because my weekends have been pretty busy and deburring holes is one of my least favorite things to do so it’s been tough to get motivated to do it. Also, I never feel like the tools I have for deburring the holes are very effective. It’s probably user error but for the most part it just seems like the tools push the burrs around without actually removing them. I’ve tried not to worry about it too much since scuffing all of the parts with the Scotch-Brite pad while prepping for priming helps to clean up the holes, but I want to make sure they are deburred properly before I dimple everything. I did some reading on the VAF forums and have decided to dry using some 3M roloc discs in an angle grinder. The blue discs, which are listed as having a fine texture, are what people use and I think they are even less aggressive than the maroon pads I use before priming. If this works the way I’m hoping it will then it should really speed up the deburring process. I’ve got some ordered and will have them later this week so I’ll be able to try them out soon.

I’m also considering using the “light deburring” Scotch-Brite wheels that I recently bought as well. I’ve got a 6-inch wheel in my bench top buffer, and a couple 1-inch wheels for use in my hand held grinder. They are MUCH less aggressive than the other wheels I have been using and do a great job of removing burs without changing the shape of the part. Of course, if I hold the part on the wheel in one spot long enough it will remove a lot of material, but it’s much slower than the “cut & polish” wheel that originally came with my tool kit.

Horizontal Stabilizer Assembled!

Two nights ago I got to see the HS assembled for the first time!

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I was surprised at how easy the cradles made it to get the nose ribs clecoed into place in the leading edge of the skin. I figured it would be a struggle to get them all the way down into the leading edge and then clecoed but the cradles made it a complete non-event. Like many other builders I think, this is the first time where I have not had enough of the silver clecos. I’m going to do the best I can with what I’ve got, but I know I’m going to need a LOT more when I get to the wings so I’ll order some more soon.

Last night, I got the rear spar clecoed into place and started final drilling. In the time I had to work on it, I managed to get the bottom of the left side of the HS drilled. It is going to take a while to get the rest of it drilled….

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Horizontal Stabilizer Update

I’ve gotten quite a bit of work done since my last update. I finished deburring almost all of the parts for the elevators, and after speaking with Ed Kranz about priming before drilling I’ve decided to stick with the original order of priming just before riveting. He pointed out that in the process of assembling to drill the parts and then disassembling to debur them that I would probably scrap off a lot of primer. It turns out that he had to clear primer out of the holes on his plane as well and he suggested just using the reamer by hand. He also suggested attaching a drill stop to the reamer to help with turning the bit in the holes.

I also found time to get the HS spars primed. It took two nights of priming because I was spraying them in the backyard and I ran out of daylight. This was pretty frustrating so I’ll make sure that any more priming I do outside happens much earlier.

I finished deburring the ribs that I replaced as well as the nose ribs. The nose ribs need to be shaped a little bit at their tip so that they don’t create little dents in the HS skin. The plans show you changing the shape of the edges to look more like where I drew the lines on the part in this picture:

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I wasn’t sure about how to do this without removing so much material that there wasn’t much left on the flanges between the hole and the edge of the flange. I emailed Van’s with the picture below to clarify how it was supposed to go and was told the one of the right was more like what I needed to do. Apparently the dents mainly come from the curved part of the flange where it isn’t very flexible.

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Here is what the nose ribs looked like when I was finished:

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I also spent some time fluting the flanges of the ribs. The process that is used to bend the ribs into shape causes them to develop a curve along there length. Fluting involves putting small crimps into some of the flanges which straightens them out. You can see the crimps I added to the rib in the picture below and how flat it sits on the work bench. I was worried about over-fluting it so I went slowly. They aren’t perfect, but they’re much better than they were and are good enough for me.

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Next, I finally started riveting together the front and rear spar assemblies.

After that I clecoed the ribs to the front spar and final drilled the holes they share with the spar web. It’s really cool seeing such a large part coming together.

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Once that was done, I deburred the HS skins and got the cradles ready that will be used to hold the whole stabilizer up while I work on it.

I also had one stringer left that I needed to trim (because I wasn’t happy with the first one I trimmed so I replaced it) and I learned a few things. First, don’t touch the aluminum right after cutting it. It gets very hot, particularly if the band saw blade is dull. I have a nice burn in my thumb showing the edge of the part that I grabbed. Second, don’t try to use a band saw with a dull blade…it doesn’t work very well. Third, I do much better with a hacksaw. I’ve made this same exact type of cut on eight or nine other pieces of aluminum angle, and the ones I did with the hack saw after burning myself and realizing how dull the band saw blade is, are by far the straightest cuts I’ve made so far.

Lots of deburring

I have primed some of the smaller parts of the HS but while waiting for a good chance to prime the spars I decided to start deburring the ribs. There’s a lot of ribs so it took me several hours over a few days. Afterwards, I noticed I got a little carried away with the deburring wheel on some of them so I decided to reorder the few that I was uncomfortable with.

In the meantime, I started deburring parts for the elevators. I’ve been working on deburring all of the elevator parts because I’ve decided I want to try switching up my process a little bit. For the elevators, and maybe the rest of the HS, I am going to try priming the parts before I do the final drilling. The issue I’m having with priming after all of the drilling is that the rivets frequently don’t fit easily into the holes. Most of the time when this happens I end up having to run a reamer through the hole to clean it up a little bit. I don’t think this has much of an affect on the size or shape of the hole, but I’d be more comfortable if I didn’t have to do this extra step.

Life got busy with a camping trip for Memorial Day and then yard work so I haven’t actually got much work done over the last couple weeks but I’m hoping to change that soon.

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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:

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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:

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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:

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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.

Catching up on the blog

It’s been a few weeks since I’ve added any blog entries talking about what I’ve done on the build so I’m going to get caught up in one post.

Rudder

I’ll starting off with the rudder shear clip problems I had. For the first shear clip I removed that had a couple enlarged holes, I followed Van’s recommendation and just used the next size larger blind rivet for those two holes. For the second shear clip I needed to drill out, I ordered a 90 degree drill which worked slightly better for most of the rivets. I still didn’t have the drill bit perfectly lined up with the rivet while I was drilling it out and that led to one misshapen hole. For the second rivet I drilled out with it, I was using a smaller drill bit than the rivet. This loosened the rivet up enough that the rivet was spinning with the drill bit and when I tried to pull the bit out of the rivet, it snapped off inside of the rivet. After emailing with some local builders I decided to dry to use a dremel tool to cut/grind the rivet with the drill bit out of the rudder. It was difficult to use because it was a very tight fit but the grinding bit actually caught the part of the drill bit that was stuck in the rivet and pulled it out of the rivet far enough to grab with pliers so I could pull it out. I went ahead and tried to drill the rest of the rivet out with a larger bit which actually just snapped the rivet head off so it came out really easily. Luckily the last two rivets were uneventful. The holes were so messed up at this point that I had to reorder the part. Since the holes in the stiffeners had matching mangled holes, I an idea that Van’s suggested for the first clip, and I fabricated a backing plate to go on the other side of the stiffeners. Here is what that looked like after it was all riveted together:

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Vertical Stabilizer

While I was waiting on the replacement parts for the rudder I started to rivet the rudder hinge brackets to the VS spar. One thing to be aware of is that the rivets the plans call for that go through the rudder hinges are a little short. I drilled two rivets out that I set before I realized that the reason they were squeezed way too thin wasn’t because of how I set the squeezer. So for these I used the next longer rivet size. Here are the two rivets that were too short for the hinge brackets.

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Using the squeezer worked really well until I got to a couple rivets on the hinge brackets where the squeezer just won’t fit so I had to use the rivet gun. This was going ok until I lost control of the rivet gun and it walked down the spar for a few inches. This put some small dents in the spar and really ruined my night but after chatting with Van’s they don’t think it is bad enough to be a problem and said to just smooth out the spots where the gun dug into the metal and re-prime it. Here is what it looked like:

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When I moved on to the upper rudder hinge bracket I thought I was doing pretty well until I looked at the rivet heads on the manufactured rivet side. If you look at the rivet in the picture above where the gun dug into the rivet before it stared walking down the spar you can get an idea of what I did to those rivet heads on the upper rudder hinge bracket, except they were much worse. They were bad enough that I felt I should drill them out and replace them. As with all of the other rivet drilling I’ve done this didn’t go so well. Clearly I need to practice doing it on some scrap but in this case I can also blame the rivet heads, particularly one of them, because of how badly I messed it up while riveting. This is the result of my struggles to get the rivet out:

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Due to all of the damage I did to that reinforcement plate I knew I should replace it, and also confirmed that with other builders and Van’s. Luckily Van’s pointed out to me that since I’m replacing the part directly under the manufactured heads of those rivets, that instead of drilling them out (which as we know now will probably lead to me damaging more of the spar) I should just grind off the heads of the rivets and then punch them out. I haven’t done this yet but I’m hopeful that I can do it well enough to salvage the rest of that spar assembly. Here’s a picture showing the whole spar assembly so far.

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Horizontal Stabilizer

I’ve done a lot of deburring on the first few HS parts that are worked on. The spars for the HS are around 11 feet long so they take up a lot of space in the workshop and the edges take a while to finish. I did get a little bit of final drilling done on the rear spar for the spar doubler and the elevator hinge brackets. I also riveted together what the plans call the inboard hinge bracket assembly. This was nice and easy and left me feeling pretty good about myself.

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