Started riveting horizontal stabilizer

Last night I got started riveting the first parts of the horizontal stabilizer together. I used the pneumatic squeezer for most of it but had to use the rivet gun for some of the rivets. The rivets I did with the gun are not perfect, but I think they turned out fairly good. At the end of the night I had an assembly that looked like this:

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In the weeks before this I spent a lot of time countersinking all of the holes in the spars and stringers and then priming everything. The single flute cutter I ordered worked really well right up until it broke so I switched back to the 3-flute cutter I had been using. A common issue people have with the 3-flute cutter is that it chatters in the hole and creates a bunch of small ridges in the countersink. I found that using my electric drill on the slow speed setting seemed to prevent this from happening, and also helped me avoid having the bit cut sideways through the hole.

I broke up the priming into two sessions. I primed the skins during the first session and everything else on second.  The second session turned out do be my longest priming session to date. Even with Meggin’s help prepping the parts for primer it was close to a 6 hour session. I wasn’t sure we removed all of the residue from etching the parts so we decided to go back and clean everything again so that added a lot of time, plus I was using a new spray gun that I had to learn how to use first.

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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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Vertical stabilizer priming and some dents

My friend Adam came over today to help out with some priming. It took us just over 3 hours but we got all of the parts for the VS cleaned, etched, and primed. I apparently have a habit of not making enough primer to finish the job. In fact, both of the last 2 priming sessions I’ve done I’ve had to make more primer twice! I’m going to work on that because it’s really frustrating to have to stop and mix more primer, but it’s just so expensive that I would hate to mix way too much and waste a bunch. I think there’s a couple spots that we didn’t get enough primer on, and there’s a couple spots that we really smudged the primer on so I think I’ll have to spray some of these parts just a little bit more before I rivet them.

Here’s Adam and all of the parts while they are drying.

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After I finished priming the VS skin I noticed that there was some distortion in the metal around the holes closest to the leading edge. I believe they happened when I was dimpling them because the way the skin folds over from the leading edge it made it a really tight fit with the DRDT-2. My best guess is that the skin wasn’t able to sit flat enough on the dimple dies so that when the dimple was formed the rest of the skin around the die was forced to bend a little. It kind of felt like the sky was falling when I first noticed these dents because in my mind the only thing people will see when they look at the finished plane is the dents. If I’m being honest with myself though, they really aren’t that bad. I’ve already asked around about them and most people think they are only a cosmetic issue so I don’t need to worry about replacing the skin. They also gave me some tips on what I could do to try to repair the skin a little but I’m not sure yet if I’ll try though because I don’t really want to risk making it worse. Everyone agrees though that this is something that can easily be covered up in the painting stage so I’ll keep my fingers crossed that it won’t be noticeable when the plane is finished.

Finished rudder priming

Today my friend Vic came over and helped me get the last couple parts of the rudder primed. He has a lot more experience using spray guns than I do so he was able to get the parts sprayed more quickly than I would have done. The primer I’m using, Ekopoxy, seems to spray on with a little texture but if you get a good wet coat it will lay down fairly smooth once it dries. It was nice having him here to confirm that the spray gun was working correctly so I now know that is just the way the primer works rather than me not setting up the gun correctly.

Now all I have to do is wait a week or so for the parts to cure and then I’ll be able to start riveting the rudder together finally!

Rudder deburring and priming

Over the last two weeks I’ve spent about 13 hours working on the plane. It was mostly tedious work since I had to final drill all of the holes in the rudder skins and skeleton, and then I had to debur all of those holes. Deburring is the least exciting task I’ve had to do while building the rudder so far but it is important so I’ll continue to do it.

I actually had a couple things happen that gave me some stress over the last week so here they are:

First, I had some trouble deburring holes.  You want to debur the holes because the burs leftover from drilling can potentially prevent the parts from fitting together properly when it comes time to rivet (or prevent the rivet from fitting properly) and can create places where stress can concentrate which could lead to cracks in the metal. I have a couple different tools that I use to debur the holes but they both work the same way. Basically you stick them into the top of the hole and spin them once, or twice and they are supposed to remove all of the burs.  They way I am using them (I’m assuming it’s user error), neither one of them seem to completely remove the bur around the edges of the holes without risking removing too much material away from the holes. Almost every time I use either of them, I can still catch my finger nail on a bur around the edge. This leads to using the tools a little more, and then a little more, and before you know it you are starting to countersink the hole rather than debur it and that’s something you really want to avoid. If the aluminum is really thin, like the skins are, then you risk enlarging the rivet hole and that’s not good either.

Since I didn’t want to risk ruining the rudder skins I did one or two rotations with the deburring tool and left it at that. There were still burs that I could feel but I didn’t want to risk it so I went ahead and dimpled the skins anyway. This lead to even worse burs on the bottom of the dimple. I worried about this for a day or so and then tried to clean up the dimples by running a file along them which may have worked well if I was more patient but I was worried about taking away aluminum that wasn’t a bur. Then I tried sandpaper and that worked pretty well. Finally I tried a maroon scotchbrite pad. This actually worked really well! Since I plan to prime all of the parts, and scuffing them with a scotchbrite pad is part of the prep process for priming, I decided to just leave them alone and make sure I went over all of the holes really well with the pad before I primed them. This created nice smooth dimples and I feel a lot better about them now. I think I may start to use a scochbrite pad to do most of the hole deburring from now on. I just need to figure out if I should clean the aluminum before I use the pad because I seem to remembera post on the Van’s Airforce forums that mentioned that you could be embedding oils and dirt in the aluminum if you don’t clean it before you scuff it and maybe I’m just overthinking this and shouldn’t worry about it so much. I tend to do that.

The other big mistake I made was when I was putting the edge break in the rudder skins. It’s a very slight bend you put in the metal at the trailing edge so that the skin will lay flat against the other piece that it will be riveted to. Well I have this edge forming tool that does just that. It’s basically vice grip pliers with some rollers on the end that have a slight bend in the top one. You put it on the edge and pull towards you and you’re done. Unless you’re me. Then you screw it up even after you’ve practiced on some scrap parts. The thing is, while you pull it towards you, you’re supposed to push it towards the skin at the same time so that it doesn’t roll off the edge. Well I’m apparently too strong for my own good because I pushed it right up onto the skin, past the flange on the roller that’s supposed to keep you from doing just that. This put a much larger bend in the skin than should have been there. Now a proper edge break is almost imperceptible unless you are looking at the right angle or have a light reflecting off of it, but here’s what I ended up with:

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And to add insult to injury, I did the exact same thing a little farther along on the skin. I did the best I could do to bend it back and smooth out the skin but there was only so much I was able to do. Here is the worst section of it:

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I haven’t decided yet if I’m going to replace it. I keep thinking well it’s probably just a cosmetic issue and I may be the only one who notices it so it’s not worth it. It’s a $45 part and will put me back a week or two while I wait for it to arrive, not to mention the work I will have to redo. But then I worry that it will affect the feel of the airplane (the plans do mention how important a straight trailing edge is after all), and heck $45 isn’t that much to fix a cosmetic issue since I just started building. To help me decide I went ahead and started a post on the forums asking if it will be more than a cosmetic issue and if there is anything I can do to clean the edge up.

I also got a bunch of priming done. I did everything except for the skin with the bad edge since I may end up replacing it, and I’m waiting on a new stiffener for that side that I will have to match drill anyway. It got countersunk while it was being deburred. I plan to add a post or a page sometime that will go more in depth in my decision to prime and what I am using but for now I am using Stewart Systems EkoPoxy. It’s water based, non-toxic, and easy to clean up. The problem is that it takes several days to fully cure so I’m not going to start riveting the rudder until it has had some time to harden.