Vertical Stabilizer work

Between yesterday and today I have deburred my replacement spar doubler and the rest of the parts that make up the vertical stabilizer. I clecoed the spar doubler to the VS spar and got all of its holes final drilled and then it was time to counter sink the holes again.

I didn’t want to make mistakes again so I started by practicing on the scrap spar doubler. I clamped the part to a 2×4 (I drilled holes in the 2×4 so that the CS cage pilot wouldn’t run into the wood) so that it was completely flat and then clamped the hole thing to the workbench. I then countersunk some holes using both my electric drill and the pneumatic drill to see which worked better. For some reason the countersink cage wobbles in the electric drill, even though nothing else does, so I stuck with the pneumatic drill. All of the holes turned out much better this time so I moved on to the real part. Luckily there isn’t much more to write about it this time because everything went well. The only real difference between this time and what I did last time, was that I clamped the part down instead of holding it in my hand. I thought I was doing a good job holding the part at the time but I think I’ve learned my lesson. In hindsight, I could have just left the part clecoed to the VS spar and had the same result, and after looking at some other builder blogs this is exactly what they did. Oh well…here’s a picture of the part after I finished countersinking it.

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Next I stared to cleco the rest of the VS together. One thing that isn’t called out in the plans at this step, but is mentioned in section 5 where they explain a bunch of techniques and things you need to know, is that you need to shape the front of the ribs where the skin is bent around them so that they don’t put little dents in the skin. I spent a lot of time at the scotchbrite wheel trying to do this and still ended up seeing some small dents as I was putting the skin on. This freaked me out so I pulled it all apart again and spent some more time at the wheel. Then I emailed a group of local RV builders and sent them pictures to see if I was on the right track and it sounded like I needed to do even more work to prevent the dents. This at least made me feel better knowing that I wasn’t ruining the parts so I went back to the wheel and tried to shape them even more. This is what I ended up with when I finally called it good.

 

Unfortunately the dents I first noticed when I was putting the skin on the first time are still there but they are really small and probably won’t be noticed by anyone unless they really look closely for them. The rest of the skin looks like it went on well though. By the way, getting the skin clecoed on can be kind of difficult because even though the skin is pre-bent it still has a long way to match the final shape of the VS. I read on another persons blog that they started at the middle, which is a good idea because I think once the top and bottom ribs are clecoed it could be impossible to get to the middle rib to cleco it. Maybe there is an easier way (I’m sure having a second person would help, but my wife is recovering from a cold so I didn’t want to bother her) but I had to put the cleco through the front hole of the skin at the middle rib position, the get myself on the other side of the skin to push the rib towards the cleco, and then once I could get the cleco in the hole a little bit I used the cleco as a lever to pull it all the way in. This flexed the flange in a really awkward way that I didn’t like so I got several more clecoes in quickly and it all went back to the normal shape.

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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!

More VS spar work and trouble countersinking

My wife Meggin helped be tonight with final drilling some holes in the VS spar, the spar doubler, and the rudder hinge brackets. It all went well until it came time to countersink several holes in the spar doubler. Apparently I’m not using the countersink cage correctly, or my technique is just bad. I was paranoid about countersinking too far so I started off by backing off the cage several clicks so that it would start cut a shallower countersink and then I could slowly work it back up to the correct depth. Once I got it set correctly it worked well for three holes but on the fourth hole, without changing the cage depth at all, it countersunk the hole too deep.

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These two holes were countersunk very well
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This hole was countersunk too deeply

I assumed it was my fault somehow so I decided to try using my drill press so that I could hopefully do a more consistent countersink. I started off the same way I did at first, I backed it off several clicks and slowly worked back to the correct depth. Once it was set, I moved on to another hole and that one ended up too deep as well. I ended up trying this on several more holes and some ended up just right, others were too shallow, and some were too deep. Maybe I have a bad countersink tool or maybe I just wasn’t positioning the part correctly on the drill press. Luckily I have a friend who has already built an RV-10 coming over tomorrow so I’m going to see if he can figure out what I’m doing wrong.

This was a REALLY frustrating end to the build session tonight. I’m sure that this part is still fine to use, and I’m getting tired of reordering so many parts so early in the build, but I’m going to replace it. I could have lived with one hole on the part that was a little too deep but now I have four and even though no one will ever see this part once the airplane is finished, I’m just not willing to accept this level of quality. I just hope I can get my problem figured out before the replacement part gets here!

Started vertical stabilizer, again

Now that I’m waiting for the rudder parts to finish curing I had some time to start the vertical stabilizer for the second time.  I went much more slowly while I was cutting the spar caps with the band saw this time, and when the blade started to wander away from where I wanted it to, I shut it down and cut off the excess metal and started the cut over from that point. I think I ended up stopping and starting the cut about five times on each spar cap. Then I used the scotchbrite wheel to clean up the edges. It’s still not perfect but much better than my first attempt and good enough for me. In the pictures below, the closer spar cap is my first attempt and the farther is my recent attempt. If you look closely you can see how much straighter the cut on the part in the back is.

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I then finished up the night by clamping the spar caps to the spar and match drilling the VS spar holes into one of the spar caps.

Oh I also got my first build injury tonight. While I was deburring one of the spar caps it slipped off the scotchbrite wheel and my finger when right into it. It took off a pretty thick layer of skin right on my knuckle but surprisingly there was no bleeding. This was a good lesson though and I’ll be much aware of where my hands will end up a part slips in the future.

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.

Rudder clecoed together

Today my wife and I got the rudder fully clecoed together for the first time. We had some concern while we were putting the second skin on and the skin was kind of bulging away from the skeleton.

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I sent a text message to a fellow builder, Justin, who already has his RV-10 flying. He offered a suggestion on a different order of putting the clecos in so we tried that but it didn’t appear to be much better. We decided to just keep going and see how it turned out with all of the holes clecoed and it actually seems to have worked itself out. The next thing we have to do is to final drill all of the holes in the skin and then take everything apart and debur all of the holes that we’ve drilled.

I also intend to prime everything inside the airplane.  I’ve been trying to figure out how to do a good job spraying the primer that I’m going to use for a week or two now and I’m still not satisfied so I think I’ll spend the next couple days getting it figured out.  I also need to build the table for my DRDT-2 since I’m going going to need to dimple the rudder skins soon and I don’t want to do it without the table so that the skins will lay flat while I am dimpling it. So basically with all of these things to do it may be a week or more before I actually get back to working on the rudder.