Several weeks ago I made the decision to replace the reinforcement plate at the top of the VS spar. Using the tip I got from Van’s, I was able to remove almost all of the rivets without any problem. Unfortunately two of the rivets were very difficult and I ended up bending the spar a little at the rivet holes before I got them out. So I just decided to replace the entire VS spar assembly.
It took me a while to get to this because I didn’t work on the plane at all for couple weeks at the end of March. I made pretty quick progress though once I started working again since this was my second time building this assembly (third time for the first few steps since the first time I replaced those parts was back in January).
I was a little concerned that holes may not line up perfectly if I replaced parts that had been final drilled while clecoed to other parts that I wasn’t replacing. I asked some other builders about it and apparently due to the precision of Van’s manufacturing process I shouldn’t have any problems.
Over the course of about 2 weeks I did all the deburring, final drilling, and priming of these parts and got started with the riveting. The riveting was going very well until one day when my wife and I were riveting the rest of the VS skeleton onto the VS spar. The middle nose rib was the first rivet we had encountered that required we use the rivet gun at an awkward angle with the offset attachment. I think I made a poor decision about which side to have the rivet gun on and this led to a very crooked rivet that I decided needed to be replaced. I didn’t trust myself to drill the rivet out without damaging more of the assembly so I decided to sacrifice the nose rib and ground the rivet head down with my Dremel tool, then pulled the rivet out from the other side.
I ordered the replacement and received it pretty quickly. I’ve already deburred, drilled, and dimpled the part. I still need to prime it but I’ve been waiting until I have other parts ready to be primed so that it’s a more efficient use of time. I’m just about ready with both of the spars of the horizontal stabilizer so I should be able to get it done soon.
I continued rivet the VS tonight. This time I did everything with the pneumatic squeezer which produced much more consistently round shop heads. Except for the two that wanted to bend over rather then squish down nicely. I drilled those two out. I’m also not thrilled that the squeezer put a small smile around the right side of the hole when it shifted. It’s not too bad but I need to do some research about when I need to be concerned about this kind of damage. It’s not the first time I’ve done it (I know I made at least a couple on the rudder spar reinforcement plates) and I’m sure it won’t be the last time I do it.
I also ran into what seemed like an issue when I was riveting the rudder hinge brackets to the VS assembly. I assumed I squeezed the first rivet way too far because it was way too thin so I adjusted it and tried again. This is what the first two looked like:
Notice how thin that shop head is? Well, that is way too thin to be a structurally sound rivet. The one just to the left of it has the right thickness but the diameter of the shop head there isn’t large enough. This is when I realized that maybe the rivets the plans called for weren’t quite long enough for this spot. I have read on the VAF forums that sometimes the rivets called for in the plans are wrong, otherwise I never would have questioned the plans and may have set all of the rivets like the one on the left. Maybe that is what I was supposed to do, but I opted for drilling them out and using the next size longer rivets. Here is the first rivet drilled out:
When I tried a new rivet in the hole it was a little loose but I think the hole is still ok. It looks offset a little, but I think the impression around the top left of the hole is just the primer that got squished out of the way by the first rivet. Here is the second rivet drilled out after I set a new rivet in the first hole:
This rivet came out much more nicely than the first rivet. I drilled out the manufactured head and then pushed the rest of the rivet out using a punch and a hammer, which is the way rivets are supposed to be removed. The first rivet I ended up drilling all the way out because I couldn’t get it to budge with the punch and hammer. I’m a little scared to really hit it too hard with the hammer because I don’t want to bend the parts.
The new rivets that I set in the bracket holes were much better. The shop head diameter and height were all the correct dimensions, so even if it would have been fine with the rivets the plans called for I’m much happier with these.
I spent a little time last night patching up some spots on the vertical stabilizer parts that I felt didn’t have enough primer. Then tonight I started riveting them together. I back riveted everything tonight, and while most of the rivets turned out well, there’s a few that I’m not too happy about because they turned out slightly oval shaped. I don’t think these are bad enough to need to be drilled out but I think I’ll leave that decision up to a tech counselor when I have one come out. Here are some pics of the work I did tonight.
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.
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.
I’ve spent several hours over the last few days making sure all of the edges of the VS parts and the holes are deburred. I’ve been using sandpaper to smooth out the edges between the flanges on the various ribs and the edges of the lightening holes. It seems to work pretty well but is also pretty time consuming. For the holes, I’ve been doing one or two twists with light pressure using the hole duburring tool, and if I can feel any bur left around the hole I’ll go over it with a scotchbrite pad or the 400 grit sandpaper. Again, this takes a lot of time but it leaves the holes perfectly smooth.
On a more interested note, my wife and I did our very first rivets tonight. It was only 7 rivets but it was very exciting! We used the pneumatic squeezer to do them so it was pretty easy. The hardest part was getting the squeezer set to the right depth. The squeezer piston needs to be able to extend a certain distance before it is able to generate the power squeeze the rivets and it took me a few tries to get it right. I had to use a thinner squeezer set than I initially started with so that the piston was able to travel farther before it contacted the rivet.
In the end we ended up have to squeeze each rivet at least twice to get it set. The first one got the rivet started, then I would adjust the squeezer and squeeze the rivet again to finish it. Maybe with more experience I’ll get it figured out so that I only have to squeeze them once but this technique got the job done tonight.
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.
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.
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.
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!