Rivet count: 349 + 254 = 603!
I got a little time to pull a few rivets last Sunday, but it was hardly worth a blog post, so I saved the pictures for this week’s posting.
I tied together the bottom rib pieces with some pop rivets. I think I did this step out of order which made riveting the skins at the trailing ends of the rib a bit harder though… I should not rush!
So I started in fresh and early this Saturday with the goal of finally riveting the trailing edge. I see a lot of people who do it right after they glue (or tape) up the trailing edge, but the instructions have you do it next to last. In the end, this makes sense because you want some play to get those tight rivets at the aft end of the rudder.
These last couple rivets are really hard to get to. I managed to get my 4″ thin nose yoke in there. As the instructions intimated, I had to uncleco and spread the trailing edge a bit. I didn’t like having to crack the epoxy, but so it goes. I used a little RTV to glue it back together after I finished the rivets.
Next you rivet most (but not all) of the left attach strip. You leave the front rivets open so that you can more easily get the rudder horn brace attached. It took a lot of finagling to get it to finally snap into place. I started with the four holes on the horn and got a couple clecos in. Then I worked it around the attach strips and finally pressed it up into the trailing edge. Here it is in all its cleco’d glory with one rivet test fit!
A lot of people seemed to have had trouble getting these rivets set (well, not the pull rivets into the bottom rib, but the ones in the horn). I decided to try my longeron yoke. Sure enough, there was just enough room to fit it over the side edge and swing it into position for all twelve of the interior rivets.
There was still a lot of work to do before getting to the dreaded trailing edge… First I riveted the skin to the countersink rib. I thought I might have to drive these, but after doing a couple with the rivet gun I realized that my 4″ yoke would reach, so I squeezed the rest. I then had to bolt the counterweight in… This wasn’t too hard (despite my long search for the bolts themselves a few weeks earlier). The bolts snugged right up and fit neatly into the countersinks. I added some Loc-tite to make sure that the lock nuts really stay in place.
With that done, I needed to rivet the skin to the spar. There are 50 holes on each side. Again, the 4″ yoke would reach, but I really didn’t want to hand squeeze that many rivets, so I finally pulled out the pneumatic squeezer. I didn’t have very good luck with it when I did the toolbox project and we did all hand squeezing in the EAA workshop, so I was a little worried. It was fine though… I knocked out the rivets cleanly and accurately. It went so well, I used it again to do the top rib. Well, most of the top rib.
The aft most rivet is a total pain to get to. The rudder tapers to a very narrow point and there is absolutely no room for even my thin nosed yoke. A bucking bar is out of the question. I puzzled for a while and then decided to try bucking the rivets with a piece of 3/16″ steel I had thought to use for a back rivet plate (I got a thicker one that I actually use for that purpose). I was able to slip the steel bar into the rivet space. Using a piece of scrap wood as a fulcrum, I was about to lean on the bar with an elbow, hold the skin up with the fingers of my left hand, and drive the rivet with my right. It sounds more complicated than it turned out to be in practice.
I had to turn the air pressure up a lot to get the rivet to drive because there wasn’t a lot to buck against. I was running close to 90 pounds (I normally drive at 40 to 44 pounds to help with control). Here’s the final result.
It’s smooth and flush and has a good shop head to boot.
No more stalling, it was time to rivet the trailing edge. I was filled with dread as the boards are rife with stories about curving and warping and oil canning and bad looking rivets. I pulled out all the clecos and rivet taped in all the rivets. I have a 5 foot long back riveting plate, so the whole thing fit easily. I shimmed the rudder to try to get the edge to lie flat. It looked like there was a pretty big curve in the edge, so I was worried.
It was a total non-event. I hit every tenth rivet lightly with the back rivet set and then started sub-dividing the rest until I had the rivets mostly set. Then I finished with the swivel mushroom head to drive the shop heads fully flush with the skin. The whole think seemed to tighten up and straighten out as I went. I don’t think it took 5 minutes total to do the whole edge. The instructions call for a .1″ tolerance across the edge. I measured at the point of largest divergence. It was about .04″. I’m calling this one straight enough.
The next step (also dreaded) is rolling the leading edges. I decided to do it with some 1″ PVC pipe (I also have some 3/4″). I screwed some pipe clamps into the table to guide the pipe. I added some cardboard and tape to make sure I didn’t drag the skin over the sharp edge of the clamp.
I added some gorilla tape to the leading edge and tried to make the bend. The first thing that became clear was that I really needed to do the three sections one at a time. I tried bending by hand, but ended up using some channel locks to help spin the pipe. I didn’t have time to complete the bends, but that will be the first order of business next weekend.
Next up… finish and hang the rudder. And then start gathering parts for the horizontal stabilizer (it’s huge!).