One of my family sayings is that “It isn’t a project until you’ve cut yourself.” Well, today, the rudder is officially a project! I caught my knuckle on a burr and got an small cut. At least blood doesn’t effect aluminum as much as it does wood!
Today was another bifurcated day. We’ve picked our contractor and we’ll start ripping up the master bedroom nine days from now. But I had to rush home to meet the contractor to sign the final documents. I got a lot done none-the-less!
I picked up trimming the rudder stiffeners. The first three cuts went great. Then, a small sliver of aluminum slipped down into the saw and cut the timing belt!
It did not cut all the way through, but now the belt slips off and so I’ll need to order a replacement. That meant that I had to finish with my straight cut snips. That worked just fine. I left a small allowance and then used my belt sander to finish. One of the stiffeners ended up a little over sanded, but it fits just fine.
The skins were next. There are a couple of quick modifications called out in the instructions. You need to cut off a small tab on the counterweight cover on both skins and trim 3/32″ from just the right skin.
I had an edge gauge that I had brought from my home shop to help make my daughter’s triangle loom (I needed an accurate line 1/4″ in from the edge). This was perfect. Now normally, one doesn’t want to scratch through the aluminum, but here I was planning on filing down below the scratch mark anyhow. I almost made a big mistake when I set the gauge on 3/16″ instead of 3/32″, but it was clear that that would make the edge allowance for the rivet holes much too small. So, I backed off the gauge to the proper depth and it make a really nice line — much easier to cut to than a wide Sharpie line.
I cut to within a 1/16″ with my straight cutters and used the bastard file to take it to the line and then the fine file and scotchbrite to finish it off.
There’s a lot of other little fixes to apply to the skins. Several of the edges need to be bent over just a little bit to help them sit flush. Thin skins have a tendency to curl up when riveted near their edges. This little turned edge helps it stay flat. On the rudder; the front rolled edge, the trailing edge, and the counterweight cover all need this edge done. If I was a big metal shop, I could do it in a brake, but I don’t have one. You can do it with a small hardwood block with a groove in it, but it’s hard to get a consistent edge. Or some shops sell a small pair of rollers on a block to try to bend over just a 1/4″ of the sheet. Or you can buy a small specialty tool to help you do it. I did the later. Cleaveland Aircraft Tools (Iowa, not Ohio!) has a nice little edge former tool built up from a pair of vice grip pliers. There are enough places that I need to do it that it seemed worthwhile to get the proper tool to do it.
The roller on the top forms a small bend. If the grip is set right, it works like a charm. If it is too tight it can stretch the skin (or just get stuck). I was very pleased with how this small edge formed. I had more trouble with wandering on the longer edges, but the edge seems fine. You also have to drill one hole in each skin out to #30 and dimple. I haven’t looked far enough ahead to see what that is for. It must be hard to reach later. With all that done, I smoothed and deburred both rudder skins. I did the work on my dimpling table which is about 8 inches higher than my work tables. It really put the skins at a nice height and simplified the fine file, deburr, sand, scotchbrite steps. The edges came out really nice! One interesting thing to note is that when you look closely, you can definitely see how the CNC cuts the skins. There is a clear case of the “jaggies” where the cutter moves over one unit of space to try to keep the line straight. This requires a lot of careful filing to fix. I also primed the insides of the skins (and the counterweight cover edge). I taped off where the trailing edge goes (I do read ahead!) so that I can scuff that to glue in the wedge later on.
The next big step is to assemble the spar. This means that I need the parts finished and primed. I could skip ahead and finish the riblets now, but I think I’ll get the spar together first so I can stay in order. I finally got an adapter for my bench grinder so now both fine and medium ScotchBrite wheels are spinning. The wheel made quick work of the spar, all the doubler plates, the top/bottom/counterweight ribs, the shim, and the rudder horn.
Oh! Nice surprise. I noticed that the tip rib has the forward third of its holes pre-dimpled! This area is really tight. No room for a squeezer and probably a tight fit for the pop-rivet dimpler. Vans just went ahead and did a couple for you.
The rudder horn needs a lot of attention because it fits into a very small slot in the bottom of the skin. At least one builder didn’t taper it enough and put a nasty small crack in his skin. See this thread for details.
After getting the parts all nice and smooth, I scuffed the faces (lightly) with ScotchBrite and cleaned them off with acetone. I was careful to remember which side faced the spar (the instructions remind you to mark that side). But the acetone removes the marker! So, as soon as I finished, I marked the side with blue Sharpie again. The “lore” says that you will be able to see the mark through the primer….. And you can!
With these parts all primed…
…I can assemble the spar. Then the riblets get set for a test fitting and match drilling. Then the rudder starts going together! That is, if I can find two missing screws… I looked through all the bags, but I cannot find the counterweight screws. They are .9″ long, 5/16″ Phillips head screws, but I cannot seem to find them anywhere! Oh well! Another email to builder support!
I’m flying my daughter back to college tomorrow, so no extra build time this weekend (sad face), but I will be flying (so happy face!).