I’m pretty sure the folks at Van’s didn’t throw the rudder at builders first, because some would walk away from the project. That’s not to say that the rudder is too difficult, but it’s a new level of complexity in the project, and (finally) now I’m actually having to really think things through. That’s ok, I like the challenge.
In what seems to be standard fashion, the new phase (Empennage Section 7: Rudder) starts off with minor fabrication of parts. I really enjoy this part of the build – it’s fun to take rough, half-created parts, then use the band saw, grinder and polishing wheels to finish off the manufacturing process and make nice looking, ready-for-assembly parts.
With parts fabricated, it’s time to begin assembling the skeleton of the rudder. You’ll see throughout the build that I’m not going crazy with primer … I spent way too much time reading the pros and cons of priming, and concluded that alclad aluminum doesn’t need primer, only the non-alclad parts such as angle aluminum. So, you’ll see below that the rudder horn is primered (though it’s tough to tell since I’m using grey SEM primer, in a rattle can, which blends in with the alclad in these pics).
When looking at Figure 1 on page 07-05, it looked like the tie clip (HW-00004) was going to go into one hole, when it was really meant to go into another. The hole which will contain the tie wrap clip is the one which gets a pop rivet (LP4-5) – which makes sense since a regularly set rivet would destroy a plastic tie wrap clip, and a pulled pop rivet won’t. Had I looked more carefully, I wouldn’t have made this mistake … but, I’m pretty sure quite a few builders will make this same mistake. So, if you’re reading this and haven’t gotten to this point yet, be careful here!
Now it’s time to complete the test-fitting by attaching the skin. This will then allow me to match-drill all the pre-drilled holes in preparation for dimpling.
It’s time to do some dimpling. The DRDT-2 dimpler got a good workout with a couple hundred dimples on both skins.
After completing the dimpling on both skins, I realized I had neglected to debur the skins prior to dimpling. I was imagining having to order new skins, re-fit, re-drill, then debur and dimple – all over again. After a quick call to Van’s builder support, I was reassured that this was not an issue … that I could simply take a polishing wheel to the tops of the male-side of the dimples to confirm they’re relatively smooth, and “build on”! So, it seems I dodged a bullet this time. Gotta pay really careful attention to the order in which you do things, or you can really cause a headache.
My First Big Challenge – Countersinking the Trailing Edge
What’s ended up being my biggest challenge, so far, was doing the machine countersinking on the trailing edge (TE). The #40 holes on the TE (the smaller ones, as seen below) need to be countersunk so that the dimples on the skin will fit into them. The TE is thin – and when I did some test countersinking on the surplus piece of VA-140 wedge, I realized that when I countersunk to a depth which completely accommodated the dimple, and did so on both sides of the TE, then the #40 hole was enlarged significantly. That’s not going to work. So, I practiced some more, getting the countersink cage dialed into exactly what would produce the deepest possible countersink with nearly zero enlarging of the hole (actually, it was maybe a millimeter larger, but not enough to really care about). But, at that point, the countersink was not large enough to accommodate the skin dimple. So, it was time to talk to Van’s builder support hotline (again – these guys are getting to know me).
While Van’s is always incredibly helpful, I found in this scenario that there really wasn’t anything I was missing … that there is no magic way to make this work perfectly. The bottom line of what I got from them was that you simply make the countersink as large as you can, without enlarging the hole very much. I was told that if one is to error on the side of a larger (better) countersink, at the cost of an enlarged hole, this can end up being a structural issue later. And, to error on the side of a smaller countersink, keeping the hole from being enlarged, can possibly make a slight cosmetic issue (the TE will not look as good, when completed, when looking from the back side of the rudder. because the skins aren’t fitting completely into the countersink). I decided that if it’s not going to be perfect, then I’ll error on the side of being only slightly cosmetically imperfect. That beats any structural issue, for sure. So … my countersinks aren’t as deep as I wanted them to be (see below).
I decided that since the margins were so close on this countersinking work, I was better off using the drill press rather than the hand air drill. I knew that the lower speed of the drill press, and the fact that it’s as steady and stationary as possible, would be best for consistently reproducing the same countersink each time. Since the countersinks have to be perpendicular to the surface of the slanted wedge, I used the surplus piece of VA-140 underneath the TE (but on the reverse side) to keep the surface of the TE perfectly horizontal while cutting the countersink.
Now, I’m waiting on an order of ProSeal which will be used to adhere the TE to the aft inside edge of the skins … meanwhile, I’ll get started on back riveting the stiffeners to the insides of the skins. Back riveting is new to me, so I’ll do lots of practice first.