It took me a few days to finish all of these, but seeing them in a row when they're attached to the skins is satisfying.
Since the rudder skins sit flush on the table top, the plans recommend putting the skins on something that you don't mind drilling into while match drilling the stiffeners to the skins. I chose to set the skins on some old (clean) carpet lying out in the garage. I ended up putting the back side of the carpet against the skins before drilling to avoid getting any fibers tangled in the reamer.
Starting with the right skin I reamed the holes to #40, then did the same for the left skin.
The next step in the plans was priming and then riveting the stiffeners to the skin, but I wasn't in a position to do that yet so I moved on to the rudder skeleton. One of the first steps here is clecoing the R-904 bottom rib to the R-902 rear spar and enlarging the hole in the rib to 3/8" using the unibit. This is probably basic tool knowledge that I didn't know due to my lack of metalworking experience, but I found the the unibit works best at slower speeds. The final hole ends up being uncomfortably close to the edge of the flange, but this is okay since the spar will handle the load of the bolt that will be secured here.
Next was fabricating a 3"x1 1/8" shim to make sure the rudder horn will sit flush on top of the rib and spar. There's a long piece of aluminum in the kit that just so happens to already be 1 1/8" wide and is the exact same thickness as the rib, and this is the piece from which you cut the shim. This seemed obvious to me, but I've seen multiple people on the forums cut the shim from a larger piece of aluminum that was part of the trim kit (extra sheets of aluminum they include with the kit for use to use however you want/need), and I have no idea if they ever realized it. All you need to do is cut a 3 1/2" section off of this piece and smooth the edges, which is way easier. The long piece of aluminum that remains will be cut in half later to make the two attach strips for the bottom rudder fairing.
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| The drawing of the piece is 1:1, so that's nice. |
The piece then needs 3 holes drilled. Instead of just measuring and drilling (and possibly allowing the drill bit to wander), I decided a better method would be to mark the approximate locations of the holes, clamp the shim into place on the spar, check the fit, then match drill the holes using the spar as a guide. This worked beautifully:
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| Shim marked with hole locations. |
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| Clamped in place. |
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| Just as I thought – they line up! |
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| One match-drill later, a good-looking piece. |
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| Perfect! |
With the shim now clecoed in place, the rudder horn could be installed. Well, almost. The forward end needed to be shaped to fit the inside of the bottom rib, otherwise it wouldn't sit flat against the spar assembly. This was easy enough to do on the Scotchbrite wheel.
Next was assembling the rest of the rudder skeleton and reaming all the holes to #30. As it turns out, the rudder skeleton is fairly well balanced on its own, which is probably a good thing:
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| Gallon of AKZO for scale. |
The skin for the rudder horn needs to be clecoed onto the skeleton and the holes enlarged to #40. Thank goodness for prepunched holes, because this is a suuuuuper tight fit. I had to start at the front, then struggle to cleco pretty much every hole evenly on each side to properly stretch the skin over the ribs.
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The rudder horn brace at the bottom needed to be put into place before I could cleco on the rest of the rudder skins. The part is purposefully left too large and must first be trimmed to fit inside the R-904 bottom rib. I took the advice of some other builders on VAF and cut the horn brace to the outside of the punched circles to avoid cutting the piece too short. There will be holes drilled into these flanges to connect the piece to the bottom rib, and those rivets won't have adequate edge distance if too much material gets cut off. Some other builders have made this mistake and ended up ordering one or more additional horn braces to try again, so I proceeded with caution to avoid wasting time and money on replacement pieces. Cutting away from the cut line, grinding little by little, and checking the fit periodically gave me a brace that fit perfectly in place while having enough edge distance on every hole. Cutting north of the machined holes did leave the final piece with some unsightly notches on the edges that had to be rounded off, but at least I don't have to worry about ordering any new parts.
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| I also rounded off the upper forward corners to allow the piece to sit better in the R-904 rib. The black marks are the minimum allowable edge distance for the rivet holes. |
