Rolling the rudder leading edge was straightforward. I found that I needed to work the upper sections with a piece of 1″ OD pipe, in order to get enough bend on them. With my 1 1/4″ rolling tool, the sections didn’t fit together cleanly enough at the top where there was not as much depth to work with.
Unlike the elevators, for some reason Van’s did not punch the rivet holes out to #30 for the rudder, so I had to match drill them. I drilled them #33, then drilled with a #30 reamer, to minimize the amount of material that had to be removed to de-burr the holes, since the skins are so thin to start with.
Time to take the rudder halves off the shelf and rivet them together. By far the hardest part of this process is riveting the rudder trailing edge without turning it into something resembling the roof of the Sydney Opera House. After researching this topic some months back, I decided to try and do this without hitting the trailing edge with a rivet gun. The method I used has been described elsewhere (and I’ve lost the link), but the description was scant so I’ll go into some detail here.
Back when I prepared the rudder components, I match drilled the trailing edge to a section of Aluminium angle, 2 metres of 50×50 angle, 5 mm thick. This is thick enough to be a sturdy reference straight edge, but still thin enough to be able to get cleco’s through the trailing edge and through the angle. Match drill this before dimpling the skins, so that the #40 holes will be as accurate as possible. Note that the holes are not perpendicular to the surface of the angle section – they are perpendicular to the chord line of the rudder, so about 5 degrees off the perpendicular.
I clamped the Aluminium angle to one edge of the workbench, flush with the surface, and placed one layer of masking tape across the bench edge and the base, just to prevent any marking of the rudder skin surface. I used the 3M F9460PC double sided construction tape (available from Van’s) but the method would work just as well with Pro-seal. With a helper to hold the other skin up off the trailing edge wedge, as each set of ribs were riveted together, I removed the remaining paper from the double sided tape up to the next set of ribs, and also cleco’d every hole in the trailing edge up to a few short of the “next” ribs to be done, working from bottom to top of the rudder. Once all ribs were riveted together, I had a continuous line of cleco’s all the way along the trailing edge, which was held down firmly against the perfectly straight Aluminium angle base. Since the rudder was held securely on the workbench at this point, I also put the front spar in place, installed all of the LP4-3 rivets from the front spar into the shear clips, and riveted the left skin (the one on top in my arrangement) to the front spar, since this was easy to do with the pneumatic squeezer. I left it this way for two days.
After that time, I removed the cleco’s holding the TE to the Aluminium base, drilled every second hole in the base out (in stages) to 13mm, and then used a step drill to go just a bit larger and effectively de-burr the holes. I further deburred the holes with a scotchbrite wheel in the die grinder, then scuffed by hand and cleaned the base to ensure that no sharp edges remained. I then re-installed the rudder back onto the base, with a cleco in every second hole. The large holes enabled me to get the rivet squeezer onto the bottom side of every second hole.
I (very carefully) used flush die to start the rivets, just enough to set the rivets in place but not enough to touch the bottom skin (which would have been a disaster). An inspection mirror is essential here, to check each rivet as it is done. To finish the rivets, I used a modified die on the fixed side of the squeezer (see picture). I ground a die down, so that it was 10 degrees off from flush, to match the angle of the rudder skins. The modified die is then held in place on the fixed part of the squeezer using a bit of gorilla tape (see pictures). Doing the initial partial set of the rivet with flush die is what allows using a single modified die to finish the rivet – it is easier to work with a single 10 degree ground die, than two die each ground at 5 degrees. Holding the squeezer upside down, with the flush die on the top skin, I was able to fully set each rivet in the trailing edge.
I backed the air pressure from the usual 90 psi down to around 60 psi for this operation. I also very carefully adjusted the squeezer gap as I did the first few rivets, checking for any witness marks around the manufactured head (from the modified die), doing some fine adjustments to the die with a file to take down any high spots. After a few adjustments, I was able to confidently squeeze the rivets to completely finish each one. The large holes in the Aluminium angle base actually helped with guidance!
At this stage, every second hole in the trailing edge was riveted. Removing all of the cleco’s, the rudder can be slid off the base. This worked so well, I decided to continue the process, and drill out every second un-drilled hole, again cleaning the base up to ensure no sharp edges remained. I then re-installed the rudder onto the base, with fewer cleco’s, and riveted the positions corresponding to the newly drilled holes.
I repeated this a third time, leaving only three cleco’s holding the rudder down. After that, I riveted the three remaining holes with the trailing edge simply hanging over the edge of the base, with no guidance.
The end result of all this is, the Aluminium angle has a large number of ugly holes in it, but that’s OK because it can now be discarded. On the other hand, the rudder trailing edge is perfectly straight. I held straight edges against the rudder trailing edge, and could not even find an air gap to try and measure how straight it is. I attribute this to the fact that the method completely avoids back riveting, and all rivets are set with the squeezer while the entire trailing edge is held completely flat.
I finished the rudder assembly to the point where the skins are ready for riveting together. Decided to put the rudder parts on the shelf until I can arrange a TC visit, since once the rudder is assembled there is not a lot of visibility into the interior. In a small mental lapse, I managed to place one of the AN470AD4 rivets in backwards on one of the rudder spar doubler plates (I’ve been following the convention of placing the manufactured head of the rivets on the thinner material).
I think this is a case where I leave it as is. There’s a small risk of making a mess if I drill the rivet out and replace it for purely cosmetic reasons, so this one will simply go into my imperfection database.
Rudder doubler plate, with plate nut for grounding strap, and one rivet backwards.
Back riveted the rudder stiffeners to their respective skins. Assembled the R-1004 halves and rudder horn, and riveted this assembly to the right skin. Instead of following the assembly instructions I should have back riveted the R-1004B half to the rudder skin, then assembled the R-1004A half, rudder horn etc. onto that, because with the R-1004 halves already combined, the aft most rivet to the skin is a complete pain to buck.
Riveted the R-1003 rib halves to their respective skins, and then used pulled rivets for the first time on the project to mount the shear clips onto the stiffeners on the right skin, ready for assembly.
Spent most of the past week recovering from a run-in with a surgeon. Glad I slept through it all.
Finished dimpling the rudder components. Now, the standard Van’s plans don’t call for electrical bonding between control surfaces and the air-frame, and don’t include any facility for static wicks. For a VFR platform, this may be OK. For an IFR platform, this may or may not be OK, it’s easy enough to find anecdotal evidence for either case on the various forums, so this topic is a bit like priming. It’s not hard to add the facility to bolt on static wicks while building the rudder. It’s messy to add static wicks after assembly if they have not been allowed for at this stage. There’s a placement document floating around – here – that describes recommended static wick positions for the RV-10.
I didn’t like the approach described by some builders, of drilling extra rivet holes in the rudder skin and countersinking those holes, using the combined thickness of the skin and stiffener to achieve adequate countersinking depth. The only extra “holes” I wanted to put in the skin are those for the wick mounting bolts, so I used existing skin rivet positions for one of the elastic anchor mounting holes, and made up a doubler so that the “other” anchor mounting hole could be an internal rivet between the rudder stiffener and the doubler. The doubler is countersunk as required. The elastic anchor nuts are cadmium plated and can’t be countersunk – that would expose raw steel across the surface of the underlying dimpled alclad. Each mount uses one MS21080-3 single lug elastic anchor and one MS21078-3 two lug elastic anchor. There’s not much room for the aft most anchor, and the bolt that is used to retain the wick will have to be carefully sized and perhaps trimmed so as to not protrude beyond the anchor (to the extent that it contacts the opposing surface).
The wick mounts are on the left side of the rudder. Although the doubler adds a fair bit of stiffness, that’s going to happen anyway since the static wick mount is completely solid/stiff. After match drilling, countersinking etc. the components were assembled onto the rudder skin and a 3.5mm drill was used to drill down through the skin, using a pair of “fitting” anchors as the drill guide. Then the holes were carefully enlarged from the outside of the skin using a tapered hand reamer. Once a sample MS35206-261 machine screw would just fit through the holes, I disassembled everything and used the hand reamer to slightly enlarge the holes in the skin to a good clearance fit, and enlarge the internal holes in the stiffener/doubler combination to be slightly larger than those in the skin. After deburring everything, the entire assembly fitted together well and the skin holes were perfect.
During assembly, I’ll use a small amount of pro seal between each internal surface around the wick mounting holes, to prevent any water ingress. If there is no wick mounted, each hole will still require a screw, so that the screw end into the elastic part of the anchor provides a weather seal.
The final step in preparation of the rudder components was to countersink the trailing edge wedge. With a little set up time it was easy to bore consistent countersinks using the drill press. It’s tedious because there are a lot of holes. I completed all of one side and just started on the other side but elected to leave the rest for another day because I looked up at the clock and it was almost beer o’clock.
While cleaning up, I had a container to label. I’ve been slowly putting common rivets from the various kits into containers, and I noticed the following interesting bag of rivets. Missed this one when I did the empennage inventory … Van’s did get something wrong after all.
Match drilled the assembled rudder. I also match drilled a 50×50 mm piece of Aluminium angle to the trailing edge, to use later on during rudder assembly. I’m planning to use the technique described here to set the trailing edge. After match drilling, I disassembled the rudder and deburred both skins. That leaves skeleton debur, R-1006 countersink, and dimpling.
Deburring rudder skin after it has been match drilled
Finished deburring rudder components. Assembled and match drilled the rudder skeleton. Deburred the skins. I cleco’d the skins together along the trailing edge, and used a vixen file to debur both skins at once so that the trailing edge of the skins stayed identical. I then cleco’d the skins onto the skeleton, ready for match drilling.
I’ve started preparing the rudder parts. I may get the rudder to a point where the parts are ready to prime, and do the rudder and vertical stabilizer in the same preparation and paint session. The following set of parts is the result of ten hours of cutting, filing and de-burring over the past two days. Still a few parts (covered in blue plastic) to go.
