Rudder & Primer Prep

 We started today by finishing the rudder.  The mantra of "cleco, drill, disassemble, debur, dimple" is becoming very familiar already.

At the lower end of the rudder is a rudder horn cover plate that needed to have the wings cut per plans, then fitted and match drilled to the skins.

I didn't get a picture of it, but we also fabricated two strips to match drill to the lower rib and skin.  These attachment strips are put in place for the fiberglass tips (installed later on).

The last build step today was the fitting of the lead counterweight.  This goes inside of the front counterweight rib at the top of the rudder.

The weather looks like it might be favorable for priming tomorrow, so we made a quick run to Home Depot to pick up acetone.  Fingers crossed that we'll be able to start and finish priming tomorrow.  That's the next big step before being able to start riveting.

Rudder

After the stiffeners were finally done, we started the rudder skeleton.  This was pretty straight forward, aside from figuring out how the rudder horn is supposed to layer together with the lower rib.  The plans just don't show the layout in enough detail to determine if the rudder horn goes on top of or underneath the rib flange.

After some back and forth (and looking at a few online build logs), we figured out that the rudder horn sits on top of the rib flange.  In hindsight, that makes sense given that there is a shim behind the rest of the rudder horn, which is there to make up the thickness of the rib flange.  The top of the horn had to be trimmed down a touch and rounded over in order to fit with the rib flange bend.

Here, the plans call for the stiffeners to be riveted to the skins before proceeding to the next steps.  I'd rather do all of the priming at once though, so we decided to just cleco the skins on without the stiffeners.

The tip rib and the counterbalance rib at the top of the rudder were a bear to get right!  The material is much thicker than the ribs of the horizontal stabilizers, so it's much more important to flute the ribs as close to perfect as possible.  We had to go back and forth with this a few times.  The ribs are so stiff that if the holes don't line up, bending them in place is not nearly as easy as with the previous ribs.  This was probably the hardest fit of anything done so far.  

The skins have a small tab that fits around the rudder horn.  This was a little too snug for my liking, so we opened it up a bit on each side.

Rudder

 Today started by finishing up the vertical stabilizer from yesterday.  It was disassembled and we deburred, countersunk and dimpled all holes and edges.

The rudder was next up on the list. The construction of the rudder is significantly different than the other surfaces we've worked on so far.  It's shockingly light weight! Instead of having ribs for all of the support, there is only an upper and lower rib, and all of the support is actually provided by angles that act as stiffeners. Van's supplies a bundle of angle for the stiffeners. These all have to be cut and shaped to fit the rudder skin.  The manual is woefully inadequate in describing how the full length angle needs to be cut to provide the correct number to match the skins. The pre-punched holes in the skin aren't evenly spaced, which makes it even more of a head scratcher.  After a lot of trial and error, we finally figured out how to place and cut the stiffeners so that they all work out.  Each stiffener gets cut (have to do so from the correct side to make it work out right!) according to marks Van's puts in the angle. We marked, cut, sanded, and deburred the stiffeners and clecoed to the skins.

Left Horizontal Stabilizer & Vertical Stabilizer

The right horizontal stabilizer was fitted yesterday, so today we disassembled everything and began deburring all holes and edges, as well as dimpling and countersinking.  Deburring has been a little bit of an experiment. Thicker material seems okay to deburr with the Cleaveland deburring bit in the powered screwdriver, but in thin material the bit either creates too much of a countersink or doesn't actually remove the burr enough to matter.  For thin material we found that using a reamer to match drill created such a smooth surface that deburring was not usually necessary.  When it was necessary, instead of using a bit, running worn out sand paper over the surface was enough to flatten the burr.  I researched deburring until blue in the face, and from what I've found, most commercial specs call for simply running something over the surface to remove the outer burr, but not worrying about creating any kind of a chamfer.  In the future, I will be a little more free with just surface deburring vs using the bit.

The spars are on the thicker side, so those get countersunk as opposed to dimpled.  After some trial and error, we landed on the correct depth for the countersink cage, clamped the spar vertically, and proceeded to countersink.

The nose ribs of the horizontal stabilizer have a front flange tab that has a single hole in them.  The edge distance is not what it should be, but I emailed Van's and they said this is very common for these ribs, and not to worry and build on.

After finishing the right stabilizer, we moved on to the left and repeated the exact same process.  Following that, we started on the vertical stabilizer.  This was actually considerably less involved and may have actually been a better place to start than the horizontal stabs.  We clecoed and drilled the vertical spar and doublers, then the hinge brackets. After finishing the edges and fluting the ribs, those were match drilled to the spar as well. Attaching the skin to the vertical stabilizer skeleton was far easier than the horizontal stabs.  It did not require a jig and wasn't nearly as tight of a fit.

Right Horizontal Stabilizer

Dad and I deburred the edges and lightening holes of all the ribs prior to starting the assembly of the tail structure.  For the most part, everything lines up with amazing accuracy.  It something isn't fitting, it's likely that you've made a mistake!  The main ribs and nose ribs are clecoed and match drilled.

All of the main ribs are identical, but the direction the flanges face can vary.  All of the main ribs except the two inboard ribs have flanges facing outboard.  The two inner rib flanges face inboard, plus those ribs are not at 90 degrees.  They have an angle to them, but that is easily determined and set once the ribs are clecoed between the front and rear spar.

Sadly, after everything is put together, it's time to take it apart (the first of many times).  At this point, we deburred all of the edges, match drilled holes, and lightening holes in the spars and deburred the remaining holes in the newly match drilled ribs.

Van's supplies a couple of pieces of plywood with a template drawn on them for jigging up the horizontal stabilizer.  We cut out the templates and screwed each to 2x4s. The templates were then clamped to the bench after squaring them to each other.  We started on the right side first - setting the skin in the jig first (taping the trailing edges together to keep them from kinking) and inserting the nose ribs.  Most nose ribs fit quite well after rounding off the front flange a little bit, and it took minimal pressure to line up the holes and cleco.  After the nose ribs are clecoed, the front spar is inserted and clecoed, followed by the main ribs and the rear spar.

The only side that really caused any trouble was the inboard-most rib where it attaches to the front spar.  All holes lined up perfectly except for this single spar hole.  It took a considerable amount of twisting to get the spar hole to line up.  I don't want to rivet it under tension just because the spar might have a very slight twist to it, so instead I drilled it to match (considering every other surrounding hole fits perfectly).  I'll take a look at the hole once the assembly is taken apart.  If it's elongated at all or too big, I'll upsize this rivet.  Either way should work just fine.

Tomorrow Dad and I will take the right stabilizer apart and start deburring and dimpling all of the parts.  We'll then move along to the left stabilizer and repeat the entire process.

Front Spar

The first parts are under construction!  I started by clecoing the two front spars together using the doubler plate, then match drilled it all.  Even though the RV9A is a relatively small plane, the length of the spar for the tail was a bit surprising.

The next step is fabricating a couple of attach angles that will attach to the front spar.

Attached the attach brackets to the front spar and match drilled.

The last step for today was to cleco and match drill the hinge brackets to the rear spar.

Here We Go!

After 5 months of waiting, my tail kit has arrived! It took about 2 hours to do a complete inventory, the only discrepancy being that I have one extra screw. Van’s does an amazing job of packing.