Initial Prep (Debur, Trim, Drill, and Cut)
6/20/23 - 1.0h
This is the last time to access the inside of the aileron counterbalance tube before it is permanently installed in the leading edge of the aileron. I took the opportunity to ensure the screws holding the counterbalance were tight. I could not get a torque wrench on the screws due to the limited access inside the flange of the nose ribs, but I feel good that they are tightened down adequately to not come loose. I also gave the holes in the counterbalance tube one more pass with the coarse grit sandpaper to remove drilling burrs and pushed a couple of clean paper towels through the tube to remove as much debris from drilling and deburring as possible.
[Hole and Edge Deburring Tools]
Assemble
6/21/23 - 2.1h
6/22/23 - 1.0h
6/23/23 - 0.7h
6/24/23 - 0.6h
6/25/23 - 2.4h
6/28/23 - 0.3h
6/29/23 - 0.8h
7/1/23 - 2.3h
Assembly starts with installing the nose ribs and counterbalance into aileron nose skin. The skin holds its final shape well where it is cleco'd to the ribs or where the workbench stands hold the top and bottom of the nose skin in shape. In other areas, the skin bows out significantly, so I used strips of tape to hold the nose skin in its roughly final shape. That makes aligning the ribs for rivets a little easier, but I found the ribs still need a fair bit of cajoling to get them into position where the rivets sit flush in the dimples.
I started riveting from the trailing edge of the nose skin forward beginning with the bottom rivets on the middle rib, then the top of the rib, then repeating the bottom / top riveting on the two end ribs. The hand squeezer has good access to all of the rivets, and I followed the note in the plans to use a 1/2” tall squeezer die on the interior shop head on the top rivets. I found access to the manufactured head on the bottom end rivets was limited by the aileron hinge brackets, so I swapped the squeezer set to put the 1/2" squeezer die on the manufactured head on the bottom end rivets. That provided the clearance needed from the hinge brackets to set the bottom end rivets squarely.
The two forward-most rivets on the top side of the aileron nose skin are pulled rivets due to the curvature of the nose skin. After setting all of the solid rivets for the nose ribs, I final drilled #34 the two forward-most rivets for the slightly larger pulled rivets, and then set the rivets with a hand rivet puller. The blind rivet process didn't present any special issues or surprises.
Pulled rivets are also used to attach the spar to the nose ribs. The holes are already final-sized, so no additional drilling is required. I set the center rivet on each rib first followed by the top and bottom rivets for a total of nine -- three rivets for each of the three ribs.
On to the top skins… This step is reminiscent of the flaps starting with inserting the top skin between the nose skin and the spar. Also like the flap, remember to keep the small tab on the inboard and outboard ribs inside the spar flange. The detail for how the rib, skin, and spar fit together is shown earlier in the plans (sheet 22-06). I didn't see a reminder or new detail drawing on the assembly sheet 22-08, so you have to remember how things go together on your own. The plans also specify clamping “a straight board to the Top Skin Assembly near the trailing edge (to hold the top skin straight while riveting).” I clamped the skin between some new paint stir sticks on the exterior side and my aluminum “U-Channel” on the inside of the skin. The U-Channel provides the straightness and some structure, and the paint sticks contribute to the straightness and provide a good place for the clamps. That setup is also relatively light, which is nice while the skin is sticking up out of the cradle. A lot of weight like a heavy board (which may or may not be straight) might also damage the skin with an unfortunate crease or bend.
Per the plans, I cleco'd every other hole in the skin to the spar. I riveted the open holes between the clecos with the gun and bucking bar from the center of the aileron out. The rivets went really well thanks to the experience from building the flaps. The trickiest area is at each end of the aileron where there is a close grouping of two (outboard) and three (inboard) holes. The nose skin does not attach to those holes, so you end up with an uneven area where the nose skin stops and the top skin continues. I came up with an experimental approach, which is an admittedly risky move but ended up working really well. The wing kit came with several small sheets of aluminum at various thicknesses. I clamped a sheet the same thickness as the nose skin over the closely spaced rivets in the top skin, and then set the rivets with the gun on the shim.
Riveting the main ribs to the spar turned out to be a whole lot harder than the top skin flush rivets. I tested a squeezer yoke to see if that would work, but clearance from the hinge brackets is not wide enough to accommodate the yoke. I went with a long, cupped set on the rivet gun, which had the best (not perfect) access to the rivet head. The longer rivets on the inboard doubler end were the easiest to get to, so I started there. I put the manufactured head on the exterior doubler side since that had the most clearance for the rivet gun. The inboard rivets went pretty will, but that was not the story on the outboard side. I repeated the manufactured head on the outboard side because there was no room for a bucking bar between the outboard aileron hinges and no room for a rivet gun next to the top skin. In addition to the very tight quarters for the rivet gun, the holes are biased slightly to one side, which prevented perfectly straight alignment of the rivet set between the hinges. Three of the rivets went reasonably well with some minor “smiles” that cannot be avoided. One of the rivets, however, was a total mess. I allowed the rivet set to come off the manufactured head, which effectively destroyed the rivet head and bent the area slightly. I decided to drill the rivet out, which ended up elongating the hole a bit. Fortunately, the interior of the hole wasn't damaged, and the new rivet fit reasonably well. The result wasn't pretty, and I've decided to build a new left aileron at some point. It's airworthy right now, but I'll have to keep an eye on it for cracks.
The last step on this sheet was installing the bottom aileron skins and riveting them to the spar. The process is nearly identical to the flaps, which helped move things along relatively quickly. The tabs on the end main ribs go inside the spar, which took a little maneuvering but wasn't difficult to get in place. The skin goes between the nose skin and the spar flange, which again isn't difficult.
Once the bottom skin was cleco'd in place, I cleco'd the main ribs together to check for twist. I was happy to see almost no twist in either aileron, and riveting the bottom skin in place didn't introduce any twist to the aileron. I removed the main rib clecos prior to riveting to help with the clearance between the skins for bucking the skin/spar rivets.
I started at the center of the aileron and worked my way inboard and outboard with every 10th rivet, and then splitting the difference from the middle out until all of the rivets were set. I used the RV-14 Elevator Bucking Bar, which had excellent access to buck the rivets without me bending the skins to get my arm inside the aileron. The only area that this method didn't work was near the stiffeners. I saved those rivets for last and used a smaller tungsten bucking bar that I could lay on the spar below the stiffeners. I had to reach in to hold the bar, but it was only for 8 or 9 rivets as opposed to all of them down the line.
The final rivets I set were the inboard and outboard rivets that are beyond the bottom skin, but hold the ends of the nose skin in place. Like the top, I couldn't set these rivets with my standard rivet set without damaging the adjacent bottom skin, but unlike the top the area on the bottom is also constrained by the hinge brackets. That negated my top-side method of sandwiching the rivet. My technique for the bottom was to remove the spring guard from my back-rivet set, and just use the very small diameter portion to set the rivet. This takes a lot of care to ensure the rivet set is square to avoid damage, and I was actually surprised at how well it turned out. I won't hesitate to go to this method again for the next tight area with flush rivets.
[Hand Squeezer, Flat Squeezer Set, #34 Drill, Blind Rivet Puller, 3X Rivet Gun, Flush Rivet Set, 1/8” Cupped Set, Tungsten Bucking Bars, RV-14 Elevator Bucking Bar, Back-Rivet Set (without spring guard)]