Initial Prep (Debur, Trim, Drill, and Cut)
5/10/23 - 2.1h
5/11/23 - 2.1h
5/12/23 - 2.0h
5/13/23 - 3.8h
5/15/23 - 1.5h
5/16/23 - 3.2h
5/17/23 - 1.2h
5/18/23 - 1.7h
5/20/23 - 4.1h
5/21/23 - 3.0h
5/24/23 - 2.3h
The time and number of work sessions spent on this step indicates a lot going on. The first item is securing the aileron counterbalance to the nose ribs, which requires match-drilling holes from the nose ribs into the stainless steel tube counterbalance. The counterbalance is sandwiched tightly between the ribs and the nose skin, which helps to hold everything in place for the first hole. The bottom hole is drilled through the bottom hole in the aft and forward rib flanges. That hole is then cleco'd and the nose skin is removed to mark the upper hole with an extended #40 drill bit. The mark is drilled #40, and both #40 holes in the counterbalance and nose ribs are final drilled with a #27 bit. Drilling stainless steel takes time and lubricant. It also takes extra drill bits - I broke 2 #40 jobber bits on this step! After the holes are drilled and deburred, the ribs are attached to the counterbalance with screws and nuts. The drawing on the first page of the plans for this section shows the nut inside the tube, so that it is the orientation I went with. I found a cleco clamp did a nice job holding the nut while I turned the screw with an offset ratchet screw driver.
The ribs and counterbalance assemblies are re-cleco'd to the spars and nose skins to match drill the holes in the leading edge to the counterbalance. I used a drill guide with a “Vee” shaped bottom to help ensure the holes were drilled square to the curved leading edge. Each hole gets cleco'd to hold the counterbalance tight to the skin as the drilling proceeds, and the clecos are removed after the drilling is complete. The drilling operation left some major burrs inside the counterbalance. I attached a piece of coarse sandpaper to the end of a long wooden dowel rod to debur the leading edge holes inside the tube as well as I could. I also used the dowel rod to shove a cleaning rag through the counterbalance pipe to remove excess lubricant and drill debris.
The next item to work on are the aileron stiffeners. The stiffeners come in 8 strips with 4 stiffeners per strip (total 32 stiffeners). The stiffeners have to be separated into individual parts, and then formed to final shape by removing bits of flanges and trimming the stiffeners to length. Separating the stiffeners went quickly with the band saw. I also used the band saw to make the shorter shaping cut in the forward part of the flange. The bandsaw did not do well with the longer cut on the aft part of the flange, though, The cut is very steep, which made it hard to push the piece accurately through the saw blade. The saw blade was also easy to get off course. The result was 2 destroyed aileron stiffeners and an order with Van's for a replacement strip of 4 aileron stiffeners ($9.25 + tax and shipping). I changed my technique to using a dremel and metal cutting disk to make the initial rough cut. Next, a bench grinder with a 6” Scotch Brite wheel fine-tuned the rough cut close to the cut-line. I then used a large flat file anchored to the workbench to file the cut straight and to the cut line. A small modelling file and fine sandpaper removed the tool marks from the flat file, and then the cut was deburred with an edge deburring tool and Scotch Brite pad. The process was time-consuming, but the results were very good. The aileron stiffeners were finished by trimming the forward edge and cutting the trailing edge to the appropriate length.
My last prep step was to put a slight edge break in the aft edges of the top and bottom skins and top and bottom edges of the nose skins. I was a bit early with this process, but wanted to ensure it got done before priming and dimpling. I've learned that the edge break should be very slight (nearly imperceptible) for good riveting results later. The goal is to “coax” the part into going the right direction. If the edge break is too severe, the result will be a puckered edge when it is riveted - exactly the opposite of what you're trying to accomplish with the break.
[Hole and Edge Deburring Tools, #40 Drill, #40 Extended Length Drill, #30 Drill, #27 Drill, Cleco Clamp, Offset Screwdriver, Long Wooden Dowel Rod, Band Saw, Hacksaw, Dremel with Metal Cutting Disks, Files, Edge Forming Tool (Vise Grip Style)]
Final Prep (Dimple, Countersink, and Shape)
5/27/23 - 0.8h
5/29/23 - 1.0h
Dimpling the main ribs, stiffeners, and skins is straight-forward with the C-Frame (or DRDT-2) dimpler, but some thought needs to go into which holes to dimple at this stage of the aileron construction. The ribs and stiffeners are easy - dimple all of the holes where those parts will contact the skins.
The skins are a little tougher to figure out. First, you need to determine the orientation of each skin for each aileron. The best way for me to do that was to cleco the skins to each of the aileron spars. The inboard end of the spar has 3 closely spaced holes, and the outboard end has 2. That will help determine the top and bottom side of each aileron skin, which is what you need to know to dimple the skins correctly. The other thing to note is the leading and trailing edges of the skins do not get dimpled just yet. The next step cleco's all the parts together again, which is easier without dimples in the leading edge of the skins, nose skins, and spars. Following that, the trailing edge of the skins and trailing edge wedges are final drilled, which is done before the skins are dimpled and the wedges are countersunk. I did dimple the 3 leading edge inboard holes and 2 leading edge outboard holes in the skins. The most inboard and outboard holes need to be dimpled before riveting the main ribs in place, and the adjacent holes are very close and could be difficult to dimple later with the ribs riveted in place right next to them.
[22” C-Frame with #40 Standard Diameter Dimple Dies]
Prime
5/25/23 - 2.3h
5/29/23 - 1.9h
I primed the top and bottom skins and aileron stiffeners after they were dimpled. Priming 4 skins and 32 aileron stiffeners takes some time, but is manageable if things are organized and ready to go. One thing to remember is the area on the skins where the trailing edge wedge attaches should not be primed.
[Grey Scotchbrite Pads, Bon-Ami Cleanser, Dupli-Color Degreaser, Rust-Oleum Automotive Self Etching Primer (Green – Rattle Can)]
Assemble
6/1/23 - 2.2h
6/2/23 - 1.3h
6/3/23 - 0.8h
Assembly at this stage consists of back-riveting the main ribs and stiffeners to the top and bottom aileron skins. Prior to back-riveting, I cleco'd the (uncut) trailing edge wedge to each skin to ensure the stiffeners didn't interfere with the wedge placement and the flanges were short enough to not interfere with the opposite skin. I ended up clecoing the trailing edge wedge, main ribs, stiffeners, and skins together to form a complete aileron, and then looked inside the cavity to check the clearance of the stiffeners at the trailing edge. I was able to insert a small piece of cardboard (a 12-pack soda box flap) between the stiffeners and the opposite skin, so I was confident that all the stiffeners were cut correctly. If not, there's still an opportunity to fine-tune the stiffeners before riveting them to the skins. Back-riveting went really well, and I was very happy with the results.
[3X Rivet Gun, Back-Rivet Set, Large Back-Rivet Plate]