Initial Prep (Debur, Trim, Drill, and Cut) 8/31/22 – 1.8h 9/1/22 – 2.2h 9/2/22 – 4.0h 9/3/22 – 3.5h 9/5/22 – 2.6h 9/6/22 – 0.8h 9/7/22 – 1.7h 9/8/22 – 0.7h 9/9/22 – 0.3h 9/10/22 – 3.3h The outboard leading edges were a good dress rehearsal for the fuel tanks. The structure is virtually the same, with the addition of some plumbing and the rear baffle. Part preparation is also nearly identical starting with straightening and deburring the fuel tank ribs. One thing I learned from the leading edges is to spread out the flutes in the ribs if possible. If there are flutes between holes that are next to each other, it is harder to buck those rivets later since you have to use a narrow bucking bar to get between the flutes. This time around I avoided putting flutes between consecutive holes as much as possible. The other thing I noticed is each rib takes me approximately an hour to prepare. The inboard rib for each fuel tank comes in two pieces (forward and aft) to allow for a tank attach bracket to be inserted between the rib pieces. The aft inboard ribs have a large hole surrounded by #30 rivet holes to attach a finger strainer flange, which holds a strainer to remove large particles from fuel exiting the tank prior to entering the rest of the fuel system. The plans detail steps to add an additional finger strainer flange hole at the top of the rib. The plans specify the center location of the 3/4" upper finger strainer flange hole, which is enlarged to final size with a step drill followed by match-drilling the flange for the rivet holes. According to another builder's log, the upper finger strainer is for future growth for a powerplant that requires a fuel return line to the tanks. The hole will ultimately be sealed for now, but is available if needed in the future. A confusing aspect of the plans for this step is the language change from only addressing the left tank and expecting the builder to mirror those instructions for the right, to discussing both left and right inboard ribs together in the plans. For example, there is a step to final drill “the two remaining finger strainer flanges that will attach to the lower region of the rib.” When I first read the plans, I mistakenly thought the reference was to the upper and lower flanges (two) on each rib. The plans actually refer to the single pre-cut flange hole at the bottom of both inboard ribs (two). The fuel tanks have several skin stiffeners that attach to the bottom skin of the tanks. The stiffeners are roughly 9” long L-channel pieces that fit between the ribs. Each tank gets 10 outboard stiffeners and 1 slightly shorter inboard stiffener, which are cut from long L-channels. The inboard stiffener L-channel also includes 2 fuel tank vent clips. The vent clips get riveted to the fuel filler flange and hold the vent line in place at the top of the tank. The plans specify step-drilling the hole in the vent clip to 7/16” for the snap bushing around the vent line. The vent clips are maybe 5/8” wide, so the vent line hole gets very close to the edges of the clips. In my case, the drilling process got a little off center on one of the clips and the final hole is right on the edge. That vent clip is too fragile to reliably hold the vent line in place, so I ordered a new L-channel from Van's to try again. The Tank Attach Zees are also attached together in two long strips, and have to be separated. Before separating, all the holes are final drilled, and the #40 holes are countersunk for flush rivets that hold nut plates in place. I learned from the skin stiffeners, that it is easier to do some of the deburring work before cutting the pieces apart. I deburred all of the holes as well as the lightening holes in each attach zee first. I also took an initial pass at deburring the long edges to remove the larger tooling marks. I used a band saw to separate the parts, and then the 6” cut and polish wheel on the bench grinder to remove the tabs that were left over. [Fluting Pliers, #12 Drill, #30 Drill, #40 Drill, Step Drill, Band Saw, 6” Scotch Brite Cut and Polish Wheel, Hole and Edge Deburring Tools] Final Prep (Dimple, Countersink, and Shape) 9/4/22 – 2.0h 9/8/22 – 0.5h 9/10/22 – 0.4h Dimpling and countersinking wrapped up the part preparation for this step. The #40 holes in the rib flanges were dimpled first. The plans include a note that “the top flange aft hole in each Tank Inboard Rib – Fwd” has limited access, so a pop rivet dimple tool is required for that hole on both inboard forward ribs. I could dimple the rest of the holes in the rib flanges with a pneumatic squeezer and reduced diameter dimple die. The aft inboard rib also has some holes in the web for nut-plates that need to be dimpled. The nut-plates are used to attach the fuel sender unit, and are dimpled flush on the outside surface of the rib. The best approach for these dimples was a reduced diameter dimple die in a 22” C-Frame. I also used the C-Frame to dimple the skin stiffeners with a standard-size dimple die. The bend for the stiffener flanges is far enough from the holes that the standard die works well here. The Tank Attach Zees are made from relatively thick aluminum, so they are countersunk rather than dimpled. The only holes that need to be countersunk are the #40 holes for the nut-plates in the top flanges of most brackets. The inboard attach zee does not have any nut-plates, so there is no countersinking required on that one. The nut-plates for the inboard attach zee were actually riveted to the main spar several steps ago. Now I know what those 3 nut-plates in the spar are for! [Scotch Brite Flap Wheel, Pneumatic Squeezer with Reduced Diameter 3/32” Dimple Die, PoP Rivet 3/32” Dimple Die, Blind Rivet Puller, 22” C-Frame with 3/32” Dimple Die and Reduced Diameter 3/32” Dimple Die, 3/32” Countersink Cutter, Microstop Countersink Cage] Prime 9/11/22 – 1.4h 9/12/22 – 0.3h The plans for the tank include the note, “Do not prime any areas that will be in the inside of the tank.” The mating surfaces get scuffed (aggressively), cleaned, and then sealant is applied to those areas. There are, however, a few exterior tank parts that can be primed if desired. The tank attach zees are outside the tank, with the exception of the bottom flange which is attached to the outside of the rear tank baffle with blind rivets. The bottom flange on the tank attach zees gets a small amount of sealant around the rivet holes. I decided to mask off the bottom flange, and prime the rest of the tank attach zees before installing the nutplates on the top flange. [Grey Scotchbrite Pads, Bon-Ami Cleanser, Dupli-Color Degreaser, Rust-Oleum Automotive Self Etching Primer (Green – Rattle Can)]