Initial Prep (Debur, Trim, Drill, and Cut) 1/13/23 – 1.4h 1/15/23 - 2.0h The rear baffle is the final major fuel tank part to install, and is also the point of no return for previous build steps. Once the baffle is in place, there is no easy way to get into the tanks to fix leaks short of cutting access holes in the baffle and then fabricating and installing leak-proof access panels. That would be a really big job, which I would like to avoid if at all possible. My approach was to perform an interim low-pressure leak test before permanently installing the rear baffle. I did not detect any leaks following the low-pressure initial test, but leaks may still manifest after the baffle is installed and the higher-pressure test is conducted. More detail on the low-pressure initial test is in section 18-09 of my builder log. Installation of the rear baffle starts with deburring baffle edges and holes, and also scuffing the contact areas between the baffle, ribs, and zee brackets for good sealant adhesion. I cleaned and degreased the baffle and contact areas. I also blew out debris (loose sealant, dust, dirt, …) from the tanks before starting installation. [Hole and Edge Deburring Tools] Final Prep (Dimple, Countersink, and Shape) 1/20/23 - 0.7h Description [Edge Forming Tool (Vise Grip Style), Hole and Edge Deburring Tools, 22” C-Frame with #40 Reduced Diameter, #30, and #40 Standard Diameter Dimple Dies, Pneumatic Squeezer with #40 Reduced Diameter Dimple Die] Assemble 1/13/23 - 3.7h 1/14/23 - 2.5h 1/16/23 - 2.2h 1/18/23 - 2.1h 1/20/23 – 0.9h The Van's fuel tank build video is organized into chapters, and I reviewed the rear baffle chapter before starting the installation. There are a few differences from the video of an RV-8 tank and the rear baffle on the RV-14, but the basic steps are the same and very helpful to prepare. The sealant has a 2-hour working time, so it's important to get everything set up and ready to go before mixing the sealant. There is a lot to do, and not a lot of time after the sealant is mixed. Parts needed for this step included the rear baffle, the tank zee brackets, AD-41H and AD-42H closed end blind rivets, and AN426-AD4-4 and 4-5 solid rivets. Supplies included a pre-measured 3.5 ounce sealant cartridge, which turned out to be the perfect amount for one tank. I was fortunate to borrow a SEMCO sealant gun from another builder, and the gun was absolutely fabulous to work with. The sealant cartridge fits neatly in the gun, and the gun at about 60 psi delivered a clean and even bead of sealant. I applied a bead of sealant just forward of the rivet holes for the baffle flange, and on the inside edges of the end rib flanges. The baffle engages the sealant bead when it is put into place. I also added an extra “glob” of sealant in the corners of the end rib flanges to seal off that gap. The video demonstrates a good tip to let gravity help get the sealant where it is needed, which made a lot of sense as I applied the sealant to the tank skins and ribs. The video also showed the application of a thin “smear” of sealant on the rivet holes of the rib flanges. The video only puts sealant on the top and bottom flange holes, but the RV-14 instructions have you put the smear on all of the holes. The tank baffle was set in place after laying down the sealant. I initially cleco'd the holes that were not countersunk in the skin to ensure good alignment, and I cleco'd the holes in the baffle web for the zee brackets to align the baffle and ribs and to pull the baffle tight to the rib flanges. I then flipped the tank over (baffle side down) to let gravity help the sealant contact the skin and baffle while I cleco'd the rest of the holes in the skin. The tank went back in the cradle after inserting all of the clecos to start setting the closed-end blind rivets at the top and bottom of the baffle web. Those rivets help pull the baffle tight to the rib flanges. A small amount of sealant is applied to the rivets before they are installed to seal the rivet holes. There are also solid rivets at the end ribs that get set with a squeezer, but don't require sealant since they are outside the sealed fuel area. I finished this work session by installing the tank attach zee brackets to the baffle web/rib flanges. The zee brackets get a very thin smear of sealant around the rivet holes where they mate to the baffle, and then get riveted into place with AD-42H closed end blind rivets. Like the blind rivets at the top and bottom of the baffle flange, this rivets are also “twirled” in sealant to help seal the rivet holes. The sealant was starting to firm up a bit at this point, but I still got good squeeze-out under the rivet heads. The end of the tank build process is finally in sight! The build wraps up with riveting the rear baffle to the skin, countersinking the screw holes in the attach brackets, and installing the fuel cap and quick drain. The pneumatic squeezer did a good job with the baffle rivets. There isn't any sealant for these rivets since they are outside the sealed fuel area, so letting the tank sit overnight before setting the rivets is not a problem. After setting the rivets in the countersunk holes, I countersank the remaining holes and riveted them as well. After that, I switched to the #19 (#8 Screw Dimple) countersink bit and finished the 5 holes on each of the attach brackets. I used some Loctite 565 on the drain fittings to block the spiral leak path around the threaded portion of the fitting. I also skipped ahead a bit to the next step and installed the inboard rib plug at the top of the tank and the fuel filter at the bottom of the tank since I had the Loctite out. All of the fluid fittings are torqued according to Section 5 of the plans to 1.5 – 2 turns after finger tight. I could only get roughly 1 turn on the plugs before they were cleared tight enough, and I didn't want to risk breaking the plug by going for the additional 1/2 turn. I plan to let the tanks sit for another week to ensure the sealant is fully cured before I start leak testing. Fingers crossed that the testing goes well - I really don't want to tear the tanks apart to chase down a leak! [SEMCO Sealant Gun, Blind Rivet Tool and Wedge, Rivet Hand Squeezer with 1/8” Cupped Set, 3/32” and 1/8” Clecos and Cleco Pliers, 3x Rivet Gun with 1/8” Cupped Rivet Set, Tungsten Bucking Bar, Pneumatic Squeezer with 1/8” Cupped and Flush Rivet Sets, Microstop Countersink Cage with #40 and #19 Countersink Cutters, Socket Wrench]