I bit the bullet and decided today was the day to fully seal the left tank! I went through the normal motions of ensuring mating surfaces were scuffed and cleaned, then just to make cleanup easier, I taped off the skins just above where the baffle will set. I've seen two methods of sealing the baffle - the Orndorff method that lays down proseal along the entire width of where the baffle flange will go, and the Van's method of only putting a bead down just inside the rivet holes. I get why Van's does it the way they do, but given that the rear baffle is the most common source of leaks, I kind of wanted to err on the side of more surface area than less. Maybe for the next tank I'll do it differently, but for this one I put proseal over the entire surface that the baffle flange will rest against.
Once proseal was in place on the skins, outside ribs, and around the outside rivet holes of each rear rib flange, I set the baffle in place and went to town with clecos. This is where using a full width of proseal gets pretty nasty. If you do the Van's method and just place it inside of the rivet line, when you push the baffle into place, it moves the proseal away from the rivet holes and makes a nice clean way to rivet. By putting proseal on the entire surface, a good bit of proseal gets pushed out through the rivet holes. All of that has to be cleaned up, otherwise the rivets will set proud in the countersinks. I used strips of paper (like in the Van's video) to scoop out the majority of the proseal from the holes, then learned that a quick spin with a Q-tip (even after it gets covered in proseal) is enough to clean out the countersink to where the proseal doesn't affect the rivets.
Thankfully, all of these skin/baffle rivets can be squeezed, which makes it go very quickly. To lock in the baffle, first I put the solid core pop rivets in the outside holes of each rib/baffle. With those done, I moved to squeezing the skin/baffle rivets. That's a lot of rivets! The top side went just fine, but for some reason the baffle was ever so slightly off on the bottom side. I had to put a punch into almost every hole to pull the baffle down a tiny bit. I suppose that could easily just be due to proseal buildup, even if it's super thin.
The Z brackets were next. I put a very thin layer of proseal on the bottom side (just enough to cover - I'm guessing 1/32" thick) and pop riveted them into place. The inboard and outboard brackets get regular rivets.
The last piece to go on was the access panel. I took one last look at it to hopefully catch anything stupid I'd done, slathered it up with proseal, and put it into place. In hindsight, I used way more proseal than I needed to. I basically put enough proseal on the ring to span the entire contact area of the rib. In reality, the only thing I need to do was put a bead around the outside portion, just beyond the screws, since based on where the nutplate rivets are, that would be enough to stop all leak paths. It doesn't really matter, other than this access panel will be a lot harder to remove if the need every arises. The final sealing is just a matter of dipping the screws in proseal and tightening them down until a nice ring of sealant squeezes out under the screw head as well as around the access plate.
So that's it for the left tank! Now it needs to sit for a few days to let the proseal cure. It's going to be a little cool for the next few days, so I'll probably give it until mid-week before I leak test it. I'll use Van's leak kit (just a balloon and a few caps over the fittings, then a bicycle pump to put a whopping 1 psi into the tank, followed by a soapy water spritz). I need to order some fuel friendly lube (EZ-Lube from Aircraft Spruce) for the fuel drain valve, so I won't put that it quite yet.
