I think the thing that most new builders fear on the tanks is working with the sealant and the possibility of a leaking tank when the work is finished. I counted myself in that group until a few weeks ago. We had one of our AOG teams (aircraft on ground) spend a couple of weeks with us dumb engineers to show us the reality of aircraft repairs on large aircraft. We did a variety of typical repairs under their supervision on a 737 we had in our boneyard and I picked up a bunch of useful information for my RV build.
They showed me how they dealt with sealant. Now I've read dozens of builder logs and many of the post on this site and nowhere was ever mentioned the tools and methods used by the professionals. I think we can adopt some, if not all, of these methods and tools to building the tanks for our RV's.
First, get a pneumatic sealant gun. If you buy a new one, it'll run you several hundred dollars. That's too expensive, but if you go to Brown Tool you can pick up a used Semco gun
for $60. Once you get this tool the possibilities open up. You can use a bunch of different attachments that will make the job of sealing easier, with less mess and higher quality. You might even find it enjoyable.
Instead of using popsicle sticks to butter up a rib flange, use a roller. I used a roller to apply sealant to my rudder trailing edge wedge. The advantage to a roller is the sealant goes only where you want to and it doesn't get into the holes. It's far superior to a popsicle stick. You can get a continuous flow roller attachment
($47) for the Semco gun and replacement rollers at SkyGeek. I'd get the 2 in. roller attachment only because for some strange reason the replacement rollers are cheap (less than $3 each) and the 1 in. rollers are expensive ($17 each).
For fillet sealing there are a wide variety of dispensing nozzles you can choose from for the specific task required. If you're fillet sealing on the non-flange side you can use a standard round opening nozzle. If you're fillet sealing over a flange there's a specialty nozzle for that. Nozzles are inexpensive. They range from $1.50 each for standard nozzles to about $6 each for specialty nozzles. They are reusable if you solvent clean them after use.
Finally, sealing each and every rivet tail is another messy job usually done with a popsicle stick. There are premolded cap seals that you fill with sealant and press and twist into place. Very clean and high quality. It looks like my RV-14A tanks need about 1500 cap seals. I'm still trying to get a quote from PPG on the price of such a small quantity, so I'm not sure if this one will be economically feasible. If I can get them for 10 cents each or less then I'd do it. Any more than that and it gets too expensive for me. I'll let you know about the price when I get the quote. The seal cap video below shows cap sealing of HiLoks, but they make caps for rivet tails too. The concept is the same.
Roller sealing video: PPG Aerospace - Semco Ribbon & Roller Nozzles
Fillet nozzle video: PPG Aerospace - Semco Fillet Nozzles
Seal cap video: PPG Seal Caps
When I get my wing kit I'm going to build the fuel tanks first. I'm now really looking forward to it.