Tank Hints
Keep in mind I am still building and not yet flying so take this for what you paid for it... Here are my top ten recommendations:
Number one hint ... have a riveting partner -- especially when riveting the rear baffle plate. Not that you couldn't do it alone due to access, but there are a lot of rivets and you are fighting time due to the limited setup time of the proseal. It really helps to have someone to help remove clecoes, place rivets, etc.
Number two ... the leading edge rivets of the tank skins (at least the leading 3 or four rivets) to ribs are much easier set with a partner. I would not attempt to set them alone -- ask me how I know.
Number three ... Don't attempt to do too much in one session. If you're fighting time you may overlook simple things like setting the rivets to the proper dimensions. With the proseal it is difficult to determine whether or not you are getting a proper shop head. Take your time and ensure proper setting of the rivets. Try two ribs in one session to begin with.
Number four ... If you have access to a pneumatic sealant gun - or even a manual sealant gun - and can afford the pre-measured proseal (Semkit) cartridges -- use them, it is MUCH easier. If not, the "frosting bag" method will work but is messier and slower. It is cheaper to buy the bulk quart supply of proseal from Van's and mix it yourself, but I cannot emphasize enough how much easier it is to use the pre-measured Semkits. Use the B2 (two hour set-up) proseal. I use the term proseal, which is a trademark, to refer to any of the recommended tank sealants. Regardless of which method you use have plenty of popsicle sticks available - they will come in handy, especially for faring the sealant edges.
Number five ... When you think you are ready to close the tank by installing the rear baffle, wait. Double and triple check to ensure all fittings, capacitance plates, tank internals are all really ready for finally closing the tank. Double and triple check everything, including but not limited to ensuring you safety wired the feed tube (flop tube or regular) which is a Van's AD, flared and torqued the tubes, etc.
Number six ... If you have the capacitance senders, ensure you have sealed the center conductor of the BNC connector completely. Ensure it is completely encapsulated. Others have experienced leaks in this area.
Number seven ... Most leaks have been found where the rear baffles meet the outboard and inboard ribs (in the corners). There are rather large openings that needs to be sealed.
Number eight ... Follow instructions regarding allowance for drainage requiremnets. Do not block drainage paths.
Number nine ... Have PLENTY of rags (buy a couple of boxes of cotton painter's rags at Home Depot) and and ample supply of MEK or acetone (either work well to clean up proseal), but USE personal protective equipment (PPE) - this stuff is nasty!
Number ten ... Everything must be VERY clean before sealing. Scuff all surfaces with scotchbrite and clean THOROUGHLY with MEK (or acetone). Tank sealant will stick to roughed up and CLEAN surfaces quite well. Even fingerprints can compromise the seal or cause problems later.
Number ten and a half ... Don't forget to install the vent tube clip at the fuel filler flange.
Number ten and three quarters - If you want to install the deluxe fuel caps, do it when you construct the tanks. The flanges are different than the stock Van's caps.
That's it. Sealing the tanks are not as bad as some portray. TAKE YOUR TIME and do it right.
Regarding fuel (vapor) return lines -- I installed return lines in mine because I intend to install an ECI FI system, which recommends a vapor return line to each tank. 1/4" aluminumm lines and fittings are sufficient and I installed mine all the way to the outboard bay (in parallel with the vent lines - high in the tank) per ECI recommendations (this allows maximum cooling of the returned fuel -- although I think returning to the middle bay or any other internal bay would be fine). If you plan to use return lines I would recommend using an ANDAIR fuel selector valve (available at VAN's) istead of the stock valve (when ordering the fuselage kit).
Regarding flop tubes vs. stock fuel pickups, that's a personal preferance and I have no recommendation. The regular pickups will work just fine unless you plan sustained inverted flight or extended slips (BTW I installed flop tubes in both wings). If installed in only one wing an additional placard is required.
I hope this helps. Good luck...
