Last thing to do before the wings go on for good was to leak test the wing tanks. I had to install the access plate and fuel quantity senders then do leak checks of the tanks. The plans call for a cork gasket between the tank rib and the access plate, then the sender comes with a thick rubber gasket. Many will throw these gasket out and just close things up with tank sealant. This has a good track record but if it ever has to come off the sealant is a bit of a pain to remove in the tight space between the tank and fuselage. I talked with a few folks and the gaskets work fine if installed properly so I am going that route. The one thing I am doing is using a screw that has an integral O-ring, many of the leaks I hear of are usually at the screws. In a perfect world the tanks should be built with enclosed nut plates but these are expensive and Van’s being the frugal guy that he is does not call for them in the plans. If I were to build my own tanks I would buy these nut plates and eliminate the worry of the leaks, but I went with quick build wings so I have to live with what is there.
I used the leak test kit which calls for sealing the gas filler cap, I used some pluming deal from Home Depot to seal the fuel tank filler hole rather than duct taping over the fuel caps. Then there is a fitting that goes into the threaded fuel drain flange, it has a tire filler valve. Then cap the fuel feed line. This leaves the tank vent as the only unsealed hole in the tank. You install a balloon there then fill the tank with air very slowly. The balloon protects the tank from too much pressure; it should break before you can exceed the tank pressure limits.
Then it was a matter of checking for big leaks. I used kids bubble maker solution and sprayed it over every connection, seam and rivet line and no leaks were noted. The only place I can’t check is the aft part of the tank, to do that I would have to remove the tank and at this point I will let things sit overnight. If the balloon has gone flat then I will
Gasket is coated with EZ turn fuel lube
My right tank and a poor seal job over the drain vavle rivets, I added some proseal here.
