I finally managed to fit my tank into the wings, thanks to a friend that was able to cut them and re-weld the sides, reducing the width of the tanks by approx. 3/4".
The tanks came without any outlet and with two Ells fitting and rubber grommet probably meant for the plastic tanks (see photo). Does anyone know if they can be used in the same way on aluminium tanks?

I've not used the grommets like you have on any tank but I would think they are meant for a tank that has more material thickness. The fuel tank on my MiniMAX years ago was made from .040" aluminum and we welded bungs to it to use thread X barb fittings. My concern would be that if your aluminum tank is thin aluminum that there's more chance of the grommet becoming loose and getting cut by the aluminum from vibration.

Since you were able to get the tank cut down and re-welded I'd add threaded bungs. They can be just a simple block of 1/4" or 3/8" aluminum about 3/4" or 1" square welded to the aluminum tank and then drilled and threaded for pipe thread.

That's only my opinion.

Lynn

Thank-you Lynn for the reply.
My tanks have two rectangular doublers welded to the underside at the corner on the aft side (see photo).  I think they are 3/16" thick. Is that what you mean by 'welded bungs'? Do you think they are enough to drill and tap for pipe thread? Maybe they are intended for the robber grommet, to give them enough wall thickness so that they do not become loose or are cut by the aluminium?

Giacomo

What's the thickness of the tank itself? Just 3/16" plates to drill and tap might be a bit thinner than I'd prefer but take a look at a 1/4" or 3/8" NPT brass fitting to estimate how many threads would be engaged. I don't have a magic number of threads that would be a minimum, but I'd think 3 thread engagement should work OK. Probably a better chance of that happening with a 1/4" fitting than a 3/8". Use a good thread "dope" that's fuel resisitant.

Since those plates are there, that also might be a good enough thickness to use your rubber grommets. I've never used the grommets but I think the hole size needs to be sized carefully so the grommet is compressed a fair amount when the metal fitting is pushed in to prevent leaks. I'd also think deburring both sides of the hole would help the seal and prevent cutting or marring the rubber grommet.

I'm just thinking out loud about what I'd do, so I hope others will post advice that might be based on their experience.

BTW...I'd say your welder friend is pretty good at welding aluminum.

Lynn

I think I will try the rubber grommet and the fittings supplied by Team. The plans shown in my first picture indicate a hole size of 1/2" min. and 17/32" max.  That is something I can do.  On the other end even if the material thickness was sufficient I would not know how to tap the tapered threads for the NPT brass fitting.

On another note, yes my friend did a very good job at cutting the tanks and reducing the overall width so that they now fit the wings. The new welds look much better than the original ones.  My friend did not have very flattering words for the original welds, especially after he saw them from the inside.

Consider adding another plate to increase the thickness. It doesn't even have to be welded on. Use a sealant. or gasket between them. Before adding the plate drill your hole, and try the grommet, if you aren't happy with the fit, add the extra plates.

Welded bungs.
https://www.aircraftspruce.com/catalog/hapages/alumflange.php?clickkey=17441