SonexBuilders.net

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Sorry to hear about your leak. It might be worth while calling Rans Aircraft. They have been working with plastic tanks for many years and have developed a special fitting that installs easily and works very well. I have installed their fittings in four S-7 tanks and recall a simple design with replaceable o-rings.

All the best,
Gunther

Before looking at the Oops fitting, here's a builder who had a similar issue (and ranted about it in a similar way :-) ), have a read of his story and how he fixed the issue:
http://www.kansasflying.com/sonex1017/P ... light.html
(right at the bottom of the page)

I'm not sure what the issue is with using the oops fitting. I had an issue with my fuel probe and had to replace the fitting as I spun it trying to remove the probe. I did the oops fitting replacement with the tank still installed in the plane. It took a few hours but was pretty painless.

Keith
#554

Mine started leaking after one winter. When I went to replace the fuel probe, it spun. Luckily, a local builder had an extra opps fitting. Not too hard to install in the plane. Had to do over, I would have just installed them while the tank was out. We bought several more opps fittings at airventure.

i recently repaired my large fitting.
for about a year my leak was just a blue stain about the fitting, then after a day parked in the sun with a plug over the breather, it developed into a leak.
on the same day, we had 6 Sonex parked together, i think i looked at 5 tanks and 4 had fuel stains around the fitting.
i did the fix without removing the tank, it was a challenge working upside down under the panel.
i removed the old fitting with a small holesaw using a plug with a hole drilled in it as a guide.
getting the old fitting out was easy, and i ended up with a perfect size hole for the fitting, i wasn't game to use a large drill bit as per the instructions.
i then spent half a day smoothing out the bump left inside the tank to get a flat surface for the oops fitting. i used a dremel tool, back grinding on the reverse edge of a grinding stone thingy.
i then spent another full day using compressed air, vacuum and a full tank of fuel to get the dust out of the tank.
i flushed the tank a couple of times, checking screens and filters each time.
the oops fitting fits nicely after shortening my fuel line to suite.
another builder had recommended i install the fitting during the build, i wished i had.

i had a couple of concerns with the new oops fitting;
there was nothing on the info sheet telling you how tight to do up the fitting, i didn't want to damage the o-ring.
was i meant to use loctite etc? i think a second, lock nut, would be a good idea.
does the o-ring need to be checked and replaced regularly?, how long should they last?

i just snugged it up, plus a bit more, a couple of months later the oops fitting seems to be working well.
Doug.

Mine started leaking after sitting in cold hangar. Large uni-bit worked well drilling out old ones. One trick I used while doing this was to stick the BLOWER end of vacuum cleaner down the filler neck to both vent fumes and push crud out. Caution! In no case use vacuum cleaner to suck in explosive fumes.

Found not all O-rings were viton, and some where over sized. I machined groves in washers of fittings to help keep O-rings from being mashed out from under the washers. No more problems

If building another would just fit these from the get go.

David A.

My oops fittings did not include washers. Are you talking about grooving the nut or the stud flange. I am installing oops fittings during build.

Yes, grooved the nuts. Sorry bout that, should have checked my files. Used two sizes of O-rings, slightly larger ones in the groove of the nuts. Grove was milled so as to leave very thin wall keeping O-ring from being damaged on threads. I think the originally supplied o-rings proved to be correct for the nuts after grooving, Also made special tools that acted as a surface mills for the bosses inside the tank, those were fed down from filler neck, same as installing the fittings, shank extending out through hole and turned by drill on outside. No drawings or photos made.

David A.

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