Fuel Tank Leaks

[DCASonex]

Replaced mine while tank was in the plane. First drilling out the larger fitting for the fuel strainer gives a handy access to work on the other two fittings down there. If going to all that work, might as well replace all in one go. Found step drill worked well for drilling out old fittings, less likely to grab and spin. Got wrong sized "O" rings with my small fittings, and do not know if they were Viton or not, replaced all with known quality rings. Machined grooves into under side of fittings and nuts so that "O" rings would not push out to side when tightening. When I got mine from Sonex and mentioned problems and fixes, was advised Sonex purchased these and did not make them. This may have changed by now, or not. Made tools for the two sizes that looked a bit like the fittings but clamped small disks of open grid sandpaper to smooth off and level inside bosses of tank for good fit of "o' rings to tank. Used BLOWER end of vacuum stuck down filler next to get positive air pressure when working to keep dust and fumes out. Not good idea to suck gasoline fumes into electric vacuums. Just found those two tools if anyone wants to borrow them, or can provide photos to make your own.

David A.

[kmacht]

Pictures of the tools would be great. I still get a small drip out of mine after installing the oops fitting. I had a heck of a time getting the o-rings to not squish out when tightening up the fitting so I think my problem is that the o-ring may have been cut causing the leak. I plan to remove the oops fitting and try again this spring to stop the drip when it gets warmer out.

Keith

[Waiex 49]

My hat is off to those who have been able to install the oops fittings with the tank installed in the aircraft. I suspect it is easier to accomplish if you are replacing the larger 3/8" NPT fitting. In my situation I have two damaged fittings and both are the smaller 1/8" fittings.

With the 1/8" NPT fittings the hole is only 9/16" in diameter. Working through these smaller holes, while laying under the tank, I don't see how I can do a quality job of smoothing any burs left from the drilling operation on the inside of the tank. Nor can I see how I could do a quality job of cleaning any debris from the tank. I was never able to get the first fitting to line up and slide through the 9/16" hole, so I don't believe the "per instructions" method is going to work for me. My conclusion, for my situation, is to remove the tank and do the rework of the fittings on a workbench.

I will probably remove the tank by unfastening the straps and sliding it out from below. However, that looks to be a pain in the butt type of a job. I am giving consideration to removing the windscreen and then drilling out the rivets that hold the glare shield in place. This is a lot of work but at least I wouldn't be spending hours and hours laying on my back under the instrument panel swearing and saying rude things about Sonex engineering.

Has anyone removed their fuel tank by going at it from the top? Any thoughts on the matter would be appreciated. I think I can drill out (and replace) all those rivets a lot easier than I could take out the tank from below.

Thanks in advance,

Don Bowen
N49YX

[SonexN76ET]

Don,

Please read the Sonex instruction sheet on the Sonex website for instructions on installing the tank. The glareshield is riveted in place before you install the tank. I am quite certain that you would have NO benefit from removing the glareshield. I think Michael is correct when he says to remove the windscreen so you have easier access to the rivets for the panel. Although you might be able to get it off with the panel in place, but free of any protrusions, it will be much easier to get off and back on by removing the panel.

Another option you may have, but you would need to discuss with Sonex, is to go with the larger OOPS fittings and then use reducers to connect the the smaller fittings.

Good luck!

Jake

[Waiex 49]

Hi jake,

I appreciate your thoughts on the tank removal.

I am exploring the removal of the glare shield as I think I could remove the rivets pretty easily. Then the tank would be completely exposed and easy to remove. I haven't made a decision yet, other than to make the decision that the tank must come out to change out the fittings.

I have retrofitted my plane with a removable, vertical panel. The panel is out of the aircraft at present, making the potential removal of the glare shield much easier.

I have seen the Sonex "instructions" for both the tank and the "oops" fitting installation. Not really impressed with either of these documents. The fuel tank instructions are for installation, not removal. The oops fitting instructions were never vetted on an in-service aircraft, rather the replacement is done on a workbench and only addresses the larger 3/8 NPT fittings.

One way or the other I will fix this problem and move on to other things. Thanks to all who have responded with their ideas.

I really wish Sonex would address the root cause of this problem and sell a tank with more robust fittings. In my opinion this is a safety of flight issue. Well......I gues if it doesn't happen in Wisconson then it really isn't a problem.

Fly safe,

Don

[SonexN76ET]

Don,

Please let us know how your fuel fitting replacements go.

One thing I would like to add to anyone reading this is that you have to be careful not to have the lines going to the fuel tank be subject to vibration or other side forces that can eventually lead to the fittings getting loose and then leaking.

Jake

[Waiex 49]

If you have followed previous posts you will know that I am in process of replacing two damaged fuel tank fittings and have decided the best course of action is to remove the fuel tank and install the "oops" fuel tank fittings on my work bench where access is much easier.

Here are my experiences in removing the tank:

The plane was long ago de fueled.

Remove interior and seat, control sticks, and rudder pedals.

Disconnect fuel lines. Remove any fittings that stick out below the tank as clearance to remove the tank is very tight.

I couldn't get the tank out past the aft stop angles. I had to remove the windshield so I could drill out the rivets holding the angles in place and removed the angles.

The guy who built my place installed a horizontal cross piece (channel stock) just behind the tank. This was installed to facilitate mounting of avionics components and wire bundles. This was in the way and prevented the tank from moving down and aft. It was riveted in place and I could not get to the rivets. I had to cut this out in pieces and will have to re-do this when I put everything together again.

Anything hanging below the instrument panel has to be removed. In my case I had to remove the headset jacks.

The tank just barely slips out between the bottom of the instrument panel and the top of the spar tunnel.

I am glad to have the tank out. Since I will be doing the fitting replacement on my workbench I am certain I will do a much better job. I will be replacing all fittings with the oops fittings.

I would suggest if anyone is considering adding any additional structure aft of the fuel tank for your avionics, etc., to take the extra effort to make this removable. I had to cut mine out and it was an ugly experience.

I would suggest if you are building a sub-panel below your instrument panel that you consider making it removable. Can't remove the tank with this in the way.

I am glad that Sonex designed the plane so the fuel tank can be removed, rather than being riveted or bonded into the structure.

The Sonex is a straightforward design and came apart in a straightforward manner. What makes this job so awful is that access under the panel is so restrictive.


If you are building, I would suggest you consider installing the oops fittings before you install the fuel tank.

I am glad the California weather is warm and I have a nice T hangar filled with tools and equipment. I sure wouldn't want to do this job out on the ramp in the cold.

Time for me to order some new oops fittings. I will post later when the job is done.

Don Bowen
N49YX

[Waiex 49]

I ordered my "oops" fittings from Sonex today.

I am glad to have the fuel tank out of the aircraft for this repair, even if it was a difficult job to remove the tank.

I was very carefull when I drilled out the 1/8" NPT fitting so that I would capture all of the drill shavings and debris and not leave anything inside the tank.

When I (finally) had the tank out of the plane and on my workbench I had a look inside the tank. I was amazed at the amount of drill shavings and debris inside the tank! It will be pretty easy to clean the inside of the tank now that it is out of the airplane.

If you are installing the oops fittings with the fuel tank installed in your aircraft be aware that there could be more debris in the tank from the drilling operation than you anticipated. Take extra care to clean out the tank as this junk could easily clog up your fuel system.

Don Bowen
N49YX

[grevaly]

Has anyone considered splitting the forward fuse floor into two sections... forward and rear with the joint...say, beneath
the spar area. This would make the forward floor fairly easy to remove to do repair work it this area.

[radfordc]

When I removed my tank for repair I did it in a way that probably no one else would ever approve. I decided that it was impossible to repair the tank in place and that it was too difficult to remove the tank the way it went in. I cut a large hole in the top of the fuselage and removed the tank out that way. When I reinstalled the tank I added some steel straps across the top of the tank for additional support and riveted patches on the glare shield. The glare shield now has a somewhat "Frankenstein" look (lots of scars and stitches). But the tank hasn't leaked again!