Fuel Tank Leaks

[SonexN76ET]

I have seriously considered putting some access holes with a doubler around them in the floor so I can reach up from underneath the airplane in order to be able to access the items mounted on the firewall. I did not have the chance to put nutplates on the firewall for everything mounted there, so I have a heck of a time tightening and loosening nuts and bolts on the firewall without someone helping. Plus, I it is difficult to squeeze in under the panel to reach the firewall.

Jake

[fjdoug]

i agree Jake, if i had to fix my tank again i would put access holes in the floor.
a builder down this way did exactly that, it looks good.
Doug.

[n502pd]

I have been thinking about this very thing! As I am a rather full sized, old guy, I have to figure out just how I am going to get in there to do inspections, at the very least! Elsewhere on this site, someone was going to split the floor half way back, leaving the front part removable for maintance. Great idea! At least I think so just now.

Has anyone done anything in this area? Any pictures? any negatives per strength? What does it look like on the inside? Maybe round holes with cover plates as in C-=172??

Finishing LH wing, will start RH wing shortly. Fuse done; tail feathers done and installed; on gear; panel done but not installed;tank in and plumbed;Thinking about windshield. Wishing I was done and flying!!!

[Waiex 49]

I have removed my fuel tank to replace two damaged 1/8" NPT fittings with Sonex "oops" fittings.

Both of these fittings have "spun out" of their molded-in plastic fuel tank mountings. The bottom fitting holds the Princeton capacitance fuel quantity probe. The original builder used some unknown pipe dope and an ample amount of torque to ensure the probe was never going to back out of the fuel tank fitting. Now I have a fuel probe that will not separate from the fitting, and the fitting is spinning in the plastic fuel tank.

My course of action is to cut off flush the fuel probe so that I can drill out the fuel tank fitting and proceed with the "oops" fitting install.

I did not build this airplane and have no idea the part number for the correct Princeton fuel quantity probe. I cannot seem to locate a web site or phone number for Princeton. Spruce (and others) sells the probes but I cannot figure out which one I need.



Does anyone know the correct Princeton fuel probe to use for a Sonex with a Dynon D-180 system?

Does anyone have a good point of contact with Princeton sales / tech support?

Thanks in advance!

Don Bowen
N49YX

[fastj22]

Check with Grand Rapids, they seem to be affiliated with Princeton.

[DCASonex]

Can also purchase Princeton probe through Sonex.

I have found that stepped Unibits work quite well in drilling out old fittings as much less likely to grab than standard twist drills. May be too late if yours is spinning freely, but would try that first.

David A.

[Waiex 49]

Thanks for the replies.

I did get a response from Sonex tech support that their fuel quantity probe system will work with my Dynon D-180. Dynon tech support confirmed this. The guy who sold me the D-180 confirmed that he was using the Sonex probe and will continue to do so with his new Dynon Sky View system, so it looks like I am good to go with the Sonex probe.

I really hated to have to cut off the probe with a hacksaw, but removing the top of the probe was the only way I could get to the spun fitting to drill it out. Oh well, at least the replacement probe isn't too expensive. I have a replacement probe on order with Sonex.

I have the tank on the bench and both of the 1/8" fittings are drilled out. There is a lot of work remaining to smooth down the inside surfaces so that the o-rings will seal properly. Tons of junk got into the tank during the drilling process. If you are doing this with the tank installed be sure to give the tank a thorough rinse to get this junk out of the tank or risk clogging the fuel system.

Another builder who has gone through the "oops" fitting installation sent me some fiber flat washers to use on the "nut" side (outside of the tank) instead of the o-ring. The seal is being performed by the o-ring on the inside of the tank. The second o-ring under the nut made things squishy and prevented him from getting the fitting to properly tighten up and be leak free. It all sounds reasonable to me, so I will use the washers under the nuts instead of the o-ring. If it doesn't work it will be easy to change out the washers for o-rings.

I have the Sonex "oops" fittings installation instructions taped up on the wall of my hangar and read them whenever I need a good laugh. They just don't reflect the real challenges of doing this job in the real world.

I am still a big fan of Sonex and their line of aircraft, but I don't like these darned fuel tank fittings.

Don Bowen
N49YX

[bakfly]

Don you can try to contact:Todd Stehouwer
Princeton Electronics, Inc.
3133 Madison Ave SE
Wyoming, MI 49548
PH 616 243-8800
FX 616 245-7707
You can also make an inquire through the Princeton website. Todd Stehouwer was very helpful solving my Princeton issue
Cheers,
Peter Sonex #1430

[Waiex 49]

Thanks for the info.

I have a replacement probe on order from Sonex.

Does Princeton have a web page? I searched but couldn't find one.

If you have a link I would like to check it out.

[Waiex 49]

Continuing the sad story of my efforts to replace the fuel tank fittings on my Waiex.........

The tank is on the workbench and I have drilled out the two 1/8" NPT fittings and the single 3/8" NPT fitting. These are the fittings at the bottom of the tank (sump).

Here is my problem - while doing a trial fit for the installation of the oops fitting on the side of the sump (this fitting was used for the fuel sight gauge plumbing) I find that the oops fitting will not line up with, or enter, the 9/16" hole drilled per instructions. The problem is that the mound of plastic (on the inside of the tank) that holds the fitting for the main fuel line (the 3/8" fitting) prevents the 1/8" oops fitting from lining up properly.

For those of you who have replaced the "side" (1/8" fitting) - please tell me how you got the oops fitting to line up with, and go into, the hole you drilled. Any info would be greatly appreciated.

At this point the only options I see are possibly reducing the height of the mound for the 3/8" fitting so the 1/8" oops fitting can slide on by, or giving up on the 1/8" oops fitting and epoxying a reducer fitting in place from the outside of the tank.

As it stands at present, there is no way I can get the 1/8" oops fitting into position.

I think Sonex calls these fittings the "oops" fittings because they made a big "oops" when they designed their fuel tanks with these incredibly awful fittings. Their "fix" for the problem is a big pain in the butt.

I think it is time for a "reality check" in the Sonex engineering and quality departments! We deserve something better.


Don Bowen
N49YX