Sonex fuel tank revision

[mike.smith]

If I'm reading this drawing revisions bulletin correctly, it sounds like Sonex is giving up on the pre-moulded fittings and going with the Oops fitting as the standard fuel fittings.

http://www.sonexaircraft.com/support/sonex_revs.html
10.14.15 SNX-G02 A -- --
Removed scratch-build detail. Removed pre-molded threaded fittings. Added Oops fitting installation details. Removed felt covering required for scratch-built aluminum tanks. Removed drawing from Sonex plans set. Drawing now included with each fuel tank. Download: SNX-G02_A_Fuel_Tank.pdf (http://www.sonexaircraft.com/documents/ ... l_Tank.pdf)

[fastj22]

This is a positive move by Sonex.

[gammaxy]

I agree... I'm currently kicking myself that I did not take the general advice of the forum and install the fittings from the beginning. The only fittings that are weeping are the unused sight-tube fittings, so I'm trying to come up with a patch to completely block them off without having to remove the tank.

[fastj22]

If you smell a hint of fuel when you open the canopy, you know you are entering a Sonex!

[Bryan Cotton]

If I was trying to stop a weep I would pro-seal over it on the outside. I know they say nothing sticks to the plastic but pro-seal is worth a try. On the outside of the tank there is no hazard.

I remember the earlier threads where builders wanted Sonex to do something. It seems they have listened!

[Waiex 49]

I believe this is a good move by Sonex.

For what it is worth:

If you have to remove the tank to replace the fittings, I found the easiest way to go was to remove the rudder pedal mounting brackets and let the entire rudder pedal assembly lay on the fuselage floor. This allows up and down movement of the tank, which I found much better than the tilt and slide method specified in the Sonex instructions. Removing the brackets requires drilling out 10 rivets, but that shouldn't hold anyone back.

I did not install the outer o-rings as specified by Sonex. The inner o-ring provides the sealing. The outer o-rings twisted and squirmed out of position as the nuts were tightened. I omitted the outer o-rings and used washers under the nuts.

Although not specified by Sonex, I used LocTite on the nuts. Maybe I am overly cautious but I didn't want these parts to come loose during flight.

I'm glad Sonex made this change. Now I can stop cursing in the general direction of Wisconsin.

[gammaxy]

If I was trying to stop a weep I would pro-seal over it on the outside.

I'd like to consider pro-seal, but the only documented pro-seal fix I've found involves sandwiching the pro-seal under an aluminum plate that is screwed into the plastic. I took this to mean pro-seal doesn't stick well, but I'd be happy to put a glob over both fittings and be done with it.

What I'm considering instead is making a patch out of ~1/8" thick HDPE sheet with a pocket machined into it so I can place it directly over the plug and fitting and it will contact the surface of the tank. Then use this system on the tank and patch:
http://www.loctiteproducts.com/p/sg_pls ... System.htm

I've experimented with the loctite system and it seems to work, so I'm cautiously optimistic that this will be a permanent solution.

[peter anson]

I used PR1422 which is a polysulphide compound like Pro-seal to repair a leak at the fuel level sender on my Sonex. The PR1422 appears to adhere to the plastic. I do have a "top-hat" fitting clamped to the fuel level sender (see photo below) and that might be holding the rubber in place, but when I did the repair I was counting on the glue bond to the top hat to give support to the sender, and it does appear to have worked that way.

Pretty isn't it? The fix was not an easy one. See http://sonexaus.wikispaces.com/Peter+Anson+-+Sonex+894 about 2/3 down the page for details.

Peter Anson
Sonex 894

[Sonex374]

This stinks new buyers get correct method and I must buy corrective measures

[kmacht]

I'm not thrilled with the oops fitting. I had to put one in where the fuel probe goes and it seems that it loosens up enough to start dripping every three to four months and I find a wet fuel soaked carpet. There is no safety or locking feature on the fitting and nothing stops the vibration from unscrewing it. It is a pretty poor design from an engineering perspective.

Keith
#554