Sonex Fuel Tank & Oops Fittings

[Bryan Cotton]

Don,
Did you just use an AN washer?

Today I finished with David's tools, I think. Need to install the fittings and do a leak check. I vacuumed out the tank as best as I could, then flushed it with a garden hose. Needs to dry before I install the fittings.

[Waiex 49]

Hi Bryan,

Sorry, I don't have a part number or source for the washers.

They were given to me by a member of this forum. What I have are thin fiber washers.

I think a metal washer would work as well. I think if you take your oops fittings down to Home Depot or Lowes Aircraft Supply you can find some washers that will fit.

I think you will find using a washer on the outside of the tank (instead of the o-ring) that the oops fitting will seat in the hole more firmly and the inner flange surface of the oops fitting will run parallel to the inside surface of the tank for a better seal.

Good luck!

Don

[Bryan Cotton]

Don,
I ended up making my own washers out of .090" 6065-T6. Figure it is the same material as the oops fittings.

[Sonex1517]

Another post for consideration by the community.

When we suggest a method or idea about something the factory does not recommend, in this case directly screwing a fitting into the fuel tank, as opposed to using their specified "oops fitting," those that read the post should be reminded that the post is just that. A post on the Internet in a discussion forum.

I am no judge of the legitimacy of these posts. However...

A member who is well respected and experienced with our aircraft contacted me offline to voice legitimate concerns about the results of someone following this suggestion to directly thread a fitting into the fuel tank.

So please - when you read these posts, use common sense and good advice. Ask the factory if you are not sure. Before making modifications to a proven design based on a forum post be certain you understand the ramifications of the suggestion.


Robbie Culver
Sonex 1517
Chicagoland
Tails and Wings complete - finishing fuselage.
N1517S reserved

[Bryan Cotton]

Here are my oops fittings. Still have to leak check. I plan to leak check just the oops fittings with water and plugs.

[Waiex 49]

Robbie,

With all due respect, people are going their own way on this because those good guys at the "factory" aren't addressing the problem.

The stock fittings are prone to leak and/or spin out during maintena nce.
The factory "fix" to this problem is to sell the "oops" fitting.
The factory instructions for installing the "oops" fitting are poorly written and inaccurate.
The "oops" fittings are made of a lightweight metal and don't seem very strong or durable.
Doing the repairs requires working under the tank or removing the tank, neither of which are any fun.
Installing the "fix" to repair the "oops" caused by Sonex's poor design is a real pain in the neck.

Neither the problems with the stock fittings nor the shortcomings of the "oops" fittings are being admitted to or addressed by the "factory". Is it any wonder that some people are going their own way on this?

"Ask the factory if you are not sure"?? Really??

What we need is for the "factory" to provide a real solution. They need to stop selling fuel tanks with sub-standard fittings and stop selling a sub-standard repair fitting. They need to design and sell some strong and reliable fuel tank fittings (red anodized, of course). Just because it isn't a problem in Wisconsin doesn't mean it isn't a problem. People are devising their own fixes in the absence of good "factory" support in this instance.

[rizzz]

I have installed my fuel tank as-is and have not done a proper leak testing at the time.

It all looked ok and I just assumed at the time any leaks in my system would be coming from my installed AN fittings & fuel lines which would be easily fixed when the time comes, even with the tank installed. I was unaware of the issues with the fittings molded in the tank itself.

The results of this poll scare the hell out of me though. I'm seriously crossing my fingers on this one.
I'll be putting fuel in the tank and hopefully starting the engine for the first time very very soon now.
I do not want to have to dive under there and replace the molded fittings with the Oops fittings even before my first engine start.
Based on the results of this poll though, even if the tank is fine now I have a 50/50 chance I will have to do it at some point in the future.

So I agree with Don, Sonex needs seriously look improving their product here. The oops fitting is a solution for existing customers but new customers should get a better product to start off with.

Even though they never admitted any issues/concerns/lacking, they did eventually come up with better cooling baffles, better brakes, and a better tail wheel solution.
Perhaps this might be the next product improvement initiative?
Sounds like it should be right at the top of the list.

[NWade]

stop selling a sub-standard repair fitting. They need to design and sell some strong and reliable fuel tank fittings

Its OK to be frustrated; but if you are going to claim that Sonex is supplying something that is "sub-standard" and not reliable, you'd better have some evidence to back up those accusations.

You think they feel lightweight and may not be durable - have you noticed that your airplane's entire airframe is made of thin Aluminum? Being light doesn't make it weak or inappropriate. If you can point to a failed Oops fitting or show where its corroded or cracked or failed through normal usage, then let's hear it.

Otherwise, vent your frustration in a more-responsible manner. You are bordering on claiming that the factory is selling something they know to be bad, and that's a serious claim to make. There's a huge gap between "I don't like it" and "Its not reliable" / "not safe".

--Noel

[Bryan Cotton]

I think the oops fittings are fine. They seem like good old 6065-t6 though I don't know that for a fact. I think the idea to make tanks without the molded fittings is a great one. Would make the job easy.

[avee8r]

Technical discussion and information will always be "out there" someplace.
It might as well be here and make it known if it's not factory approved.
Happy Landings
John
N50NX