Replace fuel tank in finished aircraft

[pfhoeycfi]

I just noticed my tank has buckled worse than it was before even with the new straps fitted quite loosely. I've had varying amounts of fuel in it all summer. It would be a nightmare to get it out now that the plane is done. It is buckling inward and pulling away from the straps so the loose straps on the bottom have no effect. My guess is the tight fit on the sides and top is still to blame. I'm using it as is for now since it doesn't leak but it definitely looks bad. 20 gallon quantity is not accurate anymore. A new type of tank should be made with slightly smaller dimensions sides and top and or a different material should be used. It would be nice if Sonex could come up with a proper solution for this.

I had a closer look and it appears the tank, for the most part, collapsed inward from both the bottom and the top as it expanded against the glareshield along the longerons...much like a milk container crushed from both ends. The tank pulled away from the straps. The aft end also expanded out slightly bending the tank stop bracket that is riveted to the glareshield. A smaller tank is needed.

[DWest]

I don't understand why these tanks are expanding/contracting and deforming. Are they vented? What is the purpose of seasoning it? I have several red gas tanks for the mowers (walmart items) and those have never deformed. How do we consider this an airworthy item from Sonex? Got pics of what has happened to the tank?

If it cracks in-flight, you get soaked with fuel. Not to speculate what happened to the Sonex that burned to ashes on the taxiway, hopefully time will tell for the benefit of everyone.

[pfhoeycfi]

It is possible to pull the tank from a finished Sonex B. Interestingly the tank just about took on its original shape once removed. New tank on the way.

Peter

[jrs]

Question for the group of "B" builders. Has everyone that installed the original tanks had problems with the install. I have the modified straps but it sounds like those don't always fix the problem. Do these tanks always fail ?

[Murray Parr]

Question for the group of "B" builders. Has everyone that installed the original tanks had problems with the install. I have the modified straps but it sounds like those don't always fix the problem. Do these tanks always fail ?

I believe there are some out there that didn't fail although I had mine fail after following the pre seasoning method. It was a massive effort removing it in a completed aircraft especially since it had expanded too much to get back out.

The new tanks are slightly smaller now and that is what I now have and it fits great with no buckling.

My advice would be to give yours a try (you wont know until fuel is in it) and if it buckles, reach out to Sonex for advice. If it is not too late, try to keep the build process with potentially removing it in mind.

[jrs]

Thanks for the pointer. I have been watching the various solutions from Sonex and have not tried installing the tank yet. Thinking that I might try a temporary assembly and then put gas in the tank. Really hadn't thought of doing that until I read your post. Thanks again.