Turned the tables on my airplane

Timbeck2

Timbeck2

Final Approach
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Timbeck2
Historically my airplane has been full of surprises in that while I'm working on one thing, I uncover something else that needs attention and so project creep sets in. This time, I've got fuel senders and a new fuel gauge on the way so in order to install them I have to remove the fuel tanks. All but one of the six thousand screws came out without a problem. (knock on wood) But as I pulled the tank out and disconnected the sender wire, I noticed that the sender had been leaking. Not enough to notice on the underside of the wing yet but enough to stain the spar blue for about 8 inches so I wasn't far from having a blue stain under the wing.

Good thing I was replacing the senders anyway. So a big middle finger to the Piper maintenance Gods. I got you this time muthascratchuh.
 
Are you talking about a leak around the edge of the sender plates? It seems like a lot of these use cork gaskets, which seem to fail over time. Lots of the Experimental guys (me included) will go solely with a thick bead of ProSeal (or FlameMaster) sealant and forgo the cork altogether, with excellent long-term results. Not sure if you have to follow a certain procedure here for a certified aircraft.

ProSeal is amazing stuff, but sooooo messy. :eek:
 
SoCal RV Flyer said:
Are you talking about a leak around the edge of the sender plates? It seems like a lot of these use cork gaskets, which seem to fail over time. Lots of the Experimental guys (me included) will go solely with a thick bead of ProSeal (or FlameMaster) sealant and forgo the cork altogether, with excellent long-term results. Not sure if you have to follow a certain procedure here for a certified aircraft.

ProSeal is amazing stuff, but sooooo messy. :eek:
Click to expand...


Seemed to be coming from the edge and the screw holes as well.
 
They used to use cork gaskets. The cork dries out (the gasoline helps do that) and it hardens and shrinks and mechanics tighten the screws to try to stop the leaks. That distorts the thin aluminum tank around the sender opening so that even a new gasket doen't help much. The aluminum has to be carefuly straightened ("carefully" so it doesn't crack) and the current gaskets are fuelproof rubber, many of which are too hard to conform nicely and just lead to more tank distortion. So one tries Fuel Lube on the gasket (Fuel Lube, or EZ-Turn) is a fuel-proof grease) and now the gasket slowly creeps out so that the fuel starts escaping around the now-elongated screw holes. Fuel Lube should be restricted to the screw threads, to keep the fuel from running up the threads and out.

There is a wide range of hardnesses for rubber components. Hardness is measured on the Durometer scale, and I have found for years that softer materials often work far better than harder stuff. For instance, when I was in the air brake component overhaul business (heavy truck and equipment and so on), using 50-Durometer O-rings gave the controls far more precision than the OEM's industry-standard 70-Durometer O-rings. Precision was nice to have in a lot of applications. Hard O-rings offer a lot more friction in sliding applications. I wish someone would come up with an STC to use fuel-resistant 50-durometer rings in aircraft primers, for instance, and 40- or 50-Durometer fuel sender gaskets.
 
I don't exactly what Durometer gaskets Cies is sending with the senders but as always, I appreciate the information Dan.
 
How old is your airplane? If it is a 60's era plane, have your tanks ever been totally refurbished. If you have gone to the trouble to take the tanks out, it might be worth considering an overhaul so you won't have to worry with it again during your flying career. Woodstock Aviation refurbished mine five years ago. I was starting to see some gas stain around some rivets. If you have any plans for painting your plane in the future I would certainly recommend this prior to a paint job for added insurance.
 
The Loctite mentioned above absolutely stops the leaks around the screws and gaskets (the mounting screws in my tank are threaded all the way through to the inside, and the sender sits a few inches below the level of the fuel when the airplane is on the ground).
Once and done.
 
MickYoumans said:
How old is your airplane? If it is a 60's era plane, have your tanks ever been totally refurbished. If you have gone to the trouble to take the tanks out, it might be worth considering an overhaul so you won't have to worry with it again during your flying career. Woodstock Aviation refurbished mine five years ago. I was starting to see some gas stain around some rivets. If you have any plans for painting your plane in the future I would certainly recommend this prior to a paint job for added insurance.
Click to expand...

'69 and tanks were re-furbished 10 years ago.
 
Dan Thomas said:
They used to use cork gaskets. The cork dries out (the gasoline helps do that) and it hardens and shrinks and mechanics tighten the screws to try to stop the leaks. That distorts the thin aluminum tank around the sender opening so that even a new gasket doen't help much. The aluminum has to be carefuly straightened ("carefully" so it doesn't crack) and the current gaskets are fuelproof rubber, many of which are too hard to conform nicely and just lead to more tank distortion. So one tries Fuel Lube on the gasket (Fuel Lube, or EZ-Turn) is a fuel-proof grease) and now the gasket slowly creeps out so that the fuel starts escaping around the now-elongated screw holes. Fuel Lube should be restricted to the screw threads, to keep the fuel from running up the threads and out.

There is a wide range of hardnesses for rubber components. Hardness is measured on the Durometer scale, and I have found for years that softer materials often work far better than harder stuff. For instance, when I was in the air brake component overhaul business (heavy truck and equipment and so on), using 50-Durometer O-rings gave the controls far more precision than the OEM's industry-standard 70-Durometer O-rings. Precision was nice to have in a lot of applications. Hard O-rings offer a lot more friction in sliding applications. I wish someone would come up with an STC to use fuel-resistant 50-durometer rings in aircraft primers, for instance, and 40- or 50-Durometer fuel sender gaskets.
Click to expand...

Is there a doubler around the opening in the tank for the sender? Would adding one help prevent the distortion?
 
I had a fuel sender leak on my my plane last year. The blue goes away on its own in a few weeks.
 
UngaWunga said:
Is there a doubler around the opening in the tank for the sender? Would adding one help prevent the distortion?
Click to expand...

There is one, at least on my right tank, which is about 3/8" thick. I haven't taken the right tank out yet.
 
UngaWunga said:
Is there a doubler around the opening in the tank for the sender? Would adding one help prevent the distortion?
Click to expand...
Not in the 100 series Cessnas. The edge of the hole is flanged inward a bit to stiffen it, but that's all. Anchor nuts are riveted to the inside.
 
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