I've a Goldberg Anniversary Cub that I bought about eight years ago at a swap meet. It was well built and has gotten a lot of flight time over the years.

Last week it went off the runway into the tall grass and when retrieving I noted the cowling mounting screws had shifted and after inspecting, the engine itself was slightly loose. When home and digging into what was going on, the answer came quickly that the firewall was fuel soaked and crumbling. A test of the tank under water confirmed what was suspected, the tank was leaking around the stopper and each time it got hung by its tail wheel, the firewall got another dose of fuel.

Fortunately the fuel soaking was mostly to the firewall itself as the builder had epoxy washed the fuel compartment and what seemed to happen is that the fuel followed the two fuel tubes that were fitted into snug hoes through the firewall where the fuel had opportunity to soak into the grain structure of the firewall plywood and spread. The entire firewall was soaked and crumbling but thankfully the fuel soaking was blocked by the glue joints around the firewall perimeter from invading the longerons.

The forward deck needed removed to get access to remove and replace the firewall and the effort was reasonably straightforward with a new deck and because the windscreen had been repaired with cellophane tape, a new windscreen.

The cause was the aging stopper. It can be noted that the stopper was well tensioned when installed as indicated by its thickness in comparison to a new but time takes its toll and the elastic qualities of the stopper had long since been lost.

So, if hanging a plane by its tailwheel, be warned to do maintenance on the tank if the plane is gaining age.

Good post and something I never think of. I just got one of my planes back in the air after hanging on the wall for a couple of years. I was having problems with getting the fuel out of the plane at the end of the day and the engine wasn't running quite right. I pulled the tank and when I pressure tested it the bung blew out. I too soak my tank and fire wall with epoxy so no real problems yet, time may change that. After reading this post it got the gray cells working and I will be hanging that plane by the LG from now on!! Thanks for the reminder, it was something I never gave any thought to. I have wondered about all that oil going into my front bearing though. Not a big deal if you fly the plane often but time would allow the castor to harden.

The fuel tank should be rebuilt every year

Or consider a Hayes tank where this type of problem won,t happen without that large compression stopper and it can,t split the seams from that compression stopper.

John

Like that's going to happen!!

I'm going to say you probably saved the fuse and some of your radio gear by hanging it by the tail. If the tank leaks, it's going to do so more when it's full and under muffler pressure than it will in storage with a trace of fuel in the tank. So the fuel collected in the tank area during your flights would have made its way to the rest of the fuse, if it had been hung by the nose.

Just food for thought.

The stopper is on the front of the tank

It's hard to refrain from answering your response with a DUH! Assuming you completely read my post, are you saying any fuel that leaks out at the FRONT of the tank during flight won't make its way to the rest of the fuse. Especially if its hung by the nose for storage? Please enlighten.

While what you say is true - When the airplane is hung by the tail, in addition to the fuel that you mention that happens to be in the fuel compartment,<u> any fuel remaining in the tank will have a week or 6 months to drip onto the firewal</u>l.

So a modeler looking to store planes vertical must decide which is less of the two evils, should a tank stopper fail and go unnoticed for a period of time. Hang it by the nose and let fuel, that very possibly leaked during flight, seep back toward the tail into maybe a servo, switch, receiver. Or let that fuel plus what is remaining in the tank after a de-fuel, soak the firewall?

There is no clear choice here, as no situation is ideal. Just trying to point out that hanging by the nose isn't a cure all in this situation. And in AA5BY's case, there is a probability that hanging the cub the tail limited damage by fuel, but we will never know.

Hard to win on that one?

what I hate is a tank accident early on in the planes life where you get fuel all in it.

I thin epoxy and coat the fuel and engine compartment at assembly. I also epoxy as far back as just beyond F2 or the landing gear mount on a tail dragger

At least on a low winger the fuel drips out the wing saddle.

After 55 years flying I have experienced all of the above at one time or another.