|
This may be a little off-topic and more
appropriate for the RV-list as it deals with leaking RV tanks, but since most on
this list use mogas, I figured I'd rather ask
here.
I
brought a few gas cans up to the airport today and topped up the main tanks and
since I had an extra couple of gallons, I just dumped it into the auxiliary
outboard tanks. I haven't used these tanks since last summer and they've been
empty of fuel since then. Before adding the fuel to the aux. tanks, I checked
the water drains. One of the tanks was bone dry, while the other had a
surprising amount of water in it (plane is not hangered). I filled my fuel
sampler tube 4 times with water, then the 5th was about 1/3 water followed by
1/2 tube of fuel, then the tank was empty. I made a note to change the o-ring on
the fuel cap and proceeded to dump several gallons of fuel into this
tank.
I
then proceeded to work on other items such as the heater valve & looking for
an electron leak in my dimmer circuit. Close to an hour after I'd added the
fuel, I suddenly heard a large amount of liquid falling to the ground and
quickly climbed out from the cockpit to find a very large flow flow of fuel
pouring from the entire wing root area. After the initial barrage of expletives
I grabbed a gas can and funnel and stuck it under the area of heaviest rainfall
of fuel, while I hurriedly removed the screws from the top wing root fairing.
This didn't reveal much, but it appeared the fuel was flowing somewhere along
the main spar. I incorrectly surmised that the main tank was leaking possibly
from somewhere in the top seam since I'd just filled this tank to capacity and
was guessing that possibly the sun was causing vapours, which somehow were
unable to vent, to pressurize the tank... etc. So I quickly removed the
drain and began draining directly from the main tank into a gas can, after
draining several gallons out of this main tank, the leaking fuel from the wing
root suddenly stopped, so I assumed I'd gotten the level below the leak. Now I
was considering draining all of the fuel from this main tank and putting it into
the auxiliary tanks, but first I checked the drain on the auxiliary tank that
I'd found the water in and found it was empty! And I'd just dumped several
gallons into it an hour previously. So the main tank wasn't leaking after all,
so I put all of the drained fuel back into it and found no
leaks.
Now what exactly happened there? It didn't leak a drop for close to an
hour, then suddenly it let several gallons leak out in less than 10 minutes. It
must have been an aggressive chemical reaction that dissolved the fuel tank
sealant. The fuel that I use is premium unleaded from a card lock, that is
supposed to be free from alcohol as it is marked for use with off-road vehicles,
which typically do not approve the use of alcohol or ethanol additives in the
fuel. I recall that alcohol only becomes corrosive when mixed with water, but I
did a quick search through the archives and couldn't find confirmation of this.
I did find mention that Jim was researching mogas for a presentation, so I'd be
curious as to your take on this Jim.
I'm hoping that it is confined to the one tank that I'd found water in,
otherwise I may find both full main tanks have leaked out next time I go up
there. And with the ridiculous price of fuel these days that's allot of $$$, not
to mention the work to re-seal these tanks. Since the fuel seemed to be running
down the main spar, I expect that the leak is somewhere long the bottom of the
rear baffle plate, but the tank will have to be removed in order to inspect this
(no small job). I don't yet no which is the best way to repair a leak of this
magnitude.
Todd Bartrim
RV9Endurance
13B Turbo Rotary
C-FSTB
|