|
|
Empty the tank of fuel.
Flush the inside of the tank with Freon (don’t let the FEDs know),
pressurize it a tiny bit, seal it, then use a “sniffer” to detect
the very smallest micro leak. Flow plenty of air over the wing areas for a
while to remove residual Freon pockets before your search begins. Freon’s
molecular size (critical dimension is about 5.3 angstroms) is close to pentane
(6 angstroms I think I remember) which means, if you can flow pentane, you can
flow Freon. So if you find a leak using a sniffer, you might have a gasoline
leak there too. Hey, I might be wrong about the numbers … it’s been
a long time since using these dimensions etc, but the sniffer should work even
if the numbers are wrong. This method removes the volumetric, atmospheric,
temperature variation issues altogether and Freon doesn’t support
combustion. Just make sure there’s positive pressure (tiny amount) in the
tank when searching for that micro amount of Freon. Plug all “holes”
into the tank. On the overflow slightly pressurize the tank with freon, now
connect a small balloon and seal around the neck. If the tank leaks a little because
you didn’t seal it really really well, that’s OK as long as you
find the leak before the tank is again at atmospheric pressure. After you find
the leak, remove the Freon or not.
Is a lack of fuel sealer
opening an area of exposure, have a crack in the wing structure, what? The
cause may be pointing to the appropriate repair.
Jim
From: Lancair Mailing
List [mailto:lml@lancaironline.net] On Behalf
Of Terrence O'Neill
Sent: Sunday, January 30, 2011
9:32 AM
To: lml@lancaironline.net
Subject: [LML] Re: Weeping wing
tank. super cool trick to fix it!!!
Neat. I didn't know about the bubbles adn amplifying the sound.
I made a manometer so I can limit the vacuum to about 6 inches water...
and I just bought some PR-1005-L ... a quart.
I think that'll be enough, as the leak seems to be in the upper part of
the front spar web. Doesn't leak when below 78 gallons in the tank.
On Jan 29, 2011, at 10:36 PM, randy snarr wrote:
|
Terrence,
Take a deep breath. I had a similar issue on mine and the cure was not that
bad.
I have a trick that should help..
First the bad news, Remove the wing. (drain fuel first duh..) leave about a
pint in the tank.
Once the wing is off you can find the leak by putting a small amount of
negative pressure on the tank and seal it up. You have to seal everything off
first. I would connect a tube to the fuel or vent line and just suck on the
tank with your mouth and then seal it off. You dont need much.
I found this completely by accident. You never get all the fuel out and in
this case that is ok.
A pint of fuel in the tank is good for this trick. With a little negative
pressure on the tank, rotate the wing and force the fuel around all the
corners in the tank where the suspected leak is and listen carefully with
your ear. When the fuel covers the hole in the tank you will hear the air
bubbles passing through the fuel as it enters the tank. The empty wing is
like a drum and the sound is amplified. I had a leak and found it at bottom
front corner of the tank where the tank close out rib meets the lower skin
forward at the spar. Now you know where the leak is.You can now remove the
pint or so of fuel and dry out the tank. I used an alum rod with paper towels
taped to the end to get it dry in the corner where gravity collects it. Once
it is DRY. orient the wing so the leak is where gravity will take your
sealer. I used the same gray epoxy based tank sealer lance recommends. U used
a large seringe ( like for a cow) and injected about 1 cup of gray sealer as
close to where the hole is through the gas cap hole.
You wont be able to see any of this but you can do it by feel. Move the tank
around slightly to completely cover the entire area where the hole is. I
would seal up the tank again and put the negative pressure back on to push
some goo into the leak hole for 20 minutes or so. Release the negative
pressure and Support the tank with the hole at the lowest point and let it
cure.
Shazam, no more leak.
Hope that helps..
Best,
Randy Snarr
235/320
N694RS
( i mean real small as you can collapse your wing with too much!)
"Flight by machines heavier than air
is unpractical and insignificant, if not utterly impossible"
-Simon Newcomb, 1902
--- On Mon, 1/24/11, Terrence O'Neill <troneill@charter.net>
wrote:
From: Terrence O'Neill <troneill@charter.net>
Subject: [LML] Weeping wing tank.
To: lml@lancaironline.net
Date: Monday, January 24, 2011, 5:57 AM
This is a request for info on the possible similar experience of other LNC2
builder-fliers... a wing tank fuel leak.
The very slow leak through the front wing spar, when fuel leveel is above
about half way up, is of course uninspectable because of the leading edge --
and further because it is possibly behind the root area secondary web ... not
to mention the fact that the spar web is sandwich construction and the
interior skin leak can propagate spanwise to another portal in the forward
web skin.
So my question is, when I slosh-seal the tank, what is recommended as a prep
for the tank inner surface?
I've read MEK and another TankPrep stuff.
For sealant I've looked at PR-1005-L, and at the automotive (supposedly)
stuff, and phenol novolac.
Any suggestions soulfully appreciated, for this worrisome job.
Thanks.
terrence N211AL
LNC2 235/320.
--
For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html
|
No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1204 / Virus Database: 1435/3412 - Release Date: 01/30/11
|
|