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Date: Sun, 27 Feb 2011 16:10:20 -0500
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From: Terrence O'Neill <TRONEILL@CHARTER.NET>
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Subject: LNC2 wing tank sloshing
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Here's some experience info which may be of some help to others with =
similar problems.
A slow-weeping leak in the left wing tank, appeared on the lower flange =
of the front wing spar, in the cockpit, accumulated on the floor. =20
By draining the tank in stages I found that with fuel at about 8 gallons =
-- half full-- the leak stopped.  Concluded the leak to be through the =
front spar web, and in upper half... but the leading edge conceals and =
prevents access to the spar web. .. so I couldn't tell where it was =
span-wise, although I made a vacuum and manometer apparatus to try to =
hear leak hissing with my stethescope... which I hope I never have to =
use.
 Therefore no alternative but to pull the wing off, and prepare for =
sloshing.

Searching for an appropriate sloshing compound was frustrating.  One 3M =
manufacturer stated "No data is available for directions to apply this =
product", or words to that effect.  Others stated 'not for aircraft =
use', but gave directions for application.  Vans blogs and some others  =
warned against use if the fuel had methanol or diesel.  One was =
recommended for use in Lancairs, a 3-gallon 2-part kit costing about =
$300.  Some were one-part rubber compound which cured by evaporation of =
MEK vehicle, PR-1005-L, which I elected to try, although directions for =
use were lacking, for one quart for almost $200.  However the cheaper, =
similar slosh for a motorcycle tank sloshing product,  gave the most =
directions.
I finally decided on a procedure which I hope worked.  I assumed one =
quart would be enough for  my 16+ gal. tank.=20
The similar cheaper product suggested a quart for only 12 gal. tank =
capacity, and indicated slosh could be thinned by about 25%R MEK added, =
and applied twice for two thin coats would reportedly would dry faster =
than one thick coat.  Its recommended directions were to first flush the =
tank with MEK, purpose not explained, but I think the purpose was to =
absorb up to 3 grams of any water remaining trapped in the tank first. =
Then the slosh applied.

I did the MEK slosh first, then drained the MEK into a container, =
through the tank fuel outlet; then blow-dried out the tank by using the =
outlet of my Shopvac, for an hour.  Then again plugged the outlet, and =
poured slosh in though the filler cap, and first rocked the wing =
horizontal for the outer tank bay (tank is divided by a rib in the tank =
center with three or four holes in top of the rib and bottom).
Then stood the tank on the leading edge to coat the outer part of the =
front spar web.  Then laid the wing flat and tilted it toward the root, =
to let the slosh drain through the rib holes to the inner bay, and =
repeated the horizontal rocking, then raising it to its leading edge to =
coat the inner part of the front spar web. Then tilted toward the =
trailing edge to coat the rear spar web, then tilted toward the wingtip =
again to flow the slosh outboard and did the same to the outer part of =
the rear spar web.
Then the wing was tipped toward the root after unplugging the fuel =
outlet, and the remaining slosh drained out.
I was happy to see that about half a quart of slosh drained out, and I =
returned it to its container for a second coat if needed, after testing =
for leaking. =20
The directioons for the similar slosh compound had suggested letting the =
slosh stand too cure in 48 hours, or to start curing for an  hour before =
blowing air through it to speed drying/curing. So i stood the wing on =
its leading edge for an hour before starting the blower again and ran it =
for an hour; then returned the wing to horizontal and let it rest with =
vent, outlet and inlet open, where it is now.  I did the sloshing in =
this order because I had no way of knowing how much slosh was going to =
be use du,p to coat the tank, and wanted to prioritize the root end of =
the front wing spar.

I suspected the drying would be slow because the hangar temp was abut =
50-55F, and a sloshing compound gave specs for 77F..  I had a sample of =
the slosh in an open container, and brought that home to observe the =
curing progress... at the same temperature,  in my shop. Where the slosh =
coating is thin it dried fairly fast... in less than an hour; but where =
it puddled about .060 to .090 thick, it has taken two days to gradually =
dry to a thinner but still softer consistency.

Today i thinned the remaining pint of slosh with 25% MEK, and poured a =
sample (sample similar) amount on top of the original sample, to test =
whether it would adhere, and to see the drying time.
It dried fairly fast at 55F, and appears to merge smoothly onto the =
first sloshing compound, so now i plan to repeat the same sloshing =
procedure with thinned slosh, as soon as the temperature get up to about =
55 to 60F, to try to be sure the leak is closed, and any future similar =
leak prevented.=20

Its hard to understand why this product could not have had Directions =
for application, perhaps suggesting a temperature for application, and =
alternate methods or preferred methods of application, prepping for =
same, re-coating, thinning the slosh, etc., for corporations like PPG =
and 3M.

Any comments welcome.
To be continued ....
Terrence
L235/320 N211AL