I guess that it has been at least 18 years since I build the fuel
tanks for my CH-300. They are of welded aluminum construction, and
were sloshed with Randolph's sloshing sealer. The Alcohol resistant
type, if I remember correctly.
Today I drained the tanks so I can replace the fuel selector valve,
which is enjoying a small leak around the selector shaft, when I
noticed that there is a small flake of sealer that has cracked loose
from the rest. Further examination shows that there are areas that
look like small blisters are forming under the sealer. I suspect that
this is not an unusual problem, as I seem to recall that others have
had this problem also. The question I have, is what to do. It seems to
me that the tanks need to be removed, (big job), and the sealer
flushed out of there. I seem to recall that some were using MEK to cut
and remove the sealer. Does this seem like the thing to do?
Advice welcomed.





Zenith CH-300 Driver.

"Tim Hickey" > wrote

> noticed that there is a small flake of sealer that has cracked loose
> from the rest. Further examination shows that there are areas that
> look like small blisters are forming under the sealer. I suspect that
> this is not an unusual problem, as I seem to recall that others have
> had this problem also. The question I have, is what to do. It seems to
> me that the tanks need to be removed, (big job), and the sealer
> flushed out of there. I seem to recall that some were using MEK to cut
> and remove the sealer. Does this seem like the thing to do?
> Advice welcomed

Man, I have no advise, but I feel your pain. Sounds like an ungodly job.

I can't help that feel sloshing is a shortcut, in many cases, to make a job
easier. It looks as though it does not pay off in the long run, for some.
(at least)

Aren't there better solutions, in nearly all cases? Fiberglass needs to
seal pinholes, why not use the same stuff the lay-up uses? Wet wings can
use sealant on seams and rivets? Metal tanks need to....to be welded
without leaks?

Just trying to anticipate a major headache.
--
Jim in NC

I don't think Randolph made the alcohol resistant sealer 18 years ago.
It is part # 912 I think. If it the old stuff and you ran auto fuel in
it that was a mixture of gas/alcohol the blistering is what usually
happens. I have a Zenith 801 and I would dread to have to unzip my
wings to get at the tanks. We all feal your pain....

Ben
N801BH
www.haaspowerair.com

Tim Hickey wrote:
> I guess that it has been at least 18 years since I build the fuel
> tanks for my CH-300. They are of welded aluminum construction, and
> were sloshed with Randolph's sloshing sealer. The Alcohol resistant
> type, if I remember correctly.
> Today I drained the tanks so I can replace the fuel selector valve,
> which is enjoying a small leak around the selector shaft, when I
> noticed that there is a small flake of sealer that has cracked loose
> from the rest. Further examination shows that there are areas that
> look like small blisters are forming under the sealer. I suspect that
> this is not an unusual problem, as I seem to recall that others have
> had this problem also. The question I have, is what to do. It seems to
> me that the tanks need to be removed, (big job), and the sealer
> flushed out of there. I seem to recall that some were using MEK to cut
> and remove the sealer. Does this seem like the thing to do?
> Advice welcomed.
>
>
>
>
>
> Zenith CH-300 Driver.

In article . com>,
"stol" > wrote:

> I don't think Randolph made the alcohol resistant sealer 18 years ago.
> It is part # 912 I think. If it the old stuff and you ran auto fuel in
> it that was a mixture of gas/alcohol the blistering is what usually
> happens. I have a Zenith 801 and I would dread to have to unzip my
> wings to get at the tanks. We all feal your pain....

Randolph 912 is white; the non-alcohol-resistant stuff (Randolph 911) is
yellow. IIRC, the best way to remove the old stuff is to slosh some MEK
around the tank to loosen up and dissolve the old stuff.

You have to do this several times, then re-slosh with 912.

--
Remve "_" from email to reply to me personally.

Tim Hickey wrote:
> I guess that it has been at least 18 years since I build the fuel
> tanks for my CH-300. They are of welded aluminum construction, and
> were sloshed with Randolph's sloshing sealer. The Alcohol resistant
> type, if I remember correctly.
> Today I drained the tanks so I can replace the fuel selector valve,
> which is enjoying a small leak around the selector shaft, when I
> noticed that there is a small flake of sealer that has cracked loose
> from the rest. Further examination shows that there are areas that
> look like small blisters are forming under the sealer. I suspect that
> this is not an unusual problem, as I seem to recall that others have
> had this problem also. The question I have, is what to do. It seems to
> me that the tanks need to be removed, (big job), and the sealer
> flushed out of there. I seem to recall that some were using MEK to cut
> and remove the sealer. Does this seem like the thing to do?
> Advice welcomed.
>
>
>
>
>
> Zenith CH-300 Driver.

That has been a problem in the RV's, When I built my tanks in 1988 it
was common practice in manufacturing to use Pro Seal on the seams and
rivets and then Slosh the complete tank. Many builders had the slosh
come loose and had to remove the tanks and and clean out all of the old
slosh. Some builders just junked the tanks and built new tanks as that
was the easier way to go in some cases. It seems that any chemicals that
you use to remove the old slosh just gums it up and makes a complete
mess. I have slosh in my tanks and and am reaching the 17 year mark with
no signs of it coming loose but am keeping my fingers crossed. Van's
have found that the tanks seal just was well just using Pro Seal with
out the slosh.

Jerry

On Thu, 12 Jan 2006 19:10:04 -0800, Jerry Springer
> wrote:

>Tim Hickey wrote:
>> I guess that it has been at least 18 years since I build the fuel
>> tanks for my CH-300. They are of welded aluminum construction, and
>> were sloshed with Randolph's sloshing sealer. The Alcohol resistant
>> type, if I remember correctly.
>> Today I drained the tanks so I can replace the fuel selector valve,
>> which is enjoying a small leak around the selector shaft, when I
>> noticed that there is a small flake of sealer that has cracked loose
>> from the rest. Further examination shows that there are areas that
>> look like small blisters are forming under the sealer. I suspect that
>> this is not an unusual problem, as I seem to recall that others have
>> had this problem also. The question I have, is what to do. It seems to
>> me that the tanks need to be removed, (big job), and the sealer
>> flushed out of there. I seem to recall that some were using MEK to cut
>> and remove the sealer. Does this seem like the thing to do?
>> Advice welcomed.
>>
>>
>>
>>
>>
>> Zenith CH-300 Driver.
>
>That has been a problem in the RV's, When I built my tanks in 1988 it
>was common practice in manufacturing to use Pro Seal on the seams and
>rivets and then Slosh the complete tank. Many builders had the slosh
>come loose and had to remove the tanks and and clean out all of the old
>slosh. Some builders just junked the tanks and built new tanks as that
>was the easier way to go in some cases. It seems that any chemicals that
>you use to remove the old slosh just gums it up and makes a complete
>mess. I have slosh in my tanks and and am reaching the 17 year mark with
>no signs of it coming loose but am keeping my fingers crossed. Van's
>have found that the tanks seal just was well just using Pro Seal with
>out the slosh.
>
>Jerry

The tanks need to be clean and etched before sloshing so the slosh
can bite.No oxide layer. Won't guarantee it will never peel, but if
you get a good bite you won't get corrosion between the metal and the
slosh, which lifts the slosh.Most slosh kits come with an etchant for
steel. Use aluma-prep (Phosphoric acir IIRC) on aluminum tanks.

Thanks, Ben.
I do run auto fuel, and here in Iowa stations must, repeat must, offer
ethanol blended fuels. I never knowingly used a blended fuel. But who
is to say that maybe someone put the wrong fuel in the big underground
tank at the local station. I have made some checks for alcohol after
filling my transport tank, but never confirmed its presence. I guess
maybe one should check every time you go to the station. My totalizer
on my pump says that I have pumped over 8000 gallons of fuel through
it. Maybe I did get a "bad" load or two in there.
By the way, there is move in the Iowa legislature to require that ALL
gas sold in the state be blended with ethanol. The proposal is being
pushed by the Iowa Corn Board. They see it as a new market for corn.
So, Iowans, write your letters to your state Senators and Reps. I
have.

Now, where is that MEK?

On 12 Jan 2006 18:05:39 -0800, "stol" > wrote:

>I don't think Randolph made the alcohol resistant sealer 18 years ago.
>It is part # 912 I think. If it the old stuff and you ran auto fuel in
>it that was a mixture of gas/alcohol the blistering is what usually
>happens. I have a Zenith 801 and I would dread to have to unzip my
>wings to get at the tanks. We all feal your pain....
>
>Ben
>N801BH
>www.haaspowerair.com
>
>
>

Zenith CH-300 Driver.

"Tim Hickey" > wrote
>
> Now, where is that MEK?

First, I must give the mandatory warning about MEK, Methyl Ethyl Ketone. Do
not let it get on your skin, so wear good chemical resistant tall gloves,
and something to protect the rest of your skin. Also use an activated
carbon respirator, in a well ventilated area. It is also very flammable.

The stuff is real nasty, and does nasty stuff to your body. It starts by
destroying your liver, messes with your blood, and the exposure is
additive, so don't let it get at you, to start down that road. It also
attacks the central nervous system, and is a carcinogen. All just
suspected, of course. This is all not to say, don't use it, but do be
careful with the stuff.

I'm sorry if you knew all of that, but someone reading this may not.

OK, that is done. You can usually get it at the larger home improvement
stores, and paint supply houses. It is usually kept around the paint
strippers, and brush cleaners.
--
Jim in NC

Why would anyone even think of using Randolph sealants when 1) Randolph
itself doesn't recommend using it on aircraft and 2) PRC makes a much
superior product called 1005-L Buna-N that Spruce sells and has been
Mil-spec'd for fuel tank slosh sealing since the days of the Connie?

"Orval Fairbairn" > wrote in message
...
> In article . com>,
> "stol" > wrote:
>
>> I don't think Randolph made the alcohol resistant sealer 18 years ago.
>> It is part # 912 I think. If it the old stuff and you ran auto fuel in
>> it that was a mixture of gas/alcohol the blistering is what usually
>> happens. I have a Zenith 801 and I would dread to have to unzip my
>> wings to get at the tanks. We all feal your pain....
>
> Randolph 912 is white; the non-alcohol-resistant stuff (Randolph 911) is
> yellow. IIRC, the best way to remove the old stuff is to slosh some MEK
> around the tank to loosen up and dissolve the old stuff.
>
> You have to do this several times, then re-slosh with 912.
>
> --
> Remve "_" from email to reply to me personally.

Don't use Randolph again. Ever. Use PRC 1005L Buna-N, available from Spruce.
The sealant is diluted in MEK, you pour, slosh, drain excess, let dry and
you're done, and its impervious to any fuel additives.

http://www.aircraftspruce.com/catalog/cspages/sloshcoat.php

"Tim Hickey" > wrote in message
...
>I guess that it has been at least 18 years since I build the fuel
> tanks for my CH-300. They are of welded aluminum construction, and
> were sloshed with Randolph's sloshing sealer. The Alcohol resistant
> type, if I remember correctly.
> Today I drained the tanks so I can replace the fuel selector valve,
> which is enjoying a small leak around the selector shaft, when I
> noticed that there is a small flake of sealer that has cracked loose
> from the rest. Further examination shows that there are areas that
> look like small blisters are forming under the sealer. I suspect that
> this is not an unusual problem, as I seem to recall that others have
> had this problem also. The question I have, is what to do. It seems to
> me that the tanks need to be removed, (big job), and the sealer
> flushed out of there. I seem to recall that some were using MEK to cut
> and remove the sealer. Does this seem like the thing to do?
> Advice welcomed.
>
>
>
>
>
> Zenith CH-300 Driver.

Jim: I don't believe it is the MEK that is so toxic. I was an organic
chemist for many years. MEK evaporates very quickly and doesn't get
past your skin surface. MEK which may have toluene in it is a different
story. Yes aromatic benzene/toluene is quite toxic.

Larry

"Larry" > wrote in message
ups.com...
> Jim: I don't believe it is the MEK that is so toxic. I was an organic
> chemist for many years. MEK evaporates very quickly and doesn't get
> past your skin surface. MEK which may have toluene in it is a different
> story. Yes aromatic benzene/toluene is quite toxic.

Well, if you are to believe the three websites I googled about the chemical
properties, it its.

Man, anything that dissolves stuff so quickly and completely as MEK, has GOT
to be nasty, bad for you stuff! <G>

Do a little googling, and report back, as to whether they are full of sh*t,
and if so, why, with some backup references as to why, of course! ;-)
--
Jim in NC

>Don't use Randolph again. Ever. Use PRC 1005L Buna-N, available from Spruce.
The sealant is diluted in MEK, you pour, slosh, drain excess, let dry
and
you're done, and its impervious to any fuel additives. <

I seem to remember the Randolph site says that 912 is no longer
available. I also can't find on the 'Spruce site where PRC 1005L Buna-N
is at all alcohol resistant.
That said, has anyone tried that POR-15 stuff? Or the 'alcohol
resistant' sealer on Hirsch Auto's site? I'm looking since my RV tanks
are over 16 years old and starting to seep.

Jim

wrote:


> That said, has anyone tried that POR-15 stuff? Or the 'alcohol
> resistant' sealer on Hirsch Auto's site? I'm looking since my RV tanks
> are over 16 years old and starting to seep.
>
> Jim
>
Don't want to read that Jim, :( my RV-6 will be 17 years on July 14,2006.

Larry, MEK is very nasty stuff, does get through the skin.

http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc01/icsc0179.htm

"Larry" > wrote in message
ups.com...
> Jim: I don't believe it is the MEK that is so toxic. I was an organic
> chemist for many years. MEK evaporates very quickly and doesn't get
> past your skin surface. MEK which may have toluene in it is a different
> story. Yes aromatic benzene/toluene is quite toxic.
>
> Larry
>

Larry wrote:
> Jim: I don't believe it is the MEK that is so toxic. I was an organic
> chemist for many years. MEK evaporates very quickly and doesn't get
> past your skin surface.

Uh, it gets past you rskin if it gets inhaled, right?

There are lots of places where the MSDS is posted, usually in .pdf
format:

http://www.palomar.edu/ehs/Chemistry%20MSDS/METHYL%20ETHYL%20KETONE.pdf


--

FF

wrote:
> Larry wrote:
>
>>Jim: I don't believe it is the MEK that is so toxic. I was an organic
>>chemist for many years. MEK evaporates very quickly and doesn't get
>>past your skin surface.
>
>
> Uh, it gets past you rskin if it gets inhaled, right?
>
> There are lots of places where the MSDS is posted, usually in .pdf
> format:
>
> http://www.palomar.edu/ehs/Chemistry%20MSDS/METHYL%20ETHYL%20KETONE.pdf
>
>

Use a good NIOSH mask when working with solvents.

It's 20 bucks well spent.