The Murphy Builders Site

Posted: **Fri Feb 17, 2012 10:08 pm**

Wayne,
You say you always fix leaks from the outside and we did two gushers that
way by cutting a handhole behind the rear bulkheads in our Elite. We have
an elusive small leak remaining. We have soapy water tested the top an
bottom skins, fuel cap, root rib, and all the fittings with no resulting
bubbles. Have used a modified stethoscope to listen as far as possible
through handholes with no joy. It seems the leaks must be at the main
spar, outboard solid rib, or possibly rear bulkheads.

Two questions:
Any suggestions as to how to locate these internal leaks without just
blindly cutting?
How do you deal with access to leaks at the main spar area? Do you cut the
leading edge skin?

Additional suggestions solicited from all sources.
Thanks,
Ralph Baker

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Posted: **Fri Feb 17, 2012 10:08 pm**

Ralph,

If you have a small leak you can consider Randolph tank sealant. Many builders don't like them but I have soaked pieces of aluminum coated with Randolph's sealant 912 in oxygenated gas for over a year with no ill effects. If you don't ever intend to use m ogas, they make a sealant just for avgas too.

Bruce G 357R

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Posted: **Fri Feb 17, 2012 10:08 pm**

Hi Bruce !

Probably better to stay with ProSeal - there IS a thinner,
2 part, brushable version that's good for small leaks. Remember
to use the recommended ProSeal conditioner to refresh the surface
of the old ProSeal, for better adhesion.

If you're sealing from the outside, it helps to stuff a
Shop Vac hose in the filler neck first - DO NOT seal TIGHTLY !
You just want to reduce the pressure inside the tank slightly,
to suck the proseal into the gap. Then turn the ShopVac off
and wait (and hope !!) ;-) :-)

This trick works well for leaky rivets, too - just put a
couple of drops of brushable ProSeal on the rivet head & wait for
it to be drawn in.

One problem with sloshes is they cover the whole inner surface,
in varying thicknesses, and what are the chances of a fingerprint
somewhere, or a sharp edge, causing it to lift, years later .....
Then a large sheet of the stuff wraps around your finger strainer and - !!!

You can put some soapy water in the tank and reverse this
trick, so the ShopVac BLOWS INTO the tank - just look for the
bubbles on the outside !!

Hope these ideas, and all the others contributed by everybody,
help those with problems get those leaks fixed !!!

.....bobp

------------------------------------orig.--------------------------
At 08:08 PM 5/2/02 EDT, you wrote:

Ralph,

If you have a small leak you can consider Randolph tank sealant. Many
builders don't like them but I have soaked pieces of aluminum coated with
Randolph's sealant 912 in oxygenated gas for over a year with no ill effects.
If you don't ever intend to use mogas, they make a sealant just for avgas too.

Bruce G 357R
<HTML>Ralph,
 
 If you have a small leak you can consider Randolph tank sealant. Many

builders don't like them but I have soaked pieces of aluminum coated with
Randolph's sealant 912 in oxygenated gas for over a year with no ill
effects. If you don't ever intend to use m

ogas, they make a sealant just for avgas too.
 
 Bruce G 357R</HTML>

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Posted: **Fri Feb 17, 2012 10:08 pm**

I figured if I ignored this thread long enough that others would throw out
some good ideas!!! Seriously I'm swamped and working 15 to16 hour days
('boy, what a hobby!!). 7 aircraft in the hanger and two in the shop, with
all but 2 needing attention/completion before mid May.

The one important thing when fixing from the outside is that you have to
build a complete dam. That is if you think you have a leaching area on a
rear bulkhead of your Rebel/Elite tank you need/should do a new fillet
(Popsicle stick is perfect) completely around the perimeter of the bulkhead,
onto freshly bared aluminum. If you don't the leaching will just work it's
way under the old stuff to the next place to leach from, now that you just
covered up the easiest area for the fuel to get out.

Fortunately have never had a main spar leak to work on. The usual area is
the rear bulkheads were the rib flange wraps around the bulkheads. It is
absolutely imperative when building to coat the bulkhead heavily in this
area, prior to putting it into the rib flange area, and then filleting it
closed and building a "damn" from the flange down onto the top flange of the
bulkhead and letting it set. Then you have a solid flange are to seal your
top skin down to without worrying about the proseal slumping away. IF you
didn't do this when building I would highly suspect this area as your leak,
or the other usual is the stringers going through the outboard tank rib. If
a slow leaker during pressure test it could very well be a cracked tank
rivet. Seem to average one or two per tank and they are hard to find, but
soapy water with an eye dropper on each mandrel hole, while the tank is
pressurize, will find them.

Good night,
Wayne

----- Original Message -----
From: "Bob Patterson" <bob.patterson@canrem.com>
To: <murphy-rebel@dcsol.com>
Sent: Thursday, May 02, 2002 10:59 PM
Subject: Re: fuel tank leaks

Hi Bruce !

Probably better to stay with ProSeal - there IS a thinner,
2 part, brushable version that's good for small leaks. Remember
to use the recommended ProSeal conditioner to refresh the surface
of the old ProSeal, for better adhesion.

If you're sealing from the outside, it helps to stuff a
Shop Vac hose in the filler neck first - DO NOT seal TIGHTLY !
You just want to reduce the pressure inside the tank slightly,
to suck the proseal into the gap. Then turn the ShopVac off
and wait (and hope !!) ;-) :-)

This trick works well for leaky rivets, too - just put a
couple of drops of brushable ProSeal on the rivet head & wait for
it to be drawn in.

One problem with sloshes is they cover the whole inner surface,
in varying thicknesses, and what are the chances of a fingerprint
somewhere, or a sharp edge, causing it to lift, years later .....
Then a large sheet of the stuff wraps around your finger strainer and -

!!!

You can put some soapy water in the tank and reverse this
trick, so the ShopVac BLOWS INTO the tank - just look for the
bubbles on the outside !!

Hope these ideas, and all the others contributed by everybody,
help those with problems get those leaks fixed !!!

.....bobp

------------------------------------orig.--------------------------
At 08:08 PM 5/2/02 EDT, you wrote:
Ralph,

If you have a small leak you can consider Randolph tank sealant. Many
builders don't like them but I have soaked pieces of aluminum coated with
Randolph's sealant 912 in oxygenated gas for over a year with no ill

effects.

If you don't ever intend to use mogas, they make a sealant just for avgas

too.

Bruce G 357R
<HTML>Ralph,
 
 If you have a small leak you can consider Randolph tank sealant. Many
builders don't like them but I have soaked pieces of aluminum coated with
Randolph's sealant 912 in oxygenated gas for over a year with no ill
effects. If you don't ever intend to use m
ogas, they make a sealant just for avgas too.
 
 Bruce G 357R</HTML>

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Posted: **Fri Feb 17, 2012 10:08 pm**

Hi Bob,

I don't think I would have added a sealant to my tanks had it not been already sloshed when I bought the partially completed Rebel. I've had to remove Kreem sloshing compound from my Kitfox fiberglass wing tanks, after two years, by sloshing them with MEK until they ran clear. The sealant lifted in sheets just like you described.

I know many Kitfox pilots that have not had problems with there sealant for many years because they deluded it 50/50 with MEK before sloshing. That seems to be the trick with Kreem which comes very thick right out of the can.

My rebel tanks don't leak so I was tempted to leave them alone with the sealant (Randolph) intact. Being concerned about the effects of oxygenated mogas for my 0320 150HP I have been soaking pieces of Randolph coated aluminum in a jar filled with oxygenat ed gas for a year and a half. I pull them out every few months and scratch at them to detect any softening or delimitation. So far no problem.

I figure it would be just as easy to slosh out the sealant with MEK later as now if it comes to that. You can believe I will keep a close eye on the tanks as I begin flying the Rebel.

What do you think, Bob?

Anyone have experience with Randolph silence? I'm all ears, pipe up please!

Bruce G 357R

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Posted: **Fri Feb 17, 2012 10:08 pm**

Hi Bruce !

I guess I'd do exactly what you're doing, in the same
circumstance - and keep a close eye on it. I do believe that the
newer Randolph is pretty good, but who knows, with most Can. mogas now
containing up to 10 % alcohol, and who knows what else ...
If it does lift, a sheet of it will cause a lot of trouble.

I'll keep my fingers crossed for you. One good thing is
yours has had a lot of time to harden without fuel ...

I did fly one Rebel that was sloshed with Randolph - about
25 hours of ferry time - with no problems, mostly on Avgas. I believe
it has held up for 7 or 8 years on different fuels, so that's encouraging.
Possibly the reason is that they didn't scrimp - 2 or 3 quarts were
dumped into each tank, and the wing rotated to coat well, before
the surplus was drained for the other tank. It was then hardened by
the Shop Vac trick - blowing into the tank for 30 hours. The warmed
air helped harden the Randolph (red) sealant. In this case, it was
a matter of needing to get it flying for the ferry trip. Still a risky
business, but that's one time it worked - there are several incidences
near here where it didn't, and left an aweful mess ...

Hope some others will help with feedback ....

.....bobp

--------------------------------orig.--------------------------------
At 09:06 PM 5/3/02 EDT, you wrote:

Hi Bob,

I don't think I would have added a sealant to my tanks had it not been
already sloshed when I bought the partially completed Rebel. I've had to
remove Kreem sloshing compound from my Kitfox fiberglass wing tanks, after
two years, by sloshing them with MEK until they ran clear. The sealant lifted
in sheets just like you described.

I know many Kitfox pilots that have not had problems with there sealant for
many years because they deluded it 50/50 with MEK before sloshing. That seems
to be the trick with Kreem which comes very thick right out of the can.

My rebel tanks don't leak so I was tempted to leave them alone with the
sealant (Randolph) intact. Being concerned about the effects of oxygenated
mogas for my 0320 150HP I have been soaking pieces of Randolph coated
aluminum in a jar filled with oxygenated gas for a year and a half. I pull
them out every few months and scratch at them to detect any softening or
delimitation. So far no problem.

I figure it would be just as easy to slosh out the sealant with MEK later as
now if it comes to that. You can believe I will keep a close eye on the tanks
as I begin flying the Rebel.

What do you think, Bob?

Anyone have experience with Randolph silence? I'm all ears, pipe up please!

Bruce G 357R

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Posted: **Fri Feb 17, 2012 10:08 pm**

Bob,

When the sealant lifted in my Kitfox it stayed in one piece. It was like a balloon inside the tank, just separated off the fiberglass. It never came apart but stayed in one piece so as to not clog the finger stainer.

I always inspected the tank's inside with a mirror. The separation was not easily detected. At annual I completely missed it until I was reinstalling the finger stainer, after removal and inspection, then noticed an odd bump in the tank about 6 inches in side. curious, I took a piece of safety wire, made a tiny hook at the end, hooked the bump and began pulling the hole balloon right out the screw hole until it tore.

You can imagine the look on my face. I have no idea how long I'd flown the plane this way but definitely not something I ever want to do again!

The previous builder sloshed the tank because he had a leak. The leak was to large for the sloshing to work. When I got it the wing it would not hold air. I cut three inspection holes in the bottom skin then cleaned, scuffed and re prosealed with popsicle sticks as Wayne described. Now it holds air.

I was tempted to do the same with the other wing, even though it didn't leak. I decided if it wasn't broke I wouldn't fix it. Hope it doesn't come back to haunt me.

I'm painting the plane this weekend and hoping to be back together and test fly in June.

Bruce G 357R

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Posted: **Fri Feb 17, 2012 10:08 pm**

Hi Bruce !

I guess the stuff made a balloon because it came from a
smooth fiberglass tank - I've seen many small chunks from inside
wet wings - there are too many odd shaped pieces in there to have
it all stay together in one smooth piece.

Sounds like you were lucky !! Also, you've done everything
right, now, and should be able to enjoy flying.

I know you're going to LOVE your Rebel when you finally get
it into the air !!! :-) :-)

.....bobp

-----------------------------------orig.---------------------------------
At 10:40 PM 5/3/02 EDT, you wrote:

Bob,

When the sealant lifted in my Kitfox it stayed in one piece. It was like a
balloon inside the tank, just separated off the fiberglass. It never came
apart but stayed in one piece so as to not clog the finger stainer.

I always inspected the tank's inside with a mirror. The separation was not
easily detected. At annual I completely missed it until I was reinstalling
the finger stainer, after removal and inspection, then noticed an odd bump in
the tank about 6 inches in side. curious, I took a piece of safety wire, made
a tiny hook at the end, hooked the bump and began pulling the hole balloon
right out the screw hole until it tore.

You can imagine the look on my face. I have no idea how long I'd flown the
plane this way but definitely not something I ever want to do again!

The previous builder sloshed the tank because he had a leak. The leak was to
large for the sloshing to work. When I got it the wing it would not hold air.
I cut three inspection holes in the bottom skin then cleaned, scuffed and re
prosealed with popsicle sticks as Wayne described. Now it holds air.

I was tempted to do the same with the other wing, even though it didn't leak.
I decided if it wasn't broke I wouldn't fix it. Hope it doesn't come back to
haunt me.

I'm painting the plane this weekend and hoping to be back together and test
fly in June.

Bruce G 357R

<HTML>Bob,
 
 When the sealant lifted in my Kitfox it stayed in one piece. It was

like a balloon inside the tank, just separated off the fiberglass. It never
came apart but stayed in one piece so as to not clog the finger stainer.

I always inspected the tank's inside with a mirror. The separation was

not easily detected. At annual I completely missed it until I was
reinstalling the finger stainer, after removal and inspection, then noticed
an odd bump in the tank about 6 inches in

side. curious, I took a piece of safety wire, made a tiny hook at the end,

hooked the bump and began pulling the hole balloon right out the screw hole
until it tore.

You can imagine the look on my face. I have no idea how long I'd flown

the plane this way but definitely not something I ever want to do again!

The previous builder sloshed the tank because he had a leak. The leak

was to large for the sloshing to work. When I got it the wing it would not
hold air. I cut three inspection holes in the bottom skin then cleaned,
scuffed and re prosealed with popsicle

sticks as Wayne described. Now it holds air.
 
 I was tempted to do the same with the other wing, even though it didn't

leak. I decided if it wasn't broke I wouldn't fix it. Hope it doesn't come
back to haunt me.

I'm painting the plane this weekend and hoping to be back together and

test fly in June.

Bruce G 357R
 
 </HTML>

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Posted: **Fri Feb 17, 2012 10:08 pm**

Just a thank you to all who suggested methods of attack. We will prevail even if the added Proseal reduces our fuel capacity to 10 gallons!
Ralph Baker
Elite 624E (reserved)