The Murphy Builders Site

Hello,

i have an aluminum welded fuel tank that was leak tested extensively prior to installation. it was rewelded to cure a few small leaks and retested and installed. after 15 months of use with av gas, it has started to leak rapidly from a lower seam after all those months. it has had fuel in it for 100 percent of that time.

my question is do you rebel guys rely on your prosealed seams or do you "slosh" your tanks also?

we may be able to proseal the lower seams through the fuel filler, but it will be a less than pretty result. our other possibility is to pull the wing and slosh the tank. i guess we could also try sloshing with the wing installed as the leak is definitely in a seam on the bottom of the tank.

any thoughts or suggestions would be very appreciated. we use av gas in the wing tanks and blend with auto fuel in the main fuselage tank. anyone have experience with sloshing materials and there success/failure with av or auto fuel?

thanks

Andy


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Do not slosh...just a ticking time bomb! (no matter what it says on the
can!)

Pull the tank..reweld if necessary to tie the crack back together and then I
would prep the entire welded seam area and an inch or so beyond with a heavy
scotchbrite disc, clean and proseal the entire seam overlapping an inch or
so out onto good clean alum.

I've done this routine for years on Zenair's porous welding of all their 601
and 701 fuel tanks with great success. Never had one leak after this
treatment.

Cheers,
Wayne

----- Original Message -----
From: "Andy Bowman" <bowmanout@yahoo.com>
To: <rebel-builders@dcsol.com>
Sent: Thursday, November 04, 2004 9:47 PM
Subject: fuel tank construction/ maint

Hello,

i have an aluminum welded fuel tank that was leak tested extensively prior

to installation. it was rewelded to cure a few small leaks and retested and
installed. after 15 months of use with av gas, it has started to leak
rapidly from a lower seam after all those months. it has had fuel in it for
100 percent of that time.

my question is do you rebel guys rely on your prosealed seams or do you

"slosh" your tanks also?

we may be able to proseal the lower seams through the fuel filler, but it

will be a less than pretty result. our other possibility is to pull the wing
and slosh the tank. i guess we could also try sloshing with the wing
installed as the leak is definitely in a seam on the bottom of the tank.

any thoughts or suggestions would be very appreciated. we use av gas in

the wing tanks and blend with auto fuel in the main fuselage tank. anyone
have experience with sloshing materials and there success/failure with av
or auto fuel?

thanks

Andy


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I also re-read that Andy and doesn't sound like removing the tank is an
option of choice.....unfortunately I cannot see how you can prep and clean
the area thru the filler neck to then go in there and spread proseal over
it. If it's not cleaned and prepped properly...no different than doing body
work and paint...don't bother prosealing as it won't stick and then you'll
have an even bigger mess to deal with.

Wayne

----- Original Message -----
From: "Wayne G. O'Shea" <oifa@irishfield.on.ca>
To: <rebel-builders@dcsol.com>
Sent: Thursday, November 04, 2004 9:51 PM
Subject: Re: fuel tank construction/ maint

Do not slosh...just a ticking time bomb! (no matter what it says on the
can!)

Pull the tank..reweld if necessary to tie the crack back together and then

I

would prep the entire welded seam area and an inch or so beyond with a

heavy

scotchbrite disc, clean and proseal the entire seam overlapping an inch or
so out onto good clean alum.

I've done this routine for years on Zenair's porous welding of all their

601

and 701 fuel tanks with great success. Never had one leak after this
treatment.

Cheers,
Wayne

----- Original Message -----
From: "Andy Bowman" <bowmanout@yahoo.com>
To: <rebel-builders@dcsol.com>
Sent: Thursday, November 04, 2004 9:47 PM
Subject: fuel tank construction/ maint

Hello,

i have an aluminum welded fuel tank that was leak tested extensively

prior

to installation. it was rewelded to cure a few small leaks and retested

and

installed. after 15 months of use with av gas, it has started to leak
rapidly from a lower seam after all those months. it has had fuel in it

for

100 percent of that time.

my question is do you rebel guys rely on your prosealed seams or do you

"slosh" your tanks also?

we may be able to proseal the lower seams through the fuel filler, but

it

will be a less than pretty result. our other possibility is to pull the

wing

and slosh the tank. i guess we could also try sloshing with the wing
installed as the leak is definitely in a seam on the bottom of the tank.

any thoughts or suggestions would be very appreciated. we use av gas in

the wing tanks and blend with auto fuel in the main fuselage tank. anyone
have experience with sloshing materials and there success/failure with av
or auto fuel?

thanks

Andy


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The PRC rep was pretty frank with me and said sloshing was a temporary
repair as far as he was concerned.

There was an interesting site documenting fuel tank testing from one of
the manufacturers that I perused once. They had a rock and roll machine
set up to simulate flight. The conclusion was that any split seams or
cracking was almost certainly caused by flexing of the tank as fuel
sloshed around. If you think that is the case then a welded sean will
crack again in the same time or sooner. You might want to consider a
design change or at least adding baffles instead of just welding the
seam...

I doubt that proseal will stop the crack from progressing if it is a
split seam.

Ken

Andy Bowman wrote:

Hello,

i have an aluminum welded fuel tank that was leak tested extensively prior to installation. it was rewelded to cure a few small leaks and retested and installed. after 15 months of use with av gas, it has started to leak rapidly from a lower seam after all those months. it has had fuel in it for 100 percent of that time.

my question is do you rebel guys rely on your prosealed seams or do you "slosh" your tanks also?

we may be able to proseal the lower seams through the fuel filler, but it will be a less than pretty result. our other possibility is to pull the wing and slosh the tank. i guess we could also try sloshing with the wing installed as the leak is definitely in a seam on the bottom of the tank.

any thoughts or suggestions would be very appreciated. we use av gas in the wing tanks and blend with auto fuel in the main fuselage tank. anyone have experience with sloshing materials and there success/failure with av or auto fuel?

thanks

Andy


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hi,

Thanks for your suggestions. we doubt that the fuel is moving a lot as we have a 7 gallon
tank that is one rib bay wide on a Christavia mk-1. our floats are 1800 amphibs and thus our interest in your group. the tank is therefore narrow, and due to weight and balance considerations has been kept full and in fact not used much in flight except for testing purposes. the leak appears to be on a lower side seam as the rear lower seam is a bend, not a welded seam. the flow is not coming from the fuel line fitting or the quick drain. the flow from the leak is fairly substantial. it will cause regular dripping from three seaplane grommets simultaneously.

as Wayne deduced, pulling the wing and then the tank from the wing does not sound like fun to us. the wing is all wood structure, fabric covered, and rib stitched. the paint is aerothane so patching in the hole we'll have to cut will probably require another coat or two of finish color.

we were fairly sure that the cure for this problem would include some less than fun stuff.
the welder is a very experienced tig equipped friend who did all three of our tanks .
my temptation is to pull the wing, open up an access hole in the fabric, open and access hatch in the tank top, and proceed to clean prep and proseal the lower seams in the tank. then I'd try to patch up the entry wounds as best i can and reassemble. i think we will fly as is with three hour of fuel instead of four until our water turns rock hard and then take her down for the repair.

any thoughts on this course of action? anyone ever had the joy of pulling a wing off a plane way up on those floats?

thanks again.

Andy




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Andy, most of the Super Cub (cert and homebuilt) guys end up making an
aluminum cover for the tank area once they pull the tank the first time (of
many) to get away from redoing fabric. Might be an option for you so you can
take the tank right out!?

As for removing a wing when way up there...yes and I do it all by myself! I
have a walk behind pallet lift. I extend the forks using 4" ABS sewer pipe,
then I lay a twin mattress across the forks..lift up into place and then
remove the lift struts and then unbolt the wing. Slide the wing over enough
to clear the fuselage and then lower.

Good luck,
Wayne

----- Original Message -----
From: "Andy Bowman" <bowmanout@yahoo.com>
To: <rebel-builders@dcsol.com>
Sent: Friday, November 05, 2004 9:38 AM
Subject: Re: fuel tank construction/ maint

hi,

Thanks for your suggestions. we doubt that the fuel is moving a lot as we

have a 7 gallon

tank that is one rib bay wide on a Christavia mk-1. our floats are 1800

amphibs and thus our interest in your group. the tank is therefore narrow,
and due to weight and balance considerations has been kept full and in fact
not used much in flight except for testing purposes. the leak appears to be
on a lower side seam as the rear lower seam is a bend, not a welded seam.
the flow is not coming from the fuel line fitting or the quick drain. the
flow from the leak is fairly substantial. it will cause regular dripping
from three seaplane grommets simultaneously.

as Wayne deduced, pulling the wing and then the tank from the wing does

not sound like fun to us. the wing is all wood structure, fabric covered,
and rib stitched. the paint is aerothane so patching in the hole we'll have
to cut will probably require another coat or two of finish color.

we were fairly sure that the cure for this problem would include some less

than fun stuff.

the welder is a very experienced tig equipped friend who did all three of

our tanks .

my temptation is to pull the wing, open up an access hole in the fabric,

open and access hatch in the tank top, and proceed to clean prep and proseal
the lower seams in the tank. then I'd try to patch up the entry wounds as
best i can and reassemble. i think we will fly as is with three hour of fuel
instead of four until our water turns rock hard and then take her down for
the repair.

any thoughts on this course of action? anyone ever had the joy of pulling

a wing off a plane way up on those floats?

thanks again.

Andy




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Andy,

A couple of us were having problems with leaking around the stringers and
the lower part of the front spar. Pulled the top tank skin, and "sloshed"
every part of the tank except for the upper tank skin. It took care of the
problem. Jeffco isn't cheap but doesn't add much weight. Aircraft Spruce
sells it.

Barny
SR103 MGDQ 20bt


----- Original Message -----
From: Ken <klehman@albedo.net>
To: <rebel-builders@dcsol.com>
Sent: Thursday, November 04, 2004 9:48 PM
Subject: Re: fuel tank construction/ maint

The PRC rep was pretty frank with me and said sloshing was a temporary
repair as far as he was concerned.

There was an interesting site documenting fuel tank testing from one of
the manufacturers that I perused once. They had a rock and roll machine
set up to simulate flight. The conclusion was that any split seams or
cracking was almost certainly caused by flexing of the tank as fuel
sloshed around. If you think that is the case then a welded sean will
crack again in the same time or sooner. You might want to consider a
design change or at least adding baffles instead of just welding the
seam...

I doubt that proseal will stop the crack from progressing if it is a
split seam.

Ken

Andy Bowman wrote:

Hello,

i have an aluminum welded fuel tank that was leak tested extensively

prior to installation. it was rewelded to cure a few small leaks and
retested and installed. after 15 months of use with av gas, it has started
to leak rapidly from a lower seam after all those months. it has had fuel in
it for 100 percent of that time.

my question is do you rebel guys rely on your prosealed seams or do you

"slosh" your tanks also?

we may be able to proseal the lower seams through the fuel filler, but it

will be a less than pretty result. our other possibility is to pull the wing
and slosh the tank. i guess we could also try sloshing with the wing
installed as the leak is definitely in a seam on the bottom of the tank.

any thoughts or suggestions would be very appreciated. we use av gas in

the wing tanks and blend with auto fuel in the main fuselage tank. anyone
have experience with sloshing materials and there success/failure with av
or auto fuel?

thanks

Andy


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