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Date: Mon, 13 Apr 1998 11:34:25 -0230
From: wayne goudie <wgoudie@nf.sympatico.ca>
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Subject: Pressure testing fuel tanks
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Hi, I tested a tank using the balloon and a leak was apparent so I
pressurized the tank to 3psi, using a low pressure guage borrowed from a
local mechanic and found three leak areas. I am wondering if those
areas would have been apparent or even all leaking at the lower balloon
pressure,assuming of course that the balloon pressure is considerably
less than 3psi,as it appeared to be in my case, although I admit I did
not measure the pressure from the balloon.Just wondering if the 3psi has
the importance of simulating more accurately the internal pressures that
could be encountered in flight.
Wayne Goudie 285R



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From: JimsRebel <JimsRebel@aol.com>
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Date: Wed, 15 Apr 1998 12:34:54 EDT
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Subject: Re: Pressure testing fuel tanks
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Hi
I used 2-3 PSI in one tank and found that it distorted the tank in the area
of
the middle two ribs. It blew up the tank and expanded the center two rib
bays
to the point where it created leaks around the rivets in the lower center
bottom ribs.
The 3 PSI number comes from FAR's in new A/C certification. The most you
will
get in flight (ram air ) is about 1/2 PSI. You can soap the outside of
the
tank to check for small leaks, like the center of the rivet heads, but when
you think it's good be sure and put gas in it for the final test. I attached
the top tank skin to the top wing skin only which allowed me to curl up the
trailing edge of the top wing skin to seal a small leak which I created when
I
forced the top wing skin between the top stringers and the tank skin. You
can
use a vacuum cleaner to put a low pressure in the tank to suck the ProSeal
in
for any repairs.
Good Luck ... Jim LePard JimsRebel@aol.com



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From: MMoreho699 <MMoreho699@aol.com>
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Date: Wed, 15 Apr 1998 20:51:23 EDT
To: JimsRebel@aol.com, murphy-rebel@dcsol.com
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Subject: Re: Re: Pressure testing fuel tanks
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Hello!

I first started using a 0-10 PSI gauge that I got at the hardware store.
Then
someone posted a message about making a water manometer.

I used a tire inflator fitting and put it into the small fitting. I took a
fitting with a valve and put it in the other hole. I used a 2 or 3" rubber
plumbing fitting with a pvc plug to close the fuel entry hole.

Take about 12' of tubing about as big around as my middle finger. If you
don't
have my middle finger, use your own. Hook one end up to a tank fitting, loop
it down off the table about two feet (I forget the exact numbers; 29" sticks
in my mind), then up above the tank about two feet. Fill the tubing with
water
until it rises to the level of the table/tank. When there is equal pressure
on
both ends of the water tubing, the levels will be the same in the loop.
Charge
the tank with air. The pressure in the tank will force the water down the
loop
on one side and up the loop on the other. You know there is enough pressure
when you get about two feet. It's much more accurate than a gauge method
since
~2 psi is spread out over about four feet.

I suggest closing the valve to the tubing to eliminate possible leaks in the
tubing system. Check the tubing level every once in awhile for a couple
days.
If the water is at the same level as you started, BINGO! I also put some
food
coloring in the manometer to help my eyes.

Take care,
Dan




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MMoreho699 wrote:

snip... You know there is enough pressure when you get about two feet.
It's much more accurate than a gauge method since ~2 psi is spread out
over about four feet.

I believe the pressure is approx. 1/2 psi per foot so for 2 psi you need
to be elevated four feet above the tank.

David James




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To: <murphy-rebel@dcsol.com> (Murphy Rebel)
From: Bob Patterson <bob.patterson@canrem.com>
Subject: Re: Pressure testing fuel tanks
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Date: Wed, 15 Apr 1998 22:41:32 -0400

Hi Wayne !
It is my understanding that the factory do NOT recommend pressurizing,
particularly over 2 psi, as distortion is already evident. (Maybe the
guage wasn't quite accurate ...)

Generally, a good sized balloon (or condom), will give enough pressure
to show up leaks. You can then use soapy water to track them down and
ProSeal them.

Glad you got all of yours ! Once you get a good seal on the tanks,
thay will never leak again.

Off to Sun 'n Fun tomorrow !!!

....bobp

-------------------------------------orig.----------------------------------
-
At 11:34 AM 4/13/98 -0230, you wrote:

Hi, I tested a tank using the balloon and a leak was apparent so I
pressurized the tank to 3psi, using a low pressure guage borrowed from a
local mechanic and found three leak areas. I am wondering if those
areas would have been apparent or even all leaking at the lower balloon
pressure,assuming of course that the balloon pressure is considerably
less than 3psi,as it appeared to be in my case, although I admit I did
not measure the pressure from the balloon.Just wondering if the 3psi has
the importance of simulating more accurately the internal pressures that
could be encountered in flight.
Wayne Goudie 285R

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To: "'murphy-rebel@dcsol.com'" <murphy-rebel@dcsol.com>
Subject: RE: Pressure testing fuel tanks
Date: Thu, 16 Apr 1998 12:14:13 -0700
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Hi gang:

I made a water manometer to measure pressure in my tank, and backed that up
with a gage. When there is about 2 PSI in the tank, it will bulge out
noticeably, especially on the end solid ribs.

I don't think you'll ever get to 3 PSI in normal flight, here is my way of
seeing it:
(if anyone finds a math or logic error here please tell me, because I have
been wrong before)

A gallon of avgas is 231 cu. in. and weighs 6 lbs. So a cubic in. of avgas
would weigh 6 lb./231 cu. in. = .0259 lb./cu. in. The tank is roughly 10
in. deep at it's deepest point, so a 10" x "1 x 1" (10 cu. in.) column of
avgas would weigh .0259 lb/cu. in. * 10 cu. in. = .259 lb. Since our
theoretical column is 1" square cross section, that is equivalent to PSI,
or .259 PSI. This is at +1g.

Design limit is +6g on the airplane, At +6g that limit that 10 cu. in.
column of gas would weigh 6 * .25 lb = 1.558 lb, which is the same as 1.558
PSI.

One could argue that you could pull 6g's while rolled 90 degrees over, and
in that case, the column of gas would be about 36" x 1" x 1", which by the
same math method would yield .935 PSI at 1g and 5.610 PSI at 6g, at which
point it might leak. If you are in that situation, a leak in the fuel tank
is probably not your biggest concern.

I've been told that "absolutely no leaks whatsoever" may never happen with
a wet wing. Who knows? I guess I will when I fill it up.

Tim
----------
From: wayne goudie[SMTP:wgoudie@nf.sympatico.ca]
Reply To: murphy-rebel@dcsol.com
Sent: Monday, April 13, 1998 7:04 AM
To: Murphy Rebel mailing list
Subject: Pressure testing fuel tanks

Hi, I tested a tank using the balloon and a leak was apparent so I
pressurized the tank to 3psi, using a low pressure guage borrowed from a
local mechanic and found three leak areas. I am wondering if those
areas would have been apparent or even all leaking at the lower balloon
pressure,assuming of course that the balloon pressure is considerably
less than 3psi,as it appeared to be in my case, although I admit I did
not measure the pressure from the balloon.Just wondering if the 3psi has
the importance of simulating more accurately the internal pressures that
could be encountered in flight.
Wayne Goudie 285R





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I am just starting to test my right tank (so far holding for 8
hrs,.....knock on aluminum). I remeber hearing somewhere about 2 pound and
even 3 pound pressure test. The three bay Rebel tank has a floor area of 650
square inches. Pumping the tank to 3 psi puts that floor under 1,950 lb
load! If you include the side and the top areas the overall resulting load
is simply staggering, bizzare!!! Overkill for leak test purposes! Don't do
it!!!
A whole gallon of fuel weighs only 6 lbs. A full tank will weigh just a tad
over 100 lbs. Even a few extra Gs will not get much over 200 lbs on the tank
floor so testing at 1/3 psi (inflated condom?) stresses the tank pretty
close to it and it is enough to reveal a leak, no need to go overboard and
possibly induce a leak by weakening the joints.

My opinion.

Paul Kucera

Rebel builder 453R

P.S.

I did have a small leak at one of the fuel fittings. Kids bubble blowing
liquid worked very well in finding it. This is available in any Dollar store
or toy sections in any bigger store.


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Your following message has been delivered to the 153 members of
the list murphy-rebel@dcsol.com at 09:10:38 on 17 May 2000.
--------------------------------------------------------------------------


This is how I have been testing tanks since 1993 although Darryl Murphy
still says they should be pumped to 3 psi(so the tank swells) and the Condom
is not enough. It has worked flawlessly (and very SAFELY) for me, so I will
stick with my method! You already have to put something over the large
filler opening, WHY NOT the test apparatus??!?!? I have never put a gauge on
the tank, but I will next time I have a Condom blown up like a water tower.
I figure around 1 PSI.

The SAFEST thing you will ever do with a condom.

Wayne G. O'Shea
www.irishfield.on.ca

-----Original Message-----
From: C&P Kucera <cpkucera@idirect.com>
To: Murphy Rebel Builders List <murphy-rebel@dcsol.com>
Date: Tuesday, May 16, 2000 10:50 PM
Subject: Pressure testing fuel tanks

I am just starting to test my right tank (so far holding for 8
hrs,.....knock on aluminum

(inflated condom?) stresses the tank pretty

close to it and it is enough to reveal a leak, no need to go overboard and
possibly induce a leak by weakening the joints.

My opinion.

Paul Kucera

Rebel builder 453R

P.S.

I did have a small leak at one of the fuel fittings. Kids bubble blowing
liquid worked very well in finding it. This is available in any Dollar

store

or toy sections in any bigger store.


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Paul
I pressure tested my tanks to 3 psi. and I agree it was probably going over
board.
I mean heck if you think about it you only run 3 or 4 psi in four wheeler
tires.
Phil&Lisa Smith #460 N414D
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It is impressive how strong this tank really is. Some visitors in my
workshop are amased how thin and delicate some of the parts are, like the
ribs or those rear spar mounting brackets. Some of it does almost seem like
magic!

Paul

----- Original Message -----
From: <LisaFly99@aol.com>
To: <murphy-rebel@dcsol.com>
Sent: Wednesday, May 17, 2000 2:35 PM
Subject: Re: Pressure testing fuel tanks

Paul
I pressure tested my tanks to 3 psi. and I agree it was probably going

over

board.
I mean heck if you think about it you only run 3 or 4 psi in four wheeler
tires.
Phil&Lisa Smith #460 N414D

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WE too used very little pressure when testing our tanks.
We had the material to put together a schrader valve and gage system so we
just pluged the other line holes and covered the filler neck with a glove.
Our first test filled the glove nicely and only put .5 lbs. of psi. in the
tank. We went home that eve after 4 hrs of inflated glove feeling very smug
and pating ourselfs on the back for a great job. Well when we returned in the
am, the glove was flat. Very upset we turned the heat back up in the hanger
and went to get a coffee and discuss the method of finding the leak. Lo and
behold on our return the glove was inflated again! The temp. change of 15deg
f was enough to make the glove de and then inflate. After then taping down 3
of the 4 fingers on the glove to remind ourselfs how simple things can
really screw you up we watched the glove go up and down for the next 3 weeks
and ended up with no leaks. The only other suggestion for loeak testing I
heard of that sounded real good was to fill the tank with an inert gas if you
have the " sniffer " equipment and look for leaks that way. Tough to recover
the gas if you have to though.
Good luck, keep at it , it's worth it. Curt N97MR
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