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Fuel Tank Leak printer friendly version
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jb92563
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Posted Monday, August 30, 2010 @ 11:07 AM  

Hi folks,

I was looking forward to a nice flight this weekend in my RF4D but alas it wanted some TLC instead.

I found my fuel tank was leaking fuel on my right rudder pedal.

Upon draining my tank I found a previous application to the inside of the tank with a repair liquid (Polysulfide?).

I suspect that since the auto fuel alcohol content has been increasing, the previously applied repair failed, due to the products inability
to handle the alcohol perhaps.

Any suggestions for a product that can withstand todays mogas fuel formulations?

The leak is at the low point mid right hand side in the weld seam.

When I need to do the fuselage recover I may opt to take the tank out and get the weld repaired but for the time being I think
a temporary tank repair is the best option.

Its also quite difficult to get at the inside due to the 2" fuel cap opening, but I can get a long tube or brush into that area of the tank to apply the coating.

Any recommendations or suggestions for a product or method of repair?

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

dannparks
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Posted Monday, August 30, 2010 @ 02:45 PM  

My RV tanks are sealed with stuff called ProSeal. It sticks well to clean aluminum, but I'm not sure about resistance to alcohol. Easy to brush inside, but it might also work from the outside.

--------------------
Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1

jb92563
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Posted Monday, August 30, 2010 @ 05:08 PM  

After doing a bit of research I ordered some Caswell tank repair epoxy.

Its a Phenol Novolac epoxy that resists alcohol in fuel and sticks well to Aluminum tanks. Its a 2 part epoxy system so the shelf life should be good.

I read that some of the other products were not holding up that well to the increased Mogas additives.

I also like it because it is reported to be thicker than the others and will be easier to apply with a long brush that I will need to use to apply the epoxy.

It also is less particular about the surface prep and will stick to just about anything, including other sealing products.

After cleaning the repair area with acetone inside and out, I apply the epoxy and then presurize the tank to force the expoxy into the pinhole.

If I can see it oozing out I will know I have the hole filed and will also coat the outside area of the tank.

I think this repair should work well and last a long time.

I'll remove one outrigger to keep the epoxy flowing into the repair area and away from the fuel pickup.

I was a little concerned about where all my lost fuel was going, and it appeared to be evaporating before getting very far thanks to the very hot last couple weeks.

It had been dripping right on to the rudder pedals rubber no slip pad but I will check to see that the wood part has not become delaminated.

Having this down time has given me some time to work on some other tasks for the RF4D like the Weld on EGT sensors (Done now), wiring and my leak-less redesigned aerobatic fuel guage.

I'll have some pictures of the prototype fuel guage progress soon.

[Edit by jb92563 on Monday, August 30, 2010 @ 05:10 PM]

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

jb92563
Second Lieutenant

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Posted Tuesday, September 7, 2010 @ 12:01 PM  

I did some work to prepare the leak for repairs.

I made a long scraper out of a piece of 3/16" steel rod, pounded the end flat and sharpened the edge.

With that I was able to lower a little LED flashlight into the dry tank and use my scraper to remove the old
polysulfide patch.

Apparently this stuff does not stand up to the increasing alcohol in 91 unleaded auto fuel in southern California.

My Caswell Epoxy tank sealer should work better with auto fuel and can be used in 100% alcohol tanks as well.


The old leak patch. Notice the dark shadows showing where the material separated from the aluminum.


After some scraping. I also applied MEK after the pic and that further loosened and disolved the remaining material.

I'm lucky I have not had a complete fuel blockage so far with this old stuff flaking off.

[Edit by jb92563 on Tuesday, September 7, 2010 @ 12:05 PM]

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

jb92563
Second Lieutenant

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Posted Monday, September 13, 2010 @ 03:15 PM  

The tank has been sealed with the Caswell epoxy tank repair.

It was brushed on in the area of the leaky seam, and pressurized for a few minutes to force the epoxy into the pinholes.

Then additional epoxy was brushed on and the exterior of the tank also had some epoxy brushed on in the area of the leak.

It is set after 30 minutes and fully cured after 3 days to allow up to 100% alcohol fuels.

It is extremely sticky stuff and adheres incredibly well to everything it came into contact with, as I found out when trying to clean up
afterwards.

It is quite exothermic and it is thin and flows well while hot from its reaction but as it cools and cures it thickens.

I will test the tank after the 3 day cure is complete and post the results.

The process ended up sealing small remaing old patch remnants as well so there is little opportunity for a stray particle coming off later on and plugging a fuel line.

[Edit by jb92563 on Monday, September 13, 2010 @ 03:19 PM]

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

Jorgen
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Posted Tuesday, September 14, 2010 @ 01:25 PM  

Thanks for sharing that Ray,
tank leaks can be a real pest. My buddy Mikael's L-4 developed a leak when I flew it to Stockholm (about 400 miles one way) and a engine out on the way to Hahnweide fly-in in Germany (not with me in the plane though)at a later occasion due to alcohol dissolving the sealant he had used. Caswell epoxy tank repair, you said?

May the 4´s be with you/ Jörgen

jb92563
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Posted Tuesday, September 14, 2010 @ 03:35 PM  

Yes, Caswell brand, here is the link:

http://www.caswellplating.com/aids/epoxygas.htm

I'll be testing in a couple days to see that the tank sealed properly
and will report the results.

Of course the long term immersion results will be evident over time.
I'll make a log book entry so if the repair out lasts me, perhaps the next owner
can update the forum.

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

jb92563
Second Lieutenant

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Posted Thursday, September 23, 2010 @ 10:42 AM  

I let the epoxy sealer cure for 3 days and it is now holding fuel.

Yeah! now I can go fly again.

I ran the engine for a while to run fuel through the lines again, and will be taking the fuel filter apart and cleaning it out
prior to flight to make sure it is clear of any debris that might have gotten down the fuel line.

I did vacuum the tank out many times throughout the process so hopefully it checks out fine.

I'll be off to Flabob airport EAA Chapter 1, on Saturday for their open house
and to hear all the fascinating speakers.

They have great presentations on all sorts of interesting stuff, plus an abundance of interesting aircraft, I highly recommend it.

[Edit by jb92563 on Thursday, September 23, 2010 @ 10:45 AM]

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

Bob Grimstead
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Posted Monday, September 23, 2013 @ 04:34 PM  

How is the Caswell sealant holding up now Ray?

Yours, Bob

Bob Grimstead
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Posted Sunday, November 8, 2015 @ 01:29 AM  

I may have a similar problem Ray, despite the so-called 'professionals' saying they made a crack check on my tank.

How did your sealant work out in the long term?

Yours, Bob

--------------------
Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

Collin
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Posted Wednesday, November 18, 2015 @ 12:52 PM  

Hi Bob,

I flew Ray's old RF4D 7 hours from Southern California to Northern California for the new owner this year there was one fuel leaks so it must be working.

Collin

dannparks
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Posted Friday, November 20, 2015 @ 01:42 AM  

My experience is that sealants for leaks applied to the outside like this are rarely effective. I'd really think about getting it re-welded. I had to create an indention in my RF4 tank to accommodate the new mag/starter. Collin got me in touch with a very experienced aircraft aluminum welder and he cut the tank and welded in a new aluminum piece. A gorgeous job and no leaks. Re-welding is the only really permanent solution. IMHO

--------------------
Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1

SteveBeaver
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Posted Friday, November 20, 2015 @ 02:41 PM    YIM

See also: http://sbeaver.com/Bucker/index.php/74-news/latest/1018-fuel-tank-vibrations
Bob Grimstead
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Posted Wednesday, March 16, 2016 @ 06:48 AM  

The main problem with getting an RF4D's fuel tank welded is getting the darned tank out of the airframe.
You have to remove everything else first... instrument panel, radio, wheel cover, control column, the lot.
And the filler neck is sealed to the ply top decking with Sikaflex or something similar, so it's a big job!

Sealing a pinhole leak from the inside with epoxy may be the most practical solution, even if it's not the most 'professional' one.

I'll let you know how it goes, Bob

--------------------
Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

Markku
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Posted Thursday, March 17, 2016 @ 05:58 AM  

I had also a small pinhole leak in my tank last spring, I knew the was leaking, and during restoration work I soldered the area with aluminium, but still there was a small leak. I used PPG Aerospace PR 1750 Class B sealant outside the tank, the leak was around the hose connection in bottom of the tank, so I could do the job just by removing the wheel cover and hose, then cleaning the surface and seling from the wheel opening.
That stuff is widely used in big aircraft tanks with kerosene and avgas, I'm using auto gas with small ethylene mixture, so that might be a problem, but so far it has worked.
Markku
Bob Grimstead
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Posted Thursday, March 17, 2016 @ 07:06 AM  

Thank you Markku,

That's great because your product will probably be easier for me to obtain in Britain.

American companies always seem unwilling to ship overseas.

Yours, Bob

--------------------
Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

Markku
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Posted Thursday, March 17, 2016 @ 07:57 AM  

Great
I got that sealing from my friend, who got it from a Finnair mechanic, couple of months over dated product, which could not be used in commercial duty anymore
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