Cleaning a fuel tank.

[Lood]

So, yesterday, I've started the mammoth task to clean out my right hand fuel tank for a complete strip and re-seal. What a job!!

It took me about half a day and two table knifes later just to remove the inspection panels and the screws holding outer fuel sender in place. I did some scraping just to determine what I'm up against and I can see a lot of cursing and bleeding knuckles lying in wait.

I've came to the conclusion that Al wasn't having a good day, at all, when he figured out the fuel tanks on his otherwise perfect airplane.

Interestingly, in the parts of the tank that has not been tampered with since my airplane left the factory in 1967, the old sealant actually peels away fairly easy and in large pieces. However, in the areas where the tank was patched, over the years, it is a totally different story. The thick and very sticky newer sealant that was applied over the old is very, very hard to remove and only comes off in small pieces.

I have thus come to the conclusion that any AME that patches a tank using new sealant over the original, should be executed, slowly, by blunt object.

Unfortunately, we don't have shop that clean Mooney tanks chemically here in SA, hence my decision to clean it myself, as far as possible, in order to save some money. My AME will do the final clean out as well as the re-seal. They did the left tank about a year or so ago and it is indeed a great pleasure to find the fuel level where I left it, every time when I return to my Mooney.

The tank that I'm cleaning now, was leaking to the tune of almost 3 gallons in 24 hours, depending on the amount of fuel in the tank. So managing that became a huge burden and sometimes impossible.

I really wish we had someone like Paul from Weep No More here...

 

[gwcolwell]

Just finished cleaning my lh tank(s).  Started sealing yesterday.  Know what your up against.  It was my first time also.  Patience, perseverance and multiple four letter words, again, appear to be the most valued human traits when cleaning Mooney tanks. 

Used Polygone 310 to soften the sealant. It creats a "snot" like substance from the old sealant and is miserable to clean down to shiny aluminum. After cleaning with 310, plastic scrapers, scotchbrite pads, brass & stainless steel tooth brushes, a vacuum cleaner and compressed air blow gun the tank compartments are as gorgeous as those seen online from "weep no more" ads.  Found really cheap "brake clean" in aerosol cans to be most helpful during the final cleaning.  MEK was also helpful.  Found Polygon 310 was the most irritating to my skin.  Even when using disposable gloves, the Polygone would seek it's way through the material and start pealing the first 6 layers of skin from my hands.  Took several weeks to bring my hands back to normal.  Am self employed truck dealer, so am used to working in dirty environments with my hands.

 Have about thirty hours of my own time(weekends only) in cleaning.  Have an I/A helping/overseeing and he has probably 6 hours in cleaning/sealing todate.  Going back this AM and seal some more.

 

Used PR 1440 A 1/2 in SEM kits to do the sealing thusfar.  Found that it helps to dilute it ever so slightly with MEK to brush it on the backside of the access panels.  A/P used it striaght out of the caulking gun with a brush( half the bristles were cut off to make it less pliable). Only sealed what was accessible from the top panels yeaterday.  Going to seal from the bottom panels today.  Have a heated hanger two thids the way up the Maine coast in KBHB. Left the heat on 50 deg f last night.  Have the wing tarped with heavy mil plastic.  Put two small ceramic heaters under the wing to hasten the cuiring process. 

 

Can see the light at the end of the tunnel.  Give me a shout if you want to expand your vocabulary.

[Lood]

Thanks a lot for your update. I've been warned not to use solvents at a too early stage for that exact same "snot" reason that you've mentioned. The two inner compartments of my tank is just about completely covered in sealant - not only at the joints where it's supposed to be. It seems easier to work on the larger, flat surfaces than in the small corners though.

I have a Turco product, certified for use on airplanes, that actually dissolves the sealant, but only while it is completely submerged in it. As soon as it is removed, the "snot" situation appears. I think that it might be helpful during the final cleaning though.

[N757DL]

I just completed a right tank reseal on a 1964 M20E and I found that Polygone was the biggest waste of money. For 300 dollars a can, I did not get my moneys worth. I ended up using normal paint stripper and it worked much better than the polygone for a fraction of the price. You just have to be careful about your paint and do small sections at a time. It will soften up the PRC and then you can scrap or brush it away. Never buy Polygone it is a huge waste of money.

[carusoam]

Interesting first post, 757DL...

Welcome aboard.

Best regards,

-a-

[danb35]

Interesting that one shop who does fuel tanks for a living has a different opinion of Poly-gone.  I don't have personal experience one way or the other, but that's what Weep No More uses, and they seem to find it helpful...

[Lood]

Maybe their method is different - continuously circulating it through the tank? My AME also warned me about using Polygone. Apparently, it makes a huge mess inside the tank if applied from the start while all the sealant is still present.

I was also advised to do only small parts at a time when using any solvents. All in all, this is a real PIA... With both my previous airplanes, leaking fuel tanks were never a factor - even less so the huge task to get them fixed.

[Lood]

I started the cleaning process officially, yesterday. After trying to scrape the sealant off as is, I realized that it would be just about impossible, so I experimented with the Turco. I am carefully optimistic that it is going to ease the job substantially.

Although not nice to work with, at all, it does loosen the sealant effectively and it makes it come off in a scale type fashion rather than creating the much feared gooey mess.

[Mooneymechanic]

I use eldarado chemical product it works well and saves a lot labour, i just did a complete strip and reseal on my neighbors c model it really is not that bad you just have to do some every day. I paint the sealant with the product close up the tank and come back the next day and clean out the loose stuff and repeat the process until it's all gone ,I make plastic scrapers from old windshield material so as not to scratch the inside of the tank ,

[JetSet1967]

What is the name of the Eldarado Product?

[Lood]

What is the name of the Eldarado Product?

 

+1.

Although the Turco works well, the problem lies with the thick layers of sealant. The Turco only dissolves the top part, about 2 - 3mm thick. It doesn't work right through the sealant to the metal, so we've scraped off most of the sealant by hand and did the remaining with the Turco. This seems to be the problem with most of the removers. We should finish at the end of next week and I surely am not going to do this again, ever. Should it become necessary in the future and I do not have to funds to have it done at the AME, I wouldn't think twice about selling.   It would be a sad day, but this is a real PIA and I still can't figure out what Al was thinking on that day.

[Mooneymechanic]

It is ppg aerospace

Elderado solutions

Sr125a

I found the stuff works quite well , but it's still a time consuming job,

I have some left if anybody needs some,

[KSMooniac]

Al wasn't the guy that heaped lots of non-conforming sealant over the top of the original stuff!    Wet-wing aluminum tanks are common industry-wide, especially in the heavy iron.  I also reckon Al and the gang never envisioned in 1960 that we would still be flying planes from the 60's in the 21st century, and likely wouldn't need to do the strip-n-seal dance.  Too bad new planes are not even remotely affordable today compared to the 60's and 70's, relatively speaking.  I'd rather be flying a 2007 instead of a 1977, but not at 4x the price, so I paid Paul to fix my tanks 5 years ago.

[KSMooniac]

Jim is correct... Harmon developed the legendary metal wing inside the existing aerodynamic envelope previously designed by Mooney.  The brilliant and efficient wet wing design has been used in countless other planes in the last 50 years too.  

[oldn0tded]

Ok, guys I'm looking for some shared experience and opinions. The forum has been a great place for both. So, here it goes. I got a 1975 F model last year and have been very pleased so far. I have "weeping" fuel tanks, not a true leak just yet, but I have been nagged about this since I got the plane.

Here's my question for the group: Just how bad does a wing need to leak before the strip and reseal need to be done? I know some of you will say any leak is bad, and I realize at some point it will HAVE to be done. What I'm trying to gauge is what is the criteria for determining when that time has come?

Thanks in advance

[Marauder]

I have a 1975 F as well. As was explained to me by a couple of MSCs when I noticed the weeping, our original sealant had some issues. My one tank was weeping into the wheel well and I smelled fuel inside. The bigger issue was I began finding red streamers in the fuel tanks. I was told that this was a coating put over our original sealant to protect the sealant and it was failing. Are you seeing these particles? I decided to go the bladder route. They were installed in 1992 and have been solid since.

[rbridges]

Ok, guys I'm looking for some shared experience and opinions. The forum has been a great place for both. So, here it goes. I got a 1975 F model last year and have been very pleased so far. I have "weeping" fuel tanks, not a true leak just yet, but I have been nagged about this since I got the plane.

Here's my question for the group: Just how bad does a wing need to leak before the strip and reseal need to be done? I know some of you will say any leak is bad, and I realize at some point it will HAVE to be done. What I'm trying to gauge is what is the criteria for determining when that time has come?

Thanks in advance

 

I guess you could keep flying until your IA says the fuel leak becomes a safety issue.  Personally, I had mine treated when I started seeing wet spots forming under the black wing walk paint on the wing.  I also noticed that I was losing the smallest amount of fuel in the passenger side wing.  They said it had been leaking pretty bad when they got into it.  

[Lood]

Well, I decided it was time when:

I started losing almost 3 gal in 24 hours wneh the tank was more than 3/4 full, the fuel actually leaked into the cockpit at the passengers' feet, giving my nice grey carpets a greenish blue Avgas tint and dissolving the glue holding the Velcro strips under the carpet, in place.

Whenever filled to full, the fuel smell inside the cockpit was also too much for my family to handle.

 

Once your tanks starts to leak, it's only a question of time. Whatever you do to patch it, it will return and when it does, it will be worse - every time.

[jetdriven]

All true, except that we don't have Al to thank for our wet wings. The wing that Al designed was the same aerodynamically as our wings but was made of wood and had welded aluminum fuel tanks. The wet wings were the doing of Ralph Harmon, who is given credit for their design. Al Mooney had left the company a few years previously. The legend which I believe to be true is that Ralph Harmon had been on the Beechcraft Bonanza design team back in the 40s. For that design he had proposed the wrap around skins that we now enjoy on our Mooneys and which are probably at least partially responsible for our wings' incredible strength. They were not incorporated into the Bonanza design, which incidentally had suffered quite a few in-flight structural failures even as early as 1960. At Mooney Ralph Harmon was allowed to build the wing his way. I personally think that in light of his wings' 50 year service history with only one or two in flight structural failures, we owe both he and Al quite a debt of gratitude for "doing it right". Especially since O&N was kind enough to come along later and fix Ralph's wings' only design shortcoming.

Jim

Jim is correct... Harmon developed the legendary metal wing inside the existing aerodynamic envelope previously designed by Mooney. The brilliant and efficient wet wing design has been used in countless other planes in the last 50 years too.

According to Bill Wheat and other sources the metal wing Mooney M20B was 5 knots slower than the wood wing M20A that preceeded it. The laminar flow wing design is extremely sensitive to surface irregularities and has more drag than a smoothly finished wood wing. But they couldn't find enough craftsmen to produce the wood wings so they had to go metal.

Ralph Harmon was pretty upset about the 1946 crash of the first prototype Bonanza, which he designed. The flight engineer got out, the pilot was killed. When he went to Mooney, he is rumored to say he wanted to build it overkill to prevent airframe failure. So we have this.

[yvesg]

Well, I decided it was time when:

I started losing almost 3 gal in 24 hours wneh the tank was more than 3/4 full, the fuel actually leaked into the cockpit at the passengers' feet, giving my nice grey carpets a greenish blue Avgas tint and dissolving the glue holding the Velcro strips under the carpet, in place.

Whenever filled to full, the fuel smell inside the cockpit was also too much for my family to handle.

 

Once your tanks starts to leak, it's only a question of time. Whatever you do to patch it, it will return and when it does, it will be worse - every time.

I am wondering if the climate has something to do? My bird is a 1965 M20C, sleeps outside in the cold Canadian climate, was seeping here and there over the years, was patched here and there and this has always been manageable.

Would lower OAT in average keep this issue away?

Yves