Fuel Tank Sealant Project

[Scott Aviation]

Im just going to start out by saying that because my M20J was a project and the fuel tank sealant was toast aka rotten I had no other option being up here in good ol Canada but to take on the challenge myself.  

Secondly after 34 years of resealing over resealing it added up to the entire tanks being coated with almost a solid 1/4" thick layer of PRC, not just the seams but the entire tanks all 6 bays....I have sworn, cursed yelled, been scarred and bruised and am nearly done, $500 of Polygone stripper later, by the way polygone only works well when the sealant is a very thin, it will not dissolve 1/4" sealant being lightly agitated in the tanks.

Just to summarize I would NOT take this project on again, I will take the wings back off, trailer the wings down to a good shop and get them to do it before I attempt such a painful job again. 

My question to my fellow mechanics and pilots is has anyone done a reseal job or know how much PRC sealant products I will need to complete a 64 Gallon tank reseal. I don't want to order too much as it's expensive and has a short shelf life and too little is obvious.  I got a list from someone on here on a DIY sealant job for 54 gallon tanks but Im just curious if anyone has a invoice from a tank repair shop on the quantities and part numbers used.  Any help or thoughts would be appreciated..

[John Pleisse]

Every IA I have ever met says even their most dutiful, eager A&P's run from it. The stripping processes by Wilmar, Muncie and or Midwest are the result of years of pain. It's all about the strip job and these guys now have it down to a science.

I have been told a gallon a side.

[fantom]

How about a sealant like Flame Master or ProSeal?

An old Mooneyspace link: http://www.mooneyspace.com/index.cfm?mainaction=posts&forumid=1&threadid=2644

A bit about ProSeal:

By following a few simple rules, it will be a lot easier for you to apply and work with Proseal. The cure rate is thermo exponential, i.e. the temperature effects the cure rate

• 
  
• You can mix smaller quantities by volume and have the same cure rates and results
  
• Like most resins and epoxies you will use a catalyst to cure the product
  
• Long strands of fiberglass (angle hair)
  
• Obtain syringes of different sizes (5 cc, 20 cc and 100 cc types) to apply the Proseal when it is mixed
  
• A small 3" paint roller cut to 1"
  
• Get latex gloves, some raiser blades, paper towels and MEK or thinner for cleanup
  

Applying proseal

After the measured components are mixed thoroughly on a flat plate for at least one full minute they are then loaded in to the plunger end of a third so called application syringe. This is usually done with a oil artists knife or spatula. Once it is in the application syringe you can apply it exactly where you need it and just the right amount of it.

Paint brush

A small 1" diameter fine felt paint roller or heavy brush can then be used to uniformly spread it on surfaces. Buying the 3" long by 1" diameter paint rollers and cutting them in to 3 separate 1" x 1" paint rollers works well. Use a small tube to take up the slack in the paint roller reel. You can rapidly measure, mix, and apply Proseal by doing it this way and there will be hardly and waste product or expense to contend with after.

What the Mooney Guru has to offer: http://www.donmaxwell.com/publications/MAPA_TEXT/_overlay/Fuel%20Tank%20Repair_How%20We%20Fix%20Them%202-05.htm

Lastly, a blurb about Weep No More: http://www.weepnomorellc.com/mapa1_sm.pdf

[Piloto]

If you want to do the job yourself it takes 12 pint cans of PRC 1422-A2 and 6 pint cans of PRC 1422-B2 for a 64 gallons tank. The B2 is the high viscosity type that does not flow. It is used for gaps greater than 1/8". The A2 is the one that flows and is used to cover the whole tank area. Best application method is by using a 1" bristle brush. Do not fill the tanks after sealing unless the tanks has passed an airtight test. Otherwise you are going to be frustrated with all the leaks.

Most of your work time will be spent on removing the old sealant.

Before you start this endeavor I would recommend to contact Wet-Wingologist (954) 938-9390 at KFXE and some of the experience shops. I personally know Wet-Wingologist. They have been doing this kind of work for over 15 years with very happy customers. This kind of work besides requiring some experience it requires some special tooling facilities and guts.

José   

[N601RX]

The PRC-1422 I've used before came in 6 oz SemKit tubes.  These tubes can be dispensed from a caulking gun after trimming the round disk on the caulking gun.  The Semikit tubes contain both parts and the mixing is done internal in the tube so there is no mess.  They are about $30 each from Skygeek.  If want some to practice with you can get some that is a week or so past the expiration date on e-bay for less than $5 tube.  Keep it in the fridge and it will last for several years.  I've used some on non aviation stuff that was kept in the fridge for 3 years past the date and I could not tell any difference in it and the new stuff.

The set time is temp dependent.  On a hot day you will not have 2 hours, on a cold day you will have longer.  When you start it will work best to have one person to apply and have a 2nd person mixing the next batch.

[flyby201]

Check with Chem-Seal in Wichita (I think).  I just called them up and told them what I was doing, make and model of aircraft and they told me how much I needed and it was right on.  I also think they had the best prices I found.  If you buy it in quarts and just mix what you need as you go (it's a 10:1 ratio of parts A and you will save a lot of money.  Also, don't forget to use the access panel sealant.  If you ever have to go back in (i.e.; pressure test fails) you won't regret it.  Some previous owner used B-2 to seal some of my access panels and I thought I was going to need dynamite to get them off.

Steve

[Piloto]

Quote: flyby201

Check with Chem-Seal in Wichita (I think).  I just called them up and told them what I was doing, make and model of aircraft and they told me how much I needed and it was right on.  I also think they had the best prices I found.  If you buy it in quarts and just mix what you need as you go (it's a 10:1 ratio of parts A and you will save a lot of money.  Also, don't forget to use the access panel sealant.  If you ever have to go back in (i.e.; pressure test fails) you won't regret it.  Some previous owner used B-2 to seal some of my access panels and I thought I was going to need dynamite to get them off.

Steve

[Shadrach]

I have been into my tanks twice and my take is the following:

1) Polygone stripper works, it does not work fast, it does not work easily, it does not even work well... but it does work.

2) A low profile handleless Semco Dispensing Gun will run circles around a "can and brush" when it comes to quickly and accurately laying sealant. I got a new one on E-bay for $35, but I was lucky. They can be had fro under $200 used.  Keep a brush handy for some of the detail work.

3) Flamemaster semkits work well. Use is CS 3204 B2 for fillet seams in the tank. Use CS 3330 B2 for access panels. A sloshing compound was used by the factory,  I used PR-1005-L, some feel that the sloshing step is unnecessary.

4) No offense to José , but advising people that access panel sealant is "non bonding" and suggesting that integral tank sealant is a better option for sealing access panels is not just lousy advice, it borders on sadistic if the tanks ever need to be opened again. Removing the access panels when they are merely sealed with the "non bonding" sealant is a job.  You could stand on the top panels with no screws in place and they would still not give way.  

5) There's a reason why Mooney put mil-specs #s in the MX manual, all of the materials I've listed meet those mil-specs or are superseded by those mil-specs. 

 

[TonyPynes]

From what I am reading on this thread it sounds a lot like the work I have done when building wooden kayaks and coating them with fiberglass cloth and resin. Lots of activated goo that is reacting as you work with it, filets needing to be made for corners, and lots of disposable gloves, applicators and cloths/rags. Except of course the stripping part which sounds like if you spray and can saturate the old sealant well you have half the battle done.  I only have a stain that was there when I bought the plane and hasnt releaked since I have flown the plane but I know I will have to reseal one wing. the other one was already done.

I have never opened a fuel tank up so I can only look at pics online and in my manual. Can you actually get to all the places within arms reach once all plates are off?

I wouldnt mind doing this myself but need to find an A&P nearby to sign off. Most, as has been stated, dont want to do this kind of work so maybe it wont be hard to find one who will inspect, especially after stripping is complete and then after the sealant is air pressure tested and then after fully fueled.

Price per wing sounds like 4k now. Sure could use that money elsewhere.

[N601RX]

The inspection plates comes pretty easy once you figure out how to do it.  Don't try to pry them off, take a heavy duty razor blade knife and work around the edge.  Don't try to cut all the way through at once, just cut a little deeper each pass and make several passes around the plate.  On the 1st one you may think it is impossible, but once you have done a few it will only take a few minutes.  Some small wedges will help, but don't force them in, it will stretch the skins.

[TonyPynes]

I may just try to take one plate off and do a patch to get my feet wet. that is the only place I see past leaks at.

[Shadrach]

Quote: AustinPynes

I may just try to take one plate off and do a repair to get my feet wet. that is the only place I see past leaks at.

[N601RX]

Quote: Shadrach

I think that's a good approach. As Mike said, the access panels aren't that bad provided that you use the proper technique and that the last person didn't seal them with regular tank sealant. Patience is a truly a virtue when it comes to tank projects.

[Piloto]

Fuel leaks have a tendency to run down. This means that where the stains shows on the outside is not ncessarily the internal point of the leak. This can be frustrating in trying to seal a leak at the wrong point. To accurately pinpoint the actual internal leak do the following:

1. Drain the tank dry.

2. Connect a hose to the vent port.

3. Set fuel selector to OFF

4. Remove the dry access panels around the perimeter of the tank area.

5. Make sure fuel cap is on.

6. Spray foamy soap in suspected areas

7. Blow air by mouth only into the hose to build up pressure in the tank.

8. With a flashlight and a good articulating mirror look for bubbles coming out.

Since air does not run down like fuel, where the bubbles are is where the internal leak is located. Rarely the structure may channel the air a few inches out from the internal leak.

Good Luck

José

 

 

[TonyPynes]

Good information in this thread. Now that my oil leak is resolved I am going to start on the right fuel tank leak.

I have now taken of the mid wing panel where the aileraon controls come through. That was where mine was leaking from.

There was a puddle of fuel in their and I also had the smell in the cockpit after it was closed up for awhile. Today afterI had landing from testing out the oil leak repair I noticed very strong fumes in the cockpit while taxiing. Not a good thing and the first time I smelled it that strong. So now that my trip this weekend was in the toilet I am commited to resolving this.

I know I should do a strip and seal and I know the right guys to do it but I am going to at least understand where it is leaking first. The seal doesnt look bad inside and I dont think it was ever patched. Course, what do I know.

From reading other threads it sounds like it might be the sending unit seal/gasket...just guessing. Monday I will fly it to the mechanic and start checking it out with him.

Any tips or tricks are welcome.

 

[jetdriven]

Bladders last twenty years with nary a fuel smell  

[MooneyMitch]

A strong fuel smell after landing could indeed be a tank or sending unit leak inside the cockpit, but it certainly could be a fuel line /connector fitting issue somewhere along the fuel line routing between the tank switch valve, the electric fuel pump and the connector fitting into the firewall bulkhead.  

Check this out as you may not have a sealant problem at all.  Just my 2 cents worth from an experience I've had.

[captsb]

Cleaning  and preparation of the tank is paramount. Very time consuming. I would look into the latest type sealant.  Military and airlines are using the EFC -100 ( they have products for both jet and av gas type fuel.

It can be sprayed or brushed on and when it drys, it is like a fuel bladder. Flexible ,long lasting and is not deadly like poly-sulfide to your lungs. Even with a respirator getting the smallest amount of fume creates havoc with that poly-sulfide stuff.

It has good long workable time--------------look into it.

[LANCECASPER]

6 hours ago, captsb said:

Cleaning  and preparation of the tank is paramount. Very time consuming. I would look into the latest type sealant.  Military and airlines are using the EFC -100 ( they have products for both jet and av gas type fuel.

It can be sprayed or brushed on and when it drys, it is like a fuel bladder. Flexible ,long lasting and is not deadly like poly-sulfide to your lungs. Even with a respirator getting the smallest amount of fume creates havoc with that poly-sulfide stuff.

It has good long workable time--------------look into it.

Welcome to Mooneyspace @captsb!!    The posts on Mooneyspace are interesting, but some haven't been active in many years. Your advice that you gave was to someone who posted in 2011. We look forward to learning more about you on Mooneyspace!

[MikeOH]

5 hours ago, LANCECASPER said:

The post you replied is from 2011.

And, why is it not useful information now?

[LANCECASPER]

1 hour ago, MikeOH said:

And, why is it not useful information now?

I've never even thought about tackling a tank, but he is telling the original poster to "look into it" which is probably not going to happen 13-1/2 years later, unless it's time to re-seal them again .

Plus he is suggesting a product that isn't mentioned in the Mooney Maintenance Manual (EFC-100), which apprarently is nearly impossible to remove when that time comes. 

Plus he is implying that polysulfide is being used to seal the tanks, when in reality it's what Weep No More and Wet-Wingologists use to remove sealant. https://www.rpm-technology.com/wp-content/uploads/2016/12/PolyGone-310-AG-Inst-v2.pdf

Other than all of that misinformation, i agree that prep being paramount is true on this and any other tedious job.

[MikeOH]

@LANCECASPER

Well, I'll quit being subtle... a guy comes on here, first time poster, and offers up useful information.  What does he get? Criticism for a necro post!  Just doesn't seem to me to be the kind of response I'd expect from the 'friendly, welcoming community' we think we are.

[LANCECASPER]

11 minutes ago, MikeOH said:

@LANCECASPER

Well, I'll quit being subtle... a guy comes on here, first time poster, and offers up useful information.  What does he get? Criticism for a necro post!  Just doesn't seem to me to be the kind of response I'd expect from the 'friendly, welcoming community' we think we are.

Sorry if it came across that way. I was just informing him that the post he replied to was from 2011. He obviously didn't notice that since he was giving advice to the original poster to try what he was suggesting. But thanks for the reminder - I'll go back and revise my response and give a welcome to him for joining Mooneyspace.

i wasn't going to even go there about the incorrect information he gave until you asked, "And, why is it not useful information now?"

If you read the post that I quoted on the EFC-100 sealant that he suggested, people are still chiseling away at that stuff trying to remove it from their tanks, very bad idea.

[MikeOH]

@LANCECASPER

Thanks for adding the info on EFC-100 to your post; that is useful!

[EricJ]

I didn't remember what EFC-100 was, but, yeah, run away from that stuff.