Tank seal... Issues afterwards

[N201MKTurbo]

FWIW,

After doing the bubble test, I hose out the tank with a Hudson sprayer with water and suck it up with a shop vac until I get no more suds.

[FlyingDude]

I don't think I have enough working space to lay and remove tape.. i like neat, I'll try but I'll be happy with a disgustingly ugly job if it doesn't leak for decades

[Shadrach]

Oh, and don’t feel bad. I closed my tanks up three weeks ago only to find that I have a small seep on the rivet line on the rib between the outer and center compartments. It’s my own fault. There are small drain holes at the base of the rib and I went to work cleaning them up with a dental pick. I should’ve re-tested for leaks afterwards but didn’t feel like going to the wash rack to flush the soap out a third time. I’m paying for that sin by now having to re-open the tanks again...

Edited October 12, 2021 by Shadrach

[Shadrach]

13 minutes ago, N201MKTurbo said:

FWIW,

After doing the bubble test, I hose out the tank with a Hudson sprayer with water and suck it up with a shop vac until I get no more suds.

Maybe I’ll try that instead. I usually taxi over to the wash rack and hose it down thoroughly. And by thoroughly I mean 40-60 gallons of water from a hose nozzle in every nook and cranny of the tank. I then hit it with a shop vac followed by compressed air. Then I walk away for two days before applying any additional sealant.

Edited October 12, 2021 by Shadrach

[Shadrach]

On 10/11/2021 at 8:51 AM, PilotCoyote said:

Painters tape is fine to use, provided you aren’t going to apply 3204 or the topcoat over any area where painters tape was applied (unless you are going to thoroughly clean the area where the tape was adhered to the aluminum with MEK prior to applying 3204 or topcoat. The area should be prepped with MEK- final wipe should be done with  MEK wetted microfiber towel, immediately followed by clean, dry microfiber towel…MEK should not be allowed to dry on the bare aluminum, for best adhesion. Best results are obtained when the surface is impeccably clean and prepared.

 

Did you strip that tank yourself? And if so what was your removal procedure? Gets remarkably clean In the all clad looks untouched. Plastic doesn’t compromise the all clad but does affect its shine. Yours looks almost like a freshly assembled wing.

[FlyingDude]

29 minutes ago, Shadrach said:

I should’ve re-tested for leaks afterwards but

Do you do bubble test after you've buttoned up everything?? How do you do a leak test before sealing the access panels? I thought of sandwiching some rubber sheet and screwing the panels in, and then filling the tank with fuel and placing a bucket under the access panels to catch any leaks from them and watch for leaks elsewhere. I'd assume that any fuel waste would be worth the cost of cs3330 for a reopening as well as time spent on cleaning the panels again...

 

[FlyingDude]

38 minutes ago, Shadrach said:

There are small drain holes at the base of the rib

How did unclogging those holes lead to a leak? 

[Prior owner]

5 hours ago, Shadrach said:

Did you strip that tank yourself? And if so what was your removal procedure? Gets remarkably clean In the all clad looks untouched. Plastic doesn’t compromise the all clad but does affect its shine. Yours looks almost like a freshly assembled wing.

Thanks. Yes, I sealed them myself. I used the [EDIT] 3M SR sealant removal cutters (carefully), then polygon…lots of it. Then MEK wiping. Polygon liquid was about twice as effective as the gel. I left the lower panels on for the first round, and poured polygon in and brushed it everywhere a million times. Lexan scrapers only… that picture was taken before I was finished cleaning out the corners of the tank. 
 

Once polygon had digested all that it could, I would vacuum it out with an old wet/dry vac  then re-apply more polygon. It was truly horrible. Won’t do one again!
 

[N201MKTurbo]

My hangar neighbor, who was a mechanic at American, gave me a bunch of plastic scrapers he kipped from work. They are the best ever! I will have to find out what kind they are. They are so sharp you can cut yourself with them, but they won't touch the aluminum.

[Shadrach]

1 hour ago, FlyingDude said:

Do you do bubble test after you've buttoned up everything?? How do you do a leak test before sealing the access panels? I thought of sandwiching some rubber sheet and screwing the panels in, and then filling the tank with fuel and placing a bucket under the access panels to catch any leaks from them and watch for leaks elsewhere. I'd assume that any fuel waste would be worth the cost of cs3330 for a reopening as well as time spent on cleaning the panels again...

 

I cut plexiglass sheets in the shape of the access panels. I Spray the inside with soapy water, position my light an mirrors and then seal the plexiglass over the access holes. 

[Shadrach]

1 hour ago, FlyingDude said:

How did unclogging those holes lead to a leak? 

 I can’t really say for sure until I determine the exact location of the seep and identify the cause. It’s about as minor as they come. It took two days to be externally visible. It’s right where the wing skin overlaps. None of the rivets are leaking. I only filled the tank 20gal. It could also be leaking from the front vertical wall of the tank and traveling down the seam. This is why we do the bubble test. You can sometimes get an idea of where something is leaking but you never really know until you see it manifested on the inside of the tank.  Drain hole is an educated guess,  but I won’t know until I open it up. It’s well under the limits spelled out in the maintenance manual so it will likely be spring before I get to it...

[FlyingDude]

What's the difference between the gray and black sealants?? Thanks...

[Shadrach]

1 hour ago, FlyingDude said:

What's the difference between the gray and black sealants?? Thanks...

For the same MIL-S?  Brand...

[A64Pilot]

In the military we use to thin B2 with MEK on a regular basis, seemed to work fine.

‘After the military I learned about A2, now instead of thinning B2 I just buy A2.

Edited October 12, 2021 by A64Pilot

[FlyingDude]

Hi guys,

How long is the minimum wait time to do soap bubble test after a reseal?  Must you wait the 72 full hours or the week that was recommended before putting in fuel, or can you do a quick soap test after tach-free time and then find any additional holes and patch them?  I just finished the reseal.  Not patch work like before, a 80% reseal of the extented tank - everything except for spar area on the outboard cell.  Waited 5 days, and it leaked from the corner of the aft spar, inboard rib.  The hardest area to reach.  What I am fearing is that, given the size of the hole there, what if too much air was coming in from there and forming bubbles; and any other potential hole was not showing, because air wouldn't come in from there, as air already found a path with much less resistance in the corner?  So I want to do the soapy thing again before closing up the access panels...  Just don't want to wait days and days.  

2 mechanics were checking on me at intervals.  Both were saying that they don't like doing tanks, so they must be enjoying the demise of this poor sucker working on his AP... Anyway.

Just FYI, if anyone wants to do this instead of mirrors: Extended tanks only have bottom access panels, nothing on the top (except for the fuel cap).  I used 2 telephones as borescope while patching the aft walls and corners: making video calls from one phone located in the tank to  the other phone on my lap.  

Thanks.

[FlyingDude]

Found this:  "Fuel tank sealant is considered to be sufficiently cured for pressure test when sealant is tack free, does not pit when firmly pressed, and feels firm to the touch (Rex Durometer reading of approximately 30 A)."

https://www.inetefb.com/Documentation/Cirrus/AMM/pdf/20-10.pdf

 

[Shadrach]

7 hours ago, FlyingDude said:

Found this:  "Fuel tank sealant is considered to be sufficiently cured for pressure test when sealant is tack free, does not pit when firmly pressed, and feels firm to the touch (Rex Durometer reading of approximately 30 A)."

https://www.inetefb.com/Documentation/Cirrus/AMM/pdf/20-10.pdf

 

Given the amount of work involved, I would be conservative. Take a break. Let it cure for a few days.

[Jim Peace]

fly plane to shop that does this every day of the week for the past several decades...

pay then fly plane away....

[LANCECASPER]

On 5/22/2022 at 6:36 PM, Jim Peace said:

fly plane to shop that does this every day of the week for the past several decades...

pay then fly plane away....

I agree completely.

One character flaw that some successful people have is that they feel that they will be good at anything they do. Thinking I will be good at something like tank stripping and reseal the first time I try it and thinking that the result will be comparable to someone’s results who has done this for decades, means I fall somewhere in between unrealistic to completely nuts.

[FlyingDude]

Thanks for your unsolicited pep talk but actually the seal is done and it's been leak-free for a few days already.  God knows what can develop overnight, though.  It's a mooney tank after all  

I'm glad that there are those of you who think the way you do, such that the famous tank sealing shops are booked through next year.  I personally am working on my AP and need the experience.  I have learned a lot from the constructive comments from people here who actually took their time to answer the questions here and provided great insight, not to mention the mechanics I am working with, who have given me great direction.  

 

[Jim Peace]

1 hour ago, FlyingDude said:

I'm glad that there are those of you who think the way you do, such that the famous tank sealing shops are booked through next year.  I personally am working on my AP and need the experience.  I have learned a lot from the constructive comments from people here who actually took their time to answer the questions here and provided great insight, not to mention the mechanics I am working with, who have given me great direction.  

 

Please do us all a favor and be the guy who opens the next shop that is an expert at this...

I am putting my plane in the shop for this in June....took 6 months to get the appointment...

If my appointment falls through and you want to do mine for your hours I am all in....

[Shadrach]

1 hour ago, FlyingDude said:

Thanks for your unsolicited pep talk but actually the seal is done and it's been leak-free for a few days already.  God knows what can develop overnight, though.  It's a mooney tank after all  

I'm glad that there are those of you who think the way you do, such that the famous tank sealing shops are booked through next year.  I personally am working on my AP and need the experience.  I have learned a lot from the constructive comments from people here who actually took their time to answer the questions here and provided great insight, not to mention the mechanics I am working with, who have given me great direction.  

 

I’m glad you got it. Even The tank specialists have to go back into a tank every now and again. The work is tedious But it’s more about patience and prep than skill. I had very good results repairing my own tanks. My IA was more than happy he was hands out of it. I still think it’s tedious, but not nearly as tedious as flying all the way to a wet wing specialist and arranging transportation to and from.   A simple repair could be done in less than eight hours work. The biggest PITA it’s removing the “non-adhesive“  sealant from the access panels.

[FlyingDude]

Guys no. No shops. On a scale from zero to hero with Paul Beck at master level, I'm barely passing. It's more an art than skill. And as with every art, it takes patience and iterations... I've been lucky that I really got good info here and know 3 mechanics with good tank experience. But they also contradict one another sometimes. One had said buy multiple small syringes of b1/2 whereas the other said to go with one big b2 can. The idea of multiple fast curing syringes is that you can split the work but get results more quickly. Well I learned it the hard way that the 30 min count starts the moment the first drop of accelerant touches the product but the tact free time counts after you're done mixing. I learned it the hard way that the first time I kept the product in my car, and it got really hot, so the 30 min shrunk to 10 min maybe. That's barely the mixing time. Whereas the hangar was already at 30C, which is pretty hot. So it didn't stick at all. This time round I learned that if there's a big hole somewhere, the soap doesn't bubble around small holes. So you discover new holes after you fixed the previous holes. Etc etc. 

 

[Andy95W]

I’ll be in touch when my tanks get worse…

[FlyingDude]

Leaking again... Grrrrrr