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Resurrection of a 1964 M20D


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In the airline business we had to physically crawl into the tanks to clean and reseal them. We used the same material called it dogs&*t because that's what it smelled like. 

I'm going to start another thread with a question I have on tank seal repairs.

"What ever happened to-"

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How did I miss this.

Amazing job. Reminds me of my own misadventures several years ago. I think between three A&Ps , myself, and 8 scratched elbows, we had 40+ hours into scraping, cleaning, alodining and resealing the tanks. They are still good 3 years later. I think I spent $2,500-$3,000 for parts and labor, so the deal is there if you can do it.

Keep posting pictures! I'm glad to see another willing to do the labor to revive another D model! Subscribed!

Edited by Raptor05121
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On 2/17/2019 at 6:02 PM, PilotCoyote said:

Flap up stop bolt sheared off..... I'm going to call LASAR on Tuesday, but has anyone dealt with this before? There might not be enough material in the threaded block to install a heli-coil. I'm thinking that the easiest solution (if heli-coil will not work) will be to remove the 3 rivets holding the block and fabricate a new block or source a good used one...

 

Check to see if this isnt the proper part:

https://lasar.com/flight-controls/flap-stop-block-210114-009?rq=flap block

or

https://lasar.com/flight-controls/hinge-block-240005-501?rq=block

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7 hours ago, PilotCoyote said:

This was the first tank that we stripped with Polygone. The one tank bay is nearly ready- just need to get a few more tiny bits cleaned out before wiping with MEK.

Posting this because I just realized that I didn’t have Pics of the stripped tank in my thread. I’ll post pics of the one I’m working on when it’s ready for sealant.

Nice work on the tank stripping

Clarence

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6 minutes ago, cliffy said:

This is why God made tank repair specialists!

I think the specialist are those of us not willing to put in the sweat equity like @PilotCoyote has. Prep plays a huge role in the outcome of the job and like Clarence said, Nice Work. Judging be the work so far his tanks will last as long as any

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20 minutes ago, cliffy said:

In no way am I knocking HIS work only THE work involved. Done it on big jets don't want to do it on my small popcorn maker. 

I did 2 top inspection plates on mine, not sure I would want to do the whole job either.....lol

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3. MEK was not very effective at removing tiny areas of sealant or the Buna-N coating. I also got a gallon of Expired liquid  Polygone from work- it has been sitting in a hazmat trailer through two hot summers and I found it to be just as effective as the new gallon of Polygone that I got from Spruce. The liquid was more effective than the gel, but only the gel will adhere to the vertical surfaces.

4. The eOx cleaner, also made by RPM Technology (they make Polygone), was used to flush the tank when I was finished. RPM recommends using eOx cleaner after Polygone. It is an excellent cleaner for bare aluminum and won’t hurt painted surfaces.

Edited by PilotCoyote
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5 hours ago, Raptor05121 said:

That is extremely clean. Good job. I think my mechanic and I alodined my tanks prior to sealing. Any plans for that or reason for/against?

There are some arguments for and against Alodining the tank...

FlameMaster, who makes the sealants I am using (3204 A&B, 3300, 3600), encourages the use of Alodine due to its ability to create an excellent surface for adhesion of its products.

The ceiling of my tank shows some very mild surface corrosion (more of a discoloration that is the natural change of state of aluminum exposed to the elements) due mostly to the cycle of condensation in the tank, I believe. 

It is a no-no to Alodine assembled structures, due to the potential for the Bonderite/Alodine to become entrapped in the faying surfaces, under river heads, etc.. 

So what to do?

How much damage will occur and how long will the progression take between the faying surfaces if there is some entrapped, dry acid? Will it take longer to decay than it will take for my steel roll cage to corrode from the inside out? Nobody seems to know.

It begs the question- how much longer will these planes last regardless of what we do/don’t do?

My take on all this: The Alodine chemicals can be applied, removed and “rinsed” very carefully with sponges to certain areas. I will certainly apply it to the roof of the tank where it was previously exposed to air/moisture without a buna-N coating. I probably won’t apply it liberally in this tank.

But this could change by next week, as I am really on the fence about coating the entire tank.  I did coat the whole inside of the last tank, but I did it with access to unlimited high pressure water (not that that guarantees anything). I pressure rinsed it for nearly 30 minutes between each step. This time I’ve only got a bug sprayer to rinse with- no more rinsing fuel tanks at the airport wash area!

Considering that some owners are using corrosive paint stripping chemicals on their tanks which can ooze into areas and gel up/harden quickly, and will be more of a challenge to rinse out than Alodine, we are probably way ahead of the game if we go in with Polygone ($115 a gal, but will not attack aluminum), and then Alodine our tanks.

Perhaps there is a method to managing the application and removal of regular paint stripper that will make it less of a future corrosive concern, but I haven’t been in this game long enough to know what that method is and to be confident that I’m not hurting this plane down the road. Someday I’ll be old enough to know these things.....

Who knows- this will probably be a never ending debate, just like which oil to use.

Edited by PilotCoyote
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For the alodyne discussion...

we have two types of aluminum in the tanks to consider... the spars and the sheet metal...

Spars are known for the tendency to acquire inter-granular type corrosion... once it starts, it proceeds somewhat quickly...

Spars are incredibly expensive to replace, compared to sheet metal...

focus on that for a bit... 

If it is easy to protect the spar... that would be great... once it gets coated with sealant, it is even hard to inspect...

Best regards,

-a-

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