Fuel tank sealant removal machine

[Yetti]

slinging paint remover with wheels never seemed like something I would like to do.   For furniture, I will use steel wool.   I don't think steel wool is proper for alum.  But the stainless brushes HF has might work good.

[Hank]

My tank sealant removal machine is named Edison, and lives in a hangar at KFXE.    (Sorry, I couldn't resist! Six pages and going strong . . . )

[carusoam]

Edison works well...

something else about solvents and sealants...

The sealant is working hard at resisting the solvent.  Solvents work at the molecular level, it may take some time or several tries to work through a thick layer or hard to access layer.

Solvents travel slowly to the next level on their own.  Scrubbing every now and then may remove the next layer exposing a fresh surface to start dissolving.

It's a similar engineering discussion of convection vs. conduction.  Use convection, wiping and scraping, to allow conduction,  the solvent's molecular transport, to do it's work.

use caution with the abrasive tools, they may be like sandpaper or sandblasting removing some metals.

Best regards,

-a-

[TargetDriver]

Hey guys, another one back from a rapid deployment issue. I finally get to work on my M20K tanks tomorrow morning !  Before i left I managed to get the two top outer small panels removed. Not too difficult, but the two larger in board ones wouldn't even budge or let me get anything started between the panels.

While I was away I got the shipment of PolyGone Gel .. yea that bucket isn't very big for 3 bills !  I got a ship notice for all my sealant and should be in any day... way ahead of being ready for it for sure.  After talking with a few guys I've given up on the internal tank sprayer for now and opted for just trying the gel and some hand labor.

Has anyone used a heat gun (careful with the paint) to help soften the access panel sealant?  I dont have elcetricity in my hanger and was wondering if it would be worth the effort to get it strung up for that?

 

[carusoam]

My observations...

1) The paint didn't survive somebody's attempt at resealing my top side panels.  

2) Gravity is working in your favor for this.

3) Get started tonight..?

Best regards,

-a-

[Hank]

Formica strips make good scrapers for inside the tanks, they won't gouge the aluminum. Buy some edge strips at your local Big Box store, one roll should be more than enough. Or grab several,of the samples sitting out to compare against your cabinets . . .  

[1524J]

1 hour ago, TargetDriver said:

Hey guys, another one back from a rapid deployment issue. I finally get to work on my M20K tanks tomorrow morning !  Before i left I managed to get the two top outer small panels removed. Not too difficult, but the two larger in board ones wouldn't even budge or let me get anything started between the panels.

While I was away I got the shipment of PolyGone Gel .. yea that bucket isn't very big for 3 bills !  I got a ship notice for all my sealant and should be in any day... way ahead of being ready for it for sure.  After talking with a few guys I've given up on the internal tank sprayer for now and opted for just trying the gel and some hand labor.

Has anyone used a heat gun (careful with the paint) to help soften the access panel sealant?  I dont have elcetricity in my hanger and was wondering if it would be worth the effort to get it strung up for that?

 

I took a putty knife and rounded the edges with a grinder, then sharpened one side. Work that slowly into the sealant just a little at a time around the circumference of the panel. The more flexible the putty knife, the better.

[kellym]

On 4/9/2016 at 8:01 PM, 1524J said:

I took a putty knife and rounded the edges with a grinder, then sharpened one side. Work that slowly into the sealant just a little at a time around the circumference of the panel. The more flexible the putty knife, the better.

That will work. Protect your paint first by covering with several strips of duct tape. Use a single edge razor to cut the tape at the parting line, then you can work your putty knife in. If you find a spot it goes in easier, go for it. Once you have a  opening in one spot you can gently work it around until you have enough to free the cover. Those under the wing walk will be difficult because they used hardening proseal there, not the non-hardening used on the rest of the access panels. Just be careful to not gouge the metal on the parting surfaces.

[Jerry Pressley]

DON Maxwell CAN POINT OUT SOME OF THE PROBLEMS INCLUDING STRIPPED PAINT. HIS IS HIDDEN AWAY BACK IN A CORNER OF HIS SHOP WITH A LABEL SAYING XXXXXSSSSXXXX

[TargetDriver]

So... I've  finally had some more alone time with my new mistress and her panels seemed to respond best with just what 24J said.. I got a stainless bladed 1 1/4" wide paint scraper. The blade is only .024 thk so its very flexible but strong enough to take good compression loading without bending. I slightly rounded the corners with a file then lightly bent the corners up with pliers. I make two good clean out cuts around the panel edge (internal to the wing skin-external to the panel itself) then with a small plastic dead blow hammer, tap the blade right under the edge. Chased it around once going about 1/8-1/4" in, then around again up to an inch in... the next pass it slides all the way in and pops right out.

 

All eight panels off, and interestingly enough, the outboard half of the tank looks like the factory sealant is in great shape and shows almost no signs of where it could leak... but that's where it was leaking the worst. Pics of some of panels inside and of the tank shown.

[TargetDriver]

Now into the fuel tank closest to the fuselage... uuugllly. Easy to see where it's been resealed, and matched the log book entry from 1990.

[carusoam]

Nice photo of the flapper doohickey thingamabob.... Valve ish looking thing that keeps fuel from leaving the area closest to the fuel pick up.  Does it operate smoothly?

the fuel pick up is pretty far off the bottom of the tank, interestingly...  

the fuel level sensor doesn't go anywhere near the bottom either... 

the spring thing, what is that?  Some K's have flapper valves on the fuel tank fill necks.

Great photos! Thank you for sharing them.

Best regards,

-a-

[TargetDriver]

I've applied Poly Gone gel to some of each internal bay to get a feel for how its going to release. you guys were correct in that its much better just to leave the stuff on for 12 horus or so, then wipe away the brown snot-like sealant. It does seem like you have to let it eat its way through the brown sealant first, then once you have that out of the way, another application of stripper really works on the grey softer primary layer much faster.

 

I've burned through half of my 5 lb tub and was being rather frugal so I decided to save the rest for working on the top inside the tank where the gel would stick. I went to Home Depot and bought several cans of paint stripper to see how it worked. It does work on the grey putty base coat pretty well but using a light thin bristle stainless and/or brass brush really knocks it off. One last coat of spray stripper and it washes off with water and looks like new. 

So here's the panels... first pic shows one panel untouched. Middle one has had two coats stripper and light scraping. Small panel is soaking in last coat of spray stripper.

Middle picture shows panels cleaned and mostly ready (except for center of fuel gauge panel)

Close up shows how clean the spray stripper works when rinsed with water after the 3rd coat.

[isaacpr7]

I've applied Poly Gone gel to some of each internal bay to get a feel for how its going to release. you guys were correct in that its much better just to leave the stuff on for 12 horus or so, then wipe away the brown snot-like sealant. It does seem like you have to let it eat its way through the brown sealant first, then once you have that out of the way, another application of stripper really works on the grey softer primary layer much faster.

 

I've burned through half of my 5 lb tub and was being rather frugal so I decided to save the rest for working on the top inside the tank where the gel would stick. I went to Home Depot and bought several cans of paint stripper to see how it worked. It does work on the grey putty base coat pretty well but using a light thin bristle stainless and/or brass brush really knocks it off. One last coat of spray stripper and it washes off with water and looks like new. 

So here's the panels... first pic shows one panel untouched. Middle one has had two coats stripper and light scraping. Small panel is soaking in last coat of spray stripper.

Middle picture shows panels cleaned and mostly ready (except for center of fuel gauge panel)

Close up shows how clean the spray stripper works when rinsed with water after the 3rd coat.

Wow! That's an amazing update. Can you post a picture of the can of stripper you are using? I've used almost half of the gel as well for the entire tank at this point. There are some areas around the upper skin rivets that are being a bit stubborn because I can't really get to them with the pressure washer. If you can place the type of brush you are using right next to the can on the picture it would help too

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[TargetDriver]

Here's the stripper, the brush and the plastic scrapers I used. The scrapers were almost too soft and dulled rather quickly so I hit them on my belt sander to re-edge them..

[1524J]

Rick, it appears from the photo the last guy to patch the tank got sealant on the screen of the pickup tube. That's a problem. I would clean the screen, then flush, clean, then flush,.....you get the idea. Then cover with plastic and tape. 

[1524J]

3 hours ago, TargetDriver said:

I've applied Poly Gone gel to some of each internal bay to get a feel for how its going to release. you guys were correct in that its much better just to leave the stuff on for 12 horus or so, then wipe away the brown snot-like sealant. It does seem like you have to let it eat its way through the brown sealant first, then once you have that out of the way, another application of stripper really works on the grey softer primary layer much faster.

If you've got time, I believe the instructions are to apply like "icing on a cake", allow to sit for 45 minutes to an hour, agitate with a brush, let sit, agitate. That way the polysulfide that's dissolved get moved so the stripper can get to fresh sealant underneath. Might help the polygone to go further. If you guys need more polygone, pm me before ordering.

[isaacpr7]

3 hours ago, TargetDriver said: I've applied Poly Gone gel to some of each internal bay to get a feel for how its going to release. you guys were correct in that its much better just to leave the stuff on for 12 horus or so, then wipe away the brown snot-like sealant. It does seem like you have to let it eat its way through the brown sealant first, then once you have that out of the way, another application of stripper really works on the grey softer primary layer much faster.

If you've got time, I believe the instructions are to apply like "icing on a cake", allow to sit for 45 minutes to an hour, agitate with a brush, let sit, agitate. That way the polysulfide that's dissolved get moved so the stripper can get to fresh sealant underneath. Might help the polygone to go further. If you guys need more polygone, pm me before ordering.

You are correct about the instructions. They also list and alternate method of allowing the gel to sit over night and remove in the morning. I've tried both and it seems that leaving overnight is most effective on the first application when there's lots of sealant. After the thick stuff is gone (using a pressure washer to rinse), then you use the first method and it just dissolves the remaining sealant but you have to agitate those areas periodically. I've used the least amount of gel using this method

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[TargetDriver]

I did see what looks like something on the screen when I was in there but couldn't see any buildup. I have an extendable mirror that I'm taking tomorrow to get a better look at the screen.

I did try the agitation with a brush and it does seem to help...but seems like it only makes the biggest difference when the brown top coat sealant is already in snot mode. That's tough stuff!.  When you lightly stir the gel (at 45 min or so) you can actually see the grey base sealant coat dissolving and stir into the mix.  

I should get a better feel for how much gel I have left after Sunday... hopefully I can get a lot of time then to hit the inside upper areas of the tank. That's a much better price for the gel, thanks !

[isaacpr7]

I did see what looks like something on the screen when I was in there but couldn't see any buildup. I have an extendable mirror that I'm taking tomorrow to get a better look at the screen.

I did try the agitation with a brush and it does seem to help...but seems like it only makes the biggest difference when the brown top coat sealant is already in snot mode. That's tough stuff!.  When you lightly stir the gel (at 45 min or so) you can actually see the grey base sealant coat dissolving and stir into the mix.  

I should get a better feel for how much gel I have left after Sunday... hopefully I can get a lot of time then to hit the inside upper areas of the tank. That's a much better price for the gel, thanks !

TargetDriver you are a genius! I used the aerosol stripper and let it sit for an hour and some change. All I did was lightly drag the plexiglass scraper I made and the red sealant just fell off completely. I'm allowing the stripper to sit for another hour on the nutplates and see how that goes. Below is a picture of what it looks like right now with the nutplates still soaked in stripper and the center cleaning results of the first coat.

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[TargetDriver]

Thanks isaac, haha. I'd much rather think of myself as cheap and resourceful! Haha  I'm glad it worked for the sealant coat. On mine it does seem to soften up the gray sealant almost to a rubber consistency so it scrapes off and actually peels off over the rivets in one piece sometimes. It's almost like removing a one piece rubber coating over all the rivet heads, then just another spray application and wire brush and it's done with the rinse.

[helitim]

"There are some areas around the upper skin rivets that are being a bit stubborn because I can't really get to them with the pressure washer."

 

Have you tried anything like the gutter cleaning attachment or the gutter cleaner 130 degree bent connector shown on the link below?

http://www.northerntool.com/shop/tools/product_200610635_200610635

 

[isaacpr7]

First coat of stripper took 98% off. It could have been 100% if I used the pressure washer; however, I found that I could not crank it because somehow it had a blown piston ring. Ugh!

After the second hour I agitated the sealant with a brush like the one recommended previously. With the only difference that the brush I purchased had stiff nylon bristles instead of steel.

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[helitim]

 

This is the second attachment I was referring to

http://www.northerntool.com/shop/tools/product_200635362_200635362

[isaacpr7]

"There are some areas around the upper skin rivets that are being a bit stubborn because I can't really get to them with the pressure washer."

 

Have you tried anything like the gutter cleaning attachment or the gutter cleaner 130 degree bent connector shown on the link below?

http://www.northerntool.com/shop/tools/product_200610635_200610635

 

I thought about that one but I got an attachment that tilts as needed instead. The problem is that I can't see where I'm spraying unless I do it from the bottom panel opening but that would fill my face with all the draining tank blob. Lol!

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