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Old 09-05-2022, 12:37   #1
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How to cut apart aluminum tank

Hi all, I have a 45g 1/8 thick aluminum holding tank that is shot and in a place where its only removal can be via cutting it up. It is complicated and baffled so I need to cut it up into small pieces.

The metal cutting blades (tried every kind) on the reciprocating tool is taking way too long and the tool is awkward. The job is already a bit disgusting ;-)

Anyone have a good approach for fast cutting? bonus points for ability to turn corners and get into tighter spaces.

Should I use (borrow) a sawzall with special blades? Those long blades seem a better approach.

Thank you.
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Old 09-05-2022, 12:45   #2
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Re: How to cut apart aluminum tank

I'd grab my 4.5 inch angle grinder, and stop by the local big box hardware store for an aluminum cutting blade. If I can get my hand on it, I can put the tip of that angle grinder on it. Careful, an aluminum cutoff blade will also eat fiberglass, so don't miss. Aluminum does not retain heat well (low coefficient of something or other), so overheating is probably not a big concern.

Did some nasty builder use aluminum for a holding tank?
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Old 09-05-2022, 13:00   #3
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Re: How to cut apart aluminum tank

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Did some nasty builder use aluminum for a holding tank?
Yeah, Valiant built a great boat, no shortcuts, 1000 great design decisions and this one strange one. To rub salt in the wound they have every other tank on the boat removable easily and whole. 2 water tanks and 4 fuel tanks.

But nooooo, not the only tank with a materials problem, let's make that one really built in there...

I'll try the angle grinder but I think a sawzall blade might allow more creative "surgical" cutting? especially without flinging dried sewage covered grindings everywhere
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Old 09-05-2022, 13:46   #4
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Re: How to cut apart aluminum tank

Cover everything and use an angle grinder. The sawzall will flex the stainless sheets and waste reciprocation thus cut poorly.
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Old 09-05-2022, 13:49   #5
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Re: How to cut apart aluminum tank

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Cover everything and use an angle grinder. The sawzall will flex the stainless sheets and waste reciprocation thus cut poorly.
Thanks Tetepare, I think the same is true for the reciprocation tool, once the tank walls start resonation with the tool all progress slows way down. Angle grinder it is, with protective gear for me and tarps for everything else.

nasty boat job.
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Old 09-05-2022, 14:08   #6
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Re: How to cut apart aluminum tank

Been there, done that: angle grinder.

And, be careful, most folks treat angle grinders way too casually...the injury potential is high. Working in tight spaces makes it higher...bad stuff can happen when a cutting wheel jams with the grinder and your appendages all wedged into a small space.
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Old 09-05-2022, 14:09   #7
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Re: How to cut apart aluminum tank

Rent a Milwaukee 10 gauge nibbler.
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Old 09-05-2022, 14:18   #8
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Re: How to cut apart aluminum tank

Cheap Harbour Freight "Sawzall" with good quality blades. Less than an hour to cut out this aluminum waste tank. I tried my grinder first but it was way too messy for my likeing.
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Old 10-05-2022, 06:50   #9
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Re: How to cut apart aluminum tank

Boaty, with due respect to your tag line concerning experience ... Your example waste tank is easily accessible right under the sole boards. Ween's issue is the tank is molded into boat, probably between hull and liner and I am certain you have dealt with that as well. How would you do the job with limited access, same tool?
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Old 10-05-2022, 07:28   #10
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Re: How to cut apart aluminum tank

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Boaty, with due respect to your tag line concerning experience ... Your example waste tank is easily accessible right under the sole boards. Ween's issue is the tank is molded into boat, probably between hull and liner and I am certain you have dealt with that as well. How would you do the job with limited access, same tool?
I think you are referring to me, not "Boaty"
There was no hatch for access to that tank. I had to cut the sole and turn it into a hatch to access the tank. The flanges mounting that tank were completely inaccessible without major structural damage which is why I had to cut piece by piece from the top.

You have also assumed that the OP's tank is between a liner and a hull, I believe you'll find the Valiant 42 is stick built and has no liner. I've also never heard of an aluminum tank being "molded" into a hull. Do you have an example of such ?

I also had to remove two fuel tanks and used the same tools. Those two tanks were steel and access was extremely limited. I'll stick by my choice of tools.
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Old 10-05-2022, 13:23   #11
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Re: How to cut apart aluminum tank

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Cheap Harbour Freight "Sawzall" with good quality blades. Less than an hour to cut out this aluminum waste tank. I tried my grinder first but it was way too messy for my likeing.
Well I went to the yard today and attacked the tank with a grinder and several narrow metal blades. It went OK but made lots of metal dust and other heated yuk dust.

Anyway: Done. The interesting thing is the stbd cockpit drain and engine exhaust thruhulls were hidden behind it, there was no way to get at those easily with the tank in the way.

My tank needed to be cut as it was starboard in the engine room and the access was small so it had to come out in pieces. I did need to disassemble the rugged tabbed nesting place and shelf built on top.
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Old 10-05-2022, 14:04   #12
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Re: How to cut apart aluminum tank

It would be best to retain access to the cockpit drain and engine exhaust. if those hoses are original, you might want to replace them, and use really top quality hose clamps in the reinstallation. We get less mobile as we age, and it makes access more difficult. Please don't ask how i know this.

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Old 12-05-2022, 11:23   #13
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Re: How to cut apart aluminum tank

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We get less mobile as we age, and it makes access more difficult. Please don't ask how i know this.
Ann
Truer words were never spoken.
I'm in the same process regarding the holding tank, although I've not had to resort to implements of destruction for removal of original tank.
The new tank set-up/location will allow access to all fittings/clamps/hoses, without being covered in bruises and blood.
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Old 12-05-2022, 12:30   #14
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Re: How to cut apart aluminum tank

I have a Rockwell Speed crafter a type of vibrating saw. It’s compact and aluminum blade Lots of cutting oil and they peel things apart very fast. Several other brands on the market.
Sorry you’re having problems. I’ve had several aluminum fuel tanks in power boats and would not consider plastic.
Safety glasses and Mask stuff
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Old 12-05-2022, 13:22   #15
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Re: How to cut apart aluminum tank

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Originally Posted by JPA Cate View Post
It would be best to retain access to the cockpit drain and engine exhaust. if those hoses are original, you might want to replace them, and use really top quality hose clamps in the reinstallation. We get less mobile as we age, and it makes access more difficult. Please don't ask how i know this.

Ann
This!

“Naw I’m not gonna do that right now” has bitten me enough time so now I just sigh and add another waypoint to the project list.

Ps the nibbler idea probably would have worked well too. Taken longer but less mess.
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