Tank Material

Bay Pelican's two 350 gallons tanks were cut up in place without removing the main engine or generator. Replaced with four 120 gallon aluminium tanks. Everything else in the engine room forward of the genset had to be removed. Process took 5 weeks and $22000 US.

My general comment is that if you are buying a 20 year old boat with steel tanks that have not been replaced you will get to replace them. Don't know about other materials.

As far as tankage is concerned, few of us need the original 700 US gallons on a Krogen 42 and thus the smaller multiple tanks.

My 58 gallon plastic tanks have baffles in them.

I went smaller because I knew I would never need to steam 1200 miles without refueling. Even with a little over 100 gallons I can still easily go 300 till fuel-up with reserve.

My trawler is a 50 foot Krogen design, 1972 model. I wanted to increase tankage as much as possible, and the originall tanks were 1/4 inch thick steel, a leak waiting to happen. Removal was VERY labor intensive and exceedingly intrusive. I went with 5086 aluminum but if I had it to do over I would build from fiberglass directly into the hull structure for added strength. I am not aware of any roto molded poly tanks with baffles, especially in the size and configuration I needed, or baffles in any size poly tank for that matter. This boat is currently being refitted (read completely rebuilt) with world cruising in mind. Fuel capacity now is about 1000 gallons. I'm planning to add about 500 gallons under the cockpit sole. I would like to have a 4000 mile range with 10% reserve. This will not be a coastal cruiser. As such "good enough" is just not what I am interested in. My goal is a boat than can handle a knockdown and get back up. Large fuel tanks are a serious issue as pertains to that. Free surface affect is a big deal. The ability to take on fuel, clean and process it thru a high capacity polishing system is also important. But, there is always the possibilty that I am addicted to overkill. After all, how many times does a power boat get knocked down. The answer is "usually just once"!!!!

My tank has a hole molded through the center of the tank and acts like any other baffle...it's a great idea and all you need on a small tank like mine...

Works well so far ....as in some pretty good pitching conditions the tanks didn't slide at all so I'm satisfied the free surface effect was definitely diminished. The have about an 1/8 of an inch to slide as I had to make the stops a tad wider than the tank as they say the plastic tanks grow a bit when first filled with fuel.

The downside of plastic for boat assemblers is time and hassle.

The plastic tanks expand when filled with fuel, so must be put in place , filled with fuel, allowed to expand , and then properly fastened usually also foamed in place .

Then the fuel ir removed and the next batch of tanks installed.Labor time is money .

Baffles can be done , but usually the tanks are sized so the head pressures caused by boat motion is low.

Biggest problem with plastic is they are simply a box of fuel, not a fuel tank.

This is OK if the setup allows the unused tanks to be drained during small fuel requirement operation.

All will work better with a dedicated day tank, so water and gunk can be drained from the bottom.

Not that I'm looking to replace my two (orig 1977 and very dry of water in & out) apparently good condition 100 gal aluminum tanks anytime soon (fingers doubly crossed!)

But...

What I've read previously as a simple remedy for tank removal is suction:

I've seen mentioned (not on this thread) that HD suction machine considerably collapses tanks inward so they become less cu ft dimension and can then be more easily maneuvered out of their location.

Any knowledge / input on this technique? Sounds as though it could be a relative slam dunk for tank removal of relatively foldable thin walled tanks... e.g aluminum! 1/4" thick mild steel might not be too conducive to using this method

Of course if they are gasoline tanks then fumes would need to be made non explosive by displaced air in tank with inert gas/vapor having NO oxygen.

Just wonderen??

Greetings,
Mr. Art. Hmm....Sounds good but....what if the tank collapses in a non-symmetrical fashion leaving awkward angles difficult to approach with a cutting device. I don't think one could achieve complete collapse before springing a vacuum leak. Could be creating more work than starting with plumb, flat surfaces.

Art said:

Not that I'm looking to replace my two (orig 1977 and very dry of water in & out) apparently good condition 100 gal aluminum tanks anytime soon (fingers doubly crossed!)

But...

What I've read previously as a simple remedy for tank removal is suction:

I've seen mentioned (not on this thread) that HD suction machine considerably collapses tanks inward so they become less cu ft dimension and can then be more easily maneuvered out of their location.

Any knowledge / input on this technique? Sounds as though it could be a relative slam dunk for tank removal of relatively foldable thin walled tanks... e.g aluminum! 1/4" thick mild steel might not be too conducive to using this method

Of course if they are gasoline tanks then fumes would need to be made non explosive by displaced air in tank with inert gas/vapor having NO oxygen.

Just wonderen??

Click to expand...

Sounds interesting but if the tanks are being replaced due to corrosion/leaks it won't work !

RT Firefly said:

Greetings,
Mr. Art. Hmm....Sounds good but....what if the tank collapses in a non-symmetrical fashion leaving awkward angles difficult to approach with a cutting device. I don't think one could achieve complete collapse before springing a vacuum leak. Could be creating more work than starting with plumb, flat surfaces.

Click to expand...

RT - True, True!

However, what I heard was to take out all easily removable adjacent structures and use a really big, high cfm suction machine (rented unit). Tank quickly collapses to 50% or less of orig size. Might or might not work?? If need to remove our tanks ever become needed... suction collapse is one technique I will closely look into. Be worth it to find some old tank at marine yard and do a test first to see how well that technique actually works. Could be inexpensive and fast tank removal process!

boatpoker said:

Sounds interesting but if the tanks are being replaced due to corrosion/leaks it won't work !

Click to expand...

See post # 39! High CFM big rig... Small leaks should not be much detraction to "suction collapse"!

psneeld said:

My tank has a hole molded through the center of the tank and acts like any other baffle...it's a great idea and all you need on a small tank like mine.

Click to expand...

Where did you get your tanks?

hobbystuff said:

Where did you get your tanks?

Click to expand...

Eastern Marine in Delaware....shipping wasn't an issue...something like $50 for the 2 tanks...

Defender wanted like $700 freight drop shipping from Moeller Tanks.

psneeld said:

Eastern Marine in Delaware....shipping wasn't an issue...something like $50 for the 2 tanks... Defender wanted like $700 freight drop shipping from Moeller Tanks.

Click to expand...

Thanks - any pictures of your installation?

hobbystuff said:

Thanks - any pictures of your installation?

Click to expand...

Tanks were set on 8 foot long 1/2 inch plywood platforms supported by 2by boards cut to fit.

The unsued portions of the platforms now hold Tupperware containers with parts, etc.

The tank with light (natural daylight) shining through it has a temporary fuel line hanging in front of it that I use to fuel my diesel heater tank.

Many MFG have deals with UPS to ship modest sized tanks at a very good rate.

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