I'm curious as to this. Why is it Aluminium tanks are frowned upon? I have two so am wanting to know what it is I am not aware of before its too late :-/
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Diesel Fuel Tank Design
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I'm curious as to this. Why is it Aluminium tanks are frowned upon? I have two so am wanting to know what it is I am not aware of before its too late :-/
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stevensibs
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Aluminum has a reputation in the boat industry of being installed quickly, cheaply and usually incorrectly. I personally had two failures due to water being trapped beneath them, and know of quite a few failures of aluminum tanks in my general boating area...some only 10 years old.
windmist
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I put FRP tanks in the Cacade 36 trawler I built about 12 years ago. I was told by an experienced boat builder to build them using vinylester resin rather than epoxy. I don't remember the reason but for sure, you don't want to use the standard and cheaper resins used in normal boat building. Vinylester is suppose to stand up to biodiesel. The bad part of using vinylester is that we had to grind the tanks between layers of glass if allowed to set up or so I was told. I also hired an experienced fiberglass guy to build these tanks. We built the water tanks using epoxy.
I have FRP tanks in my current Helmsman 38. I like them because I don't think condensation is a problem with FRP tanks. I may be wrong...
Ron
In my opinion, yes. You yourself have said you've seen steel tanks go 30 years. And I know of some boats---GB woodies-- from the 60s that still have their original iron tanks.
You are putting new tanks in the boat no matter what.. So the question is, are you still going to be running your boat in 30, 40, 50 years when the new steel or iron tanks you put in today finally need replacing?
Far better, in my opinion, to install new, properly made steel or iron tanks mounted in such a way that moisture cannot collect under or on top of them than go with fiberglass with all the variables possible in their layup plus the potential risk FF mentioned.
The only alternative to steel/iron that I believe is worth pursuing are the composite tanks being used today by companies like Grand Banks. But they are WAY expensive.
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Keith
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You could always coat the inside of steel tanks with aircraft fuel tank sealer when they're built. Epoxy or other coating on the outside.
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IF I were building a boat today I would select modest sized rotorcast polly fuel and water tanks .
Sure a proper Monel tank set would be better , but the life of polly seems to be unlimited (like the monel) so the downside is the slightly more complex installation.And the inability to have a more complex shape , like a sump directly under the fill port.
A polly tank grows after being 1st fueled , so the drill is to put it in place on its shelf , fill it with fuel and in 48 hours foam it in place , or secure it as you see fit.Then transfer the fuel to the next tank, and let it grow.
With about 40G small enough to not require internal baffels , a series of tanks would be required for long range capacity.
This would not be a problem as the 40G tank would feed about a 100G genuine monel DAY fuel tank. OR a deep but narrow polly day tank
The advantage is when the cruise is over the 40G tanks would be de-fueling by running it thru the noisemaker or heating plant or diesel range.
Eventually ONLY the snap to maintain day tank would hold fuel, so no bugs , no problems .
As said in the Graduate decades ago, Plastic is the future!
Either steel or aluminum tanks work fine BUT they MUST be installed properly.
PAY to read the issue of Pro Boat Builder to find out whats proper!!!Your boatyard may not have a clue!!
There is little rusting inside a steel tank , as even with water in the tank oxygen is also required.
A bottom drain solves the water in the fuel hassle cruedly.
A proper sump solves the water in the fuel problem to perfection.
Sure a proper Monel tank set would be better , but the life of polly seems to be unlimited (like the monel) so the downside is the slightly more complex installation.And the inability to have a more complex shape , like a sump directly under the fill port.
A polly tank grows after being 1st fueled , so the drill is to put it in place on its shelf , fill it with fuel and in 48 hours foam it in place , or secure it as you see fit.Then transfer the fuel to the next tank, and let it grow.
With about 40G small enough to not require internal baffels , a series of tanks would be required for long range capacity.
This would not be a problem as the 40G tank would feed about a 100G genuine monel DAY fuel tank. OR a deep but narrow polly day tank
The advantage is when the cruise is over the 40G tanks would be de-fueling by running it thru the noisemaker or heating plant or diesel range.
Eventually ONLY the snap to maintain day tank would hold fuel, so no bugs , no problems .
As said in the Graduate decades ago, Plastic is the future!
Either steel or aluminum tanks work fine BUT they MUST be installed properly.
PAY to read the issue of Pro Boat Builder to find out whats proper!!!Your boatyard may not have a clue!!
There is little rusting inside a steel tank , as even with water in the tank oxygen is also required.
A bottom drain solves the water in the fuel hassle cruedly.
A proper sump solves the water in the fuel problem to perfection.
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Third-Reef
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Tony Athens provides a nice description of building in fuel tanks using FRP in the "Sunstar rebuild" article on Boatdiesel.com. Very informative and hits alot of the must have and should haves for FRP tanks. If you have not joined for the $25? you should.
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stevensibs
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I have a lot to consider. "Third Reef"...I did join boatdiesel.com and will look for that article, thanks. "FF", I considered poly, but heard strories of diesel smell permeating in and out of the poly. Also the "growing" issue, so 'm a little wary. 'Boat Pro Builder'...is there a link? "Kieth", the stuff you're talking about in airplane tanks, that's a good idea! I'll check with some of the airplane mechanics at work. Plus the steel tank fabricator I'm talking to says he'd powdercoat the outside. "Marin", what kind of composite tanks on GBs? Thank you all for the valuable input. Anything else you can think of would be appreciated!
You'd have to ask them. I was simply quoting from their descriptions of their current models. But given that they are what the factory has chosen to use it's a pretty good bet they made the decision carefully and with very good reasons.
Maybe it's just the industry I work in but when I hear "composite" I think some sort of a carbon fiber layup.
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stevensibs
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Composites probably mean foam cores like coosa or airex, then glassed up with mat or cloth, I would guess. Of all the systems I have purchased for this boat, this is by far the hardest decision....
I just banged around on some ads for late model Grand Banks boats (Heritage, Eastbay, Aleutions) and while most of them listed only the fuel tank capacities I found reference to stainless steel, "plastic," "composite" and "carbon fiber" fuel tanks. So perhaps they offer options to the buyers of their new boats.
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Or iron or steel frames with a wood plank covering.
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stevensibs
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Thanks I didn't see that. But are we talking about "ball valves" here? Somebody in this thread linked me to McMaster-Carr to show me one. Are low point drains/valves not allowed? I thought they were...
The entire five-tank fuel system the previous owner installed the year before we bought the boat is gravity fed from the lowest point in each tank. Not sure what the shutoff valves are on the tanks-- they are opened and closed by rotating a round handle three or four times so I have assumed they are gate valves. The sight tube on each saddle tank has a lever operated ball valve at the bottom of the tube.
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stevensibs
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I just looked up the ABYC and you're right about the tapered plug valve..then I looked up the tapered plug valve itself...not a ball valve like Grocco or McMaster-Carr. The "spring" on this valve is on the outside and it keeps the gate closed and needs an "operator" to open it. Dunno...I guess I'll write theABYC tomoz.
Nomad Willy
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FF says;
"A bottom drain solves the water in the fuel hassle cruedly.
A proper sump solves the water in the fuel problem to perfection."
Fred, what is "crude" about a bottom drain?
And what on earth is a "proper sump"?
"A bottom drain solves the water in the fuel hassle cruedly.
A proper sump solves the water in the fuel problem to perfection."
Fred, what is "crude" about a bottom drain?
And what on earth is a "proper sump"?
CPseudonym
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No offense meant whatsoever but all things being equal why not get steel tanks?
Even poorly designed and installed ones that have never been properly maintained last well over 20 years. Well designed, smartly installed would outlive me and I'm 44.
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I agree with Tom's remarks with one addition that I think is essential for long term integrity of steel tanks and that is a skookum fuel polishing system. Delfin has 7 tanks, and I will routinely do a 12 hour polish on a tank once it gets to 90% empty. This is best done underway, when things are sloshing around. After 5 years, I have yet to see a drop of water in the polishing filters, even though the pickups are directly at the bottom of the tanks. If you keep the water out, the tanks will last a very, very long time.
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what is "crude" about a bottom drain?
And what on earth is a "proper sump"? __________________
Most "bottom" drains are in the side of the tank as the tank mounting frequently makes bottom mounting difficult.
Then the tank has to be installed with the drain at the lowest corner to be effective.
Even if the drain IS in the bottom the interval between draining will still allow water to stand , and perhaps grow garbage up the side of the tank, and all over the tank bottom.
The plans for a proper tank were given years ago, and are in the archives.
Basically the sump is directly under the fill opening which is 3 or 4 inches in diameter.
The fill plate is removed and the fuel enters a screened pipe that removes the big stuff and directs the small crap to the sump, which is below the tank.
On lifting a bail the screen as well as a close fitting cup IN the sump is lifted for cleaning as one piece..
As the sump is at the low point in the tank, big water ("ooops I thought it was the water fill" ) can slowly be removed (the speed with which the water drops is the limit).
With the use of the less common DE Emulsifier , the fresh fuel can be cleaned of any water that is normally in most delivered fuel .This saves your filters and perhaps injectors and fuel pump..
Even if the maint is slack (90% of time cruisers are in port) the water and refuse will collect in the cup in the sump, not in your fuel tank.
Easy , no electronic or electric required to buy install and maintain the fuel system,
Oil floats on water , so Gravity is all you need .
Even when its taxed , gravity will still be a bargain.
And what on earth is a "proper sump"? __________________
Most "bottom" drains are in the side of the tank as the tank mounting frequently makes bottom mounting difficult.
Then the tank has to be installed with the drain at the lowest corner to be effective.
Even if the drain IS in the bottom the interval between draining will still allow water to stand , and perhaps grow garbage up the side of the tank, and all over the tank bottom.
The plans for a proper tank were given years ago, and are in the archives.
Basically the sump is directly under the fill opening which is 3 or 4 inches in diameter.
The fill plate is removed and the fuel enters a screened pipe that removes the big stuff and directs the small crap to the sump, which is below the tank.
On lifting a bail the screen as well as a close fitting cup IN the sump is lifted for cleaning as one piece..
As the sump is at the low point in the tank, big water ("ooops I thought it was the water fill" ) can slowly be removed (the speed with which the water drops is the limit).
With the use of the less common DE Emulsifier , the fresh fuel can be cleaned of any water that is normally in most delivered fuel .This saves your filters and perhaps injectors and fuel pump..
Even if the maint is slack (90% of time cruisers are in port) the water and refuse will collect in the cup in the sump, not in your fuel tank.
Easy , no electronic or electric required to buy install and maintain the fuel system,
Oil floats on water , so Gravity is all you need .
Even when its taxed , gravity will still be a bargain.
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brian eiland
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Just found this subject thread when I was about to ask a few questions on 'what fuel tanks for a new build' ??
So what tanks did Nigel prefer?
brian eiland
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brian eiland
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Good advice also. I would have thought there would be more 'polly tank' replies/contributors?
brian eiland
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Any more info on this aspect of poly tanks?
FF
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>I considered poly, but heard strories of diesel smell permeating in and out of the poly.<
My guess would be that because polly tanks are simple boxes , with no internal baffels they are limited in size .
So 3 or 4 tanks per side might be replacing 1 large tank on either side.
That is a HUGE number of fittings , fills, drains , selector valving and perhaps tank fill depth connections.
I have been to any number of boatyards where white plumbers tefflon tape was used , instead of the yellow fuel resistant.
Dozens of fittings even with GOOD yard practice could be a problem.
With less than informed workers ,,,,,,
My guess would be that because polly tanks are simple boxes , with no internal baffels they are limited in size .
So 3 or 4 tanks per side might be replacing 1 large tank on either side.
That is a HUGE number of fittings , fills, drains , selector valving and perhaps tank fill depth connections.
I have been to any number of boatyards where white plumbers tefflon tape was used , instead of the yellow fuel resistant.
Dozens of fittings even with GOOD yard practice could be a problem.
With less than informed workers ,,,,,,
psneeld
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My poly Moeller fuel tanks (58 gallons each) actually have baffles in them...it's a circle cutout right through the center, top to bottom about 10" in diameter....makes carrying it a breeze!
I was willing to trade off lesser fuel capacity for more storage and the ability to pull my tanks out easily and clean them every couple of years...having them clear enough for fuel level inspection is important.
My poly fuel tanks (5 gal jugs) on the assistance towing vessel which are made from the same stuff have no odors after 5 or so years...maybe another 5-10 they might but if poly tanks do get smelly...they are small and cheap...change them out when they do...
Of course I think it's pretty silly if you think an engine room that gets used a lot and not washed down every use doesn't have a bit of diesel smell to it anyway.
I was willing to trade off lesser fuel capacity for more storage and the ability to pull my tanks out easily and clean them every couple of years...having them clear enough for fuel level inspection is important.
My poly fuel tanks (5 gal jugs) on the assistance towing vessel which are made from the same stuff have no odors after 5 or so years...maybe another 5-10 they might but if poly tanks do get smelly...they are small and cheap...change them out when they do...
Of course I think it's pretty silly if you think an engine room that gets used a lot and not washed down every use doesn't have a bit of diesel smell to it anyway.
