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Old 01-03-2014, 10:03   #1
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Replacing Fuel Tanks... a New Idea?

This keeps coming up again and again. The fuel tank is leaking. Liners, bladders, coatings, all tried with mixed and limited success. Removing old tankage seems like a real chore, but getting the new one in is really the biggest problem. Building one in place out of wood and glass has some merit, if done really well. "manifolding" 2 or more smaller tanks into one tank can also work well, but will be expensive, and hard to plumb in most cases.
Given the scope of the problem, and as a manufacturer of fuel tanks, I think a very reliable and permanent solution is to produce a tank "kit" which can bolt together in place. It may sound far-fetched, but with proper machined surfaces, proper gaskets, and properly torqued nuts and bolts, a permanently sealed tank is a very real possibility, and would allow passing even a larger tank through a very limited opening. We actually use this method to seal large manway openings in tanks, on vertical surfaces, well below the liquid level. A sustained pressure test in situ would be required, but I think this idea has real merit. Some testing for long term reliability in real-life marine use would be required, as would a type of "stover" nut, which locks. Such a tank would not be cheap, but, if produced in enough numbers, could be a more affordable alternative to major renos often needed to replace old tanks in many cases. It could actually work well as a custom "one-off" with the right company building it, but because this would require fairly extensive engineering and testing to gain a UL listing, or other certification to satisfy insurance companies, I throw this idea out there rather than try it myself, although I may dabble a bit at the tank plant I co-own and operate with my 2 brothers. Thoughts? Comments?
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Old 01-03-2014, 10:08   #2
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Re: replacing fuel tanks... a new idea?

What's wrong with using the original tank as a mold to build a fiberglass tank in place? Worked well for me.
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Old 01-03-2014, 10:16   #3
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Question Re: replacing fuel tanks... a new idea?

As I'm in the middle of a tank replacement (thread here) I thought I'd comment. I guess I'm not convinced that the hardest part will be installing the new tank after the old is removed. Of course, I'm not there yet (still disassembling the galley to get the old tank out) so I might change my tune later on. I'm assuming that the old tank is removed intact, rather than being "deconstructed" and removed through a small hole. If the latter approach is used though, then an assembled-in-place tank might be attractive. It would depend on complexity and cost vs. the more sophisticated bladders that are now available.

Could you elaborate on why installing a new full size tank is the hard part?
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Old 01-03-2014, 10:20   #4
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minaret i so love you. thankyou.
i have been trying to figure this one and you slam dunked it.
this method or risking burning down my boat have been the only two solutions so far that include decent capacity.
i didnt think much of the plumbing in more than one tank...that won silver medal.
.i like your idea better.
thankyou
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Old 01-03-2014, 11:35   #5
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Re: replacing fuel tanks... a new idea?

Shorebird , sounds good to me ! Go on " Sharktank " and see what the investors think !
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Old 01-03-2014, 18:23   #6
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Re: replacing fuel tanks... a new idea?

As I mentioned, glassing a tank in place has some merit, as does manifolding smaller tanks, and both methods would be used where access to the tank area is very limited, which seems to be a common problem. Removing a tank is sometimes accomplished by simply chopping it up into smaller pieces, but that doesn't help get a new tank put in, and sometimes requires very extensive (and expensive) work to get a full size tank in place. With all due respect to those of you who choose some of the aformentioned methods, If I were boat shopping, and came across a homemade fibreglass fuel tank, I would give it a quick pass, and would consider both insurability and resaleability as factors in the decision. (I'm not sure I would be wild about some bolted together contraption either.) If a bolt together, gasketed tank were a proven design, and surveyors and insurance companies were on board, it may save a lot of cutting out and reglassing in some boats.
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Old 01-03-2014, 23:09   #7
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Re: replacing fuel tanks... a new idea?

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As I mentioned, glassing a tank in place has some merit, as does manifolding smaller tanks, and both methods would be used where access to the tank area is very limited, which seems to be a common problem. Removing a tank is sometimes accomplished by simply chopping it up into smaller pieces, but that doesn't help get a new tank put in, and sometimes requires very extensive (and expensive) work to get a full size tank in place. With all due respect to those of you who choose some of the aformentioned methods, If I were boat shopping, and came across a homemade fibreglass fuel tank, I would give it a quick pass, and would consider both insurability and resaleability as factors in the decision. (I'm not sure I would be wild about some bolted together contraption either.) If a bolt together, gasketed tank were a proven design, and surveyors and insurance companies were on board, it may save a lot of cutting out and reglassing in some boats.



You mentioned building new in place in fiberglassed ply. Not what I'm suggesting. Use the original steel tank as a mold to build a solid fiberglass tank in place instead. I posted pics of the whole process. Insurance or resale should not be an issue, plenty of boats are built new with glass tanks. It's increasingly common. Glass tanks are better for obvious reasons. No failure due to corrosion. I'd buy a boat with professionally rebuilt glass tanks over a boat with original steel tanks any day. Works for any shape too. How would a bolt together unit handle complex and different shapes?
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Old 01-03-2014, 23:37   #8
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Re: replacing fuel tanks... a new idea?

Fuel tanks, AGGGG, most of the worst memories I have of boat work involves fuel and water they tanks! hate em! But they will need work someday!! Minurets Idea is the best ive seen I wish I had seen em years ago!! Ive always been the remove and replace school! but then theres that time your trying to help someone out in the middle of nowhere!! LOL I used to get myself in trouble cus I carried welders and things like that !!(had a steel boat) Ive patched and re-made lots of them over the years but those little epoxy kits they sell at the local auto store will get ya out of trouble lots of times! And remember if ya do remove or replace your fuel tank have a lower corner fitting put in to drain the water from the fuel tank !! saved me a bunch of trouble over the years!!
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Old 02-03-2014, 12:49   #9
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Re: Replacing Fuel Tanks... a New Idea?

Minaret,

Unless you are following a certified preassure test procedure you haven't built a tank that would satisfy me. Of the tanks I have had to replace, none were accessible enough to fully encase the tank in fiberglass, so I am not sure how you are expecting to get enough access to do a decent job.

Assuming you can get full access to all sides of the tank it is also likely that you can remove it pretty easily as well.
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Old 02-03-2014, 13:12   #10
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Re: Replacing Fuel Tanks... a New Idea?

I don't see any problem with bladders.
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Old 02-03-2014, 13:29   #11
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Re: Replacing Fuel Tanks... a New Idea?

Wouldn't it be easier to keelhaul the boat designer who didn't consider removal and replacement?
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Old 02-03-2014, 13:30   #12
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Re: Replacing Fuel Tanks... a New Idea?

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Minaret,

Unless you are following a certified preassure test procedure you haven't built a tank that would satisfy me. Of the tanks I have had to replace, none were accessible enough to fully encase the tank in fiberglass, so I am not sure how you are expecting to get enough access to do a decent job.

Assuming you can get full access to all sides of the tank it is also likely that you can remove it pretty easily as well.
Although it's true that it could be a really difficult job to both gain adequate access to the tank internals and do a professional glass job to the reach and geometry's involved, I think that in many circumstances it's the best solution and the least disruptive to the structure of the boat. Cutting away structural members to remove/replace tanks or replacing through the hull side is sometimes the only way possible, but I'd prefer Minaret's approach any day. I also think you may not have reviewed his approach or work quality as I assure you, at least in the example he detailed (on his own boat I believe), the new tank glassed inside of the old is of higher quality and strength than you'll find on most new boats built today. I've looked at what passes for fuel tanks in a lot of new boats and I'm not impressed. Just my own observations and experiences.
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Old 02-03-2014, 14:30   #13
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Re: Replacing Fuel Tanks... a New Idea?

Minaret may well be the master craftsman in building glass tanks, which, in and of itself, is quite a technical challenge, and the results may be very good. Most of us, however, are not skilled fiberglass fabricators, and although a novice may be able to glass over an existing tank to his or her own satisfaction, I repeat, if I were boat shopping and came across a previously leaking tank glassed over by its owner, I would run, not walk away. I think bladders have some real potential when used in containment and for smaller, non-baffled tanks many sailboats use. It could be feasable to consider my idea of a bolt/gasket tank as containment for a bladder tank, rather than the tank itself. It would require much less precision and expense, although now you would have the added cost of the bladder tank. Now, if I were boat shopping, and came across a stainless steel "tank" professionally made and lined with a properly fitted bladder, I think I would consider that a "proper" permanent tank, as would (hopefully) surveyors and insurance companies. A small opening with a plug on the bottom of the containment would serve as an indicator of internal tank failure. I also like galvanized steel as a material. In theory, 2 bladders in one containment could also address the problem of larger tanks providing some means of linking them is used. Now lets carry this just a little further. Maybe the new tank of the future is to use a containment compartment, lined with a bladder(s). If and when the bladder fails, the solution is to replace the bladder, hopefully by removing the old one, and installing the new one though an opening previously considered hopeless with a rigid tank. I really appreciate all the comments.
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Old 02-03-2014, 14:45   #14
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Re: Replacing Fuel Tanks... a New Idea?

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Wouldn't it be easier to keelhaul the boat designer who didn't consider removal and replacement?
well put
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Old 02-03-2014, 20:31   #15
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Re: Replacing Fuel Tanks... a New Idea?

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Minaret,

Unless you are following a certified preassure test procedure you haven't built a tank that would satisfy me. Of the tanks I have had to replace, none were accessible enough to fully encase the tank in fiberglass, so I am not sure how you are expecting to get enough access to do a decent job.

Assuming you can get full access to all sides of the tank it is also likely that you can remove it pretty easily as well.


You're not catching on. You use the existing tank as a female mold, ie glass the inside of it. Usually you only need to cut a bigger access panel, which is a good thing anyway. I started doing this on smaller boats after glassing fuel tanks in very large commercial fishing boats. Walk in sized tanks. They are easily insured. Pressure testing is simple and easy and definitely a must. Note that most underground large diesel storage tanks these days are fiberglass. Never had a surveyor bat an eyelid. Yes, you can cut out baffles and then glass in new fiberglass ones. It's simple.
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