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Old 09-12-2018, 03:02 PM   #21
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I have seen vessels with new fill necks welded on a say 1ft square plate and then that plate bolted on the top of tank in place of "swiss cheese" old fill.

Bud

Or gasketed and bolted to avoid welding onboard.
The overall condition of the tanks is too good to warrant removal.
The baffles should have been tall enough to help support the top of the tank, and eliminate the sag that holds water.
I would never build a flat topped tank, even a small slope towards the keel would ensure that it would shed water rather than ponding it.
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Old 09-12-2018, 03:33 PM   #22
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Or gasketed and bolted to avoid welding onboard.
The overall condition of the tanks is too good to warrant removal.
The baffles should have been tall enough to help support the top of the tank, and eliminate the sag that holds water.
I would never build a flat topped tank, even a small slope towards the keel would ensure that it would shed water rather than ponding it.
Now that's an idea... I've been afraid of an epoxy/glass patch not permanently adhering due to rust... but a few bolts and some sealant or epoxy might do it!
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Old 09-12-2018, 04:19 PM   #23
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would you buy a boat with a repair like that?
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Old 09-12-2018, 04:55 PM   #24
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Pretty sure you canít weld steel once itís been exposed to diesel oil. My concern would be what does the bottom of the tank look like given water has clearly been getting into the tank for years. A failure would be significant from not only a functional perspective but also an environmental insurance (and USCG fine) perspective.

Itís [beyond] time to replace those tanks.
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Old 09-12-2018, 05:18 PM   #25
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I'd weld in a new top. Or partial top plate. If you kept the tanks full more often, the diesel would protect the tank top from rusting worse than the sides or bottom. My mild steel tanks are 76 years old and look great.
If you seal the top with a new neck and filler, here's some sealants for aircraft tanks that has to work.
A sealed in patch could look poor to a surveyor.


https://www.aircraftspruce.com/menus...ksealants.html
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Old 09-12-2018, 05:19 PM   #26
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Let me toss out some ideas.


1) Can the engine be disconnected and temporarily slid back, over, forward to allow the tank(s) to be removed installed? Your hull should be strong enough to block up the engine without doing damage.


2) If the boat isn't used much, and therefore doesn't need a lot of fuel, why not do as you suggest and install some smaller poly tanks. Use one or two as main tanks and the other(s) as long range tanks. Diesel fuel just sitting around can trap condensate and grow bad stuff. Not to mention turning to gel.


3) Diesel is an oil as most know. I wouldn't do any repair work to them or risk cutting them up with something that creates sparks. Also, I doubt any epoxy product will stay bonded to the tanks.


4) Is there a place that a few small tanks can be located? I've seen shelves built in engine rooms specifically to hold fuel tanks. Of course none of the boats I saw this in were used offshore in foul weather. Mostly boats similar to what are found here.
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Old 09-12-2018, 08:14 PM   #27
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Let me toss out some ideas.


1) Can the engine be disconnected and temporarily slid back, over, forward to allow the tank(s) to be removed installed? Your hull should be strong enough to block up the engine without doing damage.


2) If the boat isn't used much, and therefore doesn't need a lot of fuel, why not do as you suggest and install some smaller poly tanks. Use one or two as main tanks and the other(s) as long range tanks. Diesel fuel just sitting around can trap condensate and grow bad stuff. Not to mention turning to gel.


3) Diesel is an oil as most know. I wouldn't do any repair work to them or risk cutting them up with something that creates sparks. Also, I doubt any epoxy product will stay bonded to the tanks.


4) Is there a place that a few small tanks can be located? I've seen shelves built in engine rooms specifically to hold fuel tanks. Of course none of the boats I saw this in were used offshore in foul weather. Mostly boats similar to what are found here.
1. Definitely not, I'll post more pics of the engine room if I can find them, otherwise I'll take more when I get back on the 24th.
2. Yes that's kinda my plan. By cutting the steel tanks out I'd probably be able to slide smaller tanks in place.
Alternatively I could fit a pretty big on in the lazarette but it could get in the way for rudder or AC maintenance.
3. I'll cut them up with a sawzall after washing and vacuuming the inside again. And angle grinder might be pushing it though. And I agree with you that I'm not sure anything would bond to something that rusty.
4. See #2. Under the engine room floor I may he able to get another 35 gallons but I'm not so sure it would be smart to put tanks that far below the engine/raycors/ect.
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Old 09-12-2018, 08:16 PM   #28
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I'd weld in a new top. Or partial top plate. If you kept the tanks full more often, the diesel would protect the tank top from rusting worse than the sides or bottom. My mild steel tanks are 76 years old and look great.
If you seal the top with a new neck and filler, here's some sealants for aircraft tanks that has to work.
A sealed in patch could look poor to a surveyor.


https://www.aircraftspruce.com/menus...ksealants.html
Yes I definitely believe what you said about the rust on the inside after looking inside mine!
But because of limited access to the top of the tank on all sides and the danger of welding on a fuel tank inside of a boat I'm not too sure about this idea.
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Old 09-12-2018, 08:17 PM   #29
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would you buy a boat with a repair like that?
Not sure, if I could fill the tank till diesel came out the filler neck/vents without it leaking then probably so.
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Old 09-13-2018, 02:50 AM   #30
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But because of limited access to the top of the tank on all sides and the danger of welding on a fuel tank inside of a boat I'm not too sure about this idea.
My main tanks, about 5'x5'x5', when opened at about 70 years old, had some deep rust pits in the bottom. After draining the fuel, I washed down with a detergent solution. Then welded up the pits. No issues. Used a 12v bilge blower and tubing for fumes. In my youth, I even welded gas tanks.
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Old 09-13-2018, 05:53 AM   #31
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The bladder idea seems to have faded, but let me just add that with a bladder you would lose the baffling, and the baffling is important to keeping the fuel from sloshing around and impacting stability. It's that whole free surface of liquids thing.


Now, here's another idea. Use the steel tank as a mold and lay up an FRP tank against it from the inside. It's what FF suggested a while ago, but don't build it as a liner or a repair - build it as a completely intact and self supporting tank. Then it doesn't matter whether it sticks to the metal outer tank or not. Now you have a boat with FRP tanks which I think it the ideal material. You would need to pay special attention to the materials because I gather there are special requirements for holding fuel, but some research should reveal all that. You could even get clever and pre-cut the steel tank such that once the new tank is laid up, you can pull out the old one in pieces.


Anyway, it's just a thought.
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Old 09-13-2018, 06:02 AM   #32
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One other question....


What's the approximate value of the boat? And what would you guess this repair will cost? I'm wondering about the economics of it all. Would it make any sense to sell off the engines, gears, generator, and other high value stuff, scrap the rest, and move to another boat? Probably not, but worth asking.
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Old 09-13-2018, 12:15 PM   #33
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1. Definitely not, I'll post more pics of the engine room if I can find them, otherwise I'll take more when I get back on the 24th.
2. Yes that's kinda my plan. By cutting the steel tanks out I'd probably be able to slide smaller tanks in place.
Alternatively I could fit a pretty big on in the lazarette but it could get in the way for rudder or AC maintenance.
3. I'll cut them up with a sawzall after washing and vacuuming the inside again. And angle grinder might be pushing it though. And I agree with you that I'm not sure anything would bond to something that rusty.
4. See #2. Under the engine room floor I may he able to get another 35 gallons but I'm not so sure it would be smart to put tanks that far below the engine/raycors/ect.



If you did mount a tank in the lazarette, that could be the main. Then have the smaller tanks else where. If the main needed to be moved for servicing sytems, simply transfer the fuel to the other tanks. I don't know how your boat is plumbed for fuel but in my mind it's always a good thing to be able to transfer fuel between tanks, just incase a problem comes up.
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Old 09-13-2018, 01:05 PM   #34
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I am in favor of the idea of cutting the tank out the side of the boat.

I have seen this done, and as was posted earlier when the work is complete you canít see it, and the boat is just as strong as when you started.

My money says that is the easiest, cheapest way to do this.
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Old 09-13-2018, 08:19 PM   #35
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The bladder idea seems to have faded, but let me just add that with a bladder you would lose the baffling, and the baffling is important to keeping the fuel from sloshing around and impacting stability. It's that whole free surface of liquids thing.


Now, here's another idea. Use the steel tank as a mold and lay up an FRP tank against it from the inside. It's what FF suggested a while ago, but don't build it as a liner or a repair - build it as a completely intact and self supporting tank. Then it doesn't matter whether it sticks to the metal outer tank or not. Now you have a boat with FRP tanks which I think it the ideal material. You would need to pay special attention to the materials because I gather there are special requirements for holding fuel, but some research should reveal all that. You could even get clever and pre-cut the steel tank such that once the new tank is laid up, you can pull out the old one in pieces.


Anyway, it's just a thought.
Someone did suggest this idea to me a while ago... I'm not sure exactly how it would work since the working space on the backside of the tank is so limited. I might cut the metal down 6" for better access if I go this route
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Old 09-13-2018, 08:24 PM   #36
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One other question....


What's the approximate value of the boat? And what would you guess this repair will cost? I'm wondering about the economics of it all. Would it make any sense to sell off the engines, gears, generator, and other high value stuff, scrap the rest, and move to another boat? Probably not, but worth asking.
Me thinks it would be about break even. The boat isn't perfect otherwise (needs a bottom, varnish, deck work/caulk).
I'm not even sure what a "decent" condition and good running 37 double cabin C&L is worth. I know I got it a little on the cheap side because it surveyed poorly, but I've fixed about everything besides the fuel tanks. Everything works and had been replaced in the last 10 years except the low hours FL120s, including the 9kw generator.
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Old 09-13-2018, 08:26 PM   #37
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I am in favor of the idea of cutting the tank out the side of the boat.

I have seen this done, and as was posted earlier when the work is complete you canít see it, and the boat is just as strong as when you started.

My money says that is the easiest, cheapest way to do this.
Can you find any references to this procedure? Or know of a yard who's done it? I'd like to get an idea of what this would cost to get it professionally done.
I'm a DIYr but cutting the side of the hull would be beyond my limitations.
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Old 09-13-2018, 09:29 PM   #38
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What kind of cruising do you plan to do? How much capacity do you really need?

While I would want to resolve the problem. Removing (cutting it apart) the old tank, plumbing everything off the other tank, and then adding some ballast where the old tank was, would possibly allow you to use the boat until you decide what to do. It really comes down to what type of cruising you do, how much fuel do you need as a reasonable minimum, and are fuel docks in your planned cruising area plentiful enough.

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Old 09-13-2018, 10:14 PM   #39
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What kind of cruising do you plan to do? How much capacity do you really need?

While I would want to resolve the problem. Removing (cutting it apart) the old tank, plumbing everything off the other tank, and then adding some ballast where the old tank was, would possibly allow you to use the boat until you decide what to do. It really comes down to what type of cruising you do, how much fuel do you need as a reasonable minimum, and are fuel docks in your planned cruising area plentiful enough.

Ted
I just use it for a part time live aboard and weekend cruiser.
Most I've used so far in one run. I'd like enough for a reasonable resale value though. This is a 2 mph boat.
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Old 09-14-2018, 12:29 AM   #40
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Sooo you're basically saying poly tanks are much better for resale value.


The trouble with poly tanks are that you may have to use off the shelf sizes. I could not find acceptable sizes. Custom poly tanks are not approved for fuel. Go with custom aluminum. Lots of pics about tank replacement in my blog.
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