Bladder or smaller poly tanks?

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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.
 
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.
 
Nopistn said:
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.
Click to expand...


:thumb:

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.
 
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 can’t 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.
 
twistedtree said:
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.
Click to expand...
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
 
twistedtree said:
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.
Click to expand...

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.
 
ksanders said:
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 can’t 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.
Click to expand...

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.
 
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
 
O C Diver said:
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
Click to expand...
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.
 
Nopistn said:
Sooo you're basically saying poly tanks are much better for resale value.
Click to expand...



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.
 
Nopistn said:
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.
Click to expand...

Lol I meant 2 MPG^
 
I used 56 gallon poly tanks. Off the shelf for around $300 a piece. Gives me a range of over 300 miles and LOTS more storage room in the engine room.

They have up to a 126 gallon square footprint, off the shelf tanks.
 
Nopistn said:
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
Click to expand...



I’m suggesting laying up the FRP from inside the existing tank, not outside. So only interior access required, which from the pictures you seem to have?
 
From a marine engineer friend....

"I wonder if any of the proponents of bladders give any thought to the fact that it is absolutely necessary to completely clean and mechanically "polish" the interior surfaces so that there are no points of abrasion that will puncture the bladder walls after a period of operation. Since the access required to adequately prepare for a bladder install means cutting large access ports in the tank and complete cleaning and gas freeing you may as well crop out the corroded section of the top and bolt on a new section. Since the interior has to be cleaned anyway, it would be a perfect time and in condition to use an aviation grade tank sealer top bottom and sides. "
 
Nopistn said:
Lol I meant 2 MPG^
Click to expand...
:rofl: Last time I heard some say they had a 2mph boat boat they were referring to it being a dock queen and the marina current was 2mph. :rofl:
 
twistedtree said:
I’m suggesting laying up the FRP from inside the existing tank, not outside. So only interior access required, which from the pictures you seem to have?
Click to expand...

I worry about attaching the lid along the outer edge of the tank with this route.
 
It is very difficult to glass UP, overhead , esp with epoxy that is slow curing.


Not much fun with polly either , but doable.
 
FF said:
It is very difficult to glass UP, overhead , esp with epoxy that is slow curing.


Not much fun with polly either , but doable.
Click to expand...

I can imagine
 
I have a different opinion than most here. I think you should cut out and remove the original tanks from inside. Clean sand and paint the area they are occupying, build removable supports to secure new custom bladder tanks to fit in the area that was previously occupied by the fuel tanks. You can get bladder tanks custom made in any custom shape, and they can baffle them. I think they put an open cell fuel proof foam inside of them like a fuel cell in a race car. If you do a nice job of it, I doubt it would reduce the value of the boat. If you need to clean them, repair damage on the hull, inspect, need more room during engine work, etc. You can just pump out all the fuel and remove them from the boat. I think this would be a super sweet setup.
 
Snapdragon III said:
I have a different opinion than most here. I think you should cut out and remove the original tanks from inside. Clean sand and paint the area they are occupying, build removable supports to secure new custom bladder tanks to fit in the area that was previously occupied by the fuel tanks. You can get bladder tanks custom made in any custom shape, and they can baffle them. I think they put an open cell fuel proof foam inside of them like a fuel cell in a race car. If you do a nice job of it, I doubt it would reduce the value of the boat. If you need to clean them, repair damage on the hull, inspect, need more room during engine work, etc. You can just pump out all the fuel and remove them from the boat. I think this would be a super sweet setup.
Click to expand...

I like that idea. No need to leave the rusty old tank. ATL makes that type of tank as well. The foam would baffle the fuel and keep it from sloshing around. In gasoline tanks it prevents the foam prevents explosions. It slows the flame front.
http://atlinc.com/marine.html
 
Snapdragon III said:
I have a different opinion than most here. I think you should cut out and remove the original tanks from inside. Clean sand and paint the area they are occupying, build removable supports to secure new custom bladder tanks to fit in the area that was previously occupied by the fuel tanks. You can get bladder tanks custom made in any custom shape, and they can baffle them. I think they put an open cell fuel proof foam inside of them like a fuel cell in a race car. If you do a nice job of it, I doubt it would reduce the value of the boat. If you need to clean them, repair damage on the hull, inspect, need more room during engine work, etc. You can just pump out all the fuel and remove them from the boat. I think this would be a super sweet setup.
Click to expand...
This is definitely a possibility. Others here and locally have said it's a waste of money because of the reduction in boat value.
I'm not sure. If I have a boat with these vs unknown steel I'd probably feel a little bit better.
 
You've been given lots of ideas. It seems to me that you should get some estimates. I would first get an estimated value of the boat with good tanks. I would get an estimate for 2 new aluminum fuel tanks and the cost to remove the 2 engines and generator if necessary, if you can't do the work yourself. Replacing the tanks with aluminum ones will give you the highest resale value (better than the original steel tanks). You then need to decide if the cost is justifiable to the value of the boat.

If you choose not to go with aluminum tanks, you need to realize that all the other options will likely greatly reduce the value of your boat and may prevent you from selling it for a reasonable price. Remember, you may be able to find a buyer, but ultimately it will be the surveyor and the buyer's insurance company that will be the final word.

The last consideration is your own insurance company. If you have to change companies or yours requires an insurance survey, you might find them unwilling to insure your solution. There have been some probably very viable alternative solutions offered. But, when it no longer looks like an original fuel tank, the scrutiny will begin. While I'm not familiar with your boat, I'm gathering from the thread it's maybe 30 years old. As boats get older, there are fewer companies willing to insure them. This may just give them the reason to say no. A failed bladder with 100 gallons of diesel being discharged by a bilge pump, could be a huge environmental liability.

Ted
 
My boat hit 30 this year and on the required self survey, they specifically asked if the tanks we're original.
 
O C Diver said:
You've been given lots of ideas. It seems to me that you should get some estimates. I would first get an estimated value of the boat with good tanks. I would get an estimate for 2 new aluminum fuel tanks and the cost to remove the 2 engines and generator if necessary, if you can't do the work yourself. Replacing the tanks with aluminum ones will give you the highest resale value (better than the original steel tanks). You then need to decide if the cost is justifiable to the value of the boat.

If you choose not to go with aluminum tanks, you need to realize that all the other options will likely greatly reduce the value of your boat and may prevent you from selling it for a reasonable price. Remember, you may be able to find a buyer, but ultimately it will be the surveyor and the buyer's insurance company that will be the final word.

The last consideration is your own insurance company. If you have to change companies or yours requires an insurance survey, you might find them unwilling to insure your solution. There have been some probably very viable alternative solutions offered. But, when it no longer looks like an original fuel tank, the scrutiny will begin. While I'm not familiar with your boat, I'm gathering from the thread it's maybe 30 years old. As boats get older, there are fewer companies willing to insure them. This may just give them the reason to say no. A failed bladder with 100 gallons of diesel being discharged by a bilge pump, could be a huge environmental liability.

Ted
Click to expand...
It's 40 years old and my insurance company probably doesn't care. It's liability only.
 
Moeller is the big name in plastic diesel tanks...any other manufacturers?
 
Once I read far enough into this book to understand you are a DIYer, I thought my experience in assisting with the replacement of the fuel tanks in a twin-engine (Ford Lehman 90s) 37-foot trawler. The two 250-gal tanks outboard of the engines were replaced with four aluminum tanks occupying the same footprint as the originals. While the my friend the owner did not do so, I would have placed a valve in the large diameter hoses connecting the bottoms of the two pairs of tanks.

Here's how we did it while the boat was IN THE WATER:

Remove all the main cabin engine room hatches.
Using three guys, we rigged a wooden gallows in the main cabin and lifted one engine/tranny with several come-alongs. We swayed it over top of the other engine and rested it on 4X4 timbers stretched full length of the cabin.
Using a bunch of Sawzall blades, cut out the old tank in pieces.
After cleaning up and repainting the area, we easily placed the two new tanks on that side.
Lowered the engine back into place and then repeated the process for the other side of the boat.

Costs? Some lumber, come-alongs, tank manufacture (the biggie), hoses, valves, Sawzall blades.
 
Nopistn said:
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.
Click to expand...

Check locally, I’m in the PACNW.

Look for a yard with a strong fiberglass department along with a good mechanical department.

This is not a DYI job, at least the cutting and repairing the fiberglass part.
 
rgano said:
Once I read far enough into this book to understand you are a DIYer, I thought my experience in assisting with the replacement of the fuel tanks in a twin-engine (Ford Lehman 90s) 37-foot trawler. The two 250-gal tanks outboard of the engines were replaced with four aluminum tanks occupying the same footprint as the originals. While the my friend the owner did not do so, I would have placed a valve in the large diameter hoses connecting the bottoms of the two pairs of tanks.

Here's how we did it while the boat was IN THE WATER:

Remove all the main cabin engine room hatches.
Using three guys, we rigged a wooden gallows in the main cabin and lifted one engine/tranny with several come-alongs. We swayed it over top of the other engine and rested it on 4X4 timbers stretched full length of the cabin.
Using a bunch of Sawzall blades, cut out the old tank in pieces.
After cleaning up and repainting the area, we easily placed the two new tanks on that side.
Lowered the engine back into place and then repeated the process for the other side of the boat.

Costs? Some lumber, come-alongs, tank manufacture (the biggie), hoses, valves, Sawzall blades.
Click to expand...
I like it, I would love to see this "wooden gallows" rig.
I wonder how much that saves over having a forklift do it at a yard, assuming the boat must come out this year for other maintenance anyway.
 
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