new diesel fuel tank

[joelhemington]

Originally Posted by Squanderbucks

Your existing tank has all flat surfaces and could be easily duplicated in most any material. I would recommend getting it totally out of the boat for replacement. Trying to just measure it up and have someone make is likely to not fit back into your curved space. Off a few degrees and it will bind somewhere.
For diesel my favorite material is fiberglass, second choice is aluminum. Last is Stainless steel.

Fiberglass is very forgiving and repairable or allows future modification with normal shop tools. Also it never rust, corrodes, or gets pinholes if properly sealed when made. “Fiberglass is forever”.

Several methods. Build a mold and make it then throw away the mold. 2. Build it out of foam or Cousa board and fiberglass it inside and out. No mold. Thicker but easier for some.

Personally I prefer to make a mold out of Masonite and 1x2’s, wax it up and Mamet the tank. Same for a top and bond together.
These are lighter and less bulky due to thinner walls.

What is mamet?

[jmschmidt]

Simple. Make your own using the old tank as pattern. Construct a 1/8" plywood female form in two parts, top and tank body. Leave ample room to lay on 6 to 8 layers of glass mat and cloth on both the top and body. Coat exterior of plywood form with form release before laying on glass and resin. Your pix look like the shape of the tank does not conform very good to the space in which it is mounted. Either make adjustments to your form pattern so it fits precisely in the existing space or better yet, install cross braces to act as a cradle for the new tank so it doesn't actually touch the bottom or bilge. Drill holes for the fill and vent line fitting in the body just below the top and a hole in the top for the fuel gauge apparatus. Install several battens in the tank body with arch shaped holes at the bottom of each batten to allow the fuel to flow between the compartments created by the battens. After cleaning up every thing insure a mirror image fit between top and body and glass the two together with several layer of glass tape. Some times if I have an unusual shape
and/or and sloping bilges or other areas where a tank, water lock or what have you, is to reside, I first make a mockup out of cardboard and tape until I get fit as close as possible and then proceed to the plywood form stage.

[Baba Buoy]

My forty two year old Baba 35 still has original steel tanks that have never leaked diesel. However, moisture condensation on inside top of tank created rustcicles that dirtied the diesel. I used a commercial tank liner liquid (not epoxy base) and I'm happy with result. The material uses acetone as the carrying solvent and is much less of health hazard to apply. Diesel is now always clean. Cleaning prep is a pain. I used repeated applications of simple green to degrease and phosphoric acid to convert residual rust into a stable form. Not good option, I suppose, if you have significant rust holes leaking diesel.

On a boat everything is broken. You just don't know it yet.

No fix is permanent. Nothing last forever.

[PSC63]

If it helps, when I refurbished my boat I went for a plastic fabricated tank. Here in the UK we have an excellent company called Tek-Tanks who are masters of building one off custom tanks made to measure and not at all unreasonable cost.
The benefit of a plastic tank is reduced condensation and the environment for the diesel bug to breed.
Made my in keel located water tank as well.

Tek-Tanks: Plastic Tanks for Water, Waste and Fuel

https://www.tek-tanks.com

[Pete7]

Tek Tanks are very nice but very pricey. Stainless Steel from J Wolfe likely to half that.

I viewed a nice 33ft Sigma years ago. Owner was hoping mad saying that someone had syphoned his diesel tank over the winter. Nope, when I lifted a floor board it revealed lots of lovely red diesel sloshing about in the shallow bilge. To make matters worse it was a rolly marina berth and the diesel had soaked into the bottom of the plywood bulkheads. Dread to think of the work needed to sort that out.

Time for a new tank me thinks.

Pete

[Cheechako]

I had a boat with leaking fuel tanks. The subsequent buyer just had the bottoms cut off and new bottoms welded on. So if the leaks are in the usual bottom welds... that's a cheap-ish option.

[wingssail]

Between four water tanks, two fuel tanks and a toilet holding tank we have 7 tanks on our boat, all have been custom fabricated out of either aluminum or stainless steel. Over the 35 years we have had this boat we have replaced some of them.

We find the aluminum best for weight but they corrode if exposed to a wet bilge. We have tried repairs but have been unsuccessful except for the shortest time.

Most places in the world will have custom welders willing to make the tanks. The prices are usually reasonable. They can be made from plans or duplicate of the original.

By the way, baffles and inspection plates are essential, and for wide spans, such as those pictured, bracing is needed to avoid "oil-canning" which will weaken the welds. The two pictured do not have proper external stiffeners, due to bad specifications.

[Cheechako]

Originally Posted by wingssail

Between four water tanks, two fuel tanks and a toilet holding tank we have 7 tanks on our boat, all have been custom fabricated out of either aluminum or stainless steel. Over the 35 years we have had this boat we have replaced some of them.

We find the aluminum best for weight but they corrode if exposed to a wet bilge. We have tried repairs but have been unsuccessful except for the shortest time.

Most places in the world will have custom welders willing to make the tanks. The prices are usually reasonable. They can be made from plans or duplicate of the original.

By the way, baffles and inspection plates are essential, and for wide spans, such as those pictured, bracing is needed to avoid "oil-canning" which will weaken the welds. The two pictured do not have proper external stiffeners, due to bad specifications.

SS not very good in the bilge either. The boat in my avatar had a bilge tank, it had a hole in it the size of a pencil eraser in 6-7 years from new. I fabbed a titanium tank for the bilge...

[bjor]

A small update on this post. I managed to get the tank out of the boat (first picture), and have been able to inspect it more closely. It appeared quite rusty in the bottom corner (second picture), but after I cleaned all three sides of the corner it seems that the corrosion is not that bad (last three pictures).

So now I have emptied the tank and cleaned it out, and I put chlorine in to kill germs. Now it is in my bathroom drying up.

Next I need a good, small, torchlight or similar to inspect the inside of the tank. If there is no visible corrosion on the inside I will paint it and put it back in again.

With regard to the leak, it seems that the fillingpipe connected to the tank is the culprit - leaking if it is filled up to the "brim".

So again it seems, the Cruisers Forum have made me think twice and saved me a small fortune.

All the best to all the helpful people here .

[BlueH2Obound]

[QUOTE=bjor;3430880]
So again it seems, the Cruisers Forum have made me think twice and saved me a small fortune. /QUOTE]


Just remember to put a few dollars in the tip jar!

[tkeithlu]

Wonderful outcome, bjor. On to the next task!

[Compass790]

The existing paint looks way too thin. I recommend coal tar epoxy if you can get it. You should have a few coats for a long life, i.e, follow directions.

[Uncle Bob]

Originally Posted by Compass790

The existing paint looks way too thin. I recommend coal tar epoxy if you can get it. You should have a few coats for a long life, i.e, follow directions.

Have to agree, the original looks like it was done to look nice, you don't need nice.

[neflier]

Anyone considering a repair to an aluminum fuel tank really should look into Pro-Seal, or the less expensive equivalent Chemseal. It's an aviation fuel tank sealer and available from Aircraft Spruce for not much money. This is the stuff major aircraft manufacturers use to seal their aluminum tanks, which are basically sections of the wing in which bays are sealed. I've worked with it and it does the job, just make sure the area is as clean as possible and roughed up with a scotch bright pad and cleaned again before applying.

[JBsurfin]

Originally Posted by bjor

Hi everybody,

I have an old leaky diesel tank that must be replaced (se pictures). Does anyone in this forum know if this kind of tank is mass-produced by anyone, or if this is a custom diesel tank that must be custom made.

Grateful for any suggestions / ideas for how to replace the old tank.


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I have a 83 Dickerson that I had to replace the aluminum water and fuel tanks. After a short internet search, I located several companies that will custom make a tank at a reasonable cost with your provided dimensions. Upon receiving the tanks, they fit just like the old ones. An alternative is a bladder, there were several companies that made custom bladders also.