A question of tanks, and I am sure I know the answer but...

[bobfnbw]

Thaks for the lively discussion.
Plastic is not a option here unless its custom built and that costs more than aluminum.
Far as a survey picking up the repair, I seriously doubt it. My previous survey didn't pick up on the fact that it was leaking so, I don't think thats a issue. The tank sits under the engine, only a small portion of it is visable and accessable. And if the repair is a good one, it won't be a issue.
A fiberglass tank is a possibility, but with additives attacking fiberglass... seems better to stick with aluminum. Practical sailor did a study on tanks recently and still consider aluminum to be the best.
Bill S. on Endeavour forums did a repair over a decade ago with this system and still going strong, with no leaks, using marine tex and fiberglass. He didn't seal the tank from the inside like red-Kote. This would be extra added insurance I believe.
Thinwater, more of the tank bottom is remaining than not. I believe a fix should do it. I will prep the inside of the tank with acid for the redkote.
The HDPE will keep the tank above the bilge water, and I planned on using some sort of adhesive to keep it there. Also air can circulate around the tank better, and less water will be trapped there. Ah but researching it further I now know that gluing it there like many have pointed out, will be difficult if not impossible. I could glass it in, but not sure if that is the right way or not.
Any suggestions on a alternative product that will hold up in bilge water but can be glued to the bottom of the fiber coated tank?

I considered having another bottom welded to the tank, but since this tank has had fuel in it for a long time, I don't think any welder would touch it. Even cleaned out.

Again I appreciate the responses.
If money was not a issue, this would be a moot point, I would just replace the tanks. But I can use it for other things. I would plan on having this repair last 10 years then replace with new tanks.
Bob

[mike d.]

bobfnbw there is no reason a welder wouldn't touch your tank. you just have to was it out with soap and water to get the residue out and put air into it for a while to get any vapors left out. had a small hole in my truck tank 18 wheeler brought it to welder. made sure fuel was below hole and he washed it with soapy water and put a bead right over hole. it's not the fuel that ignites it's the vapor. you can't do this when fuel is hot. so replacing bottom is not an issue.

[DeepFrz]

Glassing the bottom of a new tank is sentencing it to an early death. Aluminum needs to have air circulating around it to keep it from corroding.

Fastening strips of a very high density material to the tank wherever it comes in contact with the support structure with something like life caulk or 4200 or 5200 so that water can not collect between it and the tank should keep it healthy. I would not buy a boat with a repaired tank such as you are planning. I would get it in writing that the tank had not been repaired and the age of the tank. That is my opinion.

Steve D'Antonio has written several articles in Passagemaker magazine on tanks, how to install, etc. He believes that fiberglass is the best material, but it must be built with the proper epoxy or (his first choice) vinyl ester resin.

[bobfnbw]

Originally Posted by DeepFrz

Glassing the bottom of a new tank is sentencing it to an early death. Aluminum needs to have air circulating around it to keep it from corroding.

Fastening strips of a very high density material to the tank wherever it comes in contact with the support structure with something like life caulk or 4200 or 5200 so that water can not collect between it and the tank should keep it healthy. I would not buy a boat with a repaired tank such as you are planning. I would get it in writing that the tank had not been repaired and the age of the tank. That is my opinion.

Steve D'Antonio has written several articles in Passagemaker magazine on tanks, how to install, etc. He believes that fiberglass is the best material, but it must be built with the proper epoxy or (his first choice) vinyl ester resin.

I have looked thru back issues of pasagemaker on line to 2003 and could not find any on tanks. I will continue to look.
However I don't agree with you about buying a boat with repaired tanks.
Sorry but we repair items on board all the time. and buying a used yacht is just that. I knew that the tanks on board were probably bad even though my surveyor did not certifiy that they were or were not. After doing extensive research on the boat prior to making a offer, I feel I knew the boat better than most surveyors did. All surveyors have a clause in the contract that says something like places they could not get to or see, they are not responsible for, or something like that.
And believe me when I say that I used the best guy around. I trust him completely. 2nd survey he did for me over the years.
They cant certify everything, because its virtually impossible to see all areas.
But I agree that selling a boat with a bad tank that is undisclosed is not right, but if a repair is done that makes the tank better than it was, stops the corrosion, keep the fuel inside where it belongs, and adds life to the tank, why would that be wrong?

Anyway since I don't plan on selling this boat anytime soon, its a moot point.
My plan is to repair the tank using marine tex epoxy, and fiberglass, coat the inside after a acid wash prep with red-Kote, and reinstall it.
I was unsure of what to do when I posted this poll, and question, but after putting down the first coat of marine tex, I am impressed with how it looks. And I will finish it up with several layers of glass and epoxy, then paint. It shold be fine for a long time. But prior to retireing on this boat, I will change out the tank for a new one, which will be relatively easy now that I know how to do it.

Thanks to everyone that contributed to this thread, hope someone else will learn as well.
Here is a link to the endeavour forums on this issue is anyone is interested.
Like any boat that has tankage in the bilge area, pit corrosion is a problem on these boats. Numerous ways were attmepted to repair this, some even cut out the sides of the hull to remove the tank costing 5 thousand dollars or more, and some just said the heck with it and installed bladder tanks, or smaller tanks in other areas so they wouldn't have to mess with it.
Its a old boat problem. But one that is not insurmountable.

Endeavour Sailboat Owners Discussion Forum

Bob

[thinwater]

My comments were for a few isolated pits only. If significant metal is missing, I'd worry. Sorry.

I also condemn tanks as unrepairable. One thing I consider is the effect of failure. If you do repair it, you are not buying 20 years, and how will you know when failure is imminent? Next time expect the failure to be more sudden.

[DeepFrz]

Passagemaker Magazine
August 2007

Diesel Fuel Tank Design: Materials, Maintenance, and Connections by Steve C. D'Antonio

...and having tanks that are dry, clean, and secure is critical. Steve Reviews the pros and cons of different materials and offers advice about installation and guarding your tank against standing water...

[bobfnbw]

OK her is the update. Thanks for all your imput on this. Being a stuborn guy that I am, I deceided to comprimise, and repair the primary one and install new for the secondary.
The primary tank was steam cleaned and coated with 2 coats of marine-tex epoxy.
I then put in 7 quarts of a tank sealer, into the interior. I cut 2 additional access hatches. The tank is ready to be reinstalled and looks great. I believe it will have no problem s for the next 10 or more years when I plan to have a new one installed.
If I had to do it again, I would probable just had the new one built. Why? Cost. This wound up costing me several hundred buck, and why this is still over 1000 less than a new tank, it was enough to annoy me. But its cool.

The secondary tank I am having built by Florida Marine Tanks. The cost was reasonable due to its size, and it will most likely be the primary tank most of the time anyway. at 36 gallons. I also intalled a moeller 19g day tank, so at 55g have enough for most short term stuff, and will only need to fill the larger tank for long passages.

Bob

[David M]

Replace it with plastic, unless your time is worth three bucks an hour.

[Roy M]

I built my diesel fuel tank out of 1/2 inch plywood, epoxy coated all sides (fiberglass on the interior), built in the baffle, added two LARGE inspection plates, beer-can fillets in all corners, fuel pickup tube, fuel level dipstick, fill pipe and vent. That was over thirty years ago. Last year I removed the tank to install an electric fuel level indicator, requiring drilling a hole. No evidence of epoxy penetration to the core, in fact, the plywood plug still smells like fresh wood. Let's see now, ease of construction, cost of materials, flexibility of design, easy service and maintenance, easy removal and replacing, duration of materials, am I missing something here? Oh, the insurance company sees it as an epoxy/ fiberglass composite tank construction and moves on to other things. Did I mention cost?

[bobfnbw]

Yeah Roy in 10 or so years when I replace the engine I will probably do something like that as well, or just fiberglass the whole sump and make it into a tank. I figure I am losing a lot of space that could be fuel. But this seemed to be the easy way now.
Tanks went in yesterday everything looked good. Can't believe how bright the bilge looks now compared to the way it used to be.