Iron fuel tanks - when did they go away?

[Comodave]

Mine was completely custom. It was not a rectangular tank. They went in under the aft berth and basically followed the hull as it went down. They made a frame out of 1X2s that was the shape we wanted. Then they went to their shop and made a male plug. Laid up the tank over the plug, put in the dividers and glassed the top on. The pickup was about 1/4” off the low point and everywhere in the tank drained and sloped to that point. We had a high speed filler with 2 1” vents, one off each side. They cut out the back of the aft cabin and the deck in the cockpit to get it in and then glassed it all back and Awlgripped the cockpit and aft cabin. Wish I had that tank in my current boat.

 

[Steve DAntonio]

FRP is good for diesel fuel. And many other liquids.

For gasoline not so much. With the use of alcohol in gasoline FRP fuel tanks have experienced degrading issues.

I was referring to diesel, however, for the record, the above quote is only partially correct. Conventional polyester resin tanks (and their engines) did suffer when E10 was first introduced (BWhalers and Bertrams were especially hard hit), that in turn scared any boat builder using gas engines away from FRP, and understandably so.

Today there are resin formulations that are approved for gasoline, E10, and even E75, I'm working with a builder now who is considering using one. Virtually every gas station and dock in the US and Canada now uses FRP underground storage tanks, most made by Xerxes, again even for E75.

This manufacturer offers replacement FRP gasoline tanks for Bertram. Bertram Fiberglass Fuel Tanks From High Tide Marine - New Bertram Original and Replacement Parts - Bertram Yacht Parts, Bertram Struts, Bertram Rudders, Bertram Burgees, Bertram GearBertram Mechanical Parts for All Bertram Yachts

Provided it was one of these ethanol resistant models, I'd happily take an FRP gasoline tank over aluminum.

 

[DDW]

I know that a sump is the accepted means of building a tank, able to trap a cup of water or so. But I've always thought that a better way to build a tank would be with the fuel pickup reaching all the way to the bottom. Constantly drawing any dirt or water, which gets filtered out in the Racor. Basically constantly polishing the fuel, like what my old Jimmies did.

Aluminum tanks can corrode from the outside in, had one that did that. Tanks should never be installed so that they are resting on an active surface with no means of cleaning or ventilating.

I had the tanks for the sailboat built with a sump. This was just a small box, about 6 x 6" and 3" deep, protruding below the low point of the tanks (and the tanks were designed to have a low point. The fuel pickup stops level with the bottom of the tank proper. When it goes dry, there is only the quart or so in the sump left. Also directly over the sump is a 1 1/4 NPT plug, by removing it I can stick a suction tube down into the sump and suck it dry.

The idea is that water and most other contaminants will fall to the bottom of the tank and work their way to the low point. In this case they fall into the sump. Periodically I stick a tube down into the sump and using and oil change vacuum pump, suck a quart or a a half gallon out. The tank need not be empty, it can be done at any level. This removes any water or contaminants which have collected there.

I also had them built with channel sleepers welded to the bottom, on which they rest. This provides air and water circulation under the active tank bottom. the contact patch of the sleepers is only about 1.5" wide, so they have a much better chance of drying should they get wet. But in any case, corrosion on them where the touch the stringers will not affect the integrity of the tanks.

 

[dannc]

I didn't know you could buy metalizing guns still. That's fantastic. It would be a dream to flame spray the entire exterior of a steel boat.

I too was under the impression that thermal spraying to protect a steel hull was a thing of the past. I suspect this was because I first read about it in "old" books and I was not hearing, seeing or reading about boat builders using flame spraying. Pretty sure that Kasten mentions that flame spraying is not needed anymore with epoxy coatings. Having said that, it sure would seem to be a belt and suspender approach to flame spray and then epoxy paint the interior and exterior of a steel boat.

A few years ago I joined the AWS(American Welding Society). Not a welder but wanted to learn more. In the AWS magazine they have had advertisements for flame spraying equipment and techniques which surprised me. The little bit I know about flame spraying is that it is much more than just protecting steel now a days. There is even a thermal spray society.

Flame spraying equipment and companies are out there.

Later,
Dan

 

[FF]

Folks that want a very unusual shaped GRP tank can use the technique from custom motor cycle builders.

They glue up and carve foam like blue board into the tank shape required , then coat it with epoxy (polly) dissolves most cheap foams.

They lay up what ever thickness is required on the foam , cut a hole for the gas fill, and use old battery acid to melt the interior foam plug out.

Works great , but for a complex big tank would be loads of work.

The usual objection to a GRP tank is most are cylinders , so volume may be lost compared to a flat wall tank.