User

I am a subscriber to your magazine, which I always enjoy reading cover to cover. I've just finished reading your latest article on fuel tank construction materials and would like to get your opinion on something. I'm finishing a new lobster boat which has a builder-installed 200 gallon fiberglass fuel tank that is molded into the hull. I've called the builder to try to verify the resin used in the tank, but cannot get a reply, (I suspect the resin is polyester like the rest of the hull).

The engine is an 05 mechanical 440HP Yanmar. I've been reading every article I can find relative to the possible introduction of ethanol to diesel fuel. Since the deck is not yet installed I would like to know if you recommend cutting out the fiberglass tank and replacing it with an aluminum tank? Your opinion would be greatly appreciated. Capt. Ken Alberigi.

In short, fiberglass (often referred to as FRP or fiberglass reinforced plastic) is an excellent material for diesel fuel tank construction.  It’s durable and corrosion resistant.  I’ve worked on 35 year old motor vessels whose fiberglass tanks, after having been cleaned out, appear as good as the day they were built.  Diesel fuel that’s had ethanol added to it, referred to as E diesel, would present a problem for FRP tanks in much the same way E10 gasoline has ravaged FRP gasoline tanks, however, it has many other far reaching ramifications for diesel powered vessels, including those with aluminum tanks, not the least of which is E diesel’s near gasoline-like flammability.  My hope and belief is that E diesel will never become a reality.  Biodiesel also presents a potential problem for FRP tanks that are not built using resins designed for fuel tank applications.  Another issue you should consider is the skill with which the tank was, “molded into the hull”, referred to as an integral tank.  If the tank uses the vessel’s hull as one of its walls it’s integral.  If it’s a self contained fiberglass tank that has then been, “tabbed” into the hull, it’s not considered integral.  Because they rely heavily on secondary bonding principles, integral tanks must be built and installed by skilled, experienced fiberglass technicians.  If the bond fails, and this will sometimes happen of the vessel runs aground or if it’s blocked ashore improperly, the tank may dump its contents into the bilge.  Finally, FRP fuel tanks should be built using a vinyl ester or epoxy resin that is specifically formulated for fuel tank construction.  These are available from most commercial resin manufacturers. 

Steve D'Antonio

PMM Technical Editor