Fuel Tank

[S Ritzert]

Has anyone ever built a fuel tank?

[Carl]

You need the US Coast Guard approved tag for insurance and inspection purposes.

Aside from that what information are you looking for?

I had it made from 3/16" alum, bent with heavy radius from bottom up and TIG welding corners. Inside has baffles that mimicked the fiberglass tank. We used the old inspection and fill covers...which was helpful when adding diesel returns. Also gave tank a Coal Tar coating...nasty stuff.

[S Ritzert]

I was thinking about a coosa build, then a heavy lamination with fiberglass, using a vinylester resin. It looks like seaboard marine did the same thing in shooter. Fiberglass and gelcoat work is not outside my abilities. The knowledge proper materials for this project is outside my scope though.

I guess my questions would be:

Is there a specific resin for this project?
After fiberglassing would you coat the fiberglass with something resistant to diesel on the inside of the tank, or is raw fiberglass acceptable?

[Carl]

I was thinking about a coosa build, then a heavy lamination with fiberglass, using a vinylester resin. It looks like seaboard marine did the same thing in shooter. Fiberglass and gelcoat work is not outside my abilities. The knowledge proper materials for this project is outside my scope though.

I guess my questions would be:

Is there a specific resin for this project?
After fiberglassing would you coat the fiberglass with something resistant to diesel on the inside of the tank, or is raw fiberglass acceptable?

Glass tank...cool! Outside my pay grade. I'd speak with the Resin company before doing any work. For gasoline with ethanol there is a special resin that is compatible. I'd go that route in case the industry decides to add ethanol or ______(fill in the blank) to diesel.

[S Ritzert]

That's a good call, there's no telling what these guys will add to fuel later on in life.

[Tony Meola]

I believe the original fiberglass tank on our boats had a gel coat finish on the inside. Remember you need to put in baffles to keep it from sloshing around.

[Yannis]

You also need one inspection opening per baffled compartment, wide enough to fit your whole arm in case you have to inspect and clean the tank.

[Carl]

You also need one inspection opening per baffled compartment, wide enough to fit your whole arm in case you have to inspect and clean the tank.

That may be more of a wish list...I do not recall seeing one like that but would have made life much easier back when I thought the glass tank had to be cleaned, thinking the ethanol was dissolving the old tar and gunk off the walls. Who knew the ethanol was dissolving the walls themselves.

FYI- my tank had no gelcoat on inside...not to say there once may have been gelcoat and was dissolved by the corn juice. I did not see any flakes of coating or de lamination in my tank...I cut top off to look. Now my dad's Hatteras started started to mimic my boats engine problems after I figured out the issue was the corn juice, pulled tank and replaced with aluminum. His tank started to flake gelcoat and see raw glass. His tank was also under a Teak Deck he installed and really really did not want to pull up. That was his big push to jump on a pair of diesels getting away from the ethanol. I guess lucky as the flaking stopped and tank still holds fuel.

I mentioned diesel getting stuff added as there was talk about companies doing that for awhile...ethanol was mentioned as was combining biodiesel, soy...something and had my dad thinking here we go again knowing the problem he averted going diesel. Now it seems they want to phase diesel out period...that would solve the tank getting eaten up issue. I guess we just add batteries were fuel tank is....or a long extension cord.

[S Ritzert]

You also need one inspection opening per baffled compartment, wide enough to fit your whole arm in case you have to inspect and clean the tank.

My issue with this is the potential for leaks, but a great idea non the less. When fuel injection was first introduced in my industry (inboard tournament ski boats), at about 1995. We gasketed the inside and outside of the fuel tank plate. I only remember this because we had to re-gasket all fuel tanks the first year as a recall because the gasket deteriorated, and leaked. I was charged with doing all the Correct Crafts in Texas and the surrounding states (what fun!) What we had was a stainless ring on the inside of the tank that was studded, and those studs went from the inside of the tank out, then a plate with the pickup, return, and sender was on the outside of the tank that slipped over the studs, then nuts fit those studs to sandwich everything together. In a nutshell it was a sandwich, plate, gasket, tank, gasket, plate. Anyway, I shared that story because of my fear for leaks, and to say that I will probably gasket my tank the same way.

I believe the original fiberglass tank on our boats had a gel coat finish on the inside. Remember you need to put in baffles to keep it from sloshing around.

Roger that, and no worries there. Baffled, and vented accordingly so you can actually fill it with fuel.

So that was another question of mine is what to line it with. Gelcoat is easy enough, no liner is easier in my opinion and if that's feasible. I did talk to the glass guys yesterday at fiberglass warehouse. They did say vinyl ester resin is what is most commonly used.

[Raybo Marine NY]

what country do you live in and what fuel?
here in the USA fuel tanks cannot be built into the boat itself. There are boats that are still built today that do this , how they get away with it I don't know ( never mind EPA requirements for fuel tanks in regards to emissions on new boat built).
By built in I dont mean where you have to cut a deck to get to it I mean it cannot be the structure of the boat or support another structure such as the deck or bulkheads.

if gasoline there can also be no openings into the tank, or drains. You cannot have a removable cover on a gasoline fuel tank in the USA as per USCG regulations.

If you are outside of the USA or choose to ignore these regulations is up to you but an aluminum tank will likely outlast your gasoline engines and unless you are planning a really custom deck that you may never want to remove again changing a fuel tank 20-30+ years theres likely going to be more maintenance needed below deck at that time anyways. Unscrewing some deck panels is not a big deal and I'm a firm believer that aluminum tanks in an inboard boat live a good life due to the ventilation they get and the drying effect from the heat of the engines.

Another thing to consider if you were planning on making the boat itself the fuel tank is to allow for drainage under the tank from either a sub floor or drain tube.

edit- I now see your tear down photos so you can disregard everything above in relation to gasoline versus diesel lol
Whats the issue with your current tank?

[S Ritzert]

what country do you live in and what fuel?
here in the USA fuel tanks cannot be built into the boat itself. There are boats that are still built today that do this , how they get away with it I don't know ( never mind EPA requirements for fuel tanks in regards to emissions on new boat built).
By built in I dont mean where you have to cut a deck to get to it I mean it cannot be the structure of the boat or support another structure such as the deck or bulkheads.

if gasoline there can also be no openings into the tank, or drains. You cannot have a removable cover on a gasoline fuel tank in the USA as per USCG regulations.

If you are outside of the USA or choose to ignore these regulations is up to you but an aluminum tank will likely outlast your gasoline engines and unless you are planning a really custom deck that you may never want to remove again changing a fuel tank 20-30+ years theres likely going to be more maintenance needed below deck at that time anyways. Unscrewing some deck panels is not a big deal and I'm a firm believer that aluminum tanks in an inboard boat live a good life due to the ventilation they get and the drying effect from the heat of the engines.

Another thing to consider if you were planning on making the boat itself the fuel tank is to allow for drainage under the tank from either a sub floor or drain tube.

edit- I now see your tear down photos so you can disregard everything above in relation to gasoline versus diesel lol
Whats the issue with your current tank?

I appreciate your insight and thoughts. It looks like you figured out that I am in the US, and I am running diesels.

I do disagree on the aluminum fuel tanks, in a salt water environment, or at least in the one instance that I have experience in. My first personal boat that I restored for myself was a 1988 Fish Nautique. It had an aluminum fuel tank that was pitted terribly on the underside of it. The way that it was installed wasn't necessarily the best idea in the world. It had an aluminum plate that stretched the width of the stringers, on top of that was a rubber pad, and the fuel tank rested on top of that rubber pad, with straps that went around the tank and held it in place. Anyways, I am sure that tank rotted out because you couldn't ever rinse under side the tank, and it just held salt between the tank and rubber. The top and sides of the tank were in perfect shape. Any 80's boats that I still work on to this day that are freshwater boats still have tanks in great shape as well.

I am very capable of fiberglass work, so building a tank doesn't bother me, and I would for sure do a uni-construction if I did go that route. I would not do the project as a "part of the boat" I would think the flex of the boat would be a huge potential for a cracked tank. I am with you on that aspect.

My first issue with the tank is the drainage under it in my opinion is not adequate. I am a firm believer in water management in a boat. There is a bulkhead glassed for and aft of the tank. I think removing these bulkheads will actually give more drainage under the tank, but I cannot be certain until I remove them. My second issue is that the highest most hole in the baffle will not allow the tank to fill 100%. The highest hole is about an inch from the top of the tank.

I am about 90% sure at this point, that I will replace the stringers, and the tank is glassed to the stringers. I think if I do this project, that cutting the tank out with the stringers will be an quicker task.

I am not certain yet that I will do a tank at all, I was mainly getting my ducks in a row, and collecting thoughts on the project. I was wondering if fiber glassing coosa was a viable option, or should it be straight fiberglass. I was also wondering about a tank lining but the current tank has no lining.

[Carl]

I believe the tanks were only tabbed to stringers in a couple spots, at least mine was. Cut the tabbing, used a long saw blade to cut away the foam around tank. Couple clamps on lip of tank to a chain fall attached to a heavy pipe laid across gunnel. That n drove a couple wedges till it broke free.

[Raybo Marine NY]

The factory tank is Tabbed in and it’s also resting in bonding putty on a mostly raw plywood subfloor. Some more than others.
You can design an aluminum tank that will bolt in and allow plenty of drainage, adding drainage fore and aft

Even poorly made, raw aluminum tanks in less than ideal installation methods last decades so I feel any improvements you make to the tank and it’s design should yield better results.

As for the coatings, this is a touchy one as you can only apply what’s known today, no one knows what might happen later.
Yellowfin for example used coated fiberglass tanks and that coating later failed , the resin used to manufacture that tank was ethanol resistant on its own.
Bertram tanks suffered similar, coatings peeled off of tanks that were in service for decades due to ethanol.

I’ll personally take the chance on an aluminum tank versus a fiberglass one, even gas stations have fiberglass tanks that are mandated to be changed every few years due to age and evolving fuel additives and refining process

As you can see inside the bertram tank you can figure out how they were made.
A top and a bottom were made, a little on the thin side. Metal baffles were riveted in, I believe all monel.
The lid was riveted on and the whole deal was wrapped in more fiberglass.

If making baffles out of fiberglass is the plan I guess you can use coosa so long as it’s all glassed together with appropriate resin, but since your making baffles from fiberglass anyhow I would probably make the whole tank from fiberglass. Then glass my baffles in, lay the lid on, and wrap the whole deal in more fiberglass. a MDF mold and use all fiberglass, no coosa or other materials