Fiberglass Diesel Fuel Tank

[Agape39]

Originally Posted by DeepFrz

It could also depend on whether the tank was built by a tank fabricator following all the requirements for a fuel tank or if it was just built by a local welder who knew nothing about building fuel tanks.

The welder that built mine builds military spec tanks. And yes it costs more to weld aluminum but that is my point, why use aluminum when you can use a thinner 316 stock and have it built cheaper with next to no corrosion issues as with aluminum? I've replaced steel and aluminum tanks with poly or stainless more than once or twice. And I do agree than installation of an aluminum tank is critical on whether it will stand up to the harsh environment.

[DeepFrz]

And I do agree than installation of an aluminum tank is critical on whether it will stand up to the harsh environment.

This is also true of a stainless tank. Or any metal tank for that matter. The care for metal tanks of any kind is the same. Keep the water out and keep them dry outside as well.

[goboatingnow]

I'm now firmly of the belief that good quality custom plastic tanks are best. I use Tektanks in the UK, but I'm sure there are many.


Dave

[minaret]

Originally Posted by goboatingnow

I'm now firmly of the belief that good quality custom plastic tanks are best. I use Tektanks in the UK, but I'm sure there are many.


Dave

Why is a plastic tank better than a profesionally built integral glass tank? Cheaper, maybe, but better?
For large tanks they often aren't even cheaper, due to the baffling making the tank impossible to mold.

[goboatingnow]

Originally Posted by minaret

Why is a plastic tank better than a profesionally built integral glass tank? Cheaper, maybe, but better?
For large tanks they often aren't even cheaper, due to the baffling making the tank impossible to mold.

These are custom tanks , not moulded.

Why are they better.

1. I'd never have integral tanks or anything, if i could, Any fault requires tearing the boat apart. Some faults are virtually unrepairable.

2. If I had a choice all components of the interior should fit through the companionway and hatch. Including the tanks. Hence more smaller tanks , rather then one huge one.

3. Done properly plastic tanks are indestructible and suffer none of the problems of aluminium or stainless

4. With specific plastics, such tanks are totally impermeable , unlike fibreglass.

Dave

[over40pirate]

I would never put an integral fuel tank in my boat. My boat has 2 integral water tanks, and they both developed cracks, and needed repair. Boat hulls can move a bit.

Speaking of glass tanks. I have been thinking of making a 8 gallon gas tank, for a vintage runabout I have. I have some 1/4" thick flat fiberglass panels, I was thinking of using. One side of the panels has gelcoat on them, the other raw glass.
Should the inside of a fg tank be gel coated?

[Lojanica]

SS fuel tanks are no longer USCG approved due to corrosion and failure. Aluminum is recommended---but coal tar epoxy coat the outside----progressive epoxy has this item. Plastic is OK but it needs to be crosslinked which is not very amenable to welding like the non-crosslinked which is what water tanks can be made from thus the x-linked needs to be rotomolded and can be quite expensive. Also inspection ports in plastic tanks is not always recommended due to the potential for leaks.

Long story short aluminum is usually the best choice. I think fiberglass tanks are good too but the issue with the new fuels has yet to be fully assessed.

[minaret]

Originally Posted by goboatingnow

These are custom tanks , not moulded.

Which means they have welded baffles, an inferor method known for failure.



Why are they better.

1. I'd never have integral tanks or anything, if i could, Any fault requires tearing the boat apart. Some faults are virtually unrepairable.

Why would a fault require tearing the boat apart? Just install big inspection ports, it's easy and reliable in fiberglass. In fact most FRP tanks have the baffles glassed to the lid through the ports, so they already need to be big enough to work inside the tank with. And what sort of "fault" could possibly occur in a pro tank?


2. If I had a choice all components of the interior should fit through the companionway and hatch. Including the tanks. Hence more smaller tanks , rather then one huge one.

This is small boat thinking. For instance in my case I have 450 gallons of fuel tankage in two tanks. If you think you can fit a 225 gal. tank through a companionway you are confused. This is only an option on small boats with small tanks.


3. Done properly plastic tanks are indestructible and suffer none of the problems of aluminium or stainless

So far from true. I have seen legions of failed welds in plastic tanks of all sizes and builds, including cracks in very high quality molded tanks. FRP is much stronger and less brittle.

4. With specific plastics, such tanks are totally impermeable , unlike fibreglass.

With modern epoxy barrier coats rated for use in FRP fuel tanks there is no problem with modern fuel. I have built many and have never gotten a warranty claim, including integral tanks designed by Carl Schumacher and built in a 13 million dollar 77' ultralight, which I also built.


Dave

Integral tanks got a needless bad rep from some manufacterers poor execution back in the 80's and 90's. I have seen catastrophic failure of integral tanks that were just internally gelcoated, the fuel penetrated the hull layup entirely and it was a huge problem. When I build a glass tank I build in epoxy lam, glass the hull as well as the sidewalls and lid so the entire tank has substantial epoxy lam everywhere and the original hull lam is not exposed to fuel, and barrier coat the entire interior with 7-8 coats of 2000e. This sort of tank will never degrade or fail, short of the hull being penetrated in the location of the tank all the way through the extra tank lam. Highly unlikely since most tanks are situated above keel structure.

[downunder]

Originally Posted by minaret

Integral tanks got a needless bad rep from some manufacterers poor execution back in the 80's and 90's. I have seen catastrophic failure of integral tanks that were just internally gelcoated, the fuel penetrated the hull layup entirely and it was a huge problem. When I build a glass tank I build in epoxy lam, glass the hull as well as the sidewalls and lid so the entire tank has substantial epoxy lam everywhere and the original hull lam is not exposed to fuel, and barrier coat the entire interior with 7-8 coats of 2000e. This sort of tank will never degrade or fail, short of the hull being penetrated in the location of the tank all the way through the extra tank lam. Highly unlikely since most tanks are situated above keel structure.

Minaret,

I am with you here. Can't see a problem with a properly constructed intergral fibreglass. Easy to ensure large inspection ports.

[motion30]

I know this is a very old post but it is relevant to my current situation. I was able to remove the old steel tank from my port side with a Sawzall. I am planning on a fiberglass tank installed in three pieces and glass together and place period I have quite a questions about how to install fittings. Can anybody help?

[Roy M]

Sure. What are your questions?

[Lepke]

Design your 3 piece tank with a lip so there's a large, solid overlap that allows a wide epoxy bond. When I built epoxy diesel tanks I put all the fittings on top. Usually all fittings mounted on a large metal plate, giving a large surface area for a good bonding and additional build up over the plate, close to the fittings to sandwich the plate for a strong, leak proof seal.

[motion30]

Thanks for the response gentleman period I was going to build the tanks at a vinyl Ester when I Bond them together in the boat should I use epoxy? I have eight fittings that need to go in the tank I was going to use brass bulkhead fittings and bed them in and epoxy paste maybe fiberglass over them and drill a hole is this a good idea? Some are on the bottom side of the tank. Also would it be better to use a male or female mold in fabricating the tank

[Cyrus Safdari]

Originally Posted by Annie in WA

While our tank is small by many standards (62 gallons), a respected marine surveyor that I spoke to said the tank was too big not to have a baffle and baffles are difficult to fasten for plastic..

If baffles are your only issue, that is easily addressed: baffle balls

Surge Control Ball Baffles | Engineered For Enduranceâ„¢ - Enduraplas

Large Baffle Ball for Tanks with 16" Lid STBBS35

Others just put sections of PVC pipe inside the tank. Stops the sloshing.

[GILow]

The issue of adding fittings to fg tanks has been covered well in recent threads (< 1 year old). I don't know how to post the results of searches using this iPhone app but have a good search around and you will find them. Read them all because there were a couple of different approaches with the merits and pitfalls of each discussed at length. Good reading overall.