Composite Gasoline Tanks

[comfisherman]

Aluminum tanks certainly have a shelf life, have seen many a tank cut out and replaced from aging plastic boats over the years. Most get replaced with another, aluminum tanks are for the most part cheaper in my part of the USA and even with the shorter lifespan often out last the owners remaining career.

In an alloy boat Aluminum tanks seem to be logical choice. Or at least it is in every single alloy boat I've ever crawled on or worked on. Like kind material goes a long way to abating crevice corrosion. Only downside is alloy tanks get warmer and seem to grow bugs in diesel a bit, moot point in gas.

Keep in mind epoxy+core+reinforcement still costs something. It's not cheaper here, I'd be shocked if in another developed country it's radically cheaper.

 

[BMcF]

Aluminum tanks certainly have a shelf life, have seen many a tank cut out and replaced from aging plastic boats over the years. Most get replaced with another, aluminum tanks are for the most part cheaper in my part of the USA and even with the shorter lifespan often out last the owners remaining career.

I'd say that about half of the aluminum tanks (100s) that my company has built replacements for over the years, failed from corrosion from the outside...the practice of shooting foam around them to bed them in being the prime culprit of that. The other 50%..effects of ethanol in gasoline. Eats off the pickups..destroys the level senders...precipitates ethanol sugar that clogs the tank. I cut one tank open to show the owner what had happened to cause his to fail..more than a 5-gallon bucket full of ethanol sugar-sand in a 50-gallon tank.

 

[IronPrice]

I think the 'hint' there is the "alloy"... i.e. non combustible.
Unlike the composite!

I would have thought the scenario for a fire would be a leak, followed by an explosion caused by a spark arc in the bilge system. Is that risk any higher for a composite tank?

The only other potential source of fire would be a short in the bilge system. Can a bilge pump catch fire? I'm sure they can get hot and melt, but can they actually burn?

 

[Blueknarr]

For some inexplicable reason bilge collect bits of cloth, paper and petroleum. Mixed together and deposited adjacent to wiring. The wire doesn't need to melt before the adjacent flammables ignite.

 

[IronPrice]

My company has built a lot of aluminum fuel tanks to USCG requirements.

Not relevant in NZ.

 

[IronPrice]

For some inexplicable reason bilge collect bits of cloth, paper and petroleum. Mixed together and deposited adjacent to wiring. The wire doesn't need to melt before the adjacent flammables ignite.

Thanks, this has given me some food for thought.

 

[fallguy]

Thanks, this has given me some food for thought.

wires in bilges ought to reside in conduit~easier to modify later and you protect them from chafing

 

[comfisherman]

Does your boat have an open bilge? How many possible bare wires or wires capable of chafing are in your bilge? Seems like an odd thing to worry about, mainly due to the fact that of the thousands of outboard powered boats running around up here I've never heard of one blowing up... drunk guy filling a rod holder on an old school inboard then separating the cabin from the hull.... sure. But not a even remotely well maintained modern powered outboard boat...

I'd be more worried if the bilge had stagnant water in it, that's what makes the dreaded white dust that leads to leaks.

Bmcf, that ethanol business sounds awful, we had it up here years ago. Folks in villages got to replace a lot of broken engine parts come spring. I've no doubt it messes up tanks.

I've followed kiwi mini jet guys for years, yall have an impressive batch of very skilled alloy workers. I'd be hard pressed to not let one have a go at a tank.

 

[IronPrice]

Does your boat have an open bilge? How many possible bare wires or wires capable of chafing are in your bilge? Seems like an odd thing to worry about, mainly due to the fact that of the thousands of outboard powered boats running around up here I've never heard of one blowing up... drunk guy filling a rod holder on an old school inboard then separating the cabin from the hull.... sure. But not a even remotely well maintained modern powered outboard boat...

I'd be more worried if the bilge had stagnant water in it, that's what makes the dreaded white dust that leads to leaks.

Bmcf, that ethanol business sounds awful, we had it up here years ago. Folks in villages got to replace a lot of broken engine parts come spring. I've no doubt it messes up tanks.

I've followed kiwi mini jet guys for years, yall have an impressive batch of very skilled alloy workers. I'd be hard pressed to not let one have a go at a tank.

My in-bilge wires are sheathed triplex wires and run in PVC conduit, rated for 220v AC power. So three layers of insulation It was difficult to get the conduit there, but it's in. The conduit is combination of rigid and flexible and terminates on a sealed junction box, under the aft deck.

Unfortunately, the conduit is mostly attached to the vertical supports for the deck, about one inch away from the stbd edge of the tank position. While I have the tank out, I have the opportunity to weld in some supports closer to the stbd side of the boat. Awful job in that tight space but it probably makes sense to do it.

The issue with an alloy tank is the wait time. Because of the way the tank attached to the boat, I would need the, to be able to see the boat so it has to be someone local. There are few local manufacturers and they are all very busy.

 

[BMcF]

Not relevant in NZ.

LOL...the requirements aren't whimsical. They serve an important purpose...to assure fuel tankage is as safe as possible.

 

[baeckmo]

LOL...the requirements aren't whimsical. They serve an important purpose...to assure fuel tankage is as safe as possible.

Dear BMcF, you ain't got the point; it is not relevant since they live upside-down in NZ, the gas fumes are pouring out of the bilge......

Apart from that I would suggest a serious check on welded high density polyethene. We have previously manufactured tanks both from alu and austenitic ss, but seeing exactly the same problems as BMcF noted previously. Lately, we had a couple made from HDPE by a local firm, and I am very impressed by the results.

 

[fallguy]

Does your boat have an open bilge? How many possible bare wires or wires capable of chafing are in your bilge? Seems like an odd thing to worry about, mainly due to the fact that of the thousands of outboard powered boats running around up here I've never heard of one blowing up... drunk guy filling a rod holder on an old school inboard then separating the cabin from the hull.... sure. But not a even remotely well maintained modern powered outboard boat...

I'd be more worried if the bilge had stagnant water in it, that's what makes the dreaded white dust that leads to leaks.

Bmcf, that ethanol business sounds awful, we had it up here years ago. Folks in villages got to replace a lot of broken engine parts come spring. I've no doubt it messes up tanks.

I've followed kiwi mini jet guys for years, yall have an impressive batch of very skilled alloy workers. I'd be hard pressed to not let one have a go at a tank.

why argue against floating wires in a metal hull, though?

sure, at this point after his comment supporting presenting conduit, passe, but I see no reason to argue against cogent contributions

Any tank also needs to be about 3-5% undersized for the opening; except in NZ, where it is too cold for expansion. These are numbers for plastic, actually, composite should be much less, but some allowances are needed.

should add, the crevice corrosion here would occur against the hull

 

[BMcF]

Dear BMcF, you ain't got the point; it is not relevant since they live upside-down in NZ, the gas fumes are pouring out of the bilge......

.

I'm again reminded how smart you are.

 

[IronPrice]

Apart from that I would suggest a serious check on welded high density polyethene. We have previously manufactured tanks both from alu and austenitic ss, but seeing exactly the same problems as BMcF noted previously. Lately, we had a couple made from HDPE by a local firm, and I am very impressed by the results.

I'd love to go welded HDPE. However, the only business I know of that makes HDPE gasoline tanks for boats in NZ is a long way from me. Basically, a day and half of towing to get there. That's OK as a one time trip for getting a tank made and fitted. It's not OK if I have problem and need to get the tank repaired under warranty.

 

[BMcF]

I'd love to go welded HDPE. However, the only business I know of that makes HDPE gasoline tanks for boats in NZ is a long way from me. Basically, a day and half of towing to get there. That's OK as a one time trip for getting a tank made and fitted. It's not OK if I have problem and need to get the tank repaired under warranty.

100s of alloy tanks we've made over the last 25 or so years...not a single one has ever had a "warranty" issue. You made that up.