Alum vs Plastic tanks

[swist]

Powerboat Reports has been ranting against aluminum fuel tanks for years now. They corrode in saltwater and tend to be mounted such that they cannot dry out (foamed in, e.g.). Furthermore most small boat tanks cannot be replaced without major destruction of the deck.<br /><br />Modern plastic technology is producing roto-molded poly tanks in the 50-150 gallon range that are as strong as aluminum yet don't corrode. <br /><br />Yet use of plastic tanks is still minimal. Is this just inertia (we've always done it that way), cost, or some other issue.<br /><br />I know the first time I smell gas in the bilge of my saltwater-moored 11-year old boat, I'll know its all over - the cost of replacing the tank will not be worth it....

 

[phatmanmike]

Re: Alum vs Plastic tanks

o removed and sold my aluminum 20 gallon tank and now use 3 of the red 6 gallon plastic tanks, just because of the reasons you spoke of above

 

[cuzner]

Re: Alum vs Plastic tanks

I've thought about the same thing myself.Only conclusion I can come up with is possible distortion after heat and cold .Both my water and holding tanks are plastic. I'm not looking forward to the day I have to replace my fuel tank.<br /><br /><br /> Jim

 

[calwldlif]

Re: Alum vs Plastic tanks

I suspect the plastic tanks don't<br />have baffling to keep fuel from sloshing.<br />In a larger tank the weight shift could be dangerous.

 

[crab bait]

Re: Alum vs Plastic tanks

plastic is the way to go.. mankinds' finest achivement.. the reason mankind was placed on this world.. <br /><br />to invent ,produce an per-fect plastic.. since mankind has accomplished this,,especially fuel tanks.. mankinds' time on this world is steadily declining an about over..

 

[Tufan]

Re: Alum vs Plastic tanks

Plastic would be my choice. <br /><br />If diamonds are forever, plastic's will be there too.

 

[Bondo]

Re: Alum vs Plastic tanks

I Agree......<br />Plastic is the Only Answer........

 

[swist]

Re: Alum vs Plastic tanks

Well this has been really useful information.....<br /><br />Large plastic tanks do have baffles. So that's not an issue. <br /><br />Wish someone would reply who has some more direct knowledge of the subject. Other than it sounds bad because it's plastic. 99% of us are riding around in plastic boats, after all....

 

[BillP]

Re: Alum vs Plastic tanks

I think aluminum and steel tanks are used in enclosed areas because of fire resistance. If my memory is right the uscg doesn't allow plastic below decks on fuel systems.

 

[phatmanmike]

Re: Alum vs Plastic tanks

billP is a smart one.... i never thought of that

 

[timbo1963]

Re: Alum vs Plastic tanks

Yep, BillP is smart and Crabby is funny!

 

[mellowyellow]

Re: Alum vs Plastic tanks

MY starcraft has 2 saddle tanks mounted under<br />gunnel, a hard side impact would send fuel all<br />over everyone/everything aboard if tanks were plastic...

 

[Luna Sea]

Re: Alum vs Plastic tanks

I just looked in one of my catalogs, cause something didn't sound right here....<br /><br />"Tempo" makes lightweight polyethyline tanks, for above deck use. And, they make heavier duty ones out of a heavy duty "plastic" for below deck.<br /><br />"Todd" makes heavier duty ones as well, out of polyethyline, USCG certified, for below deck use.<br /><br />I've been seeing these things for years in the catalogs, noticing more sizes and shapes each year. To think they wouldn't be CG approved, or made to be put in the bilge of a boat. Some are even v shaped on the bottom (belly tanks they're referred to as). Clearly they're not intended to put on the roof!!! <br /><br />I've had aluminum ones welded up for my last 2 boats, and may be doing the same for my latest, the 25' straight inboard Grady. But if I find the ones I need in a catalog.......

 

[dingbat]

Re: Alum vs Plastic tanks

You can use plastic below decks on recreational boats but not on commercial crafts. <br /><br />Given an option during a fire, would you rather be chained to a metallic gas can or a plastic one? Pretty much a non- brainier as far as I’m concerned

 

[phatmanmike]

Re: Alum vs Plastic tanks

Originally posted by dingbat:<br /><br /><br />Given an option during a fire, would you rather be chained to a metallic gas can or a plastic one? Pretty much a non- brainier as far as I’m concerned

well tell us, some of us REALLY DONT KNOW....

 

[Luna Sea]

Re: Alum vs Plastic tanks

Well, if it's gonna blow, I vote the plastic, as I'd rather get hit by flying pieces of plastic than steel............<br /><br />Would you rather get hit by a water balloon made from a petrolium based product or steel?

 

[18rabbit]

Re: Alum vs Plastic tanks

If you are replacing a fuel tank it really doesn’t matter if it is aluminum or plastic. You’re going to be cutting into the deck either way. Plastic fuel tanks are nowhere near as strong as metal tanks. Metal tanks of the same dimensions as a plastic tank will be more ridged even with their thinner tank walls. Metal tanks require fewer supports and are spaced further apart. You can weld critters to metal tanks. I have push/pull control cables running under the floor to the fuel tank open/close ball valves and vent ball values. Each of those cables requires a rigid bracket welded to the tank, something you aren’t likely to be get with a plastic tank.<br /><br />Foamed in aluminum tanks can be a recipe for corrosion, but not a given if installed properly. Aluminum is similar to stainless steel in that the surface oxidation on the metal protects it from corrosion as long as there is a flow of water. Stagnant water (including sea air) will corrode aluminum as well as stainless steel.<br /><br />I have two aluminum fuel tanks. One is 20-gals and sits above deck, bolted onto a rubber gasket. Water cannot get under it. Gets hit with salt water every time out. I rinse with fresh water when we get back. Coming up on 30-yerars old without a hint of corrosion. The other tank is over 200-gals and built into the super-structure under the cabin floor. We replaced it last year when we got the boat. I am told the original aluminum tank was foamed in to mil spec. The vessel is designed to survive a roll…tho the crew might not. The tank failure was not caused by corrosion. It was 12-years old without any corrosion except very minor pitting on the top where there wasn’t any foam and the aluminum was exposed to salt air. It would have easily gone another 20-years+. Failure was caused by a braided copper grounding strap that was not secured had flopped onto the top of the tank. It ate a 6-in hole in the tank.<br /><br />Extracting the tank was a major project. Removed the entire cabin floor, chipped foam for a couple days, used a pair of 10-ton jacks to pull the tank out of the foam we couldn’t cut away. The tank could have been repaired in place but we didn’t know the extent of the problem. Had to pull it to see all sides. Once it was removed we decided to re-design the fuel system and had another aluminum tank custom made for us. We did not foam in the new tank.<br /><br />Overall, I prefer aluminum tanks if the tank is permanently installed. I don’t think they are a good choice for applications where the fuel tank will be left in any standing water. If a foamed-in aluminum tank corrodes it is an indication of another problem that needs to be addressed. Water should not be getting into or sloshing about where you fuel tank is anymore than it should be sloshing about on your engine while underway. The way my boat is designed, any bilge content that flows back into that compartment is contained in PVC pipes until it reaches the next compartment. The compartment with the fuel tank is isolated between solid bulkheads.<br /><br />I am a huge fan of Powerboat Reports but I think they missed the mark on this one. Failure of aluminum tanks in small boats is an indictment of sloppy manufacturing practices and faults in the vessel design, not the tank itself. There is absolutely nothing wrong with an aluminum fuel tank when properly designed and installed. And fwiw, if your vessel is designed properly and the tank is installed properly there is nothing wrong with foaming it in place. Indeed, it is an excellent method of securing any fuel tank in place.

 

[dingbat]

Re: Alum vs Plastic tanks

Would you rather get hit by a water balloon made from a petrolium based product or steel....

I'd pick the steel. I may have a sore head but I'm not wet. <br /><br />The plastic will melt and expose the gas to direct flame long before the aluminum tank gets hot enough to ignite it’s contents. This couple of minutes could make the difference between life and death in a critical situation.

 

[Luna Sea]

Re: Alum vs Plastic tanks

ok dingbat,<br /><br />but my comment was in reference to being "chained" to a tank. Besides, I could knaw through the plastic!

 

[Stratocaster]

Re: Alum vs Plastic tanks

Rotary molded polyethylene tanks are indeed CG approved. In fact, I have a 160 USG poly tank in my new boat. I had an aluminum one in my last boat, and I was never comfortable with it after hearing about all the corrosion problems with older aluminum tanks.<br /><br />Mike P