new fuel tanks: metal or plastic?

[sonicsby5]

Howdy all, I'm replacing the fuel tanks on a 1942 CC Sedan Cruiser. The original starboard side iron tank is gone and a newer port side aluminum tank was installed about ten years ago (we think...). Recently the newer tank started leaking from a seam where the L bracket connects the tank to the boat frames. We think it has failed because of the boat's prior galvanic problems and the tank not being insulated from the frames of the boat.

I'm considering a couple of Tempo 36 gal. plastic tanks, one for each side because of their low cost (~$200 ea.), lighter weight and ease of installation. Plus, I don't want to introduce more aluminum in a boat with a history of galvanic problems (currently under control by the way).

What do you all think? Thanks for the advice.

Mark

[Gresham CA]

My first question is are you running diesel? Second, if not, is 72 gallons gonna give you the range you want.

I would think that at just 36 gallons then the plastic will work just fine.

[ 08-04-2004, 02:51 PM: Message edited by: Gresham CA ]

[sonicsby5]

Gas. She only burns 3-4 GPH so 72 gallons will work fine. We've been living with a 40 gallon capacity since we bought the boat, so this is a big upgrade in range!

[warthog5]

Are you aware that plastic do permeate fuel thru them? The fuel actually gets sucked into the plastic over time and you will smell a small amount of fuel.

[sonicsby5]

I've heard that they absorb fuel and expand as they age, but had not heard that you can actually smell the fuel coming through. Has anyone had that occur?

m

[Bill Perkins]

I recently bought a Tempo tank through West.After I got it to my shop I noticed a rattle . I unscrewed the fuel gage and found that it's float had fallen off in shipping . I haven't been able to recover this yet . I've snagged it with a plastic hose taped to my vacuum ,but couldn't withdraw it .It's oblong .A friend has suggested filling the tank with water and floating it out , which I'm ready to try .I resent spending time on it , but returning it will just mean more time gone . Shake the tank hard before you take possession .

[Gresham CA]

Bill, Try duct tape wrapped sticky side out on the end of a stick.

[Gerald]

I bought a couple of plastic fuel tanks out of VW sedans. The tanks are about 1/4" thick, have a large screw on inspection lid, internal fuel transfer pump, and sending unit for a fuel gauge. If you really and truly think that the auto industry is allowed to install tanks on their cars that will bleed fuel, thru the plastic, over time then you should consider something else other than plastic.
Good luck
Gerald Niffenegger
Florianopolis, SC Brasil

[SC-Lion]

I’m currently in the process of installing a new Tempo plastic (polyethylene) tank. I’ve never heard of them permeating fuel. If they do it must be a very small amount. I regularly sail on a fi*&^glass boat that was built in the mid 80’s with plastic tanks and I’ve never noticed any smell. Santa Cruz Yachts uses Tempo plastic tanks in all of their boats and has for a very long time. Could it be that the permeating issue is with flexible tanks?

-Gary

[Fritz Koschmann]

The USCG regs state that all plastic fuel tanks allow fuel vapor to pass through the wall.

"All plastics and fiberglass will permit gasoline and its vapors to pass through them. This capability of the material is termed permeability. The permeability rate is the quantity of gasoline that passes through the material in a specific length of time or per unit of net compartment volume. See 183.605 of this guideline for a discussion of how to determine net compartment volume."

USCG requires ventilation for plastic tanks based on the permeability rating of the particular tank.

"a) Except for compartments open to the atmosphere, a natural ventilation system that meets the requirements of Sec. 183.630 must be provided for each compartment in a boat that:

(5) Contains a non-metallic fuel tank:

(i) With an aggregate permeability rate exceeding 1.2 grams of fuel loss in 24 hours per cubic foot of net compartment volume, or

(ii) If the net compartment volume is less than one cubic foot, having a permeability rate exceeding 1.2 grams of fuel loss in 24 hours."

I went through this when I went to install plastic fuel tanks in my catamaran. The tank manufacturer had never heard of this requirement and had no information on the permeability of their tanks. I called the national USCG information center and got through to a federal guy who wrote the requirements. He wasn't surprised about the manufacturer not having the info. He gave me a permeability number to use based on tests they did years ago. He said if I used that figure I would be safe as tanks have improved since then.

More information can be found on the USCG Marine Safety website. USCG Boatbuilders Handbook (http://www.uscgboating.org/regulations/boatbuilder/downloads/VENTILATION.pdf)

[ 08-07-2004, 12:06 PM: Message edited by: Fritz Koschmann ]

[ken mcclure]

Well now, there's a handy reference! Thanks - the USCG site is now in my favorites list! smile.gif

[Dave Fleming]

This is interesting. I read the first few posts and then went outside to my Cummins powered Dodge truck with a plastic fuel tank. I rubbed my hand over it in several spots and I could not smell any diesel odor on my hand.
Am I to believe that only Gasoline tanks are built with permeable plastic?

edited to add:
I briefly viewed the USCG Boatbuilders Handbook and could find no reference to Diesel engines just Gasoline engines and fuel systems.
Anybody find some info on Diesel?

[ 08-07-2004, 02:46 PM: Message edited by: Dave Fleming ]

[JimConlin]

Dave-
Somewhere in that swamp i found:
FEDERAL LAW:
183.605 Definitions.
As used in this subpart:
“Fuel” means gasoline.
Alcohol extended gasoline (gasohol) and other such gasoline based fuels are included in the defined
term fuel.
Diesel fuel and compressed gaseous fuels (LPG, CNG, etc.) are not included.

Happiness.
Use the Adobe search thingy for 'diesel'

Jim

[Dave Fleming]

Thanks Jim, I was not about to go cross eyed reading Federaleze, that's for sure!