Fuel tank baffle layout

RCAnderson

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Oct 5, 2011
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Due to a previous owner's lack of attention to boat storage procedures, the tank in my old boat is rusting from the inside out. I am going to fabricate a new tank from stainless steel. It is a 100 gallon rectangular tank with a 'V' shaped bottom. There is an access hatch to remove the tank, but the hatch will not come off until I remove the seats and the galley\storage lockers. What I am wondering is if there is a generally accepted practice of placing the baffles in the tank in any particular layout. I was originally thinking 2 baffles running fore and aft, basically dividing the tank into 3 equal sections lengthwise, and then staggering the crossways baffles, creating a bit of an odd tic-tac-toe pattern. Then I thought maybe I should run the baffles diagonally from corner to corner, but that might not be enough to keep the fuel sloshing to a minimum.
Any thoughts ?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Re: Fuel tank baffle layout

first, you can probably buy a new tank for less than building a tank unless you get killer deals on raw materials.

plastic tanks do not have baffles, many aluminum ones do not as well. some do. there is not much rhyme or reason to baffle placement other than to prevent fuel slosh
 

RCAnderson

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Re: Fuel tank baffle layout

I see that I can buy a 28 gallon v bottom tank right here on iboats for $390 on sale, which is not even one third the size I need, and about the same price as I pay for the raw material. I don't see very many ready made 100 gallon v bottom tanks for sale. I think I'm better off making one. The fuel outlet port in the tank is at the aft end, so maybe all I have to do is put a couple baffles around that to protect from fuel surging under acceleration, and maybe one baffle crossways just for stiffness. I'm just drafting the tank up now, I don't want to make any mistakes I will regret later.
 

Scott Danforth

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EddiePetty

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Re: Fuel tank baffle layout

...why not simply use fuel cell foam with cut-outs for the sender and supply line?
 

Chris1956

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Re: Fuel tank baffle layout

RC, My 63 gal plasic fuel tank has zero baffles, as did my 35 G aluminum tank. I therefore think they are overrated, and will serve to make it very hard to siphon water and dirt out of the tank. Fuel surge is not a big issue, just put the tank vent nipple in the front of the tank, and the fuel pickup nipple in the rear of the tank. The fill can be anywhere.
 

Georgesalmon

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Re: Fuel tank baffle layout

I would put one, or two baffels port to starboard at the 1/2, or 1/3 spots. (I can't spell athwartships) A half empty tank would have about 300 lbs of fuel sloshing back and forth. Thats what my 101 gal tank in a 26' starcraft had (2). As far as rules and regulations go, only the manufacturer has to abide by them, not the owner. However having said that, they are good rules with good reasons for them and I'm not sure how an insurance company would rule in an accident with a homemade gas tank. The reason that gas fuel tanks are so expensive is not so much materials and labor. A lot of the cost is for liability insurance because often a fuel tank issue results in serious consequense like death of everyone on board and certain loss of the boat. Many boat manufacturers don't make gas tanks just for that reason alone even though they may have the capability in house. Now if it were a diesel tank go for it.
 

RCAnderson

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Re: Fuel tank baffle layout

Thanks for the input folks. Scott, is there something I am missing in the AYBC or USCG regulations ? I have been through the Transport Canada regulations on fuel systems, which references some of the AYBC and USCG regulations, and it looks pretty straightforward to me.
 

Don S

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RCAnderson

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Oct 5, 2011
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Re: Fuel tank baffle layout

Thank you for that Don, it goes into a bit more detail on the different testing procedures. I will pressure test the tank of course, but am exempt from the other tests, because I am building a 'custom built metallic tank'. Interestingly, I didn't see anything in that document about 'custom built metallic tanks'.

This from Transport Canada Regulations :
7.3.1.2 A custom-built metallic tank does not need to undergo the fire resistance test, shock test, pressure-impulse test and slosh test. However, it shall comply with the pressure test as per ABYC H-24, ABYC H-33, or an equivalent standard for mechanical strength and leakage.

Is there an equivalent regulation from the USCG or other governing body in the States ? As far as I can tell, most of the nautical regulations are pretty much identical between our two countries.
 

Don S

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Re: Fuel tank baffle layout

I agree you are exempt from a lot of it, but it does give information and things you should think about.
I doubt there is any info on baffles and placement. You just want to stop large amounts of fuel from sloshing around, yet any fuel and water makes it to the back of the tank and not trapped behind a baffle somewhere.
 
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