gas tank vent - sailboat

[CLK]

Hi:
Our International 500 sailboat has recently been rebuilt. The International 500 was designed by Robert Henry in the early 1960s - it's about 32 feet long, has lines very much like an Alberg 30, and ours is rigged as a yawl.
Among other things, we have a new gas tank (stainless steel). There are a couple of questions:
What material should we use for the air vent line from the tank? We think it needs to be rigid to avoid low spots in which gas might collect... but metal? or something else? And if metal, stainless like the tank?
The other question is where it should be vented to. The old outlet was inboard, at the aft end of the cockpit (at deck level). It's been suggested it should be moved to exit through the hull instead, so fumes will be outboard. My concern would be the risk of spilling gas/getting water into the tank in high following seas, etc.

Any advice would be most welcome. Thank you in advance.

[Candyfloss]

The real thing petrol hose is best. You should be able to get it from an automotive parts retailer. Ensure that when you route your hose it runs uphill all the way, even with the boat at extreme heel. Venting into the cockpit as high up as possible is pretty normal. I'm not sure about thru the transom. Definitely not thru the hull.

[SamSam]

Rigid is not a good idea, vibrations or movement will break it.

You might want to look into this, to see if it effects insurance at all. I'm not sure what current practices are, but it used to be welded stainless steel tanks became brittle along the welds and could crack after prolonged vibrations.


ABYC has now approved stainless steel for diesel, but not for gasoline fuel tanks.http://books.google.com/books?id=euQZ16elT5kC&pg=RA1-PA83&lpg=RA1-PA83&dq=marine+fuel+tank+materials&source=bl&ots=dmVuGRviPp&sig=CeRPPUxYtnIoIT8mKxXnSy5iK4I&hl=en&ei=dJuNSv_GJtSQtgfUnuCBDg&sa=X&oi=book_result&ct=result&resnum=5#v=onepage&q=marine%20fuel%20tank%20materials&f=false


.

[rbgarr]

Unless your permanently installed stainless tank is cylindrical with domed heads and less than/equal to 20 gallons it won't pass an insurance survey if the surveyor adheres to ABYC Standard H-24, which is why most fuel tanks are aluminum or linear polyethylene now. The vent should have a flame arrestor (screen fitting) and be located at least fifteen inches from any ventilation opening to an accommodation space (i.e., a companionway or opening port). Sailboats sometimes need two vents, one each port and starboard depending on the size, location and/or orientation of the tank so it will vent at all angles of heel. You don't want a vent leading to the cockpit, or inside the boat as noted in H-24 even if the cockpit is self-bailing. They are rarely watertight enough (or remain forever watertight enough) to prevent an accumulation of fumes from migrating to the bilge. No check valves either.

Portable tanks for outboard motors have different standards.

[donald branscom]

Hi:
Our International 500 sailboat has recently been rebuilt. The International 500 was designed by Robert Henry in the early 1960s - it's about 32 feet long, has lines very much like an Alberg 30, and ours is rigged as a yawl.
Among other things, we have a new gas tank (stainless steel). There are a couple of questions:
What material should we use for the air vent line from the tank? We think it needs to be rigid to avoid low spots in which gas might collect... but metal? or something else? And if metal, stainless like the tank?
The other question is where it should be vented to. The old outlet was inboard, at the aft end of the cockpit (at deck level). It's been suggested it should be moved to exit through the hull instead, so fumes will be outboard. My concern would be the risk of spilling gas/getting water into the tank in high following seas, etc.

Any advice would be most welcome. Thank you in advance.

Yes there are Coast Guard and other rules about this.
Use stainless tube and it has to be 1/2 minimum.
Best place to bring it to is the highest point on the cabin next to the companion way and make sure it has a u turn downwards at the very top. Hide it next to a piece of trim or something. A one way check valve is good too.

[JimD]

Welcome to the forum. I see you are from Toronto? Canadian regs may be different from American. Check with our own agencies to be sure about what is legal if you haven't already.

[CLK]

Hi all:
Thanks for all the help. Dumb mistake in my first post - the tank is, indeed, aluminum.
Cheers,
CLK

[D Happ]

I realize you are in Canada and this doesn't apply, but here is a link to the U.S Coast Guard Boatbuilder's Handbook. Lots of useful information and explanations.
Boatbuilder's Handbook (http://www.uscgboating.org/safety/boatbuilder/index.htm)

[Hwyl]

I mostly deal with diesel, I've seen vents on dorade boxes as well as outside cockpit coamings and in one case, in a stanchion (file under, great idea in theory, awful in practice)

[Todd D]

I would suggest fuel hose. Mine is 3/4" fuel hose led to a vent fitting on the outside of the cockpuit coaming. The vent fitting is oriented so that its opening faces aft.

[Bill Huson]

About that "fuel hose." Do not use automotive fuel hose. Canada rules may differ, but the USCG requires fuel line that is USCG approved. I have examined the structure of USCG line and standard auto line and there is a difference. Yep, USCG approved line costs more but tis better than a *BOOM*.

[Candyfloss]

Yes there are Coast Guard and other rules about this.
Use stainless tube and it has to be 1/2 minimum.
Best place to bring it to is the highest point on the cabin next to the companion way and make sure it has a u turn downwards at the very top. Hide it next to a piece of trim or something. A one way check valve is good too.

Stainless tube? You must be mistaken. Surely no-one requires stainless tube.

And I wouldn't want mine on the outside of my cockpit coamings either. I get a lot of spray on my weather deck on a heavy beat & it runs along the coaming & across the stern deck..I think a copy of the requirements for your local area is a good idea. Here in NZ the New Zealand Yachting Federation publishes a booklet listing the requirements for Categorys 5 (inshore use only, trailerboats) to Category 0 (Round-The -World raceboats). Build to the highest standard you can afford, or will be using your boat for.

[Tylerdurden]

Poly tubing rated for fuels is trick to install for vent line and keep withing the ID specs. I am not a fan of rubber line as kinks are easy.
The poly fittings never corrode and stuffing stainless scrubby pad into a fitting will make a good flame arrestor and keep mud daubers from clogging the line.

http://www.megaflex.co.uk/templates/ja_xenia/images/sample_image.gif

[D Happ]

A one way check valve is good too.

Donald, a check valve is not a good idea. The tank needs to breath in and out. In when using the engine, and out when filling the tank.