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Old 17-12-2017, 11:06   #16
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Re: adding a permanent below decks gasoline tank?

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Originally Posted by S/V Alchemy View Post
I can't think of a single Atomic 4 installation I've seen with greater than, say, 15 gallons of gas in a vented locker. In fact, I reduced my own 12 Imperial (larger) gallon Monel tank to a 10 gallon (U.S.) Tempo (plastic) tank to gain space and the likelihood I would refuel more than once every couple of years.

Fifty (I presume U.S) gallons strikes me as a lot of gasoline to stow. My steel sailboat has two 50-gallon diesel keel tanks and a 10 gallon "daytank". That's about 1,100 NM of econo-cruising range.
My columbia defender originally had an atomic in it and has a 22 gallon factory tank which is mounted under the cockpit and open to the engine room. Many years ago my dads islander 29 had a similar setup but 25 gallons gasoline.
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Old 17-12-2017, 13:56   #17
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Re: adding a permanent below decks gasoline tank?

The last thing I would want below decks is petrol. During WW2 PT boats powered by the marine version of the Packard Merlin (Rolls-Royce design) had petrol as a fuel--and aviation petrol at that. It was the main fear of the crew that the vessel catch fire.

Petrol vapour is heavier than air. It has a low LEL and a comparatively high UEL, making it extremely dangerous stuff to take into an enclosed space.

If you must store fuel out of the weather, I suggest you make up some temporary tie-down deck lockers out of exterior plywood and epoxy resin and store your fuel in separate plastic containers rated for fuel in those. Lash down one on each side of the vessel, and line them with outdoors carpet to cushion the containers and stop them moving around, and allow for a little expansion when the temperature gets hot. Paint the lockers white. If you are concerned about the satbility such a mass might undermine--compensate by putting a couple of lead ingots above the keel, but on a 38 foot vessel the weight above water-line would not be too significant in my opinion.

Then you can use one fuel container from each side as needed and keep the vessel in trim. I suggest twenty litre containers--two or three to a locker edge by edge as that takes less deck space. It will cost you much less and save space below, and serve as a spray shield if they are alongside the cockpit..

The lockers can be made with lockable lids and they can be filled from a dockside bowser as required, or the individual containers can be lifted out and rowed to a fuel store.

Incidentally--diesel oil when combined with oxygen in the right proportions for complete combustion has about six times the expansion of an equivalent mass of nitroglycerine on expolosion. Petrol has about eight times--so I was taught when studying the construction of concrete underground structures.

If that does not give one cause for concern--think of the potential for agitation in a half empty tank at sea--
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Old 19-12-2017, 23:15   #18
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Re: adding a permanent below decks gasoline tank?

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You're ex Navy so you will know the risks, but I have to ask why so much petrol? two tenders and hopefully very far from anyone.
two tenders and hopefully very far from anyone.

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Sounds like a gasoline outboard is your main engine.
we have a 160 hp diesel as a main. the tank would go where a 8.5 Kw generator use to be.

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Originally Posted by GordMay View Post
ABYC H-24 / 46CFR 182.455c GASOLINE FUEL SYSTEMS (see 24.10 etc) ➥ https://law.resource.org/pub/us/cfr/....H-24.1993.pdf
Thanks ill read up!
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Old 19-12-2017, 23:29   #19
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Re: adding a permanent below decks gasoline tank?

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Unless it has internal baffles, I'd be really afraid of putting a tank that big belowdecks (or anywhere) on a sailboat. A half-empty 20-gal water tank did some serious shaking of a 27-foot sailboat I was on during a lumpy night at sea. I can only imagine what a half-full 50-gal tank will do in a seaway.
true but it theres 400 gallons of water and 300 gallons of diesel in the keel along with 12000 pounds of lead.

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Thoughts ? Only if fume detection was incorporated. Another thought would be weight distribution.


Attachment 160654
will look into it thanks!

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Originally Posted by S/V Alchemy View Post
Fifty (I presume U.S) gallons strikes me as a lot of gasoline to stow.
we have an aluminum hull and carry about 300 gallons of diesel. range 1600 at 10 knots and 2200 at 7 knots with out sail
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Old 20-12-2017, 03:23   #20
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Re: adding a permanent below decks gasoline tank?

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Originally Posted by Enginerd View Post
true but it theres 400 gallons of water and 300 gallons of diesel in the keel along with 12000 pounds of lead.
Do those tanks have internal baffles?
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Old 20-12-2017, 08:02   #21
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Re: adding a permanent below decks gasoline tank?

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Do those tanks have internal baffles?
there are six tanks, five in use each hold just over 150 gallons and are have two baffles about 50 gallon sections.
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Old 20-12-2017, 18:11   #22
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Re: adding a permanent below decks gasoline tank?

^^I would do my utmost to keep the new tank as low as possible. There's a lot less movement down in the bilge than just a few feet above, and make sure the hold downs are absolutely bombproof. Half a tank of free surface sloshing around generates a lot of force. Aren't you afraid of smelling gas fumes in your living space?
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Old 20-12-2017, 19:14   #23
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Re: adding a permanent below decks gasoline tank?

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Originally Posted by Benz View Post
^^I would do my utmost to keep the new tank as low as possible. There's a lot less movement down in the bilge than just a few feet above, and make sure the hold downs are absolutely bombproof. Half a tank of free surface sloshing around generates a lot of force. Aren't you afraid of smelling gas fumes in your living space?
Hi, a properly engineered tank with foam instead of baffles will prevent the fuel from sloshing around, think race cars, the foam consumes very little of the space within the tank yet is re-markedly good at controlling movement of the contents within. A properly engineered and installed internal tank would not allow fumes to vent internally and would be extremely safe, once again, think race cars.
Probably wouldn't be cheap though, once again think race cars.
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Old 20-12-2017, 19:39   #24
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Re: adding a permanent below decks gasoline tank?

I wonder if anyone else noted that he sails a Deerfoot 62....

Isn't the design such that there is an isolated engine room? I imagine that outward vented space could be made for a tank. In any case there would be no fumes going to the bilge or living areas.

Also, 50 gal is only a really small portion of the total displacement. Even on deck placement would likely not touch the trim much.

Any thought to ask Steve about placement for that tank? He may have already drawn up plans.

Regards!
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Old 20-12-2017, 20:09   #25
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Re: adding a permanent below decks gasoline tank?

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Originally Posted by evm1024 View Post
I wonder if anyone else noted that he sails a Deerfoot 62....

Isn't the design such that there is an isolated engine room? I imagine that outward vented space could be made for a tank. In any case there would be no fumes going to the bilge or living areas.

Also, 50 gal is only a really small portion of the total displacement. Even on deck placement would likely not touch the trim much.

Any thought to ask Steve about placement for that tank? He may have already drawn up plans.

Regards!
yes they do ours was the first one and the located in the rear of the boat instead of the center. i think that we are going to read the regulations and make sure we have a monitoring system.

Thanks again guys. its great to bounce ideas of people with different views/opinions.
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Old 21-12-2017, 02:51   #26
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Re: adding a permanent below decks gasoline tank?

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Hi, a properly engineered tank with foam instead of baffles will prevent the fuel from sloshing around, think race cars, the foam consumes very little of the space within the tank yet is re-markedly good at controlling movement of the contents within. A properly engineered and installed internal tank would not allow fumes to vent internally and would be extremely safe, once again, think race cars.
Probably wouldn't be cheap though, once again think race cars.
Bob, are you saying that race cars are expensive? 'cos that was going to be my next low-budget hobby.
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Old 20-04-2018, 18:00   #27
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Re: adding a permanent below decks gasoline tank?

Specs on baffling tanks have existed for many decades. There is no mystery about how to build a tank of any given size that will be fine in marine use. 50 gallons is a small tank from the standpoint of the 62' Deerfoot the IP owns (nice boat by the way).

Enginerd, I'd suggest you buy a copy of "Boat Mechanical Systems Handbook" by Dave Gerr. He is an eminent yacht authority and this book will give you a great deal of good, clear and practical information on how to design and build your system. Every book Gerr has written is well worth owning.
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Old 22-04-2018, 03:01   #28
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Re: adding a permanent below decks gasoline tank?

I have designed and had built to Class Approval a gasoline storage tank for a Superyacht (Approx 500 gallons) for the smaller tenders.
The key issues are basically the same
#1....leak detection (Gasoline sensor and alarm specifically for gasoline to be installed)

#2....An Approved Safety Procedure in case of onboard fire.

#2 is the challenge for internal tank as according to Class , in theory you can always jettison Jerry cans on deck full of Gasoline.

In fact, one supper yacht had 6 mock liferaft canisters on upper deck for Gasoline storage.

In our case, at the stern, just forward of the steering flat an integral gasoline storage tank was welded to the hull, with a coffer dam space on 5 sides and airtight manhole access.

This coffer dam was fitted with a gas sensors to detect any minute leak and a constant readout of air quality was part of the Fire monitoring system.

Hidden Vents went to an upper deck external location and were normally closed except when transferring fuel.
We used a chemical air pump and nozzel hose that could be reversed to clear lines.

In case of a Fire, the coffer dam area was flooded with Seawater from a dedicated emergency pump, (with manual backup)

In case of a grounding, in the unlikely case that the fuel tank was punctured (protected by the Keel), .....as the bottom was part of the hull, it would safely leak into the Sea.

Pretty much do the same for Hellicopter fuel, although I think it more prudent to store in new sealed barrels that are opened only once and put into aircraft.
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Old 22-04-2018, 11:43   #29
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Re: adding a permanent below decks gasoline tank?

I would avoid plastic for inboard gasoline tanks. Instead fabricate from metal and vent space overboard.
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