Gas on boats?

Discussion in 'Boat Design' started by Starfish, Jun 11, 2008.

  1. Starfish
    Joined: Feb 2008
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    Location: RI

    Starfish Junior Member

    I'm still working on a new design. (getting the ideas together)
    I have run into a snag. I want the sailboat to carry a surface
    air supply for Hukkha diving. It is about 60 lbs total.

    My plan is to do remote diving with this boat, and i will need to carry
    gas (while around dive spots). I would like to carry 20 gallons.

    I have had a few ideas (none I'm thrilled about)

    Carry fuel in 4- 5 gallon jerry cans, with under seat mounting for all 4 cans
    BOTH SIDES. This way i can use the fuel as ballast. But i will be diving in warm areas, so I'm worried about fumes/heat.

    I could just build in a 20 gallon tank, but its not movable, and i need to pump
    fuel up to a can anyway. Not sure i like having elec. around gas....


    So i guess the question is, If you knew for sure you had to carry 20 gallons of
    gas on the boat, which method would you opt' for? I really like the movable
    option, for ballast, but need suggestions on how to make the storage areas safe. i would guess a blower with a fire system, using military spec. steel jerry cans?

    Suggestions welcomed!


    Thanks
     
  2. bntii
    Joined: Jun 2006
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    bntii Senior Member

    Different rats for different cats..

    But have you run the numbers on installing a dive compressor?

    Skip the tie in to a hukkha?? Just fill your tanks and go. Or just free dive- more fun and less junk.

    On topic- on my boat I don't buy any argument for lashing bunches of jerry cans on deck. Just install a tank below decks and pull up the fuel with a manual pump.
     
  3. Starfish
    Joined: Feb 2008
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    Location: RI

    Starfish Junior Member


    Thanks, I had thought about the same type of thing, but i really like the idea
    of movable ballast. But again worried about the fumes/gas in the back of the boat. I should have said, this is a light displacement sailing boat (plan) along the lines of a mini 6.5 class racer. But around 33'. So it will have a water ballast system in the boat. I could use the fuel to supplement the ballast.
    I guess i could look at using the manual pump to switch the fuel from one side to the other....I need suggestions on the RIGHT way to install fuel into a boat, avoiding any problems with fumes/spark/over heating????
    With advice on gas in hot tropic weather, things to look out for above the obvious.
    I cant carry tanks, i plan on diving very remote places, wish i could!
    Hukkha = about 80 lbs + fuel total
    scuba = 100 lbs + fuel + 4 dive tanks Much more weight. Not to mention the 25 mins per fill and much higher
    gas usage per dive. So scuba out of the question on this size boat. I love free diving, but lets face it,
    There is always that time that you just need to go to 80' to see that huge coral. I love doing both.
    A good hukkha system will give 2 divers 80'++. The system will be two hoses, 150' each. diving with SS back plate
    (ultra small back plate) carrying a very small bail out tank (25% the size of a Alum. 80) Bail out bottle will be bail out only,
    and wont tie into the hukkha system at all. (for all you divers out there :D )




    Thanks
     
  4. charmc
    Joined: Jan 2007
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    Location: FL, USA

    charmc Senior Member

    If you decide a hukkaha system is really your best choice: Install a permanent fuel tank, low and centered, according to all USCG safety regs for boat builders. Jerry cans may be OK for diesel, but they are much too dangerous for gasoline.

    However: Diving on compressed air to 80' and below limits bottom time if decompression is to be avoided. A tank imposes a limit, making it more difficult to exceed safe bottom time. A hukkha is usually used for shallow water diving, where bottom times up to several hours pose no danger of getting bent. Since it provides unlimited air, there is more danger of the divers becoming preoccupied, getting slightly narc'd, or exceeding safe bottom time for any reason. Unless you are planning a decompression dive, it would be safer to carry tanks and use one for each dive.

    Just my opinion, but I've seen even experienced divemasters get careless about bottom time because their thinking got a little sloppy down below. It affects everyone a bit differently, and can start at depths as shallow as 60' for some. Computer warnings are no better than looking at a watch; if the diver does not act on the information, there will be a problem.
     
  5. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    I'm building something similar (33' MS for remote diving) I'll go with a conventional hp compressor and tanks. I've no doubt's Hukkha diving wouldn't work but, you got to fill your bailout tanks sometimes too, and I'd rather rely on filled Al80 than a "lawnmower" engine :D
     
  6. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    I would go with the 6 gal tanks that smaller outboards use.

    There tight when closed and built to transport roughly.

    The biggest advantage is there EZ to use to refill the gas tank on your car.

    Since the new weak Ethanol garbage gas pulls water out of the air its service life is about 1 month , at best.

    With rotating cans , and a marking system you can toss the trash gas into your car , where it will hurt you least.

    FF
     
  7. Starfish
    Joined: Feb 2008
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    Location: RI

    Starfish Junior Member

    Well you have a point, and i have been going back and forth on it. I add weight
    by using the Compressor, i still need gas (more) i could use the tanks as ballast.
    The boat i plan is light displacement. I really hate having that hose on me for sure. I'm 'not' worried about the lawnmower engine....It's made by Honda!:D
    The bail out is for one reason, to make it to the surface, if it is used, it was
    in a out of air emergency, and i can deal with getting it refilled if that is ever needed. Both ideas have good reasons. My way of thinking:

    I can have two hukkha systems on board with 4 hoses, the same amount of gas, one is a back up system. for the weight of one compressor. and 80's
    only 3 20's (one back up bail out) hard decision. Two people diving....


    The person above made some good points about the higher bottom times with
    surface air supplied. And he's 100% right, My scuba teacher in FL yrs ago,
    was a Cave diver (basket case IMHO :D ) But a great diver. So with his training, i go a bit overboard with my diving. I carry deco times on wrist,
    I do plan dives up top. I'm picky about who i dive with also.
    I'm kinda anal about my diving, i like to live. My equipment is back plates
    and steel 80's HP. I use little weight, and a 18# bat wing. Point is,
    hes right, some family using this thing to me is scary, the family models have 60' hose's so not so bad. Maybe i should just scrap the whole air idea, and get a Buddy rebreather and be done with it. Carry a few bailout bottles.
    HUMMMMMM i love rambling, makes ideas flow! :p Too bad i can't carry a o2 system with it....
     
  8. ted655
    Joined: May 2003
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    Location: Butte La Rose, LA.

    ted655 Senior Member

    Go with the 5 gal. cans. Under fill them to keep heat expansion from bulging the sides. Keep them exactly as you planed. in or under some protected area in an upright position.
    I carry gasoline this way, & have never had an issue. The new, self venting spouts are far safer than the older, vented cans. Your instincts are right, the versatility is important in ways you haven't thought of yet.. If you need a full 20 gal., then design for 5 jugs.
     
  9. TeddyDiver
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    TeddyDiver Gollywobbler

    Well now you saying that.. I've done a bit day dreaming about o2 and Nitrox on board. Membrane systems are so darn expensive and they are only for Nitrox (actually there are some producing 95% O2 & 5% Ar but they have other drawbacks). Having a windmill and/or panels to run electrolyser continously is another way. Having both O2 and H2 on a boat doesn't however sound sound...:D
     
  10. Starfish
    Joined: Feb 2008
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    Starfish Junior Member


    Man if i could get a safe ultra light weight o2 system onboard, i would just dive
    rebreathers. And be done with it. But O2 in the 90's Farh. no thxs! :p
     
  11. Loveofsea
    Joined: Jan 2007
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    Location: Southern California

    Loveofsea New Member

    The good skiff uses portable poly tanks that nest under the deck for a total of 54 gallons. I can change the positions of the the 4 12 gallon tanks to maintain the optimum weight distribution depending on the seas. Into the wind--heavy bow, away from the wind, light bow...

    when i make the run to the bank 100 miles offshore, i put a couple of 5's on the deck and it has never been a problem.

    I have to disagree with the gentleman who said to leave some room for the gasoline to expand. It has been my experience that the vapor in the tanks expands to a much greater degree than the liquid. For that reason, i always fill my poly gerry cans as full as i can get them. Empty poly tanks blow up like a baloon if they are not vented.
     
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  12. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    I guess the plan is to have nobody on top while two divers are down. I've never done much diving, but is that a normal procedure, especially when in very remote areas?

    If you do have two diving and one on top, or maybe even just two people total, you have a crowd for very remote places considering all the other provisions you will need, food, water, etc. Maybe you should consider a multihull. Catamarans are a wonderful invention.

    Pumping fuel every time you wanted to change tack eliminates that idea. If you had to tack in an emergency with no time to move fuel, you might fall over.
     
  13. TeddyDiver
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    TeddyDiver Gollywobbler

    It's not normal but some do it, and some are doing it solo....
     
  14. SamSam
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    Location: Coastal Georgia

    SamSam Senior Member

    A friend was always going solo. He told me one time in murky water a big sharks eyeball appeared directly in front of him within arms length. It didn't seem to bother him much, but it made me wonder if maybe his balls were too big or his brain was too small.
     

  15. Starfish
    Joined: Feb 2008
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    Location: RI

    Starfish Junior Member


    I would always have one with the boat (topside) no matter what...
    So the plan would be 3 people. But that makes it tight. But i would never
    dive without a person above. That would IMHO be super stupid in a remote location.
     
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