Barge questions

Discussion in 'Boat Design' started by Magnus W, Oct 25, 2019.

  1. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    I just thought I would post a few photos of the power cat that was built here using large diameter steel tubes as a basis for the hulls.
    It doesn't take an awful lot more work really to convert a very hydrodynamically horrible & inefficient pipe (with closed ends) into something that is reasonably 'boat shaped'.
    The hull bottoms are built from half a pipe split longitudinally, and the main cross beams connecting the hulls are smaller diameter tubes. DSCF3513.JPG DSCF3514.JPG DSCF3515.JPG M C Buccaneer at Sandy Lane.JPG
     
  2. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    If cutting and welding are available, then how about making a displacement barge out of longitudinal sections of your pipe?

    It's a lot of cutting and a lot of welding:
    Cut a 1/3 section, 12 meters long, leaving a 2/3 section, 12 meters long.
    Two of the 2/3 sections are your two gunnels.
    The remaining two 1/3 sections are welded between them forming a "bumpy" hull bottom.
    The 2 remaining pipes could be sectioned to provide six 1/3 sections to widen the hull.
    Three pipes sectioned this way could yield a barge width of about 5.7 meters.
    It would be 3/4 the weight and close to double the buoyancy.
    7 long cuts, 6 long welds.

    Just brainstorming.
     
  3. Magnus W
    Joined: Nov 2017
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    Magnus W Senior Member

    Now I have some info on the pipes, they have an OD of 1118 mm and a 12,5 mm thickness. There are three 12-meter pipes available so 36 meters in total.
    With a mass of 347 kg/m and a volume of 982 l/m I get a empty barge mass of 17,3 tons (including superstructure) and a buoyancy reserve of 18 tons if I make four 9-meter pipes and a barge with the dimensions 9 x 5 meters.
    It's not going to be a transport barge per se but I'll put a crane and hydraulics on it as well as support legs which will add around 4 tons to the empty mass.

    How bad will a barge made like this be?


    Save for cutting up the pipes and do substantial cutting and welding, what can be done to make it better? Spacing the 2 and 3 pipe somewhat, making the dimensions 9 x 6, has been mentioned and it will "only" and 1000 kg to the superstructure mass.



    (I like your idea BlueBell but in terms of labour I'd be better off building a "proper" barge. Plus I don't have the facilities for that kind of manufacturing.)
     
  4. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    If using4 tubes.
    Two stacks of 2 tubes would be more stable but deeper draft than all four tubes laid out horizontally.
     
  5. Magnus W
    Joined: Nov 2017
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    Location: Sweden

    Magnus W Senior Member

    I'm trying to wrap my head around the stability issue.

    I can put XPS between the pipes and the deck to add buoyancy. How much (ie how thick) should the XPS be in order to counter the accelerated lift from the rising pipe(s) as they rise as the barge lists (see pic)?
    Untitled.png
     
  6. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Magnus,

    347 kg / 982 kg = 0.35
    Over
    1/3 loaded in steel pontoon mass alone!

    There are too many unknown variables to comment further.
    You'll get a lot more input if you post a Statement of Requirements for what you need the barge to do.
    Example: Towing? Speed, distance, sea conditions likely to encounter? Or, maybe it won't move?
    Power? Self propelled? Towed?
    Crane work? Loading? Reach? Weight? Travel tracks? Moment arms?
    These are just examples of some of the info we need.

    At this point we are mostly guessing at what you need and what is needed.

    Maybe you'd be better off Googling barge design.
    Good luck with your adventure.
     
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  7. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Magnus,

    Would a square barge work for you?
    How much draft is allowed?
    You mentioned beaching to load and unload presumably...
     
  8. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    1/3 loaded, plus the deck, etc. is too much. Round pontoons are not supposed to be loaded past 50%, because the buoyancy rapidly decreases above that. That means that above 50%, it becomes very tippy. If you price welding rods, the cost of piecing together a barge is not a bargain, even with free pipes. Do a cost analysis of what buying steel for a proper boat would cost. Also, compare it to the cost of a used boat or barge in fair condition.
     
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  9. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Warning:
    36 meters is 12.5 Tons of pipe mass, an additional load of 5.4 Tons would be 50% of max buoyancy.
    Exceeding 33% loading without knowing all the variables of operation is foolish, especially with a crane on board.

    Square:
    A 6.5 meter by 6.5 meter barge would use up two rows of pipe in a double perimeter fashion.
    Top view would be a square inside a square.
    This would leave a 2 x 2 meter square hole in the centre ( could be handy for mooring or recovery work ).

    How it Works:
    The outer square would use 5.5m sections ( overlapping on one end, resulting in a 6.5m span ) times 4 sides = 22m of pipe.
    The inner square would use 3.5m sections ( overlapping on one end, resulting in a 4.5m span ) times 4 sides = 14m of pipe.
    Or you could miter the corners and weld them, but that's going to reduce your barge to 5.5m x 5.5m.
    Bringing the deck edge in 0.5m to the tops of the pipe rounds would help reduce loading and moment arm ( heeling ).

    That uses up all 36m of pipe and reduces your rollover risk, but by no means eliminates it.
    And it does nothing to address your serious lack of reserve buoyancy, given the round cross-section of pipe.
    Oh, and it would tow the sh*ts, but I don't know if that matters to you.

    Are you ready to consider vertical sections of pipe?
    It would eliminate the diminishing buoyancy effect of horizontal, round pipe.
    You could consider leaving the bottoms open... less welding... less weight...
     
  10. Magnus W
    Joined: Nov 2017
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    Magnus W Senior Member

    Thank you for all the time invested in replies. I've decided to pass on the pipes. Or rather, I'm passing on building a barge with the pipes a buoyancy, I might still collect them and do something else with them.

    It seems I'm better of simply buying one.
     
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  11. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Re buying a second hand barge, that sounds like an excellent idea!
     
    BlueBell likes this.
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