deadweight coefficient for tugboat?

Discussion in 'Boat Design' started by mecmec, Sep 2, 2012.

  1. mecmec
    Joined: Aug 2012
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    Location: philippines

    mecmec Junior Member

    what is d typical deadweight coefficient of a tugboat? for thesis. :D thanks!
     
  2. rxcomposite
    Joined: Jan 2005
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    Location: Philippines

    rxcomposite Senior Member

    Mecmec,

    First, let us start right. Deadweight is the weight you put on a boat to make it operational. Displacement tonnage is the weight of the boat in water which could be Light displacement or Full displacement. You will not be able to design the boat using only deadweight.

    Here are the definition from Wiki.

    "Deadweight Tonnage refers to the carrying capacity of a vessel. Deadweight tonnage can be figured by taking the weight of a vessel which is not loaded with cargo and subtracting that figure from the weight of the loaded vessel.

    A vessel that weighs 2000 tons with crew and supplies takes on 350 tons of cargo in port. The deadweight of this vessel would therefore be 350 tons.

    Displacement Tonnage is the actual weight of a vessel. The term is expressed as a displacement weight in order to reflect the amount of water which is displaced by the vessel's hull. The draft of a vessel can then be used to determine the weight using markings on the hull called load lines."

    Second, since you are in the Philippines, get a copy of the Philippine Merchant Rules and Regulations (PMMRR) published by Maritime Industry Authority (MARINA). You have to know this by heart as you will not be able to pass your Professional Engineers (PE) exam with only a partial knowledge of the rules.

    PMMRR rules says you are designing under Class D "Tugs and Dredgers" but you have to define further your Statement of Requirements (SOR). Is this a push/pull tugboat designed to operate continously or a harbor tug designed to assist only the docking and undocking of vessel?

    The Philippines is a signatory to International Association of Classification Societies ( IACS), so further down the line, we will be discussing Class Rules by which this forum contains a wealth of information and a lot of knowledgeable members.
     
  3. rxcomposite
    Joined: Jan 2005
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    rxcomposite Senior Member

    One other approach is to calculate the Equipment Number of the ship and plot the optimal weight (given in a table) of the structures, engine/gearbox, steering, amenities, outfitting, armaments, ect. You will get the optimally designed light weight of the ship.

    Next would be to define your mission range so you would know the deadweight (fixed and consumables on board) to make the ship operational.

    For a very rough estimate, the lightship should be about 40% of the total weight.
     
  4. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    Perhaps the table below can help.
     

    Attached Files:


  5. rxcomposite
    Joined: Jan 2005
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    Location: Philippines

    rxcomposite Senior Member

    Sorry none for the tugboats. Here are some.

    Typical Deadweight Coefficient Ranges
    Vessel Type Cargo DWT Ctotal DWT
    Large tankers 0.85 – 0.87 0.86 – 0.89
    Product tankers 0.77 – 0.83 0.78 – 0.85
    Container ships 0.56 – 0.63 0.70 – 0.78
    Ro-Ro ships 0.50 – 0.59 -
    Large bulk carriers 0.79 – 0.84 0.81 – 0.88
    Small bulk carriers 0.71 – 0.77 -
    Refrigerated cargo ships 0.50 – 0.59 0.60 – 0.69
    Fishing trawlers 0.37 – 0.45 -

    Where:
    C = (Displacement or Total DWT) /Displacement
     
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