Empirical Formulas for Catmaran passenger ship

Discussion in 'Boat Design' started by Tasnel Tayyar, May 4, 2020.

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  1. Ad Hoc
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    Ad Hoc Naval Architect

    When I was a student, I also struggled to get a basic idea of the main parameters and thus - where to start.
    I found several magazines that listed every high speed vessel that was built that year and the previous years, going back 10 years. I collated the data into a simple spread sheet, with L, B, Pax Speed etc.
    This was very laborious as excel and desk top PCs didn't exist in those days. But this is a simple exercise that you can now do, from those links noted above.

    Also, as a young Naval Arc at the time, the paper Design Tools for High Speed Slender Catamarans also provided some basic guidance. It is a now little dated, but it still a good reference tool, for starters to get you to a beginning frame work of a design! If you use the data you collect from those links, and then add them to the ratios in the paper, you'll have a very good up to date database of ratios, for starting a design.
     
    Last edited: May 6, 2020
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  2. rxcomposite
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    rxcomposite Senior Member

    Passenger Ferries are considered Volume based design. Consult Practical Ship Design by DGM Watson for details. The book says you should allot 1.1 m2 for each seated pax but there are more rules that governs it. Statutory rules have a much detailed rule for seating arrangement like definition of economy and luxury seating.

    For example, in economy seating, the minimum is 18" (460 mm) pitch or abreast seating and 36" (900 mm) spacing of rows. That gives only 0.414 m2 allotment for seats. The arrangement of seats is also regulated as to max number of seats abreast is allowed before the service aisle. There is also the maximum spacing of rows to allow for ingress/egress and pathways for emergency exits. Don't forget the number of heads (comfort rooms) required.

    Given that Passengers are lighter per volume displacement, a second (or third) tier must be considered to increase density. The addition of a tier will require a stairway, thus added space.

    When you have drawn the layout for seating arrangement following the pitch and spacing to fit the 400 pax capacity, then you can proceed with weight analysis.
     

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  3. Ad Hoc
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    Ad Hoc Naval Architect

    For passenger SHIPS...yes, but not for high speed catamarans.
    It is generally dictated by the area required!
     
  4. rxcomposite
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    rxcomposite Senior Member

    Thank you AH but that is my explanation. I focused on how to compute the area requirement. Of course, the headroom requirement will translate to volume.
     
  5. Ad Hoc
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    Ad Hoc Naval Architect

    Only for passenger SHIPS.

    Passengers in cruise liners and ships etc are situated IN the hull - the single hull too. Not ontop of the hull, which is the situation with a catamaran.
    The passengers are on decks above the main hull. The hull in a catamaran is merely providing the buoyancy (to carry the weight) and means to locate the engine and method of propulsion.... in a nut shell.
    That's why a catamaran - for passengers - is dictated by the deck area, not volume.
     
    Last edited: May 6, 2020
  6. rxcomposite
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    rxcomposite Senior Member

    AH- The title of the chapter is "Volume, Area and Dimension-Based Design". The first part of the article which I posted deals with areas and contains useful info on how to layout the deck area. It is only in the later pages did it deal with volumes which I did not include.

    The preceeding chapter dealt with Weight Based Design which is density/volume driven.
     
  7. Tasnel Tayyar
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    Tasnel Tayyar Junior Member

    As you said I saw that the lightship and full load weights are close to each other and I already started doing that! Lastly thanks for advice again I really appreciate that for all your answers
     

  8. Ad Hoc
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    Ad Hoc Naval Architect

    Indeed it is. But the reference is for monohull SHIPS, which house the passengers inside the hull to maximise their earning capacity. Hence it being a "volume".

    A catamaran of 30-40m will not have any passengers in the hull at all; they are above the hulls on a deck. Ergo = deck area, not volume. :D
     
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