searching for catamaran using waterjet propulsion

Discussion in 'Powerboats' started by tsuji_kenji, Sep 13, 2011.

  1. tsuji_kenji
    Joined: Jan 2011
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    Location: malaysia

    tsuji_kenji Junior Member

    hello all...im student from from malaysia that are searching catamaran using waterjet propulsion system..hope that 'old timers' can help me...
     
  2. Steve W
    Joined: Jul 2004
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    Location: Duluth, Minnesota

    Steve W Senior Member

    many of the large catamaran ferryboats have waterjet propulsion, not sure why!
     
  3. Ad Hoc
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    Ad Hoc Naval Architect

    More effecient than a prop and able to offer a lower draft and run in shallow waters too.
     
  4. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    I was under the impression that they were less efficient than props,that would make sense then but all the ferryboats ive seen dont need shallow draft as they operate from deep water docks.
    Steve.
     
  5. Ad Hoc
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    Ad Hoc Naval Architect

    The crossover threshold is around the 20-25knots. Below, prop is best, above waterjet.
    Typical effiiciencies around 0.65 for a waterjet, compared to 0.45-0.50 typ. props.

    But most fast ferries are "generally" of a low length displacement ratio hull form which also lends itself to a waterjet propulsion too.
     
  6. masalai
    Joined: Oct 2007
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    masalai masalai

    How does the performance in "water-jet drive" compare to "surface drives" in the 25 to 30 knot region?
     
  7. tsuji_kenji
    Joined: Jan 2011
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    tsuji_kenji Junior Member

    thanks for all corncerns...im very appriciate...my new question,what is the best method to calculate total resistance for catamaran?is it Molland and Insel or Holltrop..or both?
     
  8. keysdisease
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    keysdisease Senior Member

    Attached Files:


  9. Alik
    Joined: Jul 2003
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    Location: Thailand

    Alik Senior Member

    Molland works for round bilge hulls only. For sharp chine hulls we use:

    For semi-planing range:
    - VMB 89' systematic series (Muler-Graf);
    - Pham method based on regression analysis of CFD data.

    For planing range:
    - Savitsky with doubled resistance of one hull, pls additional factors such as extra friction (due to wetting of tunnel) and hulls interaction factor.
     
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