Resistance prediction methods/series for catamarans

Discussion in 'Multihulls' started by Roni, Jul 8, 2020.

  1. Roni
    Joined: May 2020
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    Roni Junior Member

    Hi there,

    I am looking for resistance prediction methods/series for catamarans around 10 m lenght, 6 ton displacement and 10 knots of speed (Froude number around 0.52). Any recommendations?

    Thanks
     
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    You can try HERE as this excellent research may give you a good first indication.
     
  3. Alik
    Joined: Jul 2003
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    Alik Senior Member

    We use following methods:
    - Molland series - see link from AdHoc, for round bilge shapes
    - Muller-Graf series - for semi-planing catamarans with chine
    - Savitsky planing method with hulls interaction factor - for planing catamarans
    - For narrow and light hulls, there is 'slender hull' method, this is originally a graph published by Doubrovsky in his book. However use with care, as comparing with tank tests seems the method underpredicts the resistance.
     
  4. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Which is also available HERE.

    But with these parameters, the M-G series is generally outside your scope. But may offer you some guidance in addition to the Molland paper.
     
  5. Richard Woods
    Joined: Jun 2006
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    Richard Woods Woods Designs

    10 knots on a 10m powercat is only just over the hump speed. So it would be best to either aim for displacement speeds of under 8 knots or go for mid teens as a minimum speed.

    see here for an example of one of my home built designs in that size range



    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  6. Roni
    Joined: May 2020
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    Location: Brazil

    Roni Junior Member

    Thanks a lot everyone, will have a fun weekend studying.

    Yes the froude number is 0.52. Maybe at around 0.4 (~8kt) would make more sense.
     

  7. Dolfiman
    Joined: Aug 2017
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    Location: France

    Dolfiman Senior Member

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