Small assymetric catamaran

Discussion in 'Multihulls' started by rosbullterrier, Jan 26, 2010.

  1. rosbullterrier
    Joined: Feb 2005
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    Location: Cornwall, UK

    rosbullterrier Junior Member

    Small asymmetric catamaran

    I'm building an asymmetric 4mtre catamaran. The hulls will have 8" flat bottoms to rise in the water but not plane.
    After reading many opinions regarding the virtues of flat vertical inside hull sides, it still has not been described how this configuration would affect the steering or speed and what the hull spacing should be - for this application.

    This catamaran is not for sailing but fitted with small Seagull engines. The motors are to be situated mid (through) hull, behind each crew.

    I need to know is whether there would be bow waves at speed up to say, 15mph, between the hulls if they are straight vertical sided.
    Certainly I can, and will, build it and experiment; I'm just trying not to reinvent the wheel or have to repeat your valuable experience!
    If it were a planing boat it would be different; it's the possible wave resistance or intereaction to determine the possible benefit of vertical inner hulls . . .
    ps my last post was 'moderated' to Powerboats. It got no response there. This is a multihull question!
     
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  2. redreuben
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    redreuben redreuben

    1 person likes this.
  3. rosbullterrier
    Joined: Feb 2005
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    Location: Cornwall, UK

    rosbullterrier Junior Member

    Thank for your reply redreuben, unfortunately 'Small asymmetric catamaran' returns me straight back to my own question and your second site http, I have already seen - only shows pics of sailing boats which would not answer my query . . .
     
  4. redreuben
    Joined: Jan 2009
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    Location: Beaconsfield Western Australia

    redreuben redreuben

    rosbullterrier,

    Bernard Kohler is probably the most knowledgeable exponent of asymmetric hulls on the web, mail him your question.
     
  5. basildog
    Joined: Dec 2008
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    Location: Gold Coast Australia

    basildog basildog

    As stated in the last post, you can mail him he does have a forum shown at his web site. It is very active and he does respond to queries there.
     
  6. rosbullterrier
    Joined: Feb 2005
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    rosbullterrier Junior Member

    Thank you gents . . .
     

  7. ThomD
    Joined: Mar 2009
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    Location: TO

    ThomD Senior Member

    I'm a little confused, your flat on the inside and curved on the outside? That is the reverse of sailing cats, though I don't know why you want either with a motorcat. Also, why would you want to semi plane. That sounds like a lot of work. I made a small motor cat, and it just turned out as it turned out. There were few real problems that I just set about to fix the next year. So possibly less bad is likely to happen than you might expect. When in doubt build a model and tank test it in a river or dragging in a pond.
     
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