What is the rule or criteria of stability for car-topper boat design?

Discussion in 'Stability' started by jimianbu, Sep 5, 2010.

  1. jimianbu
    Joined: Jun 2009
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    Location: Manjung, Perak, Malaysia

    jimianbu Junior Member

    What is the stability criteria or rule for car-topper type of boat? Is there any rule to check the stability for the car-topper boat design? TQ.
     
  2. portacruise
    Joined: Jun 2009
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    portacruise Senior Member

    Boat must hold fastened car top position without shifting, sliding or breaking loose at maximum speed?

    Porta

     
  3. jimianbu
    Joined: Jun 2009
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    jimianbu Junior Member

    No sir, I mean, the stability on water, not on top of car. Sorry for the inconvenience. Is there any rule for that?
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    No there are no rules as you suggest Jimianbu, though common sense does play a fairly big role.
     
  5. jimianbu
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    jimianbu Junior Member

    I see. So the stability criteria or rules for 10 to 15ft (small boat), isn't available and just use common sense? So, how to determine whether the design is stable or not? I'm using Maxsurf Pro in designing the hull form. TQ
     
  6. Paul Kotzebue

    Paul Kotzebue Previous Member

    ISO 12217-3:

    Small craft -- Stability and buoyancy assessment and categorization -- Part 3: Boats of hull length less than 6 m
     
  7. Petros
    Joined: Oct 2007
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    Petros Senior Member

    Find a few examples of similar size boat you want to design, and spend some time in them to see how they feel. Boats that small often depend on experience and skill of person operating it, and to what purpose it is designed.

    There is no substitute for first hand experience. Small boats have been built for thousands of years based on experience, not computer models.

    Wider, flat bottom boats will be more stable, but will usually take more effort to row or paddle through the water. Narrow round bottom boats will have less drag, but require more skill to stay upright. Take you pick.

    Good luck.
     
  8. terhohalme
    Joined: Jun 2003
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    terhohalme BEng Boat Technology

    With or without the car? :D

    No seriously, the GM of your boat should be more than 0,15 m when fully loaded. If less, the boat will feel tippy. Check metacentric height in Wikipedia.

    or all from here:
    http://www.guillemot-kayaks.com/guillemot/information/kayak_design

    Note that kayaks have lower GM than boats...

    Terho
     
  9. ancient kayaker
    Joined: Aug 2006
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    ancient kayaker aka Terry Haines

    You did not mention the type of boat and there would be a great variation between a canoe or kayak, a sailboat or a power boat. I checked your other threads: you are a student of NA & shipbuilding, One of your threads was for a project to design a 175' 3-masted schooner yacht, so I’m assuming that would not be a car-topper :)

    Another of your threads listed the following requirements -

    1. Car-topper (LOA, Beam, Depth and Draft to be suggested)
    2. No. of passengers: 2-3
    3. Outboard engine: 5-15hp
    4. Speed: (Need suggestion please)
    5. Construction: Marine Plywood Stitch and Glue Method
    6. Usage: River/Estuary

    - is that is the boat we are discussing here, or is this thread for yet another boat?

    Since you are a NA student and this is presumably a project we should not design it for you or provide detailed technical objectives, but only suggest guidelines to follow. Without more information all I can do is suggest the following, which would need to be translated into GM height based on human weight/height data which should be your job:

    canoe or kayak: just stable enough not to tip over with paddler seated
    sailboat: stable enough to withstand Force 4 wind on beam with sail sheeted in
    power boat: stable enough for single occupant to walk to anywhere on the boat except the extreme bow, heavy enough to stand bending over outboard without tipping

    As you can see, the requirements are largely common sense for a small boat.
     
  10. jimianbu
    Joined: Jun 2009
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    jimianbu Junior Member

    Thanks a ton to portacruise, PAR, Paul Kotzebue, Petros, & terhohalme. Thank you also to ancient kayaker a.k.a. Teryy Haines. Yes, indeed I am a NA & Shipbuilding student. The thread that you mentioned is the same as the one that we discussed just now. I've misplaced the thread in the wrong section. Please forgive me for that. And, about the 175ft yacht schooner, I just want to know and explore about the quotation. That one was already settled, and thank you for those who helped me. ;) I really, really appreciate and respect all of you senior members. I'm terribly sorry for any inconveniences.
     

  11. ancient kayaker
    Joined: Aug 2006
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    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    No inconvenience, glad to be of help. Good luck with your studies.
     
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