Centreboard to house clearance at pivot?

Discussion in 'Boat Design' started by welder/fitter, Aug 24, 2010.

  1. welder/fitter
    Joined: Jun 2008
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    welder/fitter Senior Member

    Centreboard of 3.25"(89.2mm) total width at pivot. Which would be better, 0.25"(6.40mm) or 0.5"(13mm) clearance per side(total width CB to inner fin house wall)?

    All associated plate is low-carbon marine grade steel w/ stainless pin & bushing.
     
    1 person likes this.
  2. dskira

    dskira Previous Member

    You are posting the most difficult question. The clearance I prefer is the larger one, giving the larger centerboard casing possible to be able to maintain it easily. Some strip of Teflon vertically placed on the side can guide the centerboard. It allow a very accessible centerboard casing.
    In case the center board is on the ballast, the smallest clearance possible, since the slot can't be accessed of from the top.
    You will find all sort of opinions, and no one is wrong or right.
    That was just mine.
    Pick your poison:)
    Daniel
     
  3. welder/fitter
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    welder/fitter Senior Member

    Thanks, Daniel!
    Centreboards aren't something I know anything about. I'd like to leave enough room for easy access for welding/maintenance, but wondered about issues of lateral movement. Can you recommend a good book for info. on all keel types?
    Mike
     
  4. philSweet
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    philSweet Senior Member

    could you post a sketch of the boat and another of the the trunk with the board fully raised and fully lowered.
     
  5. welder/fitter
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    welder/fitter Senior Member

    Sorry, it's a design I'm working on. I decided that I wanted to have a shoal draft/centreboard as an option, but the only boat I've had with a centreboard was a Macgregor. Any opinions/advice on what makes for a best approach is appreciated. By the same token, it is just practice, so I wouldn't want anyone to go to a lot of trouble. I figure that there must be a few designers on here whom are quite knowledgeable & experienced with centreboards.
    Mike
     
  6. tspeer
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    tspeer Senior Member

    Think about the pendants. If the pendant on top of the board slips off the head, it will jam. Then you have to take off the top of the CB case to reset it, risking flooding of the boat. (Trust me on this.) If the pendant on the bottom jams, you won't be able to lower the board, and it'll be a bear to clear - possibly requiring diving under the boat.

    If the clearance is less than the diameter of the pendant, you might be less susceptible to jamming.
     

  7. welder/fitter
    Joined: Jun 2008
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    welder/fitter Senior Member

    Thanks, Tom.
    I'm designing a dual-action hydraulic system for the centerboard. Yes, the cylinder will have to be rebuilt/replaced periodically & it would be prudent for me to design a manual system for redundancy(failure of the hydraulics/
    electric pump/12V supply/etc. while underway). Why a centerboard? In broad strokes, I'm designing a steel-hulled pilothouse cutter of about 27' DWL & want to keep wetted surface down, with good pointing ability, & able to carry good sail area in stronger winds, safely, but be able to anchor reasonably close to shore in most areas.
    Mike
     
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