lcb location ?

Discussion in 'Boat Design' started by frank smith, Jul 3, 2012.

  1. frank smith
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    frank smith Senior Member

    what is the best location longitudinal for center of buoyancy on a sail boat ?

    I am sure this has been covered before , but I just want to check if their are differing opinions. Most or the references I have say that about -3.7 % is good , but dont give much more detail. I cant see how this fixed value would work in all cases .

    Frank
     
  2. gonzo
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    gonzo Senior Member

    It depends on the design. Categorical statements that there is a "best" location change with fashion though
     
  3. PAR
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    PAR Yacht Designer/Builder

    About 55% of the LWL aft of the bow is common for a sailboat of typical proportions, but by no means best or ideal. I'm not sure what you mean with -3.7%, but generally the CB is determined through it's relationship with several other variables.
     
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  4. frank smith
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    frank smith Senior Member

    Richard ,
    I am interested in designing a small sailing skiff, and cant find any info on
    the implications of differing lcb locations . So that is the information I need direction to.

    Skenes says 54% to 59% aft is a reasonable range , but not much more. The -3.7% figure, is aft of the center of the water line,
    and comes from "Principles of Yacht Design".

    I can see how a small craft would benefit from having a Lcb farther aft,
    but the rest is a mystery to me.

    F
     
  5. PAR
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    PAR Yacht Designer/Builder

    Again it depends of other decisions about the design. Modern preformance dinghies can have CB's in the 60's (%), much like a powerboat, while antique craft had it well forward (40's). It's all fairly relative, as the CB moves around, especially in small craft. In little craft there are two CB's, on of which you are referring, the other CB is Center of Butt and has a huge (well depending on the personal mass of your CB) ability to fix trim and sailing lines issues. A bad handling dinghy can be made sweet, with an 8" butt scoot, one way or the other, so CB is pretty important and often quite attractive.

    Frank, base your little sailor around a known design and tinker about the edges a bit if you want. This will insure it balances reasonably well and still has your design marks all over it.
     
  6. frank smith
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    frank smith Senior Member

    Thank you, Paul
    hope you are having a nice 4th of July ,

    F
     

  7. PAR
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    PAR Yacht Designer/Builder

    Me and the woman had our usual decadence and turned up the music, when the fireworks starting going off, as we have a dog that's equally as afraid of lighting as these.
     
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