define sheer

Discussion in 'Sailboats' started by Letsgomom, Jul 6, 2011.

  1. Letsgomom
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    Letsgomom New Member

    In comparing the C&C 35 Mk I (made through 1973) with 1974 C&C Mk II, a review article states the 11" increase in the lol came about by "increasing the sheer". Did the writer mean they increased the freeboard? And in either case, how does increasing the sheer/freeboard result in an increase the length?
    I'm not a boat designer, as you've probably discerned by now. Thanks in advance.
     
  2. jehardiman
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    jehardiman Senior Member

    If the rake of the stem is held constant, and the sweep of the sheer is increased forward (increasing the freeboard forward, but perhaps not amidships), then it follows that the intersection of the sheer and the stem would be forward of the original point. This is why length overall increased.
     
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  3. messabout
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    messabout Senior Member

    Jehardiman explained the geometry perfectly, but did not elaborate on the term sheer. The word is generally taken to mean the curve of the deckline as viewed from the side. If the curve forward is raised a bit, then the nose of the boat will extend a little if the curve of the stem is kept. The reason for raising the height of the front end of the boat may be to reduce the spray or wash that comes aboard in certain sea states. Or the reason might have been a matter of styling.

    There is a substantially large school of thought, among boatmen, that a "lively sheerline" is a thing of beauty. Some contend that the sheer line fixation is a crock of horse patootie. Tastes and opinions vary.
     
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  4. PAR
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    PAR Yacht Designer/Builder

    Is that the correct spelling of patootie?
     
  5. MalSmith
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    MalSmith Boat designing looney

    While this and Jehardiman's is the most likely interpretation of the the words "increasing the sheer", it could also mean that the sheerline was simply extended forward or aft (or both) with no change to the freeboard. Letsgomom, you are right to be baffled by this because it's not a concise technical description of what was done.
     
  6. messabout
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    messabout Senior Member

    Par; that word is not in my spell checker, so I just had to wing it.
     
  7. jehardiman
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    jehardiman Senior Member

    True, but that would require building a new hull mould rather than just modifying the original (i.e. if the sheer sweep was kept the same but lengthened, the stem and/or transom would need to be changed also). If the '74 used a new mould, anything could be possible.

    And apparently it was a new mould....as the Mk 1 mould pre-dates C&C...

    http://sailboatdata.com/viewrecord.asp?class_id=1800

    http://sailboatdata.com/viewrecord.asp?class_id=2056
     
  8. Petros
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    Petros Senior Member

    I think the review statement is meaningless, the word "shear" in a boat hull comes from old dutch and just means "up turn". The length of the hull is unrelated to the amount of shear on the gunwales, unless there are more qualifying description you do not know what the writer is talking about. You have to make assumptions.

    This term btw is not to be confused with the other meanings for shear that come to us in English from old English, Latin, and German, which can also mean "translucent" (as in shear fabric), opposing forces (as in a shearing action or a pair of shears), or perpendicular (as in shear cliff).
     

  9. PAR
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    PAR Yacht Designer/Builder

    Pertos, you are using the wrong word. The term is sheer, which has nothing to do with the word shear.

    Sheer means several things, including "up turn", it also means "sweep", deck line, "spring" and an assorted other number of additives. You are correct in that we need more information on the comments about the sheer being raised. I do happen to know the MK-2 version of this hull did use a different mold, so several changes to the hull where made including a bustle, a popular addition at the time.
     
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