Info needed for sprit

Discussion in 'Boat Design' started by giorgostr, May 7, 2012.

  1. giorgostr
    Joined: May 2012
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    giorgostr New Member

    Hi everyone

    My name is George and I would appreciate if someone could help me giving info for a school project.

    I am looking for a “fomula” that will help me to do the maths for sequential cross section - diameters (i.e. Peak, middle and heel) for wooden sprit with length between 10m, 11m …. 20m.

    Is any formula, rules or tables that define these dimensions (measurements)?

    I am interesting only for wooden sprit, not for steel.

    Thanks in advance

    George
     
  2. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    Spirtsail yard? or Bowspirt? There are some historical rules of thumb for both. Typically there are dia to length rules and then ratio's for the tapers applicable to yards and masts. They vary however by nation and period and how much staying you have.
     
  3. giorgostr
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    giorgostr New Member

    Jehardiman,

    Thanks for the fast reply

    Sprit that I am looking for is not Spritsail yard or Bowsprit.

    I am looking for sequential cross section –diameters, that apply to sailing barges. To make myself more specific I am pointing with arrows on the picture bellow.

    Thanks in advance

    George

    [​IMG]
     
  4. lewisboats
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    lewisboats Obsessed Member

    That is a Spritsail yard
     
  5. giorgostr
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    giorgostr New Member

    My mistake due to I am not familiar with technical terminology and my English are not very good. I live in Greece.

    Where can I find these “historical rules” mentioned earlier?

    Thanks in advance

    George
     
  6. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    Typically, a wooden yard max diameter is 2% of it's length. What really is at issue is the taper and rigging. Is the yard fixed on a mast gooseneck or on a free snotter? You could calculate it for buckling, but generaly I'd say 2/3 to 3/5 diameter at the peak and 4/5 at the heel if you use a snotter, 2/3 if fixed. Lay out the taper in the typical quartered-arc fashion.

    There are compliations of sparring plans, but generally most people use the Royal Dockyard mast and spar rules from the Napoleonic Wars (i.e. Steel's rules). See Sir William Symonds, Instructions for the Guidance of the Mastmakers Department of His Majesty’s Dockyards, 1836 if you are really interested. In your case I took the rules for a lateen yard and upped the sections for compression. If you get really big, the weight of the spar itself becomes an issue and you may need to actually calculate it.
     

  7. giorgostr
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    giorgostr New Member

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