Mast diameter?

Discussion in 'Wooden Boat Building and Restoration' started by stefos, Dec 11, 2015.

  1. stefos
    Joined: Nov 2015
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    Location: greece

    stefos New Member

    Hullo every body there. I'm new to this forum and I would like to tell me your opinion for my mast. I have a wooden boat 9m LOD 3.2B 1.25D gaff riged. The mast is meditteranean cypress 6.5 from deck to hounds 14.5cm diam at deck 12.5cm at hounds and 1.25m to head. It has 2 shrouds per side at the hounds and 1 shroud higher and 2 back stays. The sail area is47 sq meters (27 main 10 jib 10 staysail)The question is about the strength of the mast. Are the diameters enough or is it dangerous? I know that it tappers a lot. And I m planning to build a new one. But until that day how safe am I to sail with it?
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    Gaff rig masts usually don't have much taper, particularly below the hounds and you're sounds about right for a modest cruiser. Two lowers, a cap shroud and runners are also typical for this type of rig.
     
  3. stefos
    Joined: Nov 2015
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    Location: greece

    stefos New Member

    Thank you for your reply. If I make a new mast what diameters should it be at partners and hounds to be right?
     
  4. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    These aren't things you should guess at. The mast (and the rest of the spars) should be scaled to the anticipated loads. Given the very basic dimensions you've offered, the mast you have sounds like a reasonable inshore cruiser, though a little light for serious offshore work. Precise dimensions need to be calculated and you'll need a lot more information about the boat. If you can provide the hydrostatics, I'll can check them, but anything less and you're just making a guess, which may or may not be sufficient for your needs, which is also unknown.
     
  5. SukiSolo
    Joined: Dec 2012
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    Location: Hampshire UK

    SukiSolo Senior Member

    With the various 'cargoes' being carried/shipped/transported around the Ionian Sea right now, it would be good to provide a little more valid information.....;)
     
  6. stefos
    Joined: Nov 2015
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    Location: greece

    stefos New Member

    I don t know how I can provide hydrostatics. The only I have is the survey of some sections I made for me the ballast and the approx. displacement because the boat is builded without plans just with eye. I sailed three summers between Aegean isles with good weather the most 5 to 6bf and that is the use of this boat. Anyway thank you again
     
  7. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    One way to do that is to make an inclination test. That will give you an approximate righting moment, which can be used to calculate the load on the rig.
     

  8. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

    One of the methods traditionally used for calculating mast and rig is the NORDIC BOAT STANDARD's. This method is based on determining the righting moment of the boat at 30°. After several calculations you can determine the compressive forces acting on the mast. I guess, Gonzo, that your answer has something to do with it.
    My opinion, which may be wrong, is that it is difficult to obtain this value (RM30) by inclining test. It would be necessary to tilt the boat 30 and see the heeling moment it has been necessary to achieve this.
    To get it, it is more practical to calculate the GZ values at various heeling, which can only be done by calculation.
     
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