How much mast height should be maximum / minimum meters

Discussion in 'Sailboats' started by mr.sailor, Nov 6, 2015.

  1. mr.sailor
    Joined: Nov 2015
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    mr.sailor New Member

    First of all,I'm sorry for my bad english. I have a 7.5 m. length 2.15. width and ,1.2 m. deep. And the backbone keel wooden sailing. How much mast height should be maximum / minimum meters.because,it's mast 8m.
     
  2. gggGuest
    Joined: Feb 2005
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    Location: UK

    gggGuest ...

    Its a bit like asking how big an engine should there be in your car. There isn't really a right answer.
    If you can provide a lot more detail on what the boat is like and what you want to use it for then it may be possible to narrow things down a bit.

    8m mast on a 7.5m boat doesn't sound unusual though.
     
  3. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    Agreed, an 8m mast on a 7.5m boat isn't uncommon. For example the Hunter 25 (which I have in the yard at the moment) is 7.57m long, 2.44m in beam, with a 6.15 LWL, draws 1.19m and it's P dimension is 7.56m and it's I dimension is 9.14. The mast height is about 8m.
     
  4. Petros
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    Petros Senior Member

    a larger mast will give it more sail area, and more heel when under way. So a deeper keel or more ballast will be required, which means more force on the hull, so a stronger hull is required (adding more weight).

    More sail area allows you make better headway in light wind, but means you will be reefing the sail sooner. It also means more weight aloft, adding to the heeling.

    It is a complex trade off, you can have mast lengths of as much as 1.5 times the boat length, or you can have them as short as about .6 or .7 the Length over all. A lot depends on the intened use of the boat, the desired performance, and the type of material it is made from (wood, vs. fiberglass, vs. carbon fiber composite).

    what is the intended use of the boat? is it a modern cruiser, or performance design, racer or what?. Or is it a traditional design?
     
  5. Stephen Ditmore
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    Stephen Ditmore Senior Member

    Estimate desired angle of heel (maximum upwind before reefing). Estimate righting moment at that angle of heel. Assume a sail loading of one pound per square foot of sail. The sail area and heeling arm (height of center of effort above center of lateral resistance) should be that at which heeling moment = righting moment.

    I might return and convert to metric, but not tonight. If someone else wants to, please be my guest. Assumed sail loading should be higher for multihulls.
     

  6. Joakim
    Joined: Apr 2004
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    Joakim Senior Member

    What is mast height? Height of the top of the mast above water line? Mast tube length? Mast tube length above superstructure? Mast tube length above freeboard?


    Since I is 9.14 m, isn't all of those at least 9 m? Height above water must be almost 10 m.

    Nordic Folkboat is quite close to dimensions OP has. It has P of 8.75 m and thus mast height clearly more than 9 m. It is a fractional rig, but a quite small one.
     
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