Mast Base Oriantation

Discussion in 'Multihulls' started by phmadeira, Nov 26, 2016.

  1. phmadeira
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    phmadeira Junior Member

  2. gonzo
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    gonzo Senior Member

    It is usually for water drainage. Sometimes that is also to induce bending to flatten the sail when the wind picks up and increases compression loads.
     
  3. phmadeira
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    phmadeira Junior Member

    Ok for the water drainage
    But is the mast is pointed 1 degree forward ?
    for me il will put more 1 degree backward ?

    did they cut the mast to make back the orientation as wanted
    Or the mast have follow the Mast Base orientation ?
    or can you use the mast shoe to change orientation

    cat does not have back backstay

    Hope i am clear
    thank you
     
  4. phmadeira
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    phmadeira Junior Member

    40 feet cruising cat
     
  5. gonzo
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    gonzo Senior Member

    I don´t understand what you mean by orientation.
     
  6. phmadeira
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    phmadeira Junior Member

    Hello
    see picture on the right
    if i put 1 degree on the mast base, the mast orientation will go forward (direction of Arrow) (saw two catamaran like this)

    https://drive.google.com/file/d/0B2Cwu0IkTCvtdVJPN1hidHZQb2c/view?usp=sharing

    Sorry with my english is not that clear

    On this other cat see pic the mast base is backward

    https://drive.google.com/file/d/0B2Cwu0IkTCvtX1UwOUplZFh3aTQ/view?usp=sharing

    I can understand more this type of configuration


    but why you will want to put 1 degrees to oriant the mast forward ?
    It look verry ugly if the mast pointing forward
    is the Shrouds help , to get it backward , to bend the mast backward ?

    Thank to helping me to understand
     
  7. gonzo
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    gonzo Senior Member

    The rigging controls the rake of the mast, not the mast step.
     
  8. waynemarlow
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    waynemarlow Senior Member

    Probably a fixed non rotating mast, locking the mast to a certain position is a bit of a no for me as very often with real life sail CE's you need to be able to cant the mast forward or back to get the correct loading on the centre board and rudder once the boat is built and has begun its first sail trials.
     
  9. phmadeira
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    phmadeira Junior Member

    http://www.boatdesign.net/forums/at...529-mast-base-laminate-concerns-mast-base.jpg

    and what about this one ?

    can somebody explein

    The base making 4 degrees rake
    plus you have to add 2 degrees from the shroud

    How to decide , design , to select the rake on the mast on a 40 feet catamaran

    Can i design mine with base 1 degrees forward (see this picture, begining of the forum)
    with no problem , the fine tune the rake mast with no problem
    Must be Ok because saw two cat bluild like this

    phill
     
  10. patzefran
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    patzefran patzefran

    Mast rake prediction is not a very accurate science, it depends on many parameters. You need som tuning after sea trials ! so it is better to anticipate the possibility to change your mast rake within a sufficient range !
     

  11. catsketcher
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    catsketcher Senior Member

    Mast base doesn't matter

    Gday Phil

    I wouldn't worry at all about the mast base. You will rake the mast forward and back with the stays/shrouds.

    Very few masts rake forwards - I can't think of any stayed boats on the water with such masts, rake is always aft. (Etchells and Stars often let their masts fall forwards on square runs but on the mooring or upwind the masts are raked aft.) Some junk ketches have the fore mast raked forward.

    The centre of effort of the rig has to be located near the centre of lateral resistance of the boat. Then you have to work out a black art called LEAD. On monos, lead helps with getting balance when heeled. On multis, lead is more problematic, some designs have none.

    Build the mast base flat. The boat will pitch up and down anyway and even getting a cat to sit exactly flat on its lines is pretty near impossible. 1 degree will probably not be enough slope to overcome water's adhesion to surfaces, it sounds a bit silly to me.

    cheers

    Phil
     
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