Change of mast

Discussion in 'Sailboats' started by djubaca, Aug 20, 2013.

  1. djubaca
    Joined: Aug 2013
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    Location: Carevo

    djubaca Junior Member

    Hi to all.

    I have a Carter 33 boat hand made in 1993.

    The mast of boat was in terrible condition and i was obliged to change it.

    So i bought a new mast deck stepped with height of 12,2m and boom of 4,3m.

    Old mast was keel stepped with height of 11,1 above deck and boom of 3,0m.

    The new mast came with all sails and i want to use new mast and sail without change on them.

    I will make a compression post and i will rearange backstays so they will not interrupt the boom.

    Do i have to add aditional ballast on the keel and how to calculate it.

    I accept all advice that you can give to me so start writing :)

    Thank you in advance
    George

    Sorry for my bad english.
     
  2. Petros
    Joined: Oct 2007
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    Location: Arlington, WA-USA

    Petros Senior Member

    George,

    Welcome to the forum. Your English is fine.

    It is not necessary to add ballast to the keel when installing a larger sail/mast. the design of the rig is usually done around the max righting moment forces that the keel/ballast/hull can generate. If you put a taller, presumably stronger rig on the hull without changing it, it just means for the same wind force your hull will heel over further, or you have to reef earlier. Which is to be expected with a larger sail. It also means that likely your low wind performance will improve considerably.

    If you put more ballast in the keel/hull, that means all of the forces on both the rigging and the hull will increase. All of the stays and shroud lines will have larger forces, and where they all attach to the hull, as well as the compression on the mast. I would not advise that at all. the heavier ballast will also mean your low speed/low wind performance will likely suffer as well.

    If your new mast was designed to be deck stepped it is likely good for that kind of installation. But the loading on the hull (and the rigging) is very different for keel stepped vs. deck stepped, keep this in mind when designing the compression post and the strength of the anchor points for the stays. If you are not inclined to be able to do the calculations yourself you might want to find a design professional to recommend reinforcement for your rigging anchor points.

    There are others on this forum that can advise you with more specifics, but it would be better to have someone local with marine engineering or naval architect experience that can help you out with the details.

    sounds like a good change to do for your boat, just make sure it is done properly so it does not fail or get damaged latter at a very inopportune moment.

    Post pictures of your boat if you can, and perhaps one of the rig (or a picture of the boat the rig came from).

    good luck.
     
  3. djubaca
    Joined: Aug 2013
    Posts: 5
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    Location: Carevo

    djubaca Junior Member

    Thank you Petros for hope that you gave to me with this :
    There are some old guys that know everything but cannot help to me with construction. So i have to brake the wall with my head.

    Some pictures of old mast :
    1.
    [​IMG]

    2.
    [​IMG]

    3.
    [​IMG]

    Gelcoat of boat before repair
    4.
    [​IMG]

    There is the boat after removing old gelcoat and 4 layers MARLIN BARIER
    5.
    [​IMG]
    New mast is ellipse with dimension 170/120 ( old was 155/115 ):
    6.
    [​IMG]

    Stays anchors
    7.
    [​IMG]
    [​IMG]
    8.
    [​IMG]
    9.
    [​IMG]
     
  4. Petros
    Joined: Oct 2007
    Posts: 2,936
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    Location: Arlington, WA-USA

    Petros Senior Member

    looks like a well designed boat, nice lines and excellent keel design. I would not change it. Just make all the attachments stronger for the new locations (or reinforce the old ones), you should do fine. look at how sturdy the attach points are for boats with similar size sails and masts, that should give you an idea of how strong the anchor points should be. If you can not get professional guidance, than just make it stout and you can not go wrong.

    You may have to adjust the rake of the mast to make it balance after the change over, the center of effort for the new sails might be in a different location.

    Good luck.
     
  5. djubaca
    Joined: Aug 2013
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    Location: Carevo

    djubaca Junior Member

    I draw sailplane and CE is approximately in the center of the mast.
     

    Attached Files:


  6. Petros
    Joined: Oct 2007
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    Location: Arlington, WA-USA

    Petros Senior Member

    is the second sail plan depicting the old sail plan? looks like the jib is the same but the main sail is has been enlarged. Is that dot on the sail plan the CE for both configurations? if so, how is it that the CE moves forward when you put a much larger main sail with the same jib?

    Where was the CE located on the original sail plan?
     
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