A Frame Masts

Discussion in 'Multihulls' started by Gus7119, Jan 20, 2016.

  1. brian eiland
    Joined: Jun 2002
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    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    Gus, short simplistic answer. I believe you are looking at the A-frame mast idea much as some others have in the past,...that's it just a good stable spread leg configuration that will accept compression loads readily. And your brick loading guys can make great use of that feature.

    But a sailing rig has to support quite different loads, and a very significant side loading that not so easily accommodated by the A-frame configuration. For example consider the very significant side loading by the head of the mainsail at at the top of the mast, and trying to pull the boat over on its side. Or the masthead genoa also trying to pull the top of the mast both forward and over to the side. The A-frame configuartion does not bode so well here.

    Think of a std mast rig were the windward shroud is in big tension, and the leeward one is slack. How is the A-frame going to cope here? Are there some situations where the windward leg of the A-frame going to have to provide tension force vs just compression force?

    If you look thru that extensive subject thread on Procyon you will also discover a couple of problems they experienced,...1) some significant problems tying the two heads together, 2) with the bases set out to the extreme beams of the vessel, there were several occasions where the vessel heeled over at the dock and experienced damage from the tall pilings it was docked next to.

    The A-frame is interesting, but not a cure-all.
     
  2. brian eiland
    Joined: Jun 2002
    Posts: 4,955
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    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

  3. Spiv
    Joined: Jun 2007
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    Location: The Big Wide Blue Brother

    Spiv Ancient Mariner

    Gus, I have taken lots of photos, will shrink and upload them soon...
    The designer of the A frame is Dereck Kelsall, the same designer of the cat.


    Yea, agree, time passes too quickly, especially when one is over 60......
    The cat hasn't been sailed for a while and needs hull cleaning first. I offered the owner to help him, but I live 250k from him....
    He is keen to take me for a sail and get some cat sailing comments from me.
    We are in touch and as soon as he is ready I will go and take notes, I will try and make a Polar diagram and post it to this thread.
     
  4. waikikin
    Joined: Jan 2006
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    Location: Australia

    waikikin Senior Member

    Hi Brian, some conjecture from myself in green to your post... not because I know but because I'd like to.
    Regards from Jeff
     
  5. hump101
    Joined: Oct 2004
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    Location: Brittany, France

    hump101 Senior Member

    Attached Files:

  6. Gus7119
    Joined: Dec 2015
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    Location: Sydney

    Gus7119 Senior Member

    Spaceship

    "Its a space ship!" Yep I saw that last night on its release also. Strange looking boat.
     

  7. Steveso
    Joined: Jul 2015
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    Location: Finland

    Steveso Junior Member

    Headsail sag can be controlled by adjusting the backstay tension, but How to control luff sag in the sail which is between the masts?
     
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