A-Frame Mast

Discussion in 'Boat Design' started by ericdalene, Jan 16, 2009.

  1. ericdalene
    Joined: Jan 2009
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    ericdalene New Member

    Hello - Am new to this forum, but am excited to ask a question :

    Is there anyone familiar with A-frame mast configuration for a sailboat, combined with a roller furling genoa and a roller furling main ?

    I would be very thankful for information and experiences with such a design -

    1. Practical nature

    2. Handling peculiarities

    3. Ability to head into the wind

    4. Advantages / Disadvantages

    Thank you
     
  2. chabrenas
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    chabrenas Mike K-H

    The A-frame design I remember just had a single sail - the genoa. How would you set the main? Straight up and down inside the A frame? I don't think you'd gain anything by using it - just the genoa is equivalent to a lateen (dhow) rig without the problems of tacking it. Good to windward and close reaching, but some kind of boom would help fownwind.

    I presume you plan to fit it to a multihull of some sort?
     
  3. RHP
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    RHP Senior Member

    The A frame has been discussed in some detail on other threads, do a search and you'll come up with something.
     
  4. ericdalene
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    ericdalene New Member

    A-Frame

    Thank you so much for your helpful responses. I will search the site more.

    The application in this case would be a monohull. I believe to that downwind would not be as favorable.
     
  5. Norman Brown
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    Norman Brown Junior Member

    I am also interested in the A-frame mast. If you have found any good articles I would be interested as this seems ideal for my 42.5 ft yacht now being built.
    Regards. Norman Brown
     
  6. alan white
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    alan white Senior Member

    The only problems, I assume, would be extra cost, weight, and windage. Otherwise, roller reefing and furling would be the way to go. Definitely could have a main and jib. No mast in the cabin.
    Two masts would still need to stay in column, both being a bit longer than a single mast. Otherwise the masts diameters would be quite large (remember windage?).
    Twice the weight aloft, complicated staying to keep masts light (or large diameter masts). Only masthead type rigs would make sense.
    We don't see them out there for all the above reasons, or at least I've never seen one.
     
  7. PAR
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    PAR Yacht Designer/Builder

    There was an attempt at a bi-mast rig in the early 90's. One of the major sponsors was Harken if I remember correctly. The main was on a roller furler as was the headsails. The leading edge of the main was aerodynamically clean, but the windage of the additional mast offsetted the efficiency increases. This boat was a test bed for a number of interesting innovations. I think it was called "Paragon"
     
  8. Eric Sponberg
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    Eric Sponberg Senior Member

    Actually, it is Amoco Procyon, and it has been discussed before on this forum:

    http://www.boatdesign.net/forums/sailboats/procyon-project-bold-experiment-10771.html

    In my opinion, the extra weight and cost of an A-frame rig are not attractive enough for the different aerodynamics (not necessarily better on all points) that one gets. One mast is cheaper and lighter than two masts.

    It was a test bed for a number of different ideas, including canting keels. Some of the ideas have become more prevalent in yacht design, but the bipod rig is not one of them.

    I had occasion to go aboard Amoco Procyon, I'd say about 10 years ago. It's interior design--all stainless steel--was stark to say the least. I heard one noted yacht designer say "If this is the future of yacht design, we've just gone backwards about 20 years." But the Harken brothers are to be commended to at least trying and putting their money where their mouth is.

    Eric
     
  9. alan white
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    alan white Senior Member

    I can see how Harken's Polygon would have been a good test bed for a whole boatload of equipment that would become necessary had the design caught on.
    You can have a main with a jib type luff by putting a single mast in the eyes of the boat canted back, with headsail on a sprit. 3/4 rig though, not masthead because of tensioning issues (gunter style "wing" spar extends above the masthead).
     
  10. alan white
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    alan white Senior Member

    I meant Procreation.
     
  11. tom28571
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    tom28571 Senior Member

    I saw Procyon somewhere, possibly at the Annapolis boat show but I think it was more than 10 years ago. I think they had to add a strut between the masts to reduce the span. The masts were in great compression from both sails and backstay.
     
  12. multicapt
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    multicapt New Member

    The A Frame Mast

    The A frame can be made very cheaply and will remain standing longer than a conventional mast due to the absence of shrouds/stays ,the cons however far out weigh the pros .
    As mentioned weight could be an issue aerodynamics another .
    On a big baffy stable multihull before the wind hell why not? you could climb the mast with ease and enjoy the scenery but don't expect to race round the cans on a monohull.
    I have actually made an A frame mast and attached a main and genoa with predictable results as mentioned above ...... of course it works BADLY.
     
  13. pool
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    pool Junior Member

  14. ancient kayaker
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    ancient kayaker aka Terry Haines

    The A-frame mast does have to be heavy if properly designed to take full advantage of the different ways forces are reacted to the hull. However it imposes different stresses on the hull than a conventional mast so they have to be designed as a system, especially if performance is an objective.
     

  15. Angélique
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    Angélique aka Angel (only by name)

    Hi, here a A-frame mast with a lateen rig with a boom at the bottom which front swivels. The lateen is hanging in the A-frame in with what seems to be a reefing claw.

    The original forum is not always on line and some pics are gone. So here what I once saved from the Google webcache with the original links...

    Cheers,
    Angel

    Website + pics
    Iain Oughtred - Caledonia Yawl - forum
     

    Attached Files:

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