A Frame Mast - Aft

Discussion in 'Boat Design' started by gonewalkabout, Oct 5, 2007.

  1. gonewalkabout
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    gonewalkabout New Member

    Anyone familiar with/want to comment one BRIAN EILAND ideas re a Mast Aft design you can see at http://runningtideyachts.com/sail/ ?

    Now, just to add to the discussion consider the same idea, but on a cruising Cat with a a-frame carbon mast.

    The goal is a cruising cat of 40 to 42 feet. It will be solo or short handed all the time. Safety is more important than speed. My preliminary thinking is:
    - you'd probably only need four stays to the corners leaving the deck and cabin top clear (no excuse not to be on a lifeline)
    - the 2 (or three if used for the mizzen) jib furlers are cheap (relatively), available everywhere and simple to fix.
    - all sail handling could be done from the cockpit ... I'm desperate to stay of the bow when under way.
    - The total sail area, especially with the mizzen, is the same or better than a tradition sloop and I think the mast could be lower than a traditional rig.

    Want to have more fun still ... move the cockpit to the center of the boat (sort of an aft salon).

    What would you call this rig ... a modified sloop-cat-ketch :) !

    So far just having fun but might do a fairly accurate model of this just to see.

    Advice / ideas (you nuts is fine)
     
  2. yacht371
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    yacht371 Yacht Designer

    I like the idea, but fear that it may be difficult to get sufficient stay tension to get the furling sails to set well. Unlike a conventional mast, which if through stepped, has at least some tendency to stay upright even without rigging, this on is entirely dependent on a highly tensioned rig.
     
  3. Geoh
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    Geoh Junior Member

    Troller rear mast/outrigger

    I know i am going to try this sometime when all conditions are right...:idea: I have a 26' double ended troller with aluminum mast and outriggers for trolling/flopper stoppers...with the outriggers out at 45 degrees or so, IF i wrapped canvas/blue plastic tarp from the mast to the outriggers i have a fairly decent sail area for downwind sailing. Started out thinking about a get home rig like the deisel duck rig...
    All my engineering background which is about 0 tells me that with the engine running i can keep the bow headed foreward sail assisted gain a half knot or so...without it, sooner rather than later, i am going to be "sailing" arse bckwards...
    The question: A. Should i just paint "eyes" on the stern and pretend this is what i want to do...B. Wait till after dark and "sneak" into port. :D C. If it gets me home when needed it cant be all wrong... Double ender is the key...
    :confused:
    George
     

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  4. gonewalkabout
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    gonewalkabout New Member

    Through stepping to take some of the load.

    Among my idea was that of 'through' stepping to the bridge and using the cabin/bimini 'b-pillars' to effectively take some of the load.
    There is going to be a strength vs aesthetics trade off one way or the other ... just how much I'm not sure
     
  5. Geoh
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    Geoh Junior Member

    pic worth 1000 words

    Trying to engineer a "get home sail" with the mast and outriggers i have...I know that somehow i can hang a "sail" off the aft mast and outriggers...kind of a controlled drift...
    Would like to keep the bow foreward BUT I keep seeing it stern first...:D
     

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  6. Geoh
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    Geoh Junior Member

    hmmmmmmm maybe only worth 250 words...looked better when i drew it...

    Geoh
     
  7. ChiefOren
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    ChiefOren Junior Member

    mast-aft A-Frame

    I am building in Israel a 50' sailboat, The Dragonfly of George Buehler, in which I am planning on incorporating the Mast-aft configuration with an A-Frame Mast. To this I will attach 2 main gibs, and a third staysail (Storm Sail). At first, I am planning to not also incorporate the Mizzen, (Wishbone), but may leave that as an option for latter on. I think that it is time that a new type of rigging should be thought about, and this seems reasonable, as I will be planning on sailing barehanded, and for a boat this size, the handling of the Rigging will be important. Any thoughts on that, would be appreciated.
     
  8. peterAustralia
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    peterAustralia Senior Member

    It has been done

    An all jib rig on a fairly big catamaran. I saw this on the duckworksmagazine.com website a year of so back. From memory the boat sailed from teh South of France in the Mediterranean. It was yellow in colour, home built and about 40ft long. The rig was all jib, no mainsail.

    The catamaran was fro charter work so something easy to sail was desired. Additionally a lower capital cost was desired, so dispensing with mainsails was a way of reducing cost.

    For the exact article.. you could search through the article, might take some time. Alternatively you could write a question on the yahoo group dwforum (duckworks forum) and ask if any person can remember the article in question. This may be an easier way of finding the information.

    There is also a smaller cat from shellboats. It has a lateen sail, and a small bipod forward. I am also aware of a lateen sail suspended from a bipod on a small cat that sails in the Baltic, from memory the fellow had problems with how to tack easily.

    my 2c worth is that using jibs and dispensing with a mainsail would be useful in aiding in simplicity and reducing cost. I doubt that it would be quite as fast as the normal setup, probably just a fraction slower. The Jukungs on Indonesia sometimes have a large lateen sail forward on their double outriggers.

    n peter evans
     
  9. brian eiland
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    brian eiland Senior Member

  10. ChiefOren
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    ChiefOren Junior Member

    Mast Aft A frame rigging

    As I've shown intrest into the Mast Aft configuration and using an A-Frame mast, the discussion has mainly been around the issue of raking the mast FORWARD at an angle of apr. 10 Degrees. As I do not have an engineering background, could you explain the advantage or reason for raking forward and not backward? Just thinking that if the Mast was raked backward, the tension would be more workable using less rigging. Your thoughts will be appreciated.
     
  11. GOTTABSOMEWHERE
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    GOTTABSOMEWHERE Junior Member

    "A" frame mast


    Don't know about "aft placement" but...........have placed "A"mast on a
    "hobiecat" with a "lanteen Dhow style" sail and it goes good. Simple
    cheap, ..............made sail and 22' spar in garage.........no problem
     
  12. brian eiland
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    brian eiland Senior Member

    LOTS of discussions of this concept over in this subject thread, both before this particular posting and after it:
    http://www.boatdesign.net/forums/sailboats/aftmast-rigs-623-7.html#post198605

    Yes the forward rake adds greater loading to the rig as a whole.

    Sorry I do not have more time at the moment to rehash this much discussed subject.
     
  13. yipster
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    yipster designer

    although a beliver i never came much further than thoughts, some model sticks, a scale and a ventilator. the A frame does away with slack stays but dont think its all that clear cut as many confifurations are possible. fwd mast rake is neccesairy for a single sail to swing and think the hull than may act as endplate as well. rake gives a longer leading edge and aft A masts lower better to fit the boat, may even transfer it into a motorboat. sails on the frame is another option, with or without furling or socking fore sails. sails on the masts gives some counterforce in stability. etc alinghi used inflatable battens some years back and i imagined whole sails so, even asked a rib manufacturer about feasability. yes, not really the kiss priciple i know and max sail area is another approach. there is more and like to hear others but have to run now
     
  14. capt vimes
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    capt vimes Senior Member

    i know of a cat featuring one of those A-masts... although not aft...
    it also has a center-cockpit forward the saloon...
    http://www.sail-the-difference.com/DESIGN.28.0.html

    with the design you have in mind this might be a bit harder because i do not think that you can attach any kind of boom to such an A-mast which you might need for the aft sail....
     

  15. yipster
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    yipster designer

    me? hi capt, i'm only still exploring rig and sail designs, yes, the boom(s) not worked out in my drawings yet, i know, say gogo and i might think harder ;-)
    dont know if he goes deeper into crab claws or rare rigs but am planning to read marchaj's third yet harder to find book "optimising sail design" one of these day's

    http://www.sail-the-difference.com/GALERIE.7.0.html?&gallery=3 pics of the differences sails
    in last multihull mag a good time was named with her under a small heading "the A frame works" or something. very nice boat !
     
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