AC 36 Foiling Monohulls

Discussion in 'Sailboats' started by OzFred, Sep 13, 2017.

  1. TANSL
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    TANSL Senior Member

    Whatever AC History says and the authority you want to grant them, I can not see more than one hull on the "Blue Arrow".
     
  2. Doug Lord
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    Doug Lord Flight Ready

    ============
    The same authority anyone uses to look at a single hull boat and call it "monohull".
     
  3. CT249
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    CT249 Senior Member

    Like the Moth class didn't, with the wingtip foiler and the Michigan Moth? Like Hobie didn't, with the Monocat (which despite the name, they called a cat) or Bravo (which has three buoyant surfaces in contact with the water but they all form one piece)? Like the sailors of North America didn't, with Dominion? We have one case where a boat with one hull was called a cat because of its wingtip foils, and three cases where boats with one piece with a hollow down the middle were called cats, and one case where a boat in one piece with a hollow down the middle AND a third piece of buoyancy often in the water was a cat.

    But with the "NZAC"this case we have a craft with separate devices that provide hydrodynamic lift through volume - ie hulls. It has three of them, therefore it's easily and reasonably called a trimaran - just as the HSP was called a trimaran although if it was being sailed at its optimum the floats did not touch. The difference between floats that supposedly self-right from a capsize and very small floats that prevent a capsize is not really here or there.

    Arguably Blue Arrow is irrelevant because it did not have hulls (which are what pods effectively are) and because the issue of whether it was a mono was apparently never really settled.

    I think someone on SA noted that by your own definition, the AC50s when sailed at their optimum had no hulls at all because the hulls did not touch the water.
     
  4. Dolfiman
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    Dolfiman Senior Member

    In "Voiles & Voiliers" of november (a french magazine), there is a 2 pages article on AC46, I quote :
    Title : "Monohull with foils and without keel"
    In red letters : "The AC75 should have a total beam of 18 m , so giant foils"
    In the text : " ... for a displacement of 5t ! ....monotype parts being imposed to limit the cost ..."
     
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  5. Doug Lord
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    Doug Lord Flight Ready

    Thanks-do you have a link to the article?
     
  6. Dolfiman
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    Dolfiman Senior Member

  7. CT249
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    CT249 Senior Member

    I don't really get it. If it's a foiling mono without a keel then it will have nothing to do with "mainstream" yacht racing (as GD allegedly wanted) and still be slow compared to a multi.
     
  8. schakel
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    schakel environmental project Msc

    It is getting increasingly difficult to follow the latest developments on the foiling cats, tri's and mono's at the moment.
    I agree if someone said: "Yes, foiling is a revolution."
    Is there an overview site? (Besides this forum?)
     
  9. Dolfiman
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    Dolfiman Senior Member

    If you read the German, I recommend you this article :
    http://www.quant-boats.com/media/pdf/d8/30/89/Fl-gelst-rmer458.pdf
     
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  10. OzFred
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    OzFred Senior Member

    I guess "AC46" is a typo for AC36? And that the "18m beam" means the overall width from the tip of the lateral foils if both are fully extended?
     
  11. Dolfiman
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    Dolfiman Senior Member

    Oups yes....., it is AC36 and 18m overall width.

    I wonder how 5t can be possible for a 75', seems very light, is it really the weight in sailing conditions ? And how about the necessary RM to build speed and take full foiling opportunity, with 12 heavy men put windward ?
     
  12. sharpii2
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    sharpii2 Senior Member

    IMHO, a trimaran is boat which has stability support of some kind to the lee of the leeward hull sheer. Although most conventional trimarans have full buoyancy floats, some have partial buoyancy ones. With the advent of hydrofoil technology, I can imagine a day when trimarans will have vestigial floats, which are intended mainly to prevent capsize, with the sailing initial stability being provided by the foils under the floats. I imagine significant weight and whetted surface drag reductions with this model.

    For this reason, I see the defining characteristic of a trimaran as not the floats so much as the massive cross beam(s) which extend well past both sheers, permanently. I do not consider Doug's "trapwing" concept to be a trimaran because:
    A.) no buoyancy or other stability support is provided to the lee of the hull sheer, and
    B.) the entire beam is intended to extend only past the windward hull sheer, for maximum initial stability.
    Mono-hulls, which have hiking benches, are also not trimarans, IMHO, because:
    A.) the benches do not provide any meaningful stability stability support to the lee of the hull sheer, and
    B.) they can be conceivably be sailed without the benches (with a reduced rig, of course).

    IMHO, a large scale foiling mono hull (1,500 lbs or more) is possible, as long as the foil athwart-ship center of lift is at or within the lee hull sheer line (at maximum hull beam). This sheer line must cap a straight line section, at maximum beam, or an outwardly curved one. If a particular hull has an inwardly curved section line, at the top of its maximum beam, then the sheer line should be taken as being at the center of this curve.

    Simple rules as these, IMHO, would insure that the boats in question have mostly the traits of an ordinary mono-hull, and are not merely trimarans in disguise.
     
  13. TANSL
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    TANSL Senior Member

    Instead of such a huge breadth, why do not they put some foils with much more lift?
     
  14. CT249
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    CT249 Senior Member

    It's got buoyancy pods for stability support to lee of the hull sheer, hasn't it?

    BTW the Bethwaite HSP had what appears to be smaller floats (in comparison with the main hull immersed volume) that were only there to prevent capsizing, and it was called a trimaran.
     

  15. Konstanty
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    Konstanty Junior Member

    For me the solution would be to connect a canting keel with foil on the opposite side in the same axis. Rotation on the ring outside the hull.
     
    Last edited: Oct 27, 2017
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