80 feet monohull sailboat concept

Discussion in 'Sailboats' started by F17 Francesco, Dec 27, 2012.

  1. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Hey, Mike, when they say "Geologist" are they talking about 4yr degree or PhD?

    My older brother planned to major in it at UC Berkeley, thinking it would be a "soft science" and mostly learning names of rocks. He found out it meant taking all the hardest math, physics, and chem of a major in those areas, PLUS other really hard courses.

    So he switched to "poly sci".
     
  2. CT 249
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    CT 249 Senior Member

    How will those foils work? The aspect ratio would appear to make them unbuildable and innefficient; at low speeds they could well be too high in aspect ratio and at high speeds they are too long.

    I'm not a designer but because of my old job I was able to talk to some top designers. The big difference between successful designers and unsuccessful ones is that the good guys are good sailors and/or have very close collaborations with good sailors. That way, for example, they will know that having foils that are too high in aspect ratio only looks good in theory, and that in real life such foils can just so sideways when faced with a heavy chop.
     
  3. oldsailor7
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    oldsailor7 Senior Member

    Get a look at those fees.
    http://www.cbtfco.com/Licensing_files/CBTF_FeeSchedule.pdf

    Chris is quite right.
    High aspect foils, like rigid wings or airfoils are very efficient at low angles of attack, but stall easily.
    A monohull with it's rolling and yawing, causing wide swings in AOA, is better off at lower aspect ratios which can handle them.
    Edmund Bruce covers this very well in the book "Design for Fast Sailing".
     
  4. Sailor Alan
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    Sailor Alan Senior Member

    Thin Foils and planing sailboats

    Very interesting thread. Don't go in for naval architecture, or Physics either for that matter. (I'm a retired physicist) Both are impoverishing. Do something you love, then you can make time for designing, building, and/or owning boats.

    Interesting conceptual design. I have done a couple rather smaller but similar ones, 30’ and 35’ long. Mine were to find out how far i could take 1/4” plywood matrix construction.

    I think you have been following fashion far too much.

    First the bow. One of the original reasons for rake, and eventually flair, on a boats bow was to increase the rate of change of displacement with immersion at the bow. This was to limit, or reduce, wave induced pitch, though the fishermen and sailors might have seen it simply as stopping waves sloshing over the bow in a head sea.
    The modern trend back to vertical bows started with trying to grab as much waterline length as possible, usually against the racing rules, sometimes ‘box’ rules. A vertical stem with flair was slightly sensible, but the increase in displacement forward still tended to ‘stop’ the light displacement hulls. The theory was to make the boat plane such that the bow was usually already high, or accept a very ‘wet’ deck. You only have to see video of these modern racers down in the “Screaming 60’s’ to appreciate how wet they are, and how dangerous futzing with sails etc on the foredeck is. A reverse raked bow, like a modern catamaran, looks like a misguided attempt to save a few pounds in the bow, whilst keeping maximum waterline length.

    The keel(s); Manny years ago a Herreshoff (L H?) wrote a paper on the “ideal sailboat” (I think). It revolutionized some peoples thoughts on how sailboats should be designed, trying to stop the slavish following of racing rules for cruising boats, and to think about how a sailboat actually worked. Before this, the older British deep keeled “cutters” and the relatively shallow centerboard American boats influenced disproportionally by their respective Americas Cup boats, tended to hold a lot of sway in fashion, if not function (read Clinton Crane’s book). Remember the dismay Charlton Mitchell caused when he took his wide beam, centerboard racer to Britain and won everything in sight.
    Regardless, the Herreshoff paper described separating the keels righting moment function from its leeway preventing function. “Red Herring” was an early and brave attempt to exploit this theory, but it took many years to refine. To be honest, these new swing keel boats are not too far different from the Chesapeake racing canoes with their ballast to windward, and wooden dagger boards.
    I would personally NOT use a swing keel, its hard engineering and heavy to provide the swing mechanism, and catching a wave UNDER the ‘keel’ on the surface was not fun. I would use a fixed vertical keel, blunt leading edge, with about 50% of the vertical area hinged as a kind of “flap” like an airplane wing. Actually airplane wings usually have about 20-30% chord as flaps, in this case i would have at least 50%, perhaps even 60% as a ‘flap’. I might even consider having a double hinged flap, just like a 777 rudder.

    Hull Form; my own cartoons used a ‘flat’ bottom, tapered radically from a sharp forefoot to a wide flat transom. The forefoot was barely immersed, whilst the transom was raised just enough so it was not immersed whist at hull speed or lower. At planing speeds the water should flow straight aft (Kamm effect). I also had a double chine, partially so it could be built in plywood, but also to get clean separation of flow along the sides toward the back. I didn't care about pounding, if you were even on this boat, you had to be immune to pounding.

    Rudders: even using modern materials, like carbon fiber, or beryllium fibers, it would be hard to get rudder blades of that aspect ratio to work. Twin canting rudders only work well when you can get the ‘lazy’ one out of the water.

    Sail Plan: not really workable, and far too large as well. The top batten would be unsustainable even using modern materials. It relies on mainsheet tension down, and a stiff upper mast to stand, and neither of these are available yet at this proportion even using modern materials.
     

  5. TeddyDiver
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    TeddyDiver Gollywobbler

    Butt ugly, thou have to admit that I've done some worse sketching during the years. The bright side, next one one will (=must) be better :D
    Hope you didn't give up. It would be nice to see if there's been some progress..
    BR Teddy
     
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