Where are the catamaran innovations?

Discussion in 'Multihulls' started by simon, Feb 1, 2009.

  1. Fanie
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    Fanie Fanie

    Sorry I missed your post there Dough.

    I saw the foilers on video, and yes, they do really move like in they bugger off. I thought it was quite impressive (for a MONO hull :D)

    To have a similar thing on ie a 10m (32feet) boat and larger, what will be the implications if you consider the size, weight etc ?
    How about if it gets blowed over like the 11' do :D

    Nobody drives the Ford T any more, but very few drives the formula 1's either.
     
  2. Doug Lord

    Doug Lord Guest

    ===================
    Fanie, many foilers have retractable foils! Including most of the new bi-foiling dinghies, The Rave, the new Osprey, the 26' Mirabaud-and those are just the ones I know about.
    =================
    Fanie, I and several others believe (from lots of study and number crunching) that a self-righting monohull keelboat foiler is possible. Very early projections show a speed at least as fast as an ORMA 60 tri flying the main hull for a 60 footer using this technology. But who knows when it will happen? I suggest you don't ignore the potential,though....
     
  3. Fanie
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    Fanie Fanie

    Hi Eralnd,

    I do not think the Dough meant to be offensive. Throwing all the arguments open is just a way to see what is coming back from it.

    We do not, unfortunately, know any of the answers, so usually answers bring more answers, in the hope someone that has tried something along these lines and could provide an answer to some questions, and hopefully would bring a few conclusions from that.

    Since nothing can be proven, all this discussion is just speculating, and it is human nature to argue, unless it's with your wife of course then one better always agree :D
     
  4. Doug Lord

    Doug Lord Guest

    Just say no....

    Wow, I must be right.....
     
  5. sigurd
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    sigurd Pompuous Pangolin

    Fanie, "To have a similar thing on ie a 10m (32feet) boat and larger, what will be the implications if you consider the size, weight etc ?
    How about if it gets blowed over like the 11' do "

    For some examples look at hydroptere, it is huge and fully flying.
    also the first page of the "foiler design" thread shows Tspeer's sketch of his flying tri (retractable foils).
    So the foils do get rather huge on larger boats if they are going to lift the whole boat at lower speeds.
    You also have the "banana daggers" in some multis, that seem to help with diagonal stability, keeping the lee bow up (and decreasing the wet area), but those are not crash worthy. I've seen a kickup mechanism for high aspect daggers in centerboard cases that may be coaxed to work with these but mounting externally seems easier.

    The formula for lift in Newtons is L=o.5*CL*density*area*V^2
    where CL is lift coefficient (a bit over 1 seems to be a common maximum)
    density is 1000kg/m3
    area is m^2
    V is velocity in m/s

    you can look at the lift/drag for the hull in hullcalc.xls, and compare it to the foils' L/D - some of them are between 10 and 20, i think, just for starters. Unlike the hulls it can be relatively constant over the intended speed range.

    Tipping over I imagine is like a normal boat - if you wanted it self righting, probably the easiest would be to make a mono (which could be fast, if the righting moment was assisted by outrigger foils) or a proa, or flooding an ama in a tri.
     
  6. Fanie
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    Fanie Fanie

    Eh watch it Dough, or I'll get Eralnd again :D

    Sigurd, on a bigger boat it is going to be much less fun when it capsize. If there's any remote possibility of something like that, I can tell you now the wife would never set foot on it (hey someone has to clean...) and I'm not sure what you'd do with all the stuff you use all the time.

    The other thing is cost, on larger boats it's going to be muuuch more expensive, and seeing most people are watching their finances off late...
     
  7. sigurd
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    sigurd Pompuous Pangolin

    I ment that a boat with foils is not nesecreiliy more prone to capsize. In some cases the foils gives extra righting moment and it would be tempting to use it to carry more sail. If the foil lift suddenly disappeared then, because of kelp, ventilation or other, then you might have a problem.

    Yeah, it would add some surface to the rudders and daggers, so they would be more expensive. For the cat I would put a splayed T without flap in the bow, mounted rigidly to an axle going through both hull skins. It is the simplest and strongest I can think of because it has the kickup, and the AoA adjustment (to the wand) and the retractability in one moving part.
     
  8. Gary Baigent
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    Gary Baigent Senior Member

    hey Chris
    Relax, take a deep breath man, (I've told you this before) you're ranting and making a complete and utter *** of yourself.
     
  9. Fanie
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    Fanie Fanie

    Well throw a couple of drawings up. Someone may like the idea and actually build it :D One big advantage foils have if you can get the boat up enough is it will have a very soft ride.

    I can already see the passengers lift off in their seats when you follow the line over some big waves, be like in those fast lifts that stops so suddenly going up. Me, I just like the skirts flying up :D
     
  10. Chris Ostlind

    Chris Ostlind Previous Member



    Fanie, You insouciant fellow, you.
     
  11. Fanie
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    Fanie Fanie

    Well, I used to be biking (speed freak) before I sold the last one barely before I kill myself. Anyway, when I bought the first one,
    my mother wanted to know what type of a girl do I think was going to get on a motorbike with me.

    The answer of course is the right type :D

    He he... went for a medical checkup recently to see if some spares need rebuilding or replacement due to wear and so on,
    so I said to the doc seriously, Doc I think there's a big problem with me. I'm having troubles doing it more than twice a day,
    things just aren't working as they should. Well, him being much younger than me... the disbelieve on his face. So I said Doc,
    you're watching too much tv.

    Truth of the matter is, if I say sex or work on the boat, the wife says dust off before you come in the house :rolleyes:

    So, it seems like you get three kinds of people.

    Those that watch tv,
    Those that build boats
    And those that think foils are going to take over the word :D
     
  12. Chris Ostlind

    Chris Ostlind Previous Member

    Fanie,

    I just called my lawyer and had your name put in my will as the ambassador of humor. Yes, that's a beneficiary position. He will notify you when the check is in the mail... and no, it's not transferable, so if you croak before me... there's no payout.

    Good Luck
     
  13. Doug Lord

    Doug Lord Guest

    -----------------------------------
    No,God help me no......
     
  14. sigurd
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    sigurd Pompuous Pangolin

    There are many possible configurations of this theme, depending on span, area, draft, handling requirements and structural ones. I just made some paint sketches - Hope it is understandeable. The wand can be on the bow or on the foil itself.

    A hypothetical case: If your displacement is 2 tonnes, if the load is divided equally between lee fore and rudder foil, if takeoff speed is 15 kt, if the CL is 1.3 and if the aspect ratio is 5 then each foil is about 0.25m x 1.15m. This doesn't account for the splay or downforce from sails and is just a rough "something".
    Ketterman (?) says to err on the small side but my dad says "it is not a problem with the sausage which is too long".

    pic number three I like because 1) it has nice structural efficiency 2) it can swing inboard 3) it can swing up beside the keel in a collision 4) it gives extra righting moment
     

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  15. sigurd
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    sigurd Pompuous Pangolin

    The former bearing arrangement looks silly. This is more nice.
     

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