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Advanced Sharpie design explanation in a nutshell

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  • Patric Albutat
    Hi all, this is my first post on the group. If all of this has been discussed over and over I apologize but I m not quite sure I got it right. Obviously Bolger
    Message 1 of 32 , Oct 29, 2006
      Hi all,

      this is my first post on the group. If all of this has been discussed
      over and over I apologize but I'm not quite sure I got it right.
      Obviously Bolger requires some out of the box thinking! At the moment
      however I feel like it might be slightly beyond me.
      From where do you get the required righting torque when heeled over on
      a boat with no keel? They don't get their stability from beam either
      (like multihulls), quite the contrary. The righting arm curve reaches
      it's maximum at somewhere around 30° which doesn't sound terribly
      seaworthy to me. Hardly any righting moment to stop the boat from
      capsizing after that? The internal ballast won't work beyond 90° as
      opposed to deep keels (Hmm the same could be said for bilge keels so
      I've got to be making a mistake somewere). I forgot how much
      foot-pound of righting force you ought to have at 90° but I think self
      righting from 120° was considered a minimum requirement for oceangoing
      I guess this is where the high freeboard/buoyancy comes in?
      They won't stay upside down like a cat or tri though, that's
      definitely a good point.
      Also read that stability will increase by x^4 with waterline lenght
      whilst the drag coefficient raises at x^2. Frankly I don't understand
      why a long narrow boat will have any advantage there.

      If somebody please could shed some light on this?

    • proaconstrictor
      Aside from Herreshoff s experiments in the early 1900 s, multihulls didn t really begin to develop until after WW II I know what you mean though there is a
      Message 32 of 32 , Nov 1, 2006
        "Aside from Herreshoff's experiments in
        the early 1900's, multihulls didn't really begin to develop until after
        WW II"

        I know what you mean though there is a tendency to overlook thousands
        of years of development in the rest of the world. There were other
        westerners pre-Herreshoff and on a much larger scale. There have also
        been many important experimenters from below the yachting radar between
        Amaryllis and the post war

        "and for much of the last century were sort of a counter culture boat.
        It may
        take a few more years for multihulls to become mainstream."

        Never owned one, but from what I understand the Hobbie was the largest
        category of sailboat in it's day. Sailing multihulls are now
        frequently on the covers of yachting magazine, particularly those that
        emphasize cruising. In Europe multihull yacht racing has some
        considerable prominence with financial institutions using the coverage
        of boat ownership to snake their way onto public television, the whole
        fast ferry industry has gained momentum, there are catamaran cruise
        ships, there is the big day charter cattlemaran phenon. Dennis Connor
        owned a bunch of those sailboats. There are little niches like
        coaching boats for watersports and pontoon boats. Do we get to claim
        houseboats on two pontoons? Sailing yachts are my main interest and I
        don't see a time soon when multihulls will replace monos since they are
        expensive to dock. They are a far better bet for those who actually
        use their boats. They may be reaching a point where they have a
        mainstream level of mindshare. People don't care about them one way or
        the other, but if faced with a trip on one they don't pull out a dog-
        eared copy of Herreshoff's biography and start sputtering indignantly.

        "Our combative correspondant thinks it has
        because they are good investments. I doubt that because I never met a
        boat that
        was a good investment, because pleasure in non-tangible."

        Right, then neither drugs nor gambling will ever amount to anything.
        Good tip. I did not say they were a good investment I said there were
        a lot of them being bought as an investment. In Canada during the same
        period there was a government program designed to promote boat building
        (in the absence of a nuclear navy etc...) that gave government
        subsidies to people buying boats. People would buy these boats and
        rent them out. In the extreme, three college students created a huge
        business building houseboats that popped up everywhere. In the French
        case, the charter business led to the creation of several powerhouse
        cat companies like Privilege. Insurance was available to secure the
        loans, both relative to the crossings from France, and subsequent

        "Your tone remains insulting,"

        Get over it. I don't know you, and you don't know me. I sincerely bear
        you no ill will. I think you fired the first arrow against the
        multihull, I'm firing back with equal force. If some imaginary actuary
        gets caught in the crossfire, why should anyone care? Bolger is a
        designer of multihulls among other things, and the author of Boats With
        an Open Mind. That's all this is about, certain choices made by the
        great one, and open minds.

        "Multihulls are small in number and have (compared to monohulls) a
        short history. They have often been built by inexperienced amateurs who
        less than ideal materials and sometimes suspect design/construction
        As a result, there have been many boats which have either failed
        or simply gone missing."

        Right you are, though adjusted for scale, this sounds like a summary of
        Bolger boats also.

        "Insurers and actuaries are not comfortable with these
        exposures and either refuse to insure them or charge higher premiums."

        This is where it gets tricky. Do we know this for a fact? Is it world
        wide, or a one country, one state, one office thing? Does the
        insurance industry really keep these kinds of stats?. I have been on a
        bunch of the multihull boards, and also done survey work, and even got
        quotes for insurance that would have been a rider on my household or
        car policy, and was cheap, though I decided to self insure for the
        reason that I boat in a large lake in NB where there are virtually no
        other boats. I don't remember a problem about this ever. In southern
        Ontario we have at least 5 multihull factories (none of which I have or
        have ever been connected to) business seems OK. We have a strong club,
        not a member there either, but the people there seem very normal I
        don't know what they pay for insurance, never came up. The only
        problems I have had related to the boats being wood. There is a bias
        against wooden boats. People will tell you that one can't get those
        insured either.

        I have learned one interesting "fact" in all this. In the multihull
        world Amaryllis is fondly remembered as a triumph that was only held
        back by the conservatism of the day. I did not know that there was an
        alternative spin. I wonder which was the revisionist interpretation.
        Speaking of prejudice or conservatism in yachting. I think that is a
        far more likely lens through which to see this kind of thing today and
        for the last century or so.
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