Shallow fin keel ?

Discussion in 'Sailboats' started by frank smith, Jan 25, 2011.

  1. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    By re-arranging your formula and grouping numerical constants together, you arrive to:

    0.03 / [5*sqrt(0.03)] = sqrt(0.03) / 5 = 1/28.9 = (approx.) 1/29
     
  2. sharpii2
    Joined: May 2004
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    Location: Michigan, USA

    sharpii2 Senior Member

    Hi, Viking.

    What sort of boat do you own?
    A sailboat? a motor sailor?
    Does it have a full length keel?
    How close to the wind can it point?

    I would agree with you for the most part. But I think the short, deep fin keel is here to stay. Although they can get in trouble in heavy weather, they can get out of trouble quite easily. A bigger rudder and a commitment to always keep the boat moving seems to be the ticket. At least that's what I garnered from reading books about the 'Fastnet' and 'Sydney-Hobart' disasters.

    Lets face it, ocean cruising is quite a specialty use of a sailboat. Many dream, few partake. So, the deep, short fin keel may dominate in even that for quite some time. It, with the right reenforcing and equipment add ons, can be more than enough to meet the challenge. It may actually be more sea worthy too. Not that the boat is more seaworthy, but that the crew is. They are used to this kind of boat and, over the years (hopefully), they have learned its little tricks and quirks. It's when the boat does something totally unexpected in a bad time that the real trouble begins.

    I think a return, or partial return of working sail, or working sail assist, will bring the long keel back as a more or less standard norm. It is one thing to ride a boat that rolls and pitches sharply, from time to time, across an ocean. It is quite another to work on its decks the majority of ones working life.
     
    Last edited: May 18, 2011
  3. sharpii2
    Joined: May 2004
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    Location: Michigan, USA

    sharpii2 Senior Member

    Thanks, Daiquiri.

    I see now why you are the engineer and I'm the security guard.

    The only problem I see with this is that the 0.03 number is intended to be a variable constant, meaning it can be replaced with 0.02, 0.025, and so on, depending on the S/D of the boat and its intended speed range. A higher S/D ratio can mean a lower constant, as, with the greater working sail area, the boat can be expected to be moving at a higher average speed.

    I suppose you could put it ' /29 to 35', using your version.
     
  4. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    It's your formula, I've just re-written it in imho visually simpler terms (no big deal).
    I don't have means to check if your formula is correct - perhaps Dskira, PAR, Tad Roberts or some other designer with more experience in designing classic boats with long keels could give it a try.

    Cheers!
     

  5. viking north
    Joined: Dec 2010
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    viking north VINLAND

    Motorsailer of course is there any other type :). I can sail as close or closer to the wind over a longer distance than a fin keeler, simply fire up the engine and let it tick over and assist the sails. That way I don't need a generator to charge up my batteries in route or when i arrive in port. I can also enjoy all the comforths that electricity can provide while beating to windward in messy cold weather in a cosy heated wheelhouse. Gave up that 100% sailing hero mentality years ago--not that there's anything wrong with it , just not my cup of tea anymore. Don't sleep in a tent anymore either but I do hunt deer, moose and bear without bait, the old fashion way on foot tracking. Geo.
     
    Last edited: May 18, 2011
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