Lunatic keel ?

Discussion in 'Projects & Proposals' started by Externet, May 26, 2009.

  1. Externet
    Joined: May 2009
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    Location: Mideast U.S.

    Externet Junior Member

    Greetings to all. First post here. My terminology may be imprecise, but trying...

    Imagine any plain ~40 feet sailboat, with the usual several thousand pounds of lead keel.

    Such keel instead of making it heavy, making it just strong enough but 'light'.
    A couple of horizontal fins somewhere along the keel length, could be at the bottom as an inverted T.

    The fins with controllable angle of attack pivoting at their centerlines (as to demand minimal effort to change angle)
    Both fins thin, with sharp attack and tail edges.
    The heeling of the sailboat shifts a let's say pendulum mechanism that acts differentially directly to the left and right horizontal fins attack angles in the keel to counterforce towards a vertical mast. (As starboard fin up and port fin down)
    A couple of rods inside the keel for the pendulum to actuate the fins.

    Pros ? :
    -Decreasing the weight of the keel reduces the wetted hull surface and draft, less drag.
    -Less crew or no need for the crew to use their bodies to counterbalance to keep the sail vertical, or no crew performing that task.
    -The vertical sail gets exposed to more wind; better trust efficiency.
    -Smooth effortless sailing ?
    -Plus/minus whatever you add because I don't know enough.

    Cons ? :
    -Drag from the horizontal fins.
    -Mechanism to control the fins by a let's say pendulum that acts onto the horizontal fins to keep the boat from heeling.
    -Plus/minus whatever you add because I don't know enough.

    There is more fine tuning of the contraption as to simultaneously make the fins work as hydrofoils to further reduce the draft as speed increases.

    In other words, the horizontal fins to autoforce the mast to a vertical at all times.:rolleyes:

    Shoot me ?
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    That could only work if the boat is moving and has dynamic lift on the wings. It would not have initial stability or stability at low speeds, for example right after tacking when the heeling is worst. In other words, it will capsize.
  3. Knut Sand
    Joined: Apr 2003
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    Location: Kristiansand, Norway

    Knut Sand Senior Member

    Sometimes when you... well not maybe you, but It least when I do; screw up during tacking(?) the boat suddenly loose all speed, and is located more or less completely with the full side against the wind.... A light keel as described would have minimal effect when the boat is not moving, making a situation as that pretty interesting.... Would be rather inspiring to move the flesh about a bit, fast...

    A lighter keel, adjustable fins, ok, but not too light....:D

    BTW1; I believe you'll find this if you google a bit, also swinging keel...

    BTW2; If the fins shall be effective and at the same time not cause drag due to wetted surface, there is a question of area versus fin angle in consideration to the direction of travel, too much angle can act as an pretty effective brake, also causing turbulence, loss of control....
  4. Boston

    Boston Previous Member

    how about a variable geometry keel that is basically a vertical wing with the ability to alter its section such that the lift side could be altered from one face to the other

    a single cam like device rotating and deforming the interior could be used to "bend" one side to a foil shape and allow the other side to relax to a flat shape

    would have less drag than the fins you describe but still allow you to counteract forces without the weight of the typical keel

    learn how to sail :D
  5. Knut Sand
    Joined: Apr 2003
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    Location: Kristiansand, Norway

    Knut Sand Senior Member

    Keel with wing profile with the ability to change as a plane wing profile, generating lift toward windward; I believe I've seen a paper or a patent description on that some years back... Haven't seen photos or real life though... Anyone?
    Don't think there's any cigar here.... :p

    Learn to sail...?
    I've once bought a tiiiny folder; "Sailtrim in an hour" several years back, showed that there was quite a lot of condensed knowledge in those few pages...Got a few tip, that increased the average speed during sail, although I'm no competition sailor. Problem with sail is that the wind changes direction, usually when I'm ducking down under to see how the coffe kettle is going on in progress....:D

    (Resulting in the impossible question;
    What to save first; the coffee or the boat?). :confused:
  6. Boston

    Boston Previous Member

    well at least you will have a nice warm cup in the raft

    no worries
    my sailing is rusty to say the least
    although I think if things pick up some I will make it out to the coast again
    this year I think Ill head up to Seattle as I want to dive on some of those giant octopus they have up there. Ill try to get out for a day or two sailing but I dont know anyone up there so Ill be winging it

    and put something orange on that coffee pot
    you might spot it floating past and get lucky some day
    course the guys in the life boat are going to want some
  7. MikeJohns
    Joined: Aug 2004
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    MikeJohns Senior Member

    Welcome to the forum

    Lift is accompanied by drag, if you are using dynamic lifting foils to counteract the sail force heel then the net result will be a high drag penalty. Much better to use ballast or to consider a multihull.

    As others have pointed out the foils will only work when not stalled, if you want them to operate at low speeds you will need a low AR foil to delay stall.

    Finally I doublt it's even possible to get the COG low enough without ballast for a safe 40 foot mono-hull without a very wide flat bottomed hullform, 40 footers are too big to rely on movable ballast or recovery from inversion by the crew.

  8. yipster
    Joined: Oct 2002
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    Location: netherlands

    yipster designer

    than again fins on a keel work better and with less drag on smal deep hull than on flat bottoms
    another cool keel idea from Juan K Brian posted some time back

  9. Externet
    Joined: May 2009
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    Location: Mideast U.S.

    Externet Junior Member

    Thanks, gentlemen
    Then, perhaps keeping a somewhat heavy keel would allow implementation of fins for the purpose of autoleveling a sailboat.
    The behavior at very low speed is something that I did not think before.:rolleyes:

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