Canting Keel Design

Discussion in 'Sailboats' started by MrK, Feb 25, 2005.

  1. MrK
    Joined: Feb 2005
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    MrK Junior Member

    Hey Folks,
    I'm a yacht design student and currently thinking about canting keels.
    Does anybody know how the mechanics on for example in the backman 21 work??
    How can I fit the shaft in the keel fin? How are the keel fins in littel yachts (20-30 foot) built??

    Cheers Konstantin
     
  2. Raggi_Thor
    Joined: Jan 2004
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    Raggi_Thor Nav.arch/Designer/Builder

    There is a picture of the keel on
    www.backmanboats.com

    The keel is opereated by a simple rope mechanism.
     

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  3. nemo
    Joined: Apr 2002
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    nemo Naval Architect

  4. Raggi_Thor
    Joined: Jan 2004
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    Location: Trondheim, NORWAY

    Raggi_Thor Nav.arch/Designer/Builder

    No, you better ask Mr Backman.
    All I know is that it's operated by ropes/tackles.
     
  5. Doug Lord

    Doug Lord Guest

    Canting keel/ lateral resistance

    In small boats, if you consider a canting keel you need to give a lot of thought to the type of extra lateral resistance that you will use. A lot of boats use a daggerboard either fixed or gybing.
    There are some alternatives that may be better including fixed "wings" on the keel bulb, retractable wings that fold into the bulb(kFOIL™) when not required and a new system designed by Julian Bethwaite that uses a wing shaped "bulb".Of the three, only the kFOIL™ reduces wetted surface when it's not being used.
    All three of these concepts eliminate the need for a daggerboard in the hull and can open up extra room and greatly simplify the use of a canting keel.
     
  6. Paul B

    Paul B Previous Member

    Discounting, of course, the fact that the bulb for the ****** needs to be BIGGER THAN REQUIRED and will have increased wetted area and drag.

    Of course two of the three "alternatives" mentioned have never been used on a boat yet, and the third has not been proven in head-to-head trials.
     
  7. Doug Lord

    Doug Lord Guest

    canting keel/ lateral resistance.

    The kFOIL™ has not yet been tested in a full size boat but the concept relies on wings for lateral resistance which HAVE been tested and proven in competition by Andy Dovell in Australia. Julian's concept has apparently been tested on a previous boat and thoroughly investigated in the course of design.
    For more information on the kFOIL™ and it's application to canting keel yachts-big or small- contact Eric Sponberg thru his website at: www.sponbergyachtdesign.com
     
  8. Paul B

    Paul B Previous Member

    What do those words mean? Proven to be equal to an identical design equipped with a canting keel and a daggerboard? Equal to CBTF designs?

    IF the Dovell design WAS proven to be as fast as a canter w/board, could the ****** fit wings as large as Dovell uses without the bulb becoming ridiculously large?


    So you are on first name terms with Mr. Bethwaite? Do tell us the details of the "previous boat". I'm sure you must have all sorts of "insider" info on the "thorough" investigation. Please share.


    Yes, so Mr. Lord can finally get royalties from his concept.
     
  9. Doug Lord

    Doug Lord Guest

    canting keel / lateral resistance

    I've read about Dovells success with wings in Seahorse and Australian Sailing as well as having him personally tell me about it in a telephone conversation.
    I don't know Julian Bethwaite personally but I know a lot about him and I can assure you he has thoroughly investigated his "wing" concept. Both these guys have websites and are accessible for any questions relating to their wing systems.
    The kFOIL™ can result in a slight increase in bulb area but the net loss of area(not to mention induced drag) when the wings are retracted far outweighs that very small increase.
    The gain in overall simplicity and room in not having an extra daggerboard in a small boat is a huge plus for any"winged" system.
    No only that but when using a daggerboard the CLR shifts as the keel cants and with "wings" it does not or at least if there is any shift it is in a positive direction and very small.
    At this point I think that CBTF is still the best solution for many canting keel boats especially larger ones. But its hard to beat the simplicity of wings -fixed or retracting for small boats or in larger boats where inside room matters.
    ---------------------------
    For some interesting views of Julian Bethwaite's winged canting keel 79er check this out:
    http://www.bethwaite.com
     
    Last edited by a moderator: Mar 11, 2005
  10. Paul B

    Paul B Previous Member

    So you read about it in a couple of magazines. That's not quite enough research to make the statements you make, is it?

    Oh, and that phone call. I've heard about your phone calls. :eek:


    No, you can't. You don't KNOW any details about this project. You may surmise these things, but you cannot assure us. In fact, you don't know if Julian Bethwaite even designed the keel foil. It is possible (probable?) that he was involved, but for all you know Martin Billoch may have designed it.


    Percent upsize? Give us an example. How about something like a Mini 6.5 bulb?
     
  11. Schnick
    Joined: Mar 2005
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    Schnick Junior Member

    How, exactly, is a system with two separate foils, moving around inside a bulb at the end of a canting keel simpler than a daggerboard in front of the canter?
     
  12. Doug Lord

    Doug Lord Guest

    canting keel/lateral resistance

    The kFOIL system can have a single pivoting foil or two foils pivoting together in several variations.
    The simplicity comes from the fact the daggerboard trunk is eliminated as is the manual handling of the daggerboard since the kFOIL can be set up for fully automatic operation.
    Further, the kFOIL elimintes any negative balance changes as the keel cants.
    The kFOIL can automatically retract if it contacts anything hard which is a lot simpler than trying to replace a broken daggerboard.
     
  13. usa2
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    usa2 Senior Member

    what about the water disturbance created by the slot in the bulb on Kfoil?
     
  14. Doug Lord

    Doug Lord Guest

    slot

    Gasket; somewhat similar to one on a centerboard trunk.....
     

  15. usa2
    Joined: Jan 2005
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    Location: Maine

    usa2 Senior Member

    A few years ago my father and i were considering building a canting keeler and I drew up a keel that is similar to what Andy Dovell uses. I was then flipping through a magazine about a year after drawing it and came across a picture of Atomic, which is Dovell's first winged canting keeler. Does anyone have any pictures of that boat?
     
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