International Canoe Daggerboard

Discussion in 'Sailboats' started by Doug Lord, Nov 23, 2011.

  1. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    I've been doing some research on existing classes that might be a candidate to use a single curved lifting foil as more thoroughly described in this thread:
    http://www.boatdesign.net/forums/sa...kind-performance-one-design-dinghy-39229.html
    I finally found the IC rules valid from Jan. 2005 and there is no mention of any restriction that would prevent the use of this type of board.
    The advantage of a single curved lifting board is that, if properly designed, it could significantly reduce wetted surface. The disadvantage is that you have to move it with every tack or gybe. That may be fixed by tieing the board movement into the sliding seat so that the movement is automatic.
    If anyone knows of a more recent rule than the one below please advise.
    Any comments or suggestions would be appreciated.

    Rough sketches: single curved lifting foil slides in a discontinuous athwartship trunk. Foil can be symmetrical or asymmetrical--

    click on image-
    see 2005 IC Rule below
     

    Attached Files:

  2. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    I have found out the board is legal in the IC Class.
    ---
    IMPORTANT CLARIFICATION: The board, whether symmetric or asymmetric is sailed on the LEE side at all times! It does not add to or detract from RM except in the degree to which the boat lifts vertically up. Since this is a "foil assist" application that distance is very, very, small. An additional disadvantage may include a reduction in the projected area of the foil used for lateral resistance since the IC has a maximum depth of the board of 1m below the hull.
     
  3. MalSmith
    Joined: May 2004
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    Location: Australia

    MalSmith Boat designing looney

    The latest rules (2008) are at http://www.intcanoe.org/library/APPENDIX IV Jan 2008.pdf

    The new rules prohibit more than one centreboard case. The new IC rules were framed to discourage foils but not prohibit them. The boat must be launchable with no foils projecting below the hull keel line. The foils must be able to be fitted to the boat when launching without the use of tools.

    The IC may not be a good candidate for this foil experiment as there is enough to do already during a tack, without having to tack the foil as well. It would be a challenge, to say the least.
     
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  4. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Thanks, again Mal. From those rules it is clear that the single curved lifting foil is illegal. Too bad.
    I think the moving problem could be dealt with by tieing the foil into moving the seat in some fashion. But no matter now.
    Development classes that don't allow development are unfortunate. I've always loved the IC and for a few moments thought it would be a definitive way to demonstrate this foil. The 1m projection was another stumbling block that may have spelled doom because of area. Oh,well. I appreciate your help in resolving this.
     
  5. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    IC-single curved lifting foil

    Mal, I was just looking again at the rule and noticed it didn't specifically say anything about openings-it said: ".. by no more than one centerboard trunk."
    One of the cool things about the single curved foil is that it uses only one trunk(with two openings).
    Though I think, based on this, it is technically legal- it would probably cause trouble and violate the "spirit" of the rule. And thats too damn bad......
     

  6. Steve Clark
    Joined: Jul 2004
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    Location: Narragansett Bay RI

    Steve Clark Charged Particle

    Curved daggerboard

    Come on Doug, just because you can't try every crack pot idea doesn't mean that the "class does not allow development." Seriously, the class rule does not prohibit foils, it just insists that they be practical. To the authors of the rule this meant that the boat had to be easily launched and retrieved from a dolly without spending 20 minutes on its side at the end of the launch ramp. The restrictions on "holes through the structure" prevents some unwholesome rule dodges that were worth shutting down. There is plenty of room for experiment and development, just not the particular hobby horse you are riding today.
    I have done my little bit to introduce the lifting foil into multihulls, but given my calculations and experience, the IC isn't a good candidate for a curved foil experiment. There are other boats, like scows, that would be better platforms.
    SHC
     
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