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Swing centerboard effectiveness?

Discussion in 'Trailer Sailors' started by Tsam, Sep 6, 2017. Add this thread to a FAQ

  1. Tsam


    Joined Jun 28, 2011
    21 posts, 1 likes
    S2 6.8
    US Long Lake, MN
    Have a hard time determining the effect of the three foot long, 100 lbs. swing centerboard on my S-2 6.8m shoal draft crusing day sailer. The fixed shoal draft keel has 1,000lbs of lead. Overall boat weight 3,000lbs.
    Fixed keel draft is 2ft 4inch. Swing centerboard adds another 2.5 ft of draft.
    Under what conditions should I notice the favorable effects of the swing centerboard?

  2. TomY

    TomY Alden Forum Moderator

    Joined Jun 22, 2004
    761 posts, 161 likes
    Alden 38' Challenger yawl
    US Rockport Harbor
    You may not notice the effect by how the boat feels. If the centerboard is working - creating lift going to windward - you may detect a change in your boats course over the ground, on a GPS chartplotter or App.
    The boats motion may stay the same(board up vs. board down), but the lift generated by the centerboard, lessens leeway and may show an improved course to windward (I find 5 degrees on the average).

    Larry -- DH likes this.
  3. Justin_NSA


    Joined Jul 7, 2004
    3,773 posts, 327 likes
    Hunter 30T
    US Wichita, KS
    I agree with Tom. Reduced leeway is the main advantage

  4. scoob


    Joined Dec 9, 2016
    14 posts, 3 likes
    Sage, Montgomery 17, 15, SageCat and 17
    US Denver Denver
    can also feel the difference in the helm ... depending on the boat more/less weather/lee helm. also the boat's ability to point to weather.

  5. Crazy Dave Condon

    Crazy Dave Condon

    Joined Jun 8, 2004
    5,562 posts, 310 likes
    -na -NA
    US Anywhere USA
    In layman's terms some say it helps the boat from slipping sideways. Use to sail that boat with a friend a few times. Try it with it up and then down and you will see what we are talking about.

  6. SailormanDan


    Joined Jan 24, 2009
    306 posts, 48 likes
    1981 Cherubini Hunter 27
    US Alexandria, VA Belle Haven Marina, VA
    From my C22 days, I would feel it like Dave mentions when the wind blows across the boat. You will also feel it stabilize the rocking after a powerboat blasts by, versus with the board up.
    Conversely, when running down wind, crank the keel up to reduce drag.

  7. Brian S

    Brian S

    Joined Nov 9, 2012
    2,263 posts, 125 likes
    Oday 192
    US Lake Nockamixon
    I have a keel/centerboard combo, and I can tell you that sailing anything closer than a beam reach, the boat goes noticeably faster when I put the board down. All that side slipping gets translated to forward motion. My board is not ballasted, other than weighted to have negative buoyancy. It probably doesn't markedly affect the boat's rolling motion, other than the board would slow down a roll. Honestly, having pressure on the sails probably does more than the drag of the board swinging laterally through the water.

  8. Larry -- DH

    Larry -- DH

    Joined Jun 14, 2010
    109 posts, 21 likes
    Quorning Dragonfly 1200
    US home
    Agree with above posts, but when going downwind (aka "sailing deep") you may find that raising the board allows you to go faster. Dead downwind -- raising it will reduce wetted surface, and you won't benefit from lift when it's down. Deep reach - you would lose the lift but the extra leeway (side slip) will allow you to point the boat so that the jib/genoa has more exposure to the wind (with less of it shielded behind the mainsail).

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