#centerboard__centreboard__drop_keel__sliding_keel__slidingkeel  a retractable fin keel used on sailboats to prevent drifting to leeward
  supertype:  #fin_keel__finkeel  a metal plate projecting from the keel of a shallow vessel to give it greater lateral stability
  subtype:  #daggerboard  a removable centerboard on a small sailboat that can be lowered into the water to serve as a keel
  part of:  #sailboat__sailing_boat__sailingboat  a small sailing vessel; usually with a single mast

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