Keel Types
Keels are the stabilizing element of boats and ships. On sailboats they not only prevent rolling motion, but also are the counter force to the wind blowing into the sails by providing resistence with their area and righting moment when carrying ballast.
Some boats have keels fixed to the hull, others have movable keels that lift up or swing from side to side.
Basic keel shapes
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- Fixed Keel
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- Full Keel
- A full keel is the classic keel shape with the keel starting at the bow, going all the way to the stern and ending with the attached or transom hung rudder.
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- Modified full keel
- A modified full keel starts the keel going down a bit more aft. This still provides good heel reduction and comfort while sailing, but is less slow than a full keel.
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- Fin keel
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- Bulp Keel
- A bulp keel has a big (usually) tear-drop shaped bulp at the bottom of the foil wich acts as a counter balast to the sails.
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- Winged Keel
- A winged keel has wings on the lower end of the keel in order to reduce drag in the water caused by the keels bottom end similar to a winglet on an airplanes wing.
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- Tandem keel
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- Bilge keel
- A bilge keel or twin keel has a foil on each side of the hull.
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- Tripple keel
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- Moveable Keel
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- Canting Keel
- This keel pivots on an axel to port or starboard and provides a bigger lifting moment in order to counteract the heeling forces of the sails.
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- Lifting Keel
- A lifting keel can be lifted for transport of the boat, to reduce draft in shallow waters or to reduce drag while running. In contrast to a daggerboard, this keel usually has ballast (mostly a bulb) and may not be completely retractable.
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- Centerboard Keel
- A small fixed keel with an included centerboard trunk. The centerboard can be lowered when needed to provide more stability.
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- Centerboard
- A centerboard is a keel foil that can be lifted by pivoting into the centerboard trunk and is position on the centerline of the hull.
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- Daggerboard
- A daggerboard is a keel foil that is vertically lifted into the trunk and is positioned on the centerline of the hull.
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- Leeboard
- Leeboards are positioned on port and starboard on the outside of the hull.
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- Bilgeboard
- A bilgeboard is positioned in a trunk inside the hull between the centerline and either the port or starboard side (or on both sides).