1. The centerboard usually hangs down below the hull from a pivot at one end.

2. A popular trailerable centerboard sailboat is the MacGregor 26, which with its water ballast has the advantages of centerboard boats but not all the disadvantages.

3. If the centerboard is not weighted, like the fiberglass centerboards of many small sailboats, then sailors must keep the boat upright by positioning their own weight on the upwind side of the boat.

4. If the centerboard is weighted, then it also provides weight low in the water, like a keel, to help keep the boat upright (although not as much weight as a fixed keel can supply).

5. Shallow draft centerboard vs. deep fixed keel - trailerable vs. launched by boatyard.

6. You should put down the centerboard about 10 cm during downwind.

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7. Finally, some historic craft have leeboards instead of centerboards; these boards, mounted outside the hull on both sides, can be pivoted down like a centerboard to resist leeward motion.

8. On centerboard sailboats, the centerboard functions like a keel to keep the boat from being blown sideways.

9. The alignment and positioning of rudder and centerboard is also important. Otherwise you can't get correct data.

10. A swing keel is another term used for a type of keel that like a centerboard can be raised.

11. But there is a wide range of boats from 12 to about 25 feet with either a fixed keel or a centerboard.

12. For example, in this photo the boat on the left has a fixed keel, while the boat on the right, of about the same size, has a centerboard.