Glossary Term: Centreboard
Definition:
A centreboard is a pivoting or retractable keel-like structure used in sailing vessels to improve stability and directional control. Typically located along the vessel’s centreline, the centreboard can be raised or lowered to adjust for varying water depths and sailing conditions.
Purpose and Functionality:
• Stability: The centreboard counters the lateral forces of the wind, reducing drift (leeway) and allowing the vessel to sail effectively upwind.
• Draft Adjustment: By raising or lowering the centreboard, a vessel can operate in shallow waters or enhance its stability in deeper waters.
• Ease of Transport: Retractable centreboards enable smaller vessels to be transported or stored more conveniently.
Types of Centreboards:
1. Swing Centreboard: Pivots on a hinge and swings up into a housing.
2. Daggerboard: Slides vertically into a slot and is simpler but less adaptable than a swing centreboard.
3. Ballasted Centreboard: Contains added weight to improve stability while serving as a keel.
Historical Context:
• Development: First widely used in small sailing craft, particularly on inland and coastal vessels.
• In Shipwreck Analysis: Centreboards (or their remnants) can help identify the type and function of smaller wrecked vessels, such as schooners or yawls, often used for trade or fishing on the Great Lakes.
Advantages of a Centreboard:
• Flexibility for shallow waters.
• Lightweight and retractable, reducing drag when not needed.
• Enhances manoeuvrability, making it ideal for smaller sailing vessels.
Disadvantages:
• Less effective than a fixed keel for maintaining course in rough conditions.
• Mechanical components (if present) may require maintenance or are prone to damage.
Relevance in Great Lakes History:
Centreboards were widely used in schooners and smaller trade vessels navigating the shallow harbours and rivers of the Great Lakes. Their design allowed versatility in carrying goods or passengers across varied depths and conditions.
Related Terms:
• Keel: The structural backbone of a vessel, often fixed and non-retractable.
• Draft: The vertical distance between the waterline and the bottom of the hull or keel.
• Schooner: A type of vessel commonly using centreboards in the Great Lakes region.
Keywords: Sailing vessel, retractable keel, centreline stability, Great Lakes schooners, ship design.