Keelklasside

Keelklasside is a term used in naval architecture and yachting discussions to describe the classification of keels, the underwater fins or ballast structures attached to a hull to provide stability. The phrase appears in several languages with similar roots and is not standardized in international nomenclature; in English-language texts the concept is usually referred to as keel types or keel designs.

Typical keel classes include full keel, fin keel, lifting keel, wing keel, bilge keel, and twin keel. A full keel runs a long distance along the hull bottom, offering stability and straight-line tracking but often with reduced maneuverability. A fin keel is shorter and deeper, providing improved upwind performance and agility at the cost of increased draft. A lifting keel is retractable, allowing variable draft for shallow waters or road transport. A wing keel places a horizontal fin near the bottom to reduce draft while preserving stability. A bilge keel places two shallow keels on the hull’s sides, beneficial for shallow harbors and easy grounding, while a twin keel arrangement uses two fins for similar purposes. Some designs use retractable centerboards or appendages that function similarly to keels.

The choice of keel class affects stability, righting moment, wetted surface, ballast distribution, draft, and cost. Designers consider intended waters, sailing goals, and handling characteristics when selecting a keel class. As a term, Keelklasside emphasizes keel geometry within hull design and is used in various regional and technical contexts.