Keel types: underwater trade-offs
Keel, ballast and lateral resistance are not the same thing.
In plain language
A fin keel concentrates the keel in a fin; a long keel occupies more length. Bilge or twin keels are two lateral keels. A bulb keel concentrates mass in a bulb; a wing keel has wings. A lifting keel moves a keel, often ballasted. A centreboard is a movable lateral-resistance foil and does not imply that all ballast moves.
How to interpret it
Draught, shape, mechanisms and ballast distribution matter more than a better/worse label.
Why it matters
A movable system can provide draught flexibility; some twin-keel configurations can dry out where the manufacturer permits it.
Limitations
Do not assume every twin-keel boat can dry out on any seabed. Movable systems add inspection and maintenance requirements.
In practice
Compare the exact keel version. The same model name can cover different draughts and masses.
Sources & reading
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