Boats with inflatable keel

 

— the keel bottom, in which the role of the keel is performed by an inflatable compartment-keelson.

In general, keel bottoms (of all types) are more complex and more expensive than flat bottoms, but they are better suited for high speeds and long-distance transitions: the keel provides good course stability and allows the boat to “cut the waves”, so that hitting the water at speed is not so strong. However a keel boat needs more power than a flat-bottom boat to go on planing, but the design of such boats usually allows the installation of sufficiently powerful motors.

Note that bottoms of this type should not be confused with keel bottoms (see the relevant paragraph): in this case, not the whole bottom is inflatable, but only the keel. In this case, the rigidity is low, and in boats with an inflatable keel, additional coatings have to be used. On the other hand, bottoms of this type are simpler and cheaper than NDND, and the boats themselves are more stable.