Ama (sailing)
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Image:Outrigger on Hawaiian sailing canoe.png An ama is an outrigger on a proa or trimaran, used to provide stability.
[edit] History
The term ama comes from the proa. The vaka is the main hull, the ama is the outrigger, and the aka is the support connecting the two hulls. The term ama and aka have widely been applied to modern trimarans.
[edit] Function
On a proa, the ama may provide lift or ballast, depending on whether it is designed to be used to leeward or windward; on a trimaran it is designed primarily to provide lift. There are many shapes of amas; those used in proas are generally laterally symmetric, as the proa is designed to sail with either end fowards, while trimaran amas are one-directional and may have no axis of symmetry.
The most advanced amas are composed of highly curved surfaces which generate lift when driven forward through the water, much like an airplane wing. This lift may be directed to the windward, used to counter slipping to leeward, or may be oriented vertically to counter heeling forces fron the sailing rig. The Bruce foil, for example, is a type of leeboard often attached to an ama to assist in in producing lift.
