Aka (sailing)
Encyclopedia
The aka of a multihull
sailboat
is a member of the framework that connects the hull to the ama(s)
(outrigger). The term aka originated with the proa
, but is also applied to modern trimaran
s.
The design of the akas depends on the forces it will encounter when sailing. For example, there are two modern variations of the proa, the traditional or Pacific proa, with the ama to the windward side, and the modern Atlantic proa, with the ama to the leeward. The windward ama provides stability by placing the center of gravity
far to the windward of the sail
, so it is generally heavy. Ropes leading from the mast
to the ama provide the force to lift the ama, so the akas must contend mainly with compressive forces, and the weight of the crew, who generally ride on a platform running between the akas.
An Atlantic proa or a trimaran rely on an ama to leeward to provide stability. The ama provides stability by moving the center of buoyancy to the leeward side, and well designed leeward amas will also provide dynamic lift
to increase the stability further. The aka for a leeward ama must be designed to handle significant amounts of torque
from the lift produced by the ama. Often trimarans will have a platform between the akas, so the crew can ride out on the windward side. While this is not truly necessary from a stability point of view (the ama generally provides a tremendous amount of lift) it does reduce the drag
generated by the leeward ama.
and ama
, come from the Malay
and Micronesian language group
terms for parts of the outrigger canoe
, and vaka can be roughly translated as canoe
. A proa consists of a vaka, the main canoe-like hull; an ama, the outrigger; and akas, the poles connecting the ama to the vaka. The trimaran
uses the same terminology, with a center vaka and amas and akas on each side.
Multihull
A multihull is a ship, vessel, craft or boat with more than one hull.-Description:Multihulls include: Proas, which have two differently shaped or sized hulls with lateral symmetry; catamarans, which have two hulls with longitudinal symmetry; and trimarans, which have a main hull in the center and...
sailboat
Sailboat
A sailboat or sailing boat is a boat propelled partly or entirely by sails. The term covers a variety of boats, larger than small vessels such as sailboards and smaller than sailing ships, but distinctions in the size are not strictly defined and what constitutes a sailing ship, sailboat, or a...
is a member of the framework that connects the hull to the ama(s)
Ama (sailing)
The term ama is a word in the Polynesian and Micronesian languages to describe the outrigger part of a canoe to provide stability. Today, among the various Polynesian countries, the word ama is often used together with the word vaka or waka or va'a , cognate words in various Polynesian languages...
(outrigger). The term aka originated with the proa
Proa
A proa, also seen as prau, perahu, and prahu, is a type of multihull sailing vessel.While the word perahu and proa are generic terms meaning boat their native language, proa in Western languages has come to describe a vessel consisting of two unequal length parallel hulls...
, but is also applied to modern trimaran
Trimaran
A trimaran is a multihulled boat consisting of a main hull and two smaller outrigger hulls , attached to the main hull with lateral struts...
s.
The design of the akas depends on the forces it will encounter when sailing. For example, there are two modern variations of the proa, the traditional or Pacific proa, with the ama to the windward side, and the modern Atlantic proa, with the ama to the leeward. The windward ama provides stability by placing the center of gravity
Center of gravity
In physics, a center of gravity of a material body is a point that may be used for a summary description of gravitational interactions. In a uniform gravitational field, the center of mass serves as the center of gravity...
far to the windward of the sail
Sail
A sail is any type of surface intended to move a vessel, vehicle or rotor by being placed in a wind—in essence a propulsion wing. Sails are used in sailing.-History of sails:...
, so it is generally heavy. Ropes leading from the mast
Mast (sailing)
The mast of a sailing vessel is a tall, vertical, or near vertical, spar, or arrangement of spars, which supports the sails. Large ships have several masts, with the size and configuration depending on the style of ship...
to the ama provide the force to lift the ama, so the akas must contend mainly with compressive forces, and the weight of the crew, who generally ride on a platform running between the akas.
An Atlantic proa or a trimaran rely on an ama to leeward to provide stability. The ama provides stability by moving the center of buoyancy to the leeward side, and well designed leeward amas will also provide dynamic lift
Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...
to increase the stability further. The aka for a leeward ama must be designed to handle significant amounts of torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
from the lift produced by the ama. Often trimarans will have a platform between the akas, so the crew can ride out on the windward side. While this is not truly necessary from a stability point of view (the ama generally provides a tremendous amount of lift) it does reduce the drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
generated by the leeward ama.
Origin and use of the term
The term vaka, like the related terms akaAka (sailing)
The aka of a multihull sailboat is a member of the framework that connects the hull to the ama . The term aka originated with the proa, but is also applied to modern trimarans....
and ama
Ama (sailing)
The term ama is a word in the Polynesian and Micronesian languages to describe the outrigger part of a canoe to provide stability. Today, among the various Polynesian countries, the word ama is often used together with the word vaka or waka or va'a , cognate words in various Polynesian languages...
, come from the Malay
Malay language
Malay is a major language of the Austronesian family. It is the official language of Malaysia , Indonesia , Brunei and Singapore...
and Micronesian language group
Malayo-Polynesian languages
The Malayo-Polynesian languages are a subgroup of the Austronesian languages, with approximately 385.5 million speakers. These are widely dispersed throughout the island nations of Southeast Asia and the Pacific Ocean, with a smaller number in continental Asia...
terms for parts of the outrigger canoe
Outrigger canoe
The outrigger canoe is a type of canoe featuring one or more lateral support floats known as outriggers, which are fastened to one or both sides of the main hull...
, and vaka can be roughly translated as canoe
Canoe
A canoe or Canadian canoe is a small narrow boat, typically human-powered, though it may also be powered by sails or small electric or gas motors. Canoes are usually pointed at both bow and stern and are normally open on top, but can be decked over A canoe (North American English) or Canadian...
. A proa consists of a vaka, the main canoe-like hull; an ama, the outrigger; and akas, the poles connecting the ama to the vaka. The trimaran
Trimaran
A trimaran is a multihulled boat consisting of a main hull and two smaller outrigger hulls , attached to the main hull with lateral struts...
uses the same terminology, with a center vaka and amas and akas on each side.