Raft - raft

Japanese: 筏 - いかだ

A boat made of buoyant materials such as wood, bamboo, and grass stalks tied together with strings to increase buoyancy and stability, and floated on water for transportation purposes. Those made from reeds are called ashibune (reed boats). Rafts were made as the first form of water transportation in the days when roads and railways were not yet developed, or when water transportation was more effective than land transportation in some regions. They have been improved depending on the purpose, such as adding handrails around them or sails for navigation, and they have come to have a variety of forms. When traveling, they can be floated on the water and floated down the river, or they can be used with poles, oars, rafters, sails, etc. There are two main uses for rafts: when they are assembled and floated down the river to a downstream distribution center to transport timber cut in the interior (called raft floating), and when they are used as simple boats (called raft boats). The former type is seen in Wakayama, Gifu and Nagano in Japan, and is usually operated by two or three people, a rower and a steerer. Outside of Japan, this type is seen in Europe and Southeast Asia. The latter type, used as a raft, is used not only on rivers but also on the ocean, for fishing, transportation on water, and living on water.

Rafts around the world include those in Europe that are pulled by boats on inland waters to transport timber, and those that are used for large-scale timber transport with attached houses down major rivers in Russia. In Africa, simple rafts are used in forested areas, and rafts made of balsa wood are also well developed. In Western and Central Asia, rafts are underdeveloped due to a lack of timber, but in India, small wooden rafts are well developed. These are about 1.5 meters long, made of bundles of tree trunks secured with bamboo, and are almost disposable. In Southeast Asia, they are widely used as a means of transporting timber downstream, and bamboo rafts are also widely used in Borneo and the upper reaches of the Mekong River. In China, in addition to transporting timber, they are used for canal navigation and as fishing boats. In Korea, there is a fishing raft called a palsong, and in Taiwan, a bamboo raft called a teppai is used around Anping. Teppai are used as fishing boats and ferries. In Oceania, they are widely used as water transportation, especially in northwestern Australia, the Bismarck Archipelago, the Admiralty Islands, the Solomon Islands, etc. In North America, they are not seen except in some places, but in South America, rafts are used as homes for fishing during the farming off-season in Colombia and Ecuador, and there are records of rafts with sails being used in northern Peru.

Reed boats are found in ancient Egypt, made from papyrus, as well as in Africa and South America. The large reed boats on Lake Titicaca were used for fishing and transport.

[Yukio Toyoda]

How to build a raft for transporting timber

Felled timber is dropped into a valley (called yama-otoshi), from where it is floated one by one by auger (building a dam in a mountain stream with a low water volume to store water and release it all at once to float the timber) or by pipe floating (floating the timber separately without connecting them) to a rafting area with plenty of water, where the rafts are then assembled at a place called an aba. The way the timber is assembled varies depending on the state of the river, and usually, when assembling them in a horizontal row, the ends of the timber are wrapped with wisteria vines or wire, holes called medo are drilled into the ends of the timber, or iron rings are hammered into the wood and the wisteria vines or wire are threaded through these to connect the rafts. When joining them vertically, the medos are either tied together with wisteria vines to suit the bends of the river, or long pieces of wood are added to both sides to prevent the rafts from moving. In addition, small rafts are made in the upper reaches of rivers where the water volume is low, and then reassembled into larger rafts when they reach the lower reaches where the water volume is abundant. In some parts of Southeast Asia, a method is also used in which bamboo is assembled on top of a raft made of hardwood with a specific gravity of 1 or more to give it buoyancy.

[Sanpei Yamawaki]

Transportation Method

The act of floating rafts made at fishing sites in the middle reaches of rivers downstream is called raft-floating, and was carried out on rivers around the country from the 1930s to the 1940s, including the Kiso River, Kumano River, Oi River (part of the upper reaches of the Hozu River), and Yoneshiro River. Each raft was manned by one to three rafters, known as the saki-nori, naka-nori, and atonori, who controlled it using oars, poles, and sometimes brake bars.

A raft assembled to transport timber at sea is called an ocean raft. There are various types of rafts, including vertically-linked, arrow-blade, and stacked, and they are towed by a ship. During World War II, they were used to transport large amounts of timber from the North Seas. Even today, imported timber is assembled into flat rafts from large timber yards in ports and towed downstream to timber factories.

[Sanpei Yamawaki]

[Reference items] | Reed boat | Gathering material method | Teppai

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

木や竹、草の茎など浮力のある物を紐(ひも)などで結び集めて浮力と安定性を増し、水上に浮かべて運搬などの目的に使用するもの。アシでつくったものはとくに葦舟(あしぶね)とよばれる。道路や鉄道が未発達な時代、あるいは地方によっては陸運より水運のほうが効果的であった時代、水運の初めのものとして筏がつくられた。目的に応じて周囲に手すりをつけたり、航行用に帆をつけたりなどの改良がなされ、多様な形態を示す。移動に際しては、水に浮かべて川を流し下る場合と、棹(さお)（竿）や櫂(かい)、櫓(ろ)、帆などによる場合とがある。用途は二つに大別され、奥地で切り出した木材を輸送するためにそれらを組んで下流の集散地まで河川を流して下っていく場合（筏流しとよばれる）と、簡単な船として使用する場合（筏船とよばれる）とがある。前者の場合、日本では和歌山、岐阜、長野地方でみられ、通常は、こぎ手とかじ取りの2、3人が筏を操る。国外ではヨーロッパや東南アジアにこの形態がみられる。後者の筏船として使用する場合は、単に河川だけでなく海洋上でも利用され、漁労、水上運搬、水上生活の場などが目的となる。

　世界のさまざまな筏の例をあげてみると、まずヨーロッパでは、木材運搬として内陸水面を船で引かせる筏や、ロシアの大河川を下る住居付きの大規模な木材運搬の形式がある。アフリカでは森林地帯に簡単な筏が使用されるほか、バルサ材を使用した筏船も発達している。西アジア、中央アジアは木材が乏しいので未発達であるが、インドでは小型の木製筏船がよく発達している。これは木の幹を束ねて竹で固定した長さ1.5メートル程度のもので、使い捨てに近い。東南アジアでは木材を下流に運搬する手段として広く使用され、ボルネオ島やメコン川上流では竹の筏も盛んに利用される。中国では木材の運搬のほかに運河の航行、漁船の目的で使用される。朝鮮にはパルソンとよばれる漁労用の筏、台湾では安平付近で使用される竹製の筏、テッパイがある。テッパイは漁船や渡船として使用される。オセアニアでは広く水上運搬具として利用され、とくにオーストラリア北西部、ビスマーク諸島、アドミラルティ諸島、ソロモン諸島などにみられる。北アメリカでは一部を除いてみられないが、南アメリカではコロンビア、エクアドルなどで農閑期に筏を住居として魚をとるほか、ペルー北部では帆のついた筏が使用されていた記録がある。

　葦舟としては、パピルスでつくった古代エジプトの例のほか、アフリカや南アメリカにある。ティティカカ湖の大型の葦舟は漁労や運搬用に用いられている。

［豊田由貴夫］

木材流送用の筏の組み方

伐採した木材を谷間に落とし（山落としという）、そこから1本ずつ鉄砲流し（水量が少ない渓流に堰(せき)をつくって貯水し、一度に放流して木材を流す）、管(くだ)流し（木材を連結せずばらばらに流す）などの方法で、水量の豊富な筏場まで流し、網場(あば)と称する所で筏を組み立てる。組み方は、河川の状態などにより異なり、普通、横列に組むときは、材端を藤(ふじ)づるや針金で巻き付けたり、材端に目途(めど)とよばれる穴をあけるか、または鉄環を打ち込んで、これに藤づるや針金を通して連結する。さらにこれを縦列に連結するときは、河川の屈曲状態にあわせ、目途と目途を藤づるで結ぶか、前後の筏が動かないように両側に長材を添えて連結する。また、水量の少ない上流河川では小形の筏をつくり、水量の豊富な下流にきて大形の筏に組み直して流送する。東南アジアの一部では、比重1以上の硬木の筏の上部に竹を組んで浮力をつける方法もとられている。

［山脇三平］

移送方法

河川中流部の網場で組まれた筏を下流へ流す作業を筏流しといい、1930年代から1940年代ごろまで木曽(きそ)川、熊野(くまの)川、大堰(おおい)川（保津(ほづ)川の上流の一部）、米代(よねしろ)川など各地の河川で行われた。筏には、さきのり、なかのり、あとのりとよばれる筏師が1～3人乗り、櫂(かい)、棹、ときには制動棒などを使って操った。

　海上で木材を輸送するために組む筏を海洋筏という。これには縦連式、矢羽根(やばね)式、重積式などの組み方があり、船で曳航(えいこう)する。第二次世界大戦中、北洋材の大量輸送に用いられた。現在でも、港湾内の大貯木場から輸入材を平筏に組み、河川下流沿いの木材工場まで曳航する方法が行われている。

［山脇三平］

[参照項目] | 葦舟 | 集運材法 | テッパイ

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