Ship type - Senkei

(1) The three-dimensional shape of a ship. It mainly refers to its relationship with water resistance during navigation. (2) Generally, the shape of the side of a ship above the waterline. The topmost full-length deck of a ship is called the upper deck. Structures above that that reach both sides of the ship are called towers (bridge towers), and those that do not are called deckhouses. The names of ship shapes vary depending on whether there is a tower on the upper deck and where it is located.

Flat-deck ships, which do not have a tower on the upper deck, are used on large ships that are not subject to much wave action. Flat-deck ships with a tower at the bow of a flat-deck ship with a forecastle are often seen on general cargo ships and specialized ships. Flat-deck ships with a forecastle and a stern tower or a sunken deck are often found on large tankers and large ore carriers. Ships with a tower at the bow, stern, and in the center are called "three islands" ships because they look like three islands. Most cargo ships before World War II were of this three-island type, but they are no longer seen in new ships these days. In addition to the tower, there are structures on the upper deck such as deckhouses, engine room openings, masts, and loading and unloading facilities, but even if these structures change the appearance, they do not affect the name of the ship type. The shape of a ship below the waterline changes depending on its purpose and speed, and it is sometimes called a slender ship or a large blunt ship according to its characteristics, but there is no consistent name for it like there is for the side shape.

[Morita Tomoharu]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

（1）船の立体的形状。おもに運航時の水の抵抗との関係についていう。（2）一般的には船の喫水線より上の側面の形状。船の最上層の全通甲板を上甲板という。その上の構造物で左右の船側まで達するものを船楼（船橋楼）、達しないものを甲板室とよぶ。上甲板に船楼があるかないか、またどの位置に設けられるかによって船型の呼称が分かれる。

　上甲板上に船楼がない平(ひら)甲板船は、波の打ち込みが少ない大型船などで採用されている。平甲板船の船首部に船楼がある船首楼付平甲板船は、一般貨物船や専用船に多くみられる。また、船首楼と船尾楼を設けた船首尾楼付平甲板船または凹甲板船は大型タンカーや大型鉱石船などに多い。船首・船尾のほか中央にも船楼のある船型は、三つの島のようにみえるので三島(さんとう)船とよばれる。第二次世界大戦前の貨物船はほとんどこの三島船型だったが、最近の新造船にはみられなくなった。上甲板上には船楼のほかに甲板室、機関室開口、マスト、荷役設備などの構造物があるが、これらによって外見が変わっても船型の名称には関係がない。船の水面下の形状は用途や速力などで変わり、やせ型船とか大型肥大船などと特徴にしたがってよばれることもあるが、船側形状ほど一定した呼び方はない。

［森田知治］

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