A new design of an oil tanker is proposed, in which the special attention is paid to the following points:-(a) To reduce the abrupt change of strength or form as far as possible.(b) To make the longitudinal members continuous.(c) To fit the necessary girders in the holds.To solve these points, the following means are taken:-(a-1) Boundary flanged pieces are used in lieu of boundary angles, connecting the transverse bulkheads to the longitudinal members, such as, longitudinal bulkhead, shell and deck plating, which will reduce the abrupt change of forms at these connections.(a-2) The upper deck corners on ship sides are made round, just like the turn of bilge, which will also reduce the abrupt change of form to a remarkable extent, and, as a result, the strong gunnel bars will be omitted, and the sheerstrakes and stringer plates are lightened.(a-3) In the construction of the bridge, the girder works are accepted instead of superstructure constructions, without shell and end bulkhead plating, which will eliminate the abrupt change of strength and form caused by the superstructure of the bridge deck, and make the water on deck free from there very rapidly. But it will be necessary to prepare a break water bulkhead of simple construction in front of the poop front bulkhead, against the rushing water from the ship bow toward the poop front bulkhead.(a-4) Longitudinal members, such as, deck plates, longitudinal bulkhead plates and their connecting angles are arranged to co-operate in good balance.(a-5) The landing edges of the lap joints of the upper deck plates at their seams are not scarphed, but taper liners are used to make sound joints.(a-6) The oil hatchways of the upper deck are made in circular form instead of therectangular ones, and the beams continuous across the hatchway.(b-1) The stringers and keelsons are made continuous through the transverse bulkheads, using watertight flanged collar pieces, which will eliminate the unsupported areas of the shell plates at the bracket connections of these members.(b-2) The longitudinal members, such as, deck girders, side stringers, etc., are not slotted, but the beams or frames are cut off at these longitudinals and bracketted on them.(c) As the clearness of hold is not needed in oil tanker, necessary girders are fitted in the holds longitudinally, transversely, diagonally, and also pillared. Both the end bulkheads of tanks specified, being connected by the boundary flanged collar pieces to the deck and shell, and stayed by the longitudinal girders, the construction of such tanks is just like that of the boiler, which is, of course, the most economical, stable and efficient construction.(d) The flanged pieces are made as flanging plates, or rolling out from the ingot like section bars rolled. The workmanship of the flanged pieces, such as, joggling, bending or corner piece making, is much easier than that of angles or other section bars.