Hobikisen has a large sail for its size. The width of a sail is twice as wide as the body of the boat.
A sail consists of 15 to 16 long narrow slips of cloth, each of which is made up of three pieces of cloth (each is about 10.6 m x 30 cm).
Ropes are twined with the slips of cloth in order to make the sail to catch more wind or to haul in the sail with the ropes.
Cotton cloth was used in olden days but now nylon cloth is used for sightseeing hobikisen .
The slips of cloth are tied with ropes in a cross-coupled manner.
As boats became large, so did sails.
The present sightseeing hobikisen uses 19 to 20 slips of cloth.
When the entire sail catches wind, it is swollen with the wind, becoming nearly hemisphere . Each of the slip is also designed to swell in the same manner. A swollen sail can retain the wind power. The more a sail swells, the more it can retain the wind. Swelling also allows for an efficient response to temporary shifts in wind. Therefore, the sails of hobikisen can be said to have an excellent design in terms of dynamics.