Abstract
The effect of winds and waves upon any one ship's speed seems to be different from that upon any other owing to type, size, condition, ability, etc., of a ship ; the author has some interest in the problem of whether the speed reduction of a modern ship has the same tendency as that of a old-type ship or not even if they are the same kind of ship and sail the same sea. In this paper, he has attempted, for example, on a cargo-boat, to analyze the navigational records of the connecting steamer "Hiyama-maru" in Tsugaru Straits. 1. As shown in Fig.1, all data is separated into 7 sections according to the direction of the winds. 2. The relation between the time elapsed after leaving the dock and the slip is shown in Fig. 2. 3. As the speed reductions are changed sccording to the revolutions of the main engine he collected data when the revolutions were from 200 to 220 RPM. 4. The mean speed reductions of the ship, weights of data, are indicated in Table 2 against each section and wind wave grades. 5. Let the speed reduction be expressed by equation (Δ) =aD+bD^2 with parameter D, and a smooth curve is drawn along the points plotted from data, the speed reduction due to wind wave grade is shown by forms (1)〜(7) in each section in Fig. 4. 6. When the values calculated by forms (1)〜(7) are plotted and the smooth curve is drawn along the plotted points, the speed reduction due to the wind direction is obtained as forms (8)〜(11) ; Fig. 5 shown them. 7. Using the wave height deduced from the average values of the grades of wind waves and the meanig of Fig. 4, the relation is expressed by a simple equation as shown in Fig. 6, excepting in the cases of side and favorable winds. 8. The relation between wind wave grade and wind velocity in the strait (1961) is shown in Fig. 8, and the relation between wind velocity and wave height is shown in Fig. 9.
