An appliance for computing and indicating the effect of load and ballast on the draft and trim of marine vessels

摘要

309,309. Weir, S. G. April 10, 1928. Calculatin.g-apparat2cs. - An appliance for ascertaining the effect of load and ballast on the draft and trim of marine vessels comprises a chart provided with draft and tonnage scales and having strings, rods or other indicators adapted to show the load, draft and trim when adjusted in relation to the scales. As shown in Figs. 1 and 2, a panel or frame 1 bears a squared chart 2, a tonnage scale a disposed in the middle of the chart, and side scales b of draft representing submergence at the bow and stern of the vessel. The scales are set in accordance with the rates of submergence in inches per ton of the ship and may read up to total tonnage and full draft. The scales, however, as shown are interchangeable the graduations being formed on tapes 4 passing around guide rollers to spools 6 on shafts 10 with squared ends 11 for operation by a key or handle. The tapes are kept taut by friction blocks 7 mounted on adjustable spring blades 8. To facilitate the choice of scales for a particular rate of submergence a table as shown in Fig. 6 is provided, the tonnage scale numbers being arranged across the top and bottom and the draft scale numbers down the sides, the space enclosed thereby being divided into squares and marked with the rates. Above the chart is arranged a number of indicators constituted of elastic string 12 connected at the ends to sliders 13 working in grooves 14 on the frame 1. The chart is provided with an auxiliary chart marked with a curve c from which the effect of a given load on the trim of the vessel can be read when the distance of the centre of gravity of the load from the mid-line of the ship is known. The curve may be plotted from results obtained by observation on a given load or by the formula 420W/A(1+6.91Wh/A) = S where A = Area of water plane of the vessel h = distance from the mid-ship section S = the submergence at the end towards which the load is applied.