Architectura Navalis Mercatoria by Fredrik Henrik Af Chapman

Author:Fredrik Henrik Af Chapman
Language: eng
Format: epub
Publisher: Dover Publications
Published: 2012-07-17T16:00:00+00:00

Fig. 32

To find immediately the properties of ships, proportioned according to table N°. 1, Figure 32 is constructed, where the numbers 20, 40, 60, &c. represent the length from the stem to the stern-post.

If AB be the load water-line for a bark, CCB is the locus of the center of gravity of displacement; DDB that of the metacenter; EEB that of the center of gravity of the ship and the lading. For a frigate, FFB is the locus of the center of gravity of the displacement; GGB that of the metacenter, HHB that of the ship with its lading. So that for a vessel of the form of a bark 80 feet long, the distance from the load water-line to the center of gravity of displacement = LC; the height of the metacenter above the load water-line = LD, this load water-line is above the center of gravity of the vessel with its lading by a quantity = LE.

But for a frigate, the distance of the center of gravity of the displacement below the water = LF, the height of the metacenter above the water = LG; the center of gravity of the ship and the lading is below the water by a quantity = LH. The line IIB determines the length the main-mast ought to have, so as to have the proper proportion according to the stability; that is to say, the length of the main-mast is as the distance of IIB from AB.

If there be given to large and small ships a form similar to that which is 110 feet in length, then the straight line MB will be the locus of the metacenter, and the other line KKB will determine the length of the main-mast, in the proportion required by the stability.

In determining the center of gravity of the ship and its lading, we have supposed the cargoes of ships to be similar; so that, if the bark of 80 feet in length has its center of gravity in E, the centers of gravity of other barks may be in the line EEB; in like manner, the centers of gravity of all frigates are in the line HHB.

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