Centre of Centre of The areas of these several planes being calculated, will be as follow : Gravity. 4037.6768 for that of double the plane 8 d IG, and its momentum 4037.6768X85-35= 344615-7149 51.12 the area of double the trapezium AR d8, and its momentum 51.12*8.47= 432.9804 12555-5676 0.2233 130.7152 357735.2074 Then 357735.2074 = 85.80, the distance of the fourth horizontal section from the aft side of the stern-post. 4169.4968 79.16 V. Determination of the Centre of Gravity of the Fifth Horizontal Section. Distance of the centre of gravity of double the plane 8 ck G from its first ordinate 8 c. 328 6 Hence the distance of the centre of gravity of double the plane 8ck G from its first ordinate is 2358 3 2358.25 X10 4= X10.03= 72.10 Distance of this ordinate from the aft side of the post 13.50 85.60 Distance of the centre of gravity of the plane from the aft side of the post 7.42 0.58 Distance of centre of gravity of trapezium from aft side of the post 8.00 Distance of the centre of gravity of the foremost trapezium from its ordinate Gle 4.22 153.78 158.00 Distance of the centre of gravity of the foremost trapezium from the aft side of the post 0.29 169.76 The Centre of 31.21 Centre of The areas of these several planes being calculated, will be as follow : Gravity. 3290.2412 for the area of double the plane 8 ck G, and its momentum 3290.2412X85.6= 281644.6467 the area of double the trapezium AR c 8, and its momentum 31.21 X 8= 249.68 42.43 the area of the foremost trapezium, and its momentum 42.43 X 158= 6703.94 0.77 the area of the section of the post, and its momentum 0.77 x 0.29= 0.2233 0.77 the area of the section of the stem, and its momentum 0.77 x 169.76= 130.7152 3365.4212 Sum 288729.2052 Now 288729.20 52=85.79, the distance of the centre of gravity of the whole section from the aft side of the 3365-4212 VI. Determination of the Centre of Gravity of the Sixth Horizontal Section. Feet. In. L. Feet. In. L. 4 0 2 1 3 I 14 7 1 3 I2 I 21 I 24 2 6 1 26 6 193 4 I 27 7 6 8 1 27 2 9 I 25 4 10 6 6 210 10 21 1 14 JIO 6 I 9 13 5 9 of I 2 I I 4 10 4 10 17 8 8 10 IO ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܪܕ ܘ ܘ ܘ ܘ ܘ ܚ ܘ ܘ ܘ ܘ ܘ ܘ ܚܗ Ноооооооооооооо ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ ܘ 3 10 I 2 12 2 1 Hence the distance of the centre of gravity of double the plane 8 b v G from its first ordinate 8 6 is 1639.77 70.84 232.24 Distance of this ordinate from aft side of post 13.50 Hence the distance of the centre of gravity of the plane from the ast side of the post is 6.88 0.38 7.46 Distance of the centre of gravity of the trapezium from the aft side of the post 2.92 153.78 156.70 0.29 169.76 Distance of the centre of gravity of this trapezium from the aft side of the post The areas of these planes will be found to be as follow: 21.52 for the area of double the trapezium AR b 8, and its momentum 21.52 X 7.46 = 196374.2366 160.5392 2356.7680 0.2233 130.7152 2366.4642 Sum 199022.4823 Now Centre of Centre of Now 1990 22.4823 -84.1, the distance of the centre of gravity of the whole from the aft side of the post. 2366.4642 VII. Determination of the Centre of Gravity of the Seventh Horizontal Section. Distance of the centre of gravity of double the plane 8 ah G from its first ordinate 8 a. 35 I 6 35.12 Hence the distance of the centre of gravity of double 352.2536, the area of double the plan 8 ah G, and its momentum this plane from its first ordipate is 205 4 6 X10 O 4 352.2536 x 72.15= 25415 9 2 205.37 17.1570, the area of double the rectanX 10.83= 58.65 gle A R a 8, and its moThe distance of this ordinate from aft side of mentum 17.1570 X 7.03= 120.6137 post = 3.3250, the area of the foremost rect13.50 angle, and its momentum Hence the distance of the centre of gravity of 3.3250 X 155.03= 515.4747 this plane from the aft side of the post is 72.15 the area of the section of the 0.77, Distance of the centre of gravity of double the post, and its momentum rectangle A R a 8 from its ordinate AR 0.77 X 0.29 0.2233 Distance of this ordinate from the aft side of 0.77, the area of the section of the stem and its momentum 130.7152 374.2756 Sum 26182.1 242 7.03 2618 2.1 242 =69.95, the distance of the 374.2756 6.45 the post the post of the post. Distance of the centre of gravity of this rect- 155.03 VII. Determination of the Centre of Gravity of the Eighth Plane. 0.29 This plane is equal in length to the seventh horizon- 169.76 tal plane, and its breadth is equal to that of the keel. The distance between the seventh and eighth planes is Now, the areas of these several plans being calculat- three feet, but which is here taken equal to 2 feet 11 ed will be as follows. inches. Vol. XIX. Part I. + Distance I 1 1 1 5974.16((348)—4) *• 19913,87 Centre of Distance between the aft side of the post and Hor. Planes. Ist Fact. ist Products. 2d Faci. 2d Products. Centre el 13.5 208.00 es 34.67 os 104.00 Gravity. 374.27 374.27 374.27 4732.92 2366.46 3 10096.26 3365.42 4169.50 4 16678.00 4169.50 5 24696.35 4939.27 1.33 5592.27 33553.62 5592.27 of 2987.08 110079.96 23898.27 78.06 110079.96 Now X 2.95=13.588, the height of the centre of gravity of the bottom of the ship above the lower edge of the keel, . We have now found the distance of the centre of gra- Hence the ship being supposed in an upright position, this centre of gravity will necessarily be in the vertical and similar parts; the position of this centre is therefore determined. It now remains to find the height of the metacenter 70 Determina- height of V center now apply to determine the metacenter of the ship of above the 74 guns, whose centre of gravity we have already found. centre of gravity. Ord. of the Plane of Floatation. Cub.of Ordinates. feet. Inches. Feet and dec, uf foot 14 9 14.7 3209.046 251518.86 17 5000.211 473560.31 18.7 6597.797 7762.392 20.6 8741.816 9 9595.703 21 6 3 21.5 9938.375 21682.12 7 9 10289.109 8118.24 ng 9 10289.109 21.7 10289. 109 2022451.09 4 9663.597 9129.329 19.7 7703.734 4 5268.024 13 3 13.1 2248.091 291.1 115719.442 Ordinate at 10.03 feet abaft the ordi- nate 8 g,=4, of which the cube is 32. 108. 115859.442 10.03 1162070.20326 Product 1 1 19.8 I I I I 32. a enbic feet: hence *sy'* =77517.26 Centre of Product Appendix. Gtavity. Half the cube of the after the following directions are given for cutting sails. most ordinate " The width and depth being given, find the number Half the cube of the thick. of cloths the width requires, allowing for seams, tabling ness of the stem 0.14 on the leeches, and slack cloth ; and, in the depth, al low for tabling on the head and foot. For sails cut Sum 32.14 square on the head and foot, with gorés only on the Distance between the ordinates 3.0 leeches, as some topsails, &c. the cloths on the head, between the leeches, are cut square to the depth ; and Product 96.42 the gores on the leeches are found by dividing the depth of the sail by the number of cloths gored, which gives the length of each gore. The gore is set down from a square with the opposite selvage; and the canvas being ness of the stem .14 cut diagonally, the longest gored side of one cloth makes the shortest side of the next; consequently, the Sum 108.14 first gore being known, the rest are cut by it. In the Distance between the ordinates 5.5 leeches of topsaily cat hollow, the upper gores are long er than the lower ones ; and in sails cut with a roach Product 594.77 leech, the lower gores are longer than the upper ones. This must be regulated by judgment, and care taken sys 1162761.393 26 that the whole of the gores do not exceed the depth of the leech. Or, by drawing on paper the gored side of 23 y: x 2325522.78652 the sail, and delineating the breadth of every cloth by a convenient scale of equal parts of an inch to a foot, sye a 775174.26217 the length of every gore may be found with precision. The solidity of the bottom is 25271 tons=70018.67 Sails, gored with a sweep on the bead or the foot, or on both, have the depth of their gores marked on the : =11.07 feet, the selvage, from the square of the given depth on each 70018.67 cloth, and are cut as above ; the longest selvage of one ginning with the first gored cloth next the middle in others. For those gorės that are irregular no strict rule can be given; they can only be determined by the judge ment of the sail-maker, or by a drawing. When a ship is built, she must be fitted with masts, “ In the royal navy, mizen topsails are cut with Elements yards, sails, ropes, and blocks, or in other words, she three quarters of a yard hollow in the foot; bat, in the and Pracmust be rigged before she can go to sea. To complete merchant service, top and topgallant sails are cut with this article, it may therefore be thought necessary to more or lesz hollow in the foot. Flying jibs are cut and Soatreat of the art of rigging vessels ; but tre have else- with a roach curve on the stay, and a thrie-inch gore minship, where (see Mast-Rigging, Rore-Making, and SAIL) in each cloth, shortening from the tack to the clue. vol. 1. p. 91. shown how the several parts of a ship's rigging are Lower studding-sails are cat with square leeches, and mades, and the art of putting them properly together, topmast and topgallant-mast studding sails with goring so as to make the ship best anstrer the purpose for which leeches. she is intended, depends upon a jast knowledge of the “ The length of reef and middle bands is governed by impulse and resistance of fluids, and of the theory and the width of the sail at their respective places; the leechpractice of seamanship. See Resistance of Fluids linings, buntline-cloths, top-linings, mast-cloths, and corand SEAMANSHIP). Nothing, therefore, of the subject ner-pieces, are cut agreeably to the depth of the sail; is left to us here, except we were to state in few words each cloth and every article should be properly marked the progressive method of rigging ships; but there is no with charcoal, to prevent confusion or mistake. Sails one undeviating mode which is porsued, as the nature of that have bonnets are cut out the whole depth of the the operation is such that all the parts of it may be ad- sail and bonnet included, alloiring enough for the tavancing at the same time. We shall therefore take our blings on the foot of the sail and head and foot of the leave of ships and ship-building with a few general ob- bonnet. The bonnet iz cut off after the sail is serred toservations on sail-making, and refer our readers for far- gether. If a drabler is required, it is allowed for in the ther information to the very elegant work on the Ele- cutting out the same as the bonnet. ments and Practice of Rigging and Scamanship in two When the cloth is thus properly cut, the different volumes onarto. pieces are to be joined together in the form of a sail; Sails are made of canvas, of different textures, and are and for doing this properly we have the following diestended on or between the masts, to receive the wind rections in the work already quoted. “ Sails have a that forces the vessel through the water. They are double flat seam, and should be se wed with the best quadrilateral or triangular, as bas been else where de- English made twine of three threads, spun 360 failiomis scribed, and are cut out of the canvas cloth by cloth. to the pound, and have from one hundred and eight to The width is governed by the length of the yard, gaff, one hundred and sixteen stitches in every yard in length. boom, or stay; the depth by the height of the mast. The twine for large sails, in the royal navy, is based tice of Rigging |