# Explanation of the following Tables of Freeboard for the various Types of Steam and Sailing Vessels

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## Explanation of the following Tables of Freeboard for the various Types of Steam and Sailing Vessels.

In the following Tables the word Freeboard denotes the height of the side of a ship above the waterline at the middle of her length, measured from the top of the deck at the side, or, in cases where a waterway is fitted, from the curved line of the top of the deck continued through to the side. The freeboards and the corresponding percentages of reserve buoyancy necessary for flush-deck steamers not having spar or awning decks, for awning-deck steamers, and for flush-deck sailing vessels, are given in Tables A, C, and D for vessels of these classes and of various dimensions and proportions. The freeboards necessary for spar- deck steamers are given in Tables B. The latter are determined by considerations of structural strength, and they denote the limitations to depth of loading which are thereby imposed upon first class vessels of this type. The freeboards and percentages of reserve buoyancy thus obtained being in excess of what would otherwise be required, the amounts of such percentages are not given in Tables B.

The exact freeboard required for a given ship belonging to any of the classes comprised in Tables A, C, and D, may be calculated by constructing a displacement scale to the height of the deck to which the freeboard is measured, so as to give the whole external volume up to the upper surface of that deck. The percentage of the total volume which is given in the Tables as the reserve buoyancy for a vessel of given type and dimensions will be the amount of volume that must be left out of the water. If a water-line be drawn upon the displacement scale aforesaid to cut off the given percentage of total volume, the height of side above this lino will be the freeboard required.

In order to simplify and reduce the work that would be involved by the above mode of determining the water line and the consequent freeboard, that correspond to a given percentage of reserve buoyancy, an approximate method is adopted in the following tables, which enables the freeboard of a vessel to be page 8 calculated with a sufficient degree of accuracy for all ordinary working purposes. The use of this method not only saves the time and labour that would be involved by making a complete displacement scale for the whole external volume of a ship, but, what is much more important, it makes the Tables easily and directly applicable in cases where such a displacement scale for a vessel is not at hand, or where the data requisite for constructing one is not procurable.

In this approximate method the form of the ship is taken into account by means of proportionate quantities, which are termed coefficients of fineness, instead of by the exact volumes that a displacement scale would give. It is found that the whole internal volume of a ship as measured for register tonnage divided by the product of the length, breadth, and depth, measured as described in the following clauses 1, 2, and 3, gives a fractional quantity or coefficient which bears a nearly constant relation to the quantity that would be obtained by dividing the whole external volume below the upper surface of the deck by the product of the length, breadth, and depth. This fractional quantity is called the "coefficient of fineness" for freeboard purposes; and it serves the same practical object, when combined with the dimensions of the ship in the manner explained in the Tables, as the volume itself would do.

In applying such an approximate method as the above, it is necessary to connect the coefficients of fineness given in the Tables with a standard sheer and round of beam. The standard scales for sheer and round of beam that have been adapted for this purpose are given in clauses 16 and 17 hereafter. Descriptions are also there given of the corrections that should be made for deviations from these standard amounts.

The freeboards given in the Tables are for flush-deck vessels in all cases. Such reductions in freeboard as may be allowed for deck-erections of various kinds and sizes in steamers not having spar or awning decks, and in sailing vessels, are described in paragraphs 11, 12, 13, 14, and 15.

No reduction of freeboard should be allowed on account of deck-erections in spar-deck and awning-deck steamers.

Tables A and D give the minimum freeboards for first class iron and steel vessels, the strength of which is at least equal to page 9 the requirements of the 100 A class in Lloyd's Register for three-deck and smaller vessels. The freeboard of all other iron and steel vessels, classed or unclassed, should be regulated by the same standard; the increase of freeboard required in each case being determined by the limit at which the stress per square inch upon the material of the hull amidships shall not exceed that of the standard class, of the same proportions, form, and moulded depth, when loaded to the freeboards required by Tables A and D. Tables B and C give the freeboards for vessels built in accordance with, or equal to the requirements of Lloyd's Register for the spar and awning deck classes; and are subject to the conditions just stated for any modifications of strength in excess or diminution of the requirements of their respective classes.

1.Length.—The length of the vessel is measured on the load-line from the foreside of the stem to the aft side of the stern post in sailing vessels, and to the aft side of the after post in steamers.
2.Breadth.—The breadth used in obtaining the coefficient of fineness is the extreme breadth measured to the outside of plank or plating as given in the Register Book, or on the Certificate of the Ship's Registry.
3.Depth of Hold.—The depth used in obtaining the coefficient, of fineness is the depth of hold as given in the Register Book, or on the Certificate of the Ship's Registry. This dimension is subject to modification in determining the coefficient of fineness as explained in clause 4.
4.Coefficient of Fineness.—The coefficient of fineness in one, two, and three-deck and spar-deck vessels, is found by dividing 100 times the gross registered tonnage of the vessel below the upper deck by the product of the length, breadth, and depth of hold. In awning-deck vessels the registered depth and tonnage are taken below the main deck.
 (a.) It is of importance in the application of the rules and tables of freeboard that the coefficient of fineness deduced from the under-deck tonnage, and the principal dimensions should be a correct index to the vessel's relative fulness of form, and that a change in any of those elements which affect the coefficient, determined in accordance with the rule page 10 set forth should be considered, and the necessary correction, having regard to the special circumstances of the case, introduced. Among the cases that have from time to time come under notice are the following:— (b.) Vessel having a cellular bottom, throughout, or floors of greater depth than those usually fitted.—In such a case the coefficient as determined from the under-deck tonnage is in most instances slightly greater than it would be if the vessel were framed on the ordinary transverse system with floors of the usual depth. No general rule can be given for guidance, but it is not difficult, if the depth and slope of the top of the cellular bottom or floor be compared on the midship section with the depth and slope of an ordinary floor, to determine very closely the amount of the correction necessary. (c.) Vessel constructed with floors of the ordinary hind, but until a cellular bottom for a part of the length amidships under the engines and boilers.—In such a case the registered under-deck tonnage is smaller than it would be if the vessel were framed with ordinary floors throughout, the difference being the tonnage of the space between the top of the cellular bottom in the part amidships, and the level of the ordinary floor. The depth of hold is also measured by the customs officials to the top of the cellular bottom, and this depth is inserted in the register. Under such circumstances, in order to arrive at the coefficient of fineness the vessel would have if built on the ordinary system throughout, and for which the tables are framed, the tonnage of the volume between the top of the cellular bottom and the level of the ordinary floor should be calculated and added to the registered under-deck tonnage. The tonnage so corrected used in conjunction with the depth of hold to the top of the ordinary floor, gives the coefficient to be used in the Tables. (d.) Vessel constructed with a cellular bottom throughout the fore and after holds, but with floors of the ordinary hind fitted for a part of the length amidships under the engines and boilers.—In such a case the tonnage of the space between the top of the ordinary floors in the part amidships, and the page 11 top of the cellular bottom, if made continuous, should be estimated, and deducted from the registered under-deck tonnage, and the remainder employed in conjunction with the depth of hold to the top of the cellular bottom in determining the coefficient of fineness. (e.) Other cases may in practice arise in which the registered under-deck tonnage, or the registered depth of hold, or both, require modification before being used in the determination of the coefficient of fineness, but little difficulty will be experienced in making the necessary correction, if it be remembered that the coefficient sought is the coefficient the vessel would have if framed on the ordinary transverse system.
5.Moulded Depth.—The moulded depth of an iron or steel vessel, as given in the Tables, is the perpendicular depth taken from the top of the upper deck beam at side, at the middle of the length of the vessel, to the top of the keel and the bottom of the frame at the middle line, except in spar and awning deck vessels, in which the depth is measured from the top of the main deck beams. In wooden and composite vessels the moulded depth is taken to be the perpendicular depth from the top of the upper deck beam at the side of the vessel amidships to the lower edge of the rabbet of the keel.
 (a.) The form at the lower part of the midship transverse section of many wooden and composite vessels being of a hollow character, as in cases where thick garboard strakes are fitted, the moulded depth in such instances should be measured from the point where the line of the flat of the bottom continued cuts the keel.
6.Freeboard.—The moulded depth, taken as above described, is that used in the tables for ascertaining the amount of reserve buoyancy and corresponding freeboard in vessels having a wood deck, and the freeboard is measured from the top of the wood deck at side, at the middle of the length of the vessel.
 (a.) On the same principle, in flush-deck vessels, other than spar or awning decked, and in vessels fitted with short poop and forecastle, having an iron upper deck, not covered with wood, the usual thickness of a wood deck should be deducted from the moulded depth of the vessel measured as page 12 above, and the amount of reserve buoyancy and corresponding freeboard taken from the column in the tables corresponding with this diminished moulded depth: Example—In a steamer fitted with an iron upper deck, not covered with wood, and having a moulded depth of 19 ft. 10 ins., four inches, or the usual thickness of a wood deck, must be deducted from this, leaving a depth of 19 ft. 6 ins. The freeboard of such a vessel with a coefficient of fineness of 076, taken from the column under 19 ft. 6 ins., is 3 ft. 8½ ins., which should be measured from the top of the iron upper deck. (b.) In spar-deck vessels having iron spar decks, and in awning-deck vessels having iron main decks, the freeboard required by the Tables should be measured as if those decks were wood covered. Also in vessels where 7/10 ths, or more, of the main deck is covered by substantial erections, the freeboard found from the Tables should be measured amidships from a wood deck, whether the deck be of wood or iron. In applying this principle to vessels having shorter lengths of substantial enclosed erections the reduction in freeboard in consideration of its being measured from the iron deck, is to be regulated in proportion to the length of the deck covered by such erections. Thus in a vessel having erections covering 6/10 ths of the length, the reduction is -6/10 ths of 3½ inches, or 2 inches.
 7 For vessels which trim very much by the stern, through the engines being fitted aft, the freeboard, as ascertained from the Tables if set off amidships would not cut off the amount of surplus buoyancy deemed necessary, and in such cases the suitable freeboard amidships could only be determined after full information is obtained regarding the vessel's trim. 8 The following example will illustrate the general application of the Tables:—

In a steamer of the following dimensions, viz., length 204 ft.; breadth extreme, 29 ft.; depth of hold 16.0 ft.; registered tonnage under deck, 682 tons; and moulded depth, 17.0 ft., the under deck capacity in cubic feet is 68,200; by dividing this by 94,656, that is, the product of the length, breadth, and depth of hold, the quotient is 0.72, or the coefficient of fineness.

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If we now refer to Table A at 17.0 ft. moulded depth, and trace the line opposite the coefficient 0.72 to the column corresponding with this depth, it is found that the winter freeboard given for a first-class steam vessel without erections, whose length is twelve times the moulded depth, is 2 ft. 11 ins., corresponding with a reserve buoyancy of 25 per cent, of the total bulk.

9.Vessels of Extreme Proportions.—For vessels whose length is greater or less than that of the vessel of the same moulded depth for which the Tables are framed, the freeboard should be increased or diminished as specified in the footnote to the Tables. Thus, if the vessel in the example clause 8 were 224 ft. long, the winter freeboard required would be 2 ft. 11 ins. plus 2 ins. or 3 ft. 1 in. For steam vessels with top-gallant forecastles, having long poops or raised quarter decks connected with bridge-houses, the whole extending over 6/10 ths, or more, of the length of the vessel, the correction for length should be one-half that specified in Tables A.
10.Breadth and Depth.—In framing the Tables it has been assumed that the relation between the breadth and depth is such as to ensure safety at sea with the freeboard assigned when the vessel is laden with homogeneous cargo; for vessels of less relative breadth, the freeboard should be so increased as to provide a sufficient range of stability, or other means adopted to secure the same.
11.Erections on Deck.—For steam vessels with topgallant forecastles having long poops, or raised quarter decks connected with bridge-houses, covering in the engine and boiler openings, the latter being entered from the top, and having an efficiently constructed iron bulkhead at the fore end, a deduction may be made from the reserve buoyancy given in the Tables, according to the following scale:—
 (a.) When the combined length of the poop, or raised quarter-deck, bridge-house, and top-gallant forecastle is— 9/10 ths of the length of the vessel, deduct 85 per cent, of the reduction in the reserve buoyancy allowed for a com-plete awning deck, or 85/100 ths of the difference between freeboards in Tables A (after correction for sheer), and Tables C.page 14 8/10 ths of the length of the vessel, deduct 75 per cent, of the reduction in the reserve buoyancy allowed for a complete awning deck, or 75/100 ths of the difference between freeboards in Tables A (after correction for sheer), and Tables C. 7/10 ths of the length of the vessel, deduct 63 per cent, of the reduction in the reserve buoyancy allowed for a complete awning deck, or 63/100 ths of the difference between freeboards in Tables A (after correction for sheer), and Tables C. 6/10 ths of the length of the vessel, deduct 50 per cent, of the reduction in the reserve buoyancy allowed for a complete awning deck, or 50/100 ths of the difference between freeboards in Tables A (after correction for sheer), and Tables C.

When the engine and boiler openings are protected only by a long raised quarter-deck, a less reduction in freeboard will be allowed.

 (b.) For intermediate lengths of erections the amount of the reduction in freeboard should be ascertained by interpolation. (c.) The above scale of allowance is prepared for vessels having long poops or raised quarter decks 4 ft. high or above. For raised quarter decks of less height, extending over four- tenths of the length, and forming an integral portion of the vessel, the amount of the allowance should be diminished, as shown in the following table:—

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 (d.) For shorter lengths of raised quarter-deck a proportionate increase should be made. (e.) It is to be understood in the application of this scale of allowance for erections on deck to vessels with long poops or with raised quarter-decks, and bridge-houses combined, that the deduction is a maximum deduction, applicable only to vessels of these types in which the erections are of a most substantial character, the deck openings most effectually protected, and the crew are either berthed in the bridge house, or the arrangements to enable them to get backwards and forwards from their quarters are of a satisfactory character. For other vessels of the same class the amount of the deduction should be fixed only after a careful survey. Also such vessels when employed in the Atlantic trade will require to have specially provided greater freeboard than that given in the Tables. (f.) A sufficient number of clearing ports, as large as practicable, and with shutters properly hung, should be formed in the bulwarks of these vessels, between the forecastle and the bridge-house for the purpose of speedily clearing this part of the deck of water.
12.When the erections on a vessel consist of a top-gallant forecastle, a short poop having an efficient bulkhead, and bridge-house disconnected, the latter in steamers covering the engine and boiler openings, and being efficiently enclosed with an iron bulkhead at each end, a deduction may be made from the reserve buoyancy given in the Tables according to the following scale:—
 (a.) When the combined length of the erections is— 5/10ths of the length of the vessel, deduct 40 per cent, of the reduction in reserve buoyancy allowed for a complete awning deck or 2/5 th of the difference between the freeboards in Tables A (after correction for sheer and length) and Tables C (after correction for length). 4/10 ths of the length of the vessel, deduct 33 per cent, of the reduction in reserve buoyancy allowed for a complete awning deck or 1/3 rd of the difference between the freeboards in Tables A (after correction for sheer and length) and Tables C (after correction for length).
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13.When the erections on a vessel consist of a top-gallant forecastle and bridge-house only, the latter in steamers covering the engine and boiler openings, and being efficiently enclosed with an iron bulkhead at each end, a deduction may be made from the reserve buoyancy given in the Tables according to the following scale:—
 (a.) When the combined length of the erections is— 4/10 ths of the length of the vessel, deduct 30 per cent, of the reduction in reserve buoyancy allowed for a complete awning deck or 3/10 th of the difference between the freeboards in Tables A (after correction for sheer and length) and Tables C (after correction for length). 3/10 ths of the length of the vessel, deduct 25 per cent, of the reduction in reserve buoyancy allowed for a complete awning deck or th of the difference between the freeboards in Tables A (after correction for sheer and length) and Tables C (after correction for length).
14.When the erections on a vessel consist of a short poop and top-gallant forecastle only, the former enclosed at the fore-end with an efficient bulkhead, the deduction from the reserve buoyancy given in the tables should be according to the following scale:—
 (a.) When the combined length of the erections is— 3/8 ths of the length of the vessel, deduct 8 per cent. of the reserve buoyancy or 10 per cent, of the freeboard required for the vessel flush decked after correction for length; 2/8 ths of the length of the vessel, deduct, 6 per cent, of the reserve buoyancy or 8 per cent, of the freeboard required for the vessel flush decked after correction for length; and so on in proportion.
 15 When a vessel is fitted with a topgallant forecastle only, the reduction in reserve buoyancy should be one-half that prescribed by the previous paragraph for the case where, in addition to the forecastle, the vessel is fitted with a poop of the same length.page 17 16 Sheer.—The Tables are framed for vessels having a mean sheer of deck measured at the side, as shown in the following Table.

 (a.) In flush - deck vessels and in vessels to which clauses 11 and 12 apply, when the sheer of deck is greater or less than the above, and is of a gradual character, divide the difference in inches between it and the mean sheer provided for by 4, and the result in inches is the amount by which the freeboard amidships should be diminished or increased according as the sheer is greater or less. (b.) In vessels having short poops and forecastles, and in those having short forecastles only, the freeboard should be corrected in respect of the excess of or deficiency in reserve buoyancy due to variations in sheer from the standard amount over the length uncovered by substantial erections, as provided in the above Table. One-fourth the difference between the mean sheer specified and that measured as described, is approximately the amount by which the freeboard should be modified in respect of sheer. (c.) The divisor 4 is to be used when the sheer is of a gradual character, and is not strictly applicable either to those cases in which the sheer is suddenly increased at the bow or stern, or to those in which it does not maintain its normal rate of increase to the ends of the vessel.page 18 (d.) In all cases the rise in sheer forward and aft is measured with reference to the deck at the middle of the length, and where the lowest point of the sheer is abaft the middle of the length, one-half of the difference between the sheer amidships and the lowest point, should be added to the freeboard specified in the Tables for flush-deck vessels, and for vessels having short poops and forecastles only. (e.) Where, as in some instances, vessels fitted with long poops or raised quarter decks connected with bridge houses have the deck line rising rapidly from amidships to the front of the bridge, and from that point onwards gradually approaching the normal sheer line, the freeboard may be slightly modified in consideration of the increase of height of deck in the "well." (f.) In flush-deck vessels and in vessels having short poops and forecastles the excess of sheer for which an allowance is made shall not exceed one-half the total standard mean sheer for the size of ship. (g.) No decrease should be made in the freeboard of spar and awning deck vessels, in respect of excess of sheer.
 17 Round of Beam.—In calculating the reserve of buoyancy, an allowance has been made of one-quarter of an inch for every foot of the length of the midship beam for the round up. When the round of the beam in flush-decked vessels is greater or less than given by this rule, divide the difference in inches by 2, and diminish or increase the freeboard by this amount. For vessels with erections on deck the amount of the allowance should depend on the extent of the main deck uncovered. This rule for round of beam does not apply to spar or awning deck vessels. 18 As a general illustration of the way in which the Tables should be used in modifying the freeboard on account of erections on deck, extreme proportions and variations in sheer, the following may be taken as an example.

A vessel is 234 ft. long, 29 ft. broad, and has a moulded depth of 17.0 ft., the coefficient of fineness being .72. Suppose the vessel to have a poop and bridge house of the united length of page 19 121 ft., and a forecastle 20 ft. in length, and let the sheer forward, measured at the side, be 4ft. 6 ins., and aft 2 ft. 1 in.

 Ft in. Freeboard by Tables A if of the normal length, without erections, and with the normal amount of sheer 2 11 The mean sheer by rule is 33.4 ins., or 6 ins. less than that in the vessel, and the reduction in freeboard is 6 ins. divided by 4 01½ Freeboard of vessel without erections and with 39½ ins. mean sheer 2 9½ Freeboard by Tables C as awning-decked 1 4½ Difference 1 5

The combined length of the erections is 14½34 ths or 6/10 ths of the length of the vessel, and the allowance for erections under clause 11 will be therefore 5/10 ths of 17 ins., or 8½ ins.

 Deduct. We have therefore— in. Amount deducted from freeboard for excess of sheer 1½ Amount deducted from the freeboard for erections 8½ Amount deducted if vessel be fitted with an un-covered iron main deck (clause 6) = 6/10 x 3½ 2 12
 The length being 30 ft. in excess of that for which the Tables are framed, the addition to the freeboard in respect of the same is one-half of 30/20 ths of 2 ins., or 1½ 10½

That is 10½ ins. to be deducted from 2 ft. 11 ins., leaving a winter freeboard of 2 ft. 0½ in. Corresponding summer freeboard 1 ft, 10½ in.

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19. Vessels loaded in fresh water may have less freeboard than that given in the several Tables according to the following scale:—

Memo.—The weight of a cubic foot of salt water is taken, in the above Table, to be 64 lbs., and that of fresh water 62.5 lbs.