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A is for American rules, B

Curves showing gradation of Freeboard for vessels of different depths of hull, from 10 ft. to 34ft. moulded.

22 ft (Deck Line) 26ft of hull 30ft. Depth of hull 34ft

is for British rules

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covering with an awning-deck lessens the freeboard 13.5 inches, or 46.7 per cent., and for the larger vessels it reduces the freeboard 24.1 inches, or 23.3 per cent. By the British tables these reductions are, respectively, 14.5 or 51 per cent., and 29.5 or 25 per cent.; and the differences between the reductions only average 3 per cent. On the score of buoyancy, no good reason appears why so much more freeboard should be required, proportionately, for the larger vessels. If it be said it is on account of weakness in the larger ships that the difference is made, the plea is bad, as it reflects upon Lloyd's building rules for awning-deck steamers.

The American rules, based on the principle of proportioning freeboards to the pressure and motion of the sea, if correct for 14 feet depth of hull, cannot be wrong for a depth of 34 feet. However, the manifest distrust of the British tables may be fitting for such awning-deck steamers as are built for British service. If that is the case, Lloyds should look to the improvement of their rules.

One has only to inspect the curves of freeboard, in the accompanying cuts, showing the increase from small to large vessels, to perceive the regularity and symmetry of the gradation accomplished by the American rules; and to note, at the same time, the misproportioned and ill-formed curves produced by the British tables, particularly, in the cases of spar and awning deck steamers. A gradation that violates the laws of progression cannot lay claim to science, but belongs to the rule of thumb. It is simply impossible for the British tables to deal justly with all sizes and classes of ships. To steamers they are partial. To wooden ships unfair.

Sharpness of Hulls Considered. In the British tables sharpness of hull receives much consideration, and this without reference to the proportionate dimensions. Long and short, wide and narrow, deep and shallow ships, with equal coefficients, are treated alike and as analogous bodies, which, geometrically, they are not.

An inspection of the accompanying figures, I., II., III., Comparisons of Coefficients, will show at a glance that vessels of equal coefficients may have very unequal sharpness of form; that vessels of equal fineness of ends may have great disparity in coefficients of body; and that vessels of the same length may have different coefficients and degrees of sharpness.

In Figure I. we see that the body A, B, C, D has the same coefficient as the body E, B, F, D inscribed in the parallelogram 1, 2, 3, 4, but the one is blunt and the other is sharp. In Figure II. the four different bodies inscribed have the same angle of sharpness and the same length of bow, but the shortest body has a coefficient of 50 per cent., the next longer body of 75 per cent., the next of 83.33 per cent., and the longest body of 87.5 per cent.

In Figure III. there is the same length of body with different angles or sharpness, but a difference of 27.5 per cent. in the coefficients of fineness of ends.

What is also strange, the British tables give the least freeboard, and, consequently, the greatest draft of water to the sharpest body, which could not fail to be the one that would descend the deepest, and be the wettest in a storm at sea. There is no experience to warrant the loading of sharp vessels deeper than full ones. Nor is there any proving that sharp vessels are stronger built than full ones of the same dimensions. Nor is there any sound basis for this discrimination. It is wrong in all respects, and should have no recognition in the United States. It has long been a common error with naval architects to compare the fineness of vessel models, of promiscuous dimensions, by coefficients of body, whereas only vessels of similar, or strictly proportionate, dimensions, can be so compared with accuracy and fitness.

Imposition on Wooden Vessels. The discrimination against loading wooden vessels so deeply as iron or composite (iron frames and wooden planking) is another characteristic of the British tables that has no basis in practical knowledge. To reason that metal, as a material for ships, has buoyancy in excess of wood is absurd. Any difference existing between these materials is in favor of wood. The favoritism shown cannot stand on the ground of greater strength, for, whatever may be said of iron, as against wooden vessels, the mask falls when composite is also set against wood, since it is well known that composite construction is rarely the equal of either wood or iron. Good mechanical reasons explain this fact.

But affirmation is not made that wooden vessels are not strong enough to carry loads as great as buoyancy in due reserve will determine. That would reflect upon the Lloyd's

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Comparisons of Coefficients.

Fig.1. Vessels of equal coefficients may have very unequal fineness of form.

50%

50%

Fig. Vessels of equal fineness of ends may have very unequal coefficients of body.

4/8

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8725%

83.33%

1/2

75%

50%

Fig.3. Representing vessels of different coefficients and degrees of fineness

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87.5%

75%

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