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August, 1909 that the tendency has been to bring the spar, awning and shelter deck types to a great extent in line with the full scantling vessel by a redistribution of material, strengthening the _ topsides, and making in each case the upper deck to be the strength deck of the ship, The loading of spar deck and full scantling vessels has been to a great extent identical, but the loading of the shelter deck type has, however, been restricted on account of tonnage open- ings. ' Taking all these circumstances into account it is considered that there is now no necessity for retaining separate rules for each of the several types re- ferred to. It would appear to be sufficient if provision were made in the rules for two main types only, one in which the numbers for regulating the scantlings would be taken to the uppermost deck, and this would be the full scantling vessel. In the other the _ scantling numbers would be taken to the deck next below the uppermost deck as at present is done for the spar and awning deck types, and in this type the water- tight bulkheads would stop at the deck next below the uppermost one. This second type may be looked upon as a vessel having a continuous superstruc- ture, but with strong sides and deck as is at present the practice with such erections. IIl--The New Rules. The revised rules and tables are framed to include vessels up to about 680 ft. in length, and they cover all the vessels previously classed by the society, except the large Cunard steamers Lusitania and Mauretania. Provision is made in these rules for two main types only, namely (1) the full scantling vessel, and (2) the ves- sel having a continuous superstructure, such as an awning or shelter deck. In both types the frame number will be taken to the uppermost continuous deck, with a deduction in the awning or shelter deck type of the height between Shelter deck and deck next below, provided this does not exceed 8 ft. The continuous superstructure is to have strong sides and deck as is at present the practice, with the water- tight bulkheads (except collision bulk- head) stopping at the deck below the shelter or awning deck. The machinery casings are to be trunked to the shelter deck or the machinery space bulk- heads extended to this deck. In computing the frame number no account is taken of the half girth of the midship section as is done in the pres- ent rules; such half girth being a meas- ure of the fullness of the midship sec- tion only, and not of the entire body 'THE MarRINE REVIEW of the vessel. A vessel may. have full ends and a fine midship section, and thus have a_ larger capacity than one of similar dimensions with a full form of midship section and fine ends. In this way, under the present rules; <4 vessel having a, larger capacity but with a smaller girth amidships, may yet re- quire lighter scantlings both for fram- ing and plating, than a vessel of the same dimensions but having © smaller capacity; and this is known to have oc- curred in some instances. Many of our fastest vessels with exceptionally fine ends, have very full sections amidships; and this is now the usual practice in vessels of fine form, except with such small craft as trawlers or yachts. The frame number or "transverse number" is the sum of the molded depth at the middle of the length of the vessel, and the greatest molded breadth. The molded depth is the depth generally used when dealing with the dimensions of a vessel, and there will be no need to correct it for vary- ing rounds of beam, as often has to be done with the present rule depth, which -is taken at the middle line. molded depth can always be _ readily ascertained for any classed vessel as it is recorded in the register book, and is, moreover, the depth used for freeboard purposes. By using the full breadth in place of the half breadth in the frame num- ber, a similar addition to either of the dimensions, breadth or depth, will have the same effect on the frame num- ber. By the present basis of scantlings, which uses the half breadth in conjunc- tion with the depth, the latter dimen- sion can only be increased one-half as much as the former to have the same effect on the frame number. It will thus be seen that this basis puts a greater restriction breadth, which will be obviated by the new _ basis. The rule length is measured from the fore side of stem to after side of post on the upper deck, instead of from after 'side of stem to fore side of post. This length will, in most cases, agree with the registered length of the vessel, and it is more generally used than the present rule length when deal- ing with the dimensions of a_ vessel. The plating number or 'Jongitudinal number" is obtained by multiplying the frame number by the length as at pres- ent. The proportions of length to depth are taken to the uppermost continuous deck, and in the way of a long bridge deck, making the side plating of uni- form thickness up to the strake below the bridge sheerstrake, which sheerstrake for the length of the bridge becomes The: on depth than on 251 the main sheerstrake of the vessel, The additions for proportions in way of the bridge are made to the bridge deck plating and stringer, bridge sheerstrake and strake below, suitable provision be- ing made for maintaining the strength of the topsides at the ends of the deck erections. .Beyond the ends of a long bridge and right through in way of a short bridge the additions where re- quired are based on the proportions to the upper deck and will be fitted at that deck, By using the greater length in con- junction with the reduced depth (mold- ed depth) the nominal proportions are increased, that is to say, a vessel which is 13 depths to length. on the present basis is about 1314 depths to length on the new basis. Smaller grades have been introduced into the tables in order to render the increase in weight from one grade to another as small as possible, having regard to the strength required. These smaller grades necessitate the increases in frame spacing to be made by half inches, and make desirable that small- er divisions than 1/20 of an inch be used to insure a slight increase with each grade, otherwise the same _ scant- lings would have to be used for more than one grade. Smaller divisions are obtained by using decimal thicknesses, as has already been approved by the committee in the cases of standard sections for angles, bulk angles, chan- nels, etc. and given on pages 181 to 187 of the rules for steel ships; and the bulb angles, channels, etc, given in the tables are, with few exceptions, standard sections. In the preparation of the tables of scantlings in the new rules, it has thus been considered of primary importance to depart from the divisions of 1/20 of an inch hitherto adopted, and to substitute for them decimal divisions. The unit selected as best fitting the circumstances of the case is one-fif- tieth, -or 0.02 of an inch, -- This wal not only simplify the work of the drawing office and of the counting house by reason of the recognized su- periority of the decimal system, but it will also serve to bring the -British measurements into almost identical cor- respondence with those adopted by our continental neighbors. It so happens that 0.02 of an inch is, to all intents and purposes, a full millimetre. Al- ready the committee of Lloyds regis- ter have adopted these divisions in the preparation of the tables of scantlings for yachts built of steel for the international rating classes, and the result has been so satisfactory as to justify the belief that the applica- tion of the same unit of division in the