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Practical Ideas for the Engineer Revised Rules Issued for Steel Vessels—Proper Use of Varnish— Repair Costs— Painting Lake Ships tion and classification of steel ships Lloyds. |e rules for the construc- were recently adopted by These came into force on Jan. 13, 1923, but: -were, however, adopted previously with the — sanction of the owner in the. case of any ves- sel already* contracted for, or which had been contracted for before that date. In recent years, many changes and developments in shipbuilding have tak- en place and greater attention has been paid to the scientific study of the functions of the particular parts of the structure. From time to time, various new points of view have been presented, the adoption of which has helped to make the con- struction of ships cheaper by the simplification of design and _ conse- quent saving of labor, while, on the other hand, by the abolition of re- dundant members of the structure and the redistribution of material, it has been possible to secure some saving in weight. Relation of Scantlifigs and Draft The last revision of the rules of Lloyd’s Register was made in 1909, prior to which time the basis of scantlings had remained practically unaltered for many years, and had led to the recognition of numerous types of vessels, such as awning deck, shelter deck, spar deck, and. shade deck. The revision in 1909 reduced the number of types of vessels for which provision was made to the full scant- ling vessel and the shelter deck ves- sel. Experience has indicat-d that it is possible to make freeboard assign- ment independent of type, with the consequence that in the new rules the relation of scantlings ‘to draft has been definitely taken into account for the first time. The result is the abolition of what may be _ termed “type” classification, and ithe rules of the society as now issued nay be said to complete the transformation commenced in 1909, bringing them into line with modern practice and the most up-to-date ideas of ship- building. Greater attention has been paid to the study and analysis of the part that is played (by the various mem- bers of the structure in meeting the different strains to which a_ vessel is subject in the course career. The existing practice, after analysis and adjustment on scientific lines, has been standardized, and_ generally speaking, some saving in weight has been achieved, more particularly for vessels of a restricted draft. One of the most important points in which the new rules differ from their predecessors is to be found in the fact that ‘Lloyd’s Register has recognized the principle that within limits scantkings should be based on draft, a feature the importance of which will no doubt appeal both to owners and builders. For this. pur- pose, the new rules provide sets of tables for two classes of’ vessels: (1) The full scantling vessel, which obtains the maximum loading per- mitted by the dimensions. (2) The complete superstructure vessel, in which the scantlings are adjusted to a freeboard approximate to that of the present shelter deck type with tonnage opening. Scantlings for vessels intermediate in draft between these two types can be readily derived from the two standards iby proportional interpola- tion. : By this system, the rules are di- rectly applicable to practically the whole range of vessels suitable for modern requirements, and it is thought tthat designers and builders will obtain greater elasticity in ad- justing deadweight and capacity for there will be a of her cargo. In addition, fairer relation throughout ‘between the deadweight carried, and _ the weight. of hull involved, while the same standard of performance will be maintained. Simplify Scantling Rules for determining the has been somewhat modified from the present practice, with a view to securing simplicity and directness of application. Prior to 1909, the scantlings of the frames were regulated by a numeral formed by the addition of half-breadth, depth and half-girth. The latter dimension was dropped in 1909, leaving the frame number to be determined by The method main scantlings the sum of the breadth and depth. The considerations which led to this revision have now been carried fur- ther, and under the new rules the size of tthe frame and frame spacing will depend on the depth of the ves= 143 sel, associated, as at present, with the unsupported span of the frame. In accordance with the general tendency in shipbuilding, opportunity has been taken in the new rules to provide for an increase of frame spac- ing in excess of the present practice of the society, an increase which is considered to be justified by exper- ience, and to have the advantage of reducing the cost of construction. Certain simplifications ‘have been made in regard to ordinary connec- tion ‘bars, which were formerly con- sidered to be parts of the main struc- ture, but which are now looked upon as means of connection only. Plating Around Deck Openings A marked improvement has been effected in the tables giving the scant- lings for the topsides, particularly Pe regards ‘the permissible breadths of hatchways and their openings in the decks. In the new rules, it is pro- vided that where the breadth of the deck openings differ from that stipu- lated, the thickness of the deck plat- ing is ‘to ‘tbe increased, or reduced, subject to the provision of a min- imum thickness. In the case of full scantling vessels, provision has been made to vary the scantlings of the frames and the thickness of the top side material in proportion ‘to the length of vessels. covered by super- structures, such as poops, bridges, and forecastle. The ‘bulkhead committee, in their report issued in 1915, included tables giving suggested bulkhead — scant- lings. This question has_ recently been under consideration internation- ally, and ‘there have been included in the new rules the modified scant- lings, which. show some _ reduction from previous requirements. Reviewing broadly the revision of the rules, it may be said that there have been reductions in the material at the sides of vessels and increases at the decks, which together with the advantages obtained by the corelation of scantlings and draft have pro- duced a combination which affords some economy in weight of material, at the same time maintaining a high standard of construction. Regulations have also been formu- lated for vessels in which the full seagoing requirements are not neces- sary, and in particular special tables