This is a reproduction of a library book that was digitized by Google as part of an ongoing effort to preserve the information in books and make it universally accessible. http://books.google.com Knowyourownship ThomasWalton S>■ '<QtRAS& r KNOW YOUR OWN SHIP: A SIMPLE EXPLANATION THE STABILITY, TRIM, CONSTRUCTION, TONNAGE, AND FREEBOARD OF SHIPS, TOGETHER WITH A FULLY WORKED OUT SET OF THE USUAL SHIP CALCULATIONS (FROM DRAWINGS). SPECIALLY ARRANGED FOR THE USE OF SHIPS' OFFICERS, SUPERINTENDENTS, ENGINEERS, DRAUGHTSMEN, AND OTHERS. THOMAS WALTON, LATE LECTURER ON NAVAL ARCHITECTURE TO SHIPS' OFFICERS AND STUDENTS IN THE GOVERNMENT NAVIGATION SCHOOL, LEITH, AND IN MIDDLESBROUGH SCIENCE SCHOOL; AUTHOR OF "CONSTRUCTION AND MAINTENANCE OF SHIPS BUILT OF STEEL. TOUtb IRumerouB illustrations. FOURTH EDITION, GREATLY ENLARGED. LONDON: CHARLES GRIFFIN AND COMPANY, LIMITED; EXETER STREET, STRAND. 1899. [All Eights Reserved.] USv . VV2. 4- /399 PREFACE TO FOURTH EDITION. Duking the three years which have elapsed since the First Edition of this work was issued, the Author has received numerous responses to the invitation then given for " sug gestions and communications." These have come from ships' officers, engineers, and from students of naval architecture, working in shipyards. Though the original intention was to exclude the somewhat elaborate calculations involved in arriv ing at many of the conclusions dealt with in this work — dis placement, moment of inertia, righting moment of stability, etc., etc., — the communications received have proved beyond doubt that such calculations would be welcomed by a very large section of readers as a valuable addition to the book The author has been agreeably surprised to discover that many sea-going folk are not satisfied to merely understand and use the results of calculations given to them, but are determined to know and understand the whole process of calculation, by means of which these results are obtained, and, in consequence, very many hours have been spent in replying to queries of this nature. It will be evident that, as we come to deal with some of the more intricate calculations, a moderate amount of mathematical knowledge is required. However, it is hoped that by first dealing with the simple preliminary calculations in Chapter X., and then following on to the actual set of ship calculations, for which the necessary drawings are given, together with brief notes and explanations VI PREFACE. of the various steps taken, the reader will be able to trace the arithmetical application of the rules given. Considerable additions have been made in Chapter III. on the subject of water pressures, and in Chapter VI. (Section III.) on , the subject of * waterballast, to illustrate which numerous new diagrams have been inserted. Trim (Chapter VII.) is entirely new, and, it is hoped, will meet the require ments of those readers at whose suggestions it has been intro duced. This chapter, in the form of a paper, was read before the Shipmasters' Society in London, in March 1898, and the request was there repeated that it should find a place in Know Your Own Ship. The other sections of the book have been revised, and, as far as possible, brought up to date. Suggestions involving details of ship construction will be fully dealt with in the companion volume, Construction and Maintenance of Steel Ships, undertaken by the Author at the special request of the publishers. - In its enlarged and improved form, it is hoped that this volume will meet with the same cordial acceptance which has been the chief characteristic of its history during its three years' existence. * Extracted largely from a paper read by the Author before the Ship masters' Society, London, November, 1897. London, April, 1899. AUTHOR'S PREFACE TO THE FIRST EDITION. Experience is a wonderful teacher, though often a very slow one. In the course of time, it will instil into a seaman's mind a considerable knowledge of the capabilities and behaviour of his vessel under varying circumstances — her strength, her carrying capacity, her stability, or, in other words, her sea qualities. This mode of obtaining knowledge is, however, far too costly for the intelligent seaman of to-day. He knows that many a good ship, and what is worse, many precious lives have been lost before it has been acquired, and all through pure — though it would be unjust to say, wilful — ignorance. As regards the subject of stability, it has been said that it is useless to provide a captain with curves of stability, for he does not understand them, and if he did, they are of little use, all he requires being a statement of certain conditions of loading, beyond which he must not go, or his vessel will be unsafe. This is all very good in its way, but why does the captain not understand curves of stability, or, more broadly speaking, the subject of stability ? Is not the answer this, that very little indeed has been done to provide the means of his obtaining such important information ? Besides, if the curves are of little use, and a statement of conditions to Vlll PREFACE. ensure safety is sufficient, some credit must be given to the intelligence of the ship's officer of to-day. Let him not be put down as a machine to. steer a ship, incapable of compre hending what may be reduced to a subject of comparative simplicity. On the other hand, let it not be supposed that lengthy experience in navigating ships necessarily means capability to so load any ship as to produce seaworthiness. The ignorance often displayed in loading and ballasting vessels, and the loss resulting therefrom, prove that such is not the case. It is evidently often imagined that able, valuable, and in structive papers and lectures on vital subjects relating to ships, are only for, and interesting to, naval architects and experts, and that to ships' officers they are either unnecessary or else they have no interest in this means of instruction. A more f oolish and unjust conclusion could scarcely be arrived at. If the stability of a vessel depends so much upon the loading, and officers superintend the loading of their own vessels, at any rate in foreign ports, if not always at home, the importance of an intelligent knowledge of the subject must be evident. Moreover, is it not a fact that, with this knowledge, the ship's officer would be able to supply a great amount of valuable data to the shipbuilder and naval architect concern ing the behaviour and capabilities of his vessel under every condition of weather and loading, which could not fail to be of immense value in the designing of future ships ? By this means, the designer, who, as a rule, sees little of the ship he designs after a few hours' trial trip, generally under the most favourable circumstances, would then be the better able to produce a vessel more perfectly adapted to her requirements. That such is the case is proved by the fact that some leading shipbuilding firms do everything in their power to encourage 1 PREFACE. ship captains to give all the information they possibly can regarding the behaviour and performance of the vessels which they have built. The best method of supplying this kind of instruction to seamen is believed to be by means of lectures thoroughly illustrated by diagrams and experiments. During the past few years the writer has, in the Govern ment Navigation School, Leith, N.B., given courses of lectures, specially designed for the instruction of seamen. The eagerness and enthusiasm displayed to obtain such in formation made it manifest that seamen are fully awake to its importance, and appreciate and understand its value. The able discussion which often followed these lectures, and the important points and features brought out in connection with personal experience, furthermore proved that seamen want no rule-of-thumb methods for guidance, but that a thorough grasp of the principles of the subject is required. This, together with the repeated requests which have been made to publish these lectures, has tempted the writer to do so in the form of this book. The old-fashioned method of "beginning at the beginning " of the subject has been adopted as the only trust worthy way of dealing with it; and while endeavouring to cover as much ground as possible, the aim has been to con dense the matter as far as compatible with clearness, to present it in language easy enough to be understood by every seaman, and stripped of laborious mathematical formulae, and at a cost which will place it within reach of seamen of limited means. It is felt that no apology is necessary in presenting this book, for while the excellent work of Sir E. J. Eeed and also that of Sir W. H. White are admirably adapted to the require ments of the naval architect and the shipbuilder, it is believed X PREFACE. that no special attempt has been made to supply the need of seamen generally. It is further hoped that the chapters on Construction, Tonnage, and Freeboard, while interesting and important subjects to seamen, will make the book acceptable to the ship owner, ship superintendent, ship draughtsman, and to those generally interested in shipping. The Author's sincerest thanks are due to Messrs. W. Denny & Brothers, Dumbarton ; to Messrs. J. L. Thompson & Sons, Ltd., Sunderland ; and to Messrs. Eamage & Ferguson, Ltd., Leith, for permission to use curves of stability of vessels built by them ; and also to J. Bolam, Esq., Head Master of the Government Navigation School, Leith, for the kindly sympathy and interest which he has manifested in the preparation of the book.