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May, 1909 naval architect ment which a must always keep in view. Dealing with Channel Sections. When we came to deal with chan- nel sections, whose use is somewhat modern, it found that practice had developed in the wrong direction, owing to the rolls having been cut to supply special orders of specified thick- nesses, without reference to any gen- eral principle of design or distribution of mateérial, and. to the fact. that in rolling channels the flanges must re- main of a constant thickness, as the only way to increase the strength or weight of any particular section by adding thickness to the back of the web, and it was quite usual in ship building practice to have channels with webs very much thicker than the flanges. This was obviously wrong in principle, and for the minimum thickness of the standard sections for ship building my committee made the webs 2/20 of an inch less in thickness than the flanges, the webs being kept sufficiently thick to provide a margin for corrosion, and a reasonably pro- portionate section. A study of the table of the standards, as published, will show that there are certain sec- tions, e. g., the 6-in. by 3-in, channels, which are given in two profiles, and that one of them has a thinner web than the other. This thinner section is used by the underftame builders for -railway. rolling stock, and 1s stronger in proportion to the weight of material than the ship section, but my committee did not see their way to go so far with ship sections as the underframe makers felt was desirable. The H girders which wére got out by the bridge committee. have webs much thinner than the flanges, but these sections have not hitherto been greatly used in ship building, while they indicate the line of economical development in sectionaY material. We dealt with Z sections in practi- cally the same way as with channels, and as T sections are not greatly used in ship building, it was decided to leave this part to be dealt with by the bridge committee. The maxima and minima for the thicknesses of all sections were settled only after a thorough discussion of the technical and practical necessi- ties of each case, discussion in which was the voice of the steelmakers had great weight. I have thought it right to publish the considerations that weighed with my committee in deciding upon the profiles. After this preliminary work was completed, the important point was "TAE Marine. REVIEW taken up as to how many sections should be standardized, but here strong conflicting interests were at once evi- dent, and the final result was a com- promise--that method of arriving at a decision which is so peculiarly Brit- ish, and so practically effective. Eliminating Multiplicity of Sections. It was thought essential that some- thing ought to be done to arrest the continual increase in the number of sections demanded from the rolling mills, and therefore in the number of rolls which it was necessary for the steelmakers to keep. This multi- plication of sections was accomplished by no commensurate practical ad- vantage, and it brought in its train very serious drawbacks, such as de- lay in delivery, when small quanti- ties of material: were required, because the manufacturers had to wait until. a sufficient number of orders had been received for a particular section to warrant the putting in of the set of rolls; sor: to watrant the cutting of special rolls. These rolls, when once cut, might only be used again on rare occasions, thus involving the steelmakers and the users in wun- remunerative expenditure. The extent to which this had ben carried was emphasized in the evidence laid be- fore the main committee by a steel maker, who asserted that eight- tenths of the special rolls which his firm had been obliged to cut were never again required. The sums wast- ed in' this way must have been very considerable in view of the fact that the cost of a set of rolls is roughly £200. It was only natural that the steel- makers should desire to work with the fewest number of sections possi- ble; but, on the other hand, the shipbuilders and classification socie- ties wanted to have the very fullest range which could be obtained. Be- tween these opposing views the com- mittee struck what I hope may be re- garded as a happy mean; in any case, the number of sections standardized was very considerably less than the total number of sections published by the different steelmakers. The advantage of having a standard pro- file laid down is now, I think, 'fully recognized by all, and there does not appear to be much complaint as to want of comprehensiveness in the lists. re Conferences between the committees were arranged, with the result that the final standard lists contained the following number of sizes:-- Equal angles Unequal angles Re Se eR ee EO Se) 88k 85 Bulb angles -..4) Aa 20 Bulb. tees! 7), er 6 Bulb plates: c(i 7 Ze bars. 3s... 3e 8 Channels. 72710) = 27 Beams = 20.9.6 ee 30 bars ¢ 2352 Aa Za Making Existing Sizes Uniform. In any list of standards it iz clearly desirable that the incremen:s in size should be such that uniform and pro- portional increments in strength and weight will be maintained throughout the series. Practical considerations in regard to existing sizes in current use made it obvious that it would be impossible to design a _ purely theoretical series, and that- the best solution under the circumstances was one which would bring in as many existing sizes as possible, while so arranging their weights that the list would be as nearly uniform as practi- cable. Diagrams were prepared giv- ing the ideal solutions, and the fig- ures given by the standard sizes when plotted thereon showed that the sizes agreed upon lay very evenly along the ideal lines. When the exigencies of ship building require additions to the standard lists it is: hoped that 'the sizes so added may approach the ideal sections as nearly as_ practical conditions will permit, and that when the steel makers are preparing to make rolls for such sections, they will, before actually 'cutting them, consult the standards committee as to the dimensions which should be adopted, as by this means only can uniformity be maintained and the full benefit ot the work of standardization be reaped. It will be observed that the profiles are stated in inches and fractions of inches for the flanges and webs, and in decimals for the thicknesses. This latter point was a little difficult to decide, because the admiralty and the three classification societies had each a different method; the admiralty. speci- fied in pounds per foot, Lloyds in 20ths of an inch, the Bureau Veritas in 16ths and 32ds, and the British Corporation in 40ths. The commit- tee finally decided to use decimals of an inch for thicknesses, adopting steps of .025 of an inch, this leaves ihe various bodies free to specify their thicknesses by any unit they please, the standard profiles only being fixed and expressed as is noted. During the early discussions of the conmittee evidence was laid before them of the trouble and vexation caused in the steel works by the dif- ferent methods which were in vogue in regard to ordering and measuring