PRESENT DAY STATUS OF THE ART. 55 



The British Board of Trade's recent instructions to steamers in the danger 

 zone throw an interesting light on this point, applicable almost as much to peace as 

 to war damage : 



"In order to prevent the vessel taking a sudden list if holed by a torpedo, the 

 stability should be increased to the utmost extent practicable by filling ballast tanks 

 or otherwise." 



Another paragraph follows, relating to longitudinally bulkheaded ships of small 

 initial stability; both these paragraphs point towards increased beam. 



The same reasoning points to increased beam in our line of battleships; for a 

 31,500-ton ship a beam of no feet is already responsibly suggested abroad, and the 

 paper by General Goulaeff before the London Institution in 1908 is well worth look- 

 ing up, in the light of recent happenings. Who knows but that battleships laid 

 down abroad since the war began are not of this largely increased beam? It is 

 probable that less weight will be available for machinery, owing to increased pro- 

 tective weights ; and that this, together with the new proportions, will mean a de- 

 crease in speed. The beam to draught ratio is about 3.25 in recent battleship de- 

 signs, whereas in the no- foot ship mentioned above it goes up to 4.40. In this 

 connection, the speed curves given by General Goulaefif are of interest. The York- 

 town experiments quoted by Admiral Taylor in his Manual indicate an approxi- 

 mate increase in power of about 11 per cent for the same speed for battleships of 

 this displacement and with proportions varying as above. 



EFFECT OF WIND AND SEA. 



A good smooth-water performance is not necessarily a good sea performance; 

 considerable attention has recently been given to this question and some interesting 

 facts brought to light. There was the hollow versus straight lines discussion in 

 the London Institution, 1905 (Vol. 47) ; Admiral Taylor referring briefly to the 

 question in his new Manual on speed and power (p. 121). Baker in his new book 

 also discusses this point. 



Early this year Sir A. Denny referred to the matter before the Institute of 

 Marine Engineers, citing instances of improvement in sea performances due to 

 decrease in fullness compared with previously accepted practice. His point was 

 that low first cost and low operating costs did not always go hand in hand. 



Mr. A. Hamilton in 191 1 before the Liverpool Engineering Society gave data 

 based on the comparative performances of ships of varying fullness, all tending to 

 show that the somewhat finer vessel (particularly forward) more than balanced 

 the loss in dead weight per trip by an increased number of trips per year. 



It is difficult to deduce any rule, but the general lines to follow are obvious — 

 the speed curves of a design should be run well up beyond the designed speed and 

 attention given to the characteristics of the curves at the speeds beyond the smooth- 



