PRESENT DAY STATUS OF THE ART. 57 



tion from the point of view of bank erosion as well as power saving, if it is 

 possible to separate the two as far as rivers of moderate breadth are concerned. 



CRUISER STERNS. 



Of late years an increasing number of merchant vessels have been built with 

 the form of stern considered peculiar to battleships and cruisers. 



There is much to be said in their favor and the effect on speed may well be 

 noted here; for a given overall length this stern gives the maximum mean im- 

 mersed length and a resulting decrease in power and consequently machinery 

 weight, necessary for a given speed, varying with the size of the ship, being 

 greater in the smaller ship. The adoption of this stern is attended with increase in 

 stability, in deck room and in protection to screws in harbor. A full discussion is 

 to be found in the Times Engineering Supplement (London) of April 24, 1914. 



The chief objection is increased first cost, appearance is another in some eyes, 

 but small increased first cost will have a hard struggle against a possible 8 per cent 

 saving in coal bills. The arguments are very much in favor of the cruiser stern 

 for all twin or more screw designs, with a good chance in the single-screw de- 

 sign providing the draught is large. 



Shipbuilding and Shipping Record (London) of January 22, 1914, also has an 

 interesting article on cruiser sterns. 



Modified cruiser sterns are common in our waters for ships that do a large 

 amount of warping into and out of docks, notably in the Chesapeake Bay and sim- 

 ilar waters ; also on the coast in a few cases, some Old Dominion liners being built 

 that way. Doubtless many other instances could be found. 



EFFECT OF TEMPERATURE ON RESISTANCE. 



It has been known for some time in the experimental tanks that temperature 

 plays a part in ship resistance. 



Messrs. Denny Brothers of Dumbarton are reported to have been unable to 

 account for differences in summer and winter trials of sister ships in any other 

 way, and the matter is also under investigation at the Teddington tank in England, 



Differences in resistance as high as 4 per cent per 10 degrees difference in tem- 

 perature are reported, the lesser resistance corresponding to the higher temperature. 



APPENDAGE RESISTANCE. 



Lately this has received renewed attention; since Taylor's experiments in the 

 Washington tank, showing the run of the stream lines on ship models, designers 

 have studied more carefully the placing of bilge and docking keels. 



Sadler's experiments on enclosed shaft bossings have also given valuable aid 

 in properly placing these appendages. The author recalls a large vessel which had 

 her bossing altered to better form with the result that the speed at constant dis- 



