*«.- ..« ^- 



IJA ^•M^'^^W 



I-v i:n(i permission of 



— ^h.^ys. -^\T '-^.% ■"n-^^.^.-isa.^ 



tiic Dirc':tor of the National Physical Laboratory. 



FiGt'RE 1, Tho Mxperiiuental IJ.isin and Carriage for towing Models, 



THE NATIONAL EXPERLMENTAL TANK. 



WORK AT THE NATIONAL PHYSICAL LABORATORY. 



Bv E. S. GREW 



At last the National Experimental Tank, which models represent. The National Experimental Tank 

 public subscription and private benefaction have set is intended for much more recondite experiments 



up within the precincts of the National Phwsical 

 Laboratorv, Bushy 

 Park, is completed : its 

 equipment is undergoing 

 test : and \\ ithin a \-er\" 

 short time the ship- 

 building i n d u s t r \- of 

 Great Britain will be 

 served bv an instrument 

 of precision unsurpassed 

 in anv other country. 

 Speaking roughly, one 

 may say that an experi- 

 mental tank is designed to 

 test the resistance which 

 is offered bv the hulls of 

 ships to passage through 

 the water. The desired 

 knowledge is obtained 

 bv tow ing wax models of 

 hulls of given shape and 

 dimensions through 

 the water of the tank, 



and (after their resistance to towing has been ascer 

 tained bv the most refined methods of measurement 



than are indicated in 



the foregomg sentence ; 

 but the uses of such 

 experiments — which 

 are constantly- being 

 made in the experimental 

 tanks of the German 

 shipbuilders, as well as 

 in the tank belonging 

 to Messrs. Dennv, of 

 Dumbarton, and in the 

 naval yards of the great 



Powers — ma\- be readil\- 

 made clear. 



Let us consider, for 

 example, some of the 

 problems which confront 

 the designer of a tor- 

 pedo-boat destroyer. 

 He has first of all to 

 derive a high speed from 

 his craft. But he can- 

 not put in as much 

 engine power as he 

 pleases, because that plan may result in an undue 

 weakening of the hull, or in sinking the hull too 

 by converting the results thus arrived at into terms low in the water, or in depriving the vessel of the 



Hy khtd pt-rttthsijn o/ the Diuxtof o/ the A^ationa! Phys'ual Laboat.^'y, 



Figure 2. 



Small Tank to be used for experiments with the water flowing 

 past the Model, the latter being held in a tixed position. 



of the larger hulls of iron, wood or steel which the necessar\- room for armament 



accommodati 



169 



