128 EKMAN. ON DEAD-WATER. [norw. pol. exp. 



in Fig. 9 PL VI. By means of these values and the corresponding velo- 

 cities in the 5th column, Curve (3) in the same figure, is constructed. This 

 curve then, represents the same case as Curve (2), only with the difference, 

 that in the latter case, the boat is moving in a 40 cm. wide channel, 

 while the former case refers to a 20 cm. wide channel. [The numbers in 

 the 6th column should really be calculated by adding to the numbers in the 

 4th column the resistances in homogeneous water in a 20 cm. wide channel. 

 But as our object is to compare the dead-water resistances, it was more 

 suitable to reckon them from a common curve, e. g. from Curve (1). In any 

 case the difference is very small.] 



A comparison between the two curves seems to prove that the narrow- 

 ness of the channel has no remarkable influence on the maximum resistance 

 as it has been defined on p. 90. The velocities corresponding to given resi- 

 stances are, however, somewhat smaller in the narrow channel than in the 

 wide one 1 . As shown by Fig. 1 PI. I, the large tank is rather spacious for 

 the small boat-model; and the photographs on PI. XIII seem to show that 

 the waves have spread just as in open water. It is therefore probable that 

 the resistance in open water would follow a curve, much nearer to Curve (2) 

 than the latter is to Curve (3). As the influence of the narrowness of the 

 channel is then, not very great and, especially as it does not effect the 

 maximum resistance appreciably, it is not necessary to make any allowance 

 for it in applying the results. 



Unfortunately, hardly sufficient experiments were made with the small 

 boat-model in the large tank, to answer the above questions so completely 

 and positively as had been desirable. At the time, it was not noticed that 

 these particular experiments would be of such especial interest, and it was 

 afterwards too late to have them repeated. 



The influence of the shape of the boat-model. 



According to some of the narrators in Chapter I, vessels of different 

 shapes should be to different extents, liable to dead-water. Their statements 



1 It seems therefore probable that the difference between the resistance-curves (4) and (5) 

 in Fig. 3 PI. VI (see p. 126) depends on the different width of the channels. For, as 

 shown by Fig. 1 PI. I, the small tank is narrower compared with the small Frani- 

 model, than is the large tank compared with the large Fram -model. 



