130 



EKMAN. ON DEAD-WATER. 



[norw. POL. EXP. 



2 is very considerable, it may therefore be concluded that the trim of a 

 vessel has practically no influence on the dead-water resistance. In what 

 follows, only the mean draught is therefore taken into account. 



The experiments with Models 3 and 4 were to show the influence of the 

 athwart-section of the vessel. They represent two extreme types of vessels 

 which are both used, and which may be characterized by a nearly rectan- 

 gular section (flat-bottomed vessels) and a nearly triangular section (sharp- 

 bottomed vessels). Between these extremes is Model 1 with a round (circular 

 or elliptical) athwart-section. The resistance-curves PI. X seem to show that 

 there is a marked difference of resistance to the 3 models. I shall here only 

 compare the maximum dead-water resistance, which is of special interest to 

 us; the corresponding velocities of the different boat-models are practically 

 equal to one another. The following table gives the maximum dead-water 

 resistance to each model, in water-layers of different thickness; the spec, gra- 

 vity of the salt-water being in all cases 1"030. 



As, however, the models 1, 3, and 4, have not the same weight and 

 draught, it is not possible by directly comparing these numbers to find the 

 influence of the different athwart-sections; it is necessary for that purpose to 

 reduce them to refer to vessels of the same weight and the same mean draught, 

 but with different cross-sections. To directly apply the results to the case of 

 full-sized ships, I have chosen the weight 800 tons (800000 kgr.) and 44 m., 

 which is the mean draught of the Fram at that displacement. First imagine 

 all linear dimensions (particularly the depth of the surface- layer and the di- 

 mensions of the boat-model) increased in the same ratio, so that its draught 



