106 EKMAN. ON DEAD-WATER. [norw. pol. EXP. 



much space, to try to explain the particular effect upon the steering, in each 

 separate case reported. On the other hand it appears worth while to try to 

 show how the dead-water might affect the steering in the different ways 

 related in the accounts received, and consequently to show that these are not 

 in disagreement with the explanation of the phenomenon here given. 



Screw-steamers do not lose their steering at all, because the screw throws 

 a jet of water astern, against which the rudder is able to work. 



The steering of sailing-vessels may be affected in different degrees; in 

 some cases the vessel becomes quite unmanageable (see accounts Nos. 5, 6, 

 7, 8, 10), in others she can still be manoeuvred, but only with difficulty 

 (accounts Nos. 8, 9, 12, 38), again she may even have her steering-power 

 uneffected, while her speed is almost lost (account No. 11). These differences may 

 for instance, be explained as due to different thicknesses of the surface-layer; the 

 thinner the forward-moving surface-layer, the larger will be that part of the 

 rudder which reaches into the salt-water, and has its power unaffected. The 

 shape of the stern will very likely be of importance too, since the forward- 

 motion of the water will be a minimum if the lines of the stern are sharp 

 and fine. Finally, the dead-water may have a very marked effect upon the 

 steering, whenever the wind or current tends to turn the vessel round from 

 her course with great force; while it may be of no influence, if the vessel 

 be set to have no inclination to turn from her course into one or the other 

 direction. In this respect the difference of draught fore and aft, may often 

 be of great importance, as was pointed out by Mr. Colin Archer (p. 15). 



Dead-water often causes a vessel to turn in one particular direction, 

 as for instance, when she runs up into the wind and lies with her sails shivering. 

 This is obviously only a consequence of the powerlessness of the helm; for 

 a vessel is usually, owing to the arrangement of her sails, liable to run up 

 into the wind, and she will succeed in doing so, when the power of the helm 

 from any cause becomes reduced. 



In other cases a surface-current may cause similar effects, especially if 

 at the same time the steering-power is reduced by dead-water. If the fresh- 

 water is running on the top of the sea-water, as a surface-current somewhat 

 shallower than the draught of the vessel, this will be carried away in the 

 direction of the current, and the sea-water below, having another velocity, 

 will take hold of her keel. It might then take better hold of one end of the 



