VARIATIONS OF AFTER SECTIONS. 63 



fective length of model D is greater than that of the others and, when the curves 

 of the others are past the 4j4-knot hump and drop down into the succeeding hol- 

 low curve, D is still on the hump. 



Other conclusions might be drawn from the curves, but it would not be safe to 

 generalize from a few results. Bearing in mind that a ship of the displacement 

 length coefficient involved would not be powered in practice for speeds above 4 

 knots, the results appear to indicate that gain could be made at practical speeds 

 by departing from the conventional type of after body, but that they would be 

 comparatively small after all. They would be of the 5 per cent order, not 15 or 

 20 per cent. 



DISCUSSION. 



The Chairman :— Gentlemen, these two papers are very brief, but they represent a 

 good deal of research and contain very interesting data. Discussion is now in order. 



Professor Herbert C. Sadler, Member of Council: — In connection with Naval Con- 

 structor Taylor's paper I may say that it confirms in every respect some experiments that I 

 conducted some years ago in connection with barge forms. They were somewhat more sim- 

 ple forms even than those of Mr. Taylor, having square corners. We found that the form 

 such as shown in the stern F was, on the whole, the best for ordinary working conditions, 

 and provided that we got the correct angle of the line through the bilge, that that form had 

 very little more resistance than the best ship shape form. 



With regard to the other forms, the stern C, which is a straight-sided vessel, we found 

 that it was decidedly bad under ordinary conditions of depth of water, but in shallow water 

 that type of stern, and bow as a matter of fact also, seemed to show up slightly better than 

 some others. In this connection it is interesting to note that in very shallow water the flow 

 would only take place in two directions, and consequently a form that is easy in those direc- 

 tions only, viz., length and breadth, will probably give the form of least resistance; but 

 when you come to deeper water, where the water wants to flow in a diagonal direction, then 

 a form such as shown in stern C is decidedly bad. The same thing applies in a lesser degree 

 to stern D — the ordinary scow-shaped stern — -the water does not want to follow in exactly 

 fore-and-aft lines; evidently it wants to come in from the side, from part of the hull, and 

 come up from the bottom from the other part, and consequently the stern D will give 

 slightly more resistance than a stern such as F, which is a compromise between the two. 



With regard to the stern E, that is interesting as illustrating the fact that it is quite 

 possible to make a stern too fine, that is, particularly toward the extreme ends. Evidently 

 in that case the water does not want to flow up on quite such a fine bilge diagonal as shown 

 there, and a fuller form of bilge diagonal will give a more natural flow line and conse- 

 quently less resistance. 



I think from an analysis of some of these simple forms we can get, perhaps, even more 



