RESISTANCE OF BILGE KEELS. 

 By Professor C. H. Peabody, Member of Council. 



[Read at the twenty-first general meeting of the Society of Naval Architects and Marine Engineers, held in 



New York, December 11 and 12, 1913.] 



The experimental boat Fulton, belonging to the Massachusetts Institute of 

 Technology, was used during the past summer to investigate the resistance of bilge 

 keels, for which purpose the boat was exceptionally adapted, both because the ap- 

 paratus on the boat permits of the determination of small variations in resistance 

 and because the prototype, the U. S. Navy tug Sotoyomo, after which the Fulton 

 was modeled, was investigated by Naval Constructor D. W. Taylor, U. S. N., at 

 the Washington Model Basin, and her stream lines were reported by him in the 

 Transactions, Vol. 15, page i. 



The stream lines for the Fulton, properly reduced from those of her proto- 

 type, were laid out on her hull while she was hauled up in the spring and are rep- 

 resented on Plate 13, together with the various bilge keels used for experiment. 

 The stream lines shown are for 6 knots speed of the Fulton, corresponding to 

 10.31 knots of the prototype. 



After a careful study of the stream lines on the hull, and a consideration of 

 the customary way of applying bilge keels, it was decided to take for the nor- 

 mal bilge keels a length of 15 feet and a depth of 3 inches. All the keels were three- 

 fourths of an inch thick, made of oak and through bolted to the hull. They were 

 set approximately at the middle of the length. 



In order to get fuller and more certain indications of the effect of bilge keels, 

 the depth of the keels was doubled and trebled. In addition experiments were 

 made with the 3-inch keels abnormally extended toward both bow and stern ; these 

 extensions were both 2 feet long, giving a total length of about 19 feet. 



The depth of the keel was doubled by bolting an additional 3-inch strake 

 through both the normal strake and the planking, and the depth was in like manner 

 trebled by bolting a third 3-inch strake outside. When the boat was fitted out 

 the bare hull was given two coats of anti-fouling paint and keels 9 inches deep 

 and 15 feet long were fitted as described, properly painted. As the experi- 

 ments proceeded the extra strakes were cast off by driving out the bolts which 

 secured them, plugging the holes with wood. After the double and treble depths 

 of keel were cast off the boat was hauled up and the bow and stern extensions of 

 the 3-inch keels were fitted. Experiments were made with extensions at both bow 

 and stern; afterwards the stern extensions were cast off and experiments were 

 made with the bow extensions only. The keels in all cases were faired down 

 to sharp edges at both ends to form faii: waters 2^ inches long. Where the bow 



