EXPERIMENTS ON THE FUI.TON AND THE FROUDE. 3 



PROPELLERS FOR THE FULTON, 1912. 



Projected 

 Pitch-ratio. area-ratio. 



No. 1 0.8 0.56 



No. 2 i.o 0.53 



No. 3 1.29 o . 48 



The propeller No. 3 was a close copy to one-third the size of the pro- 

 peller of the Sotoyomo — which is represented by Plate 2, made from a 

 drawing kindly furnished by Admiral H. I. Cone, U. S. N. — with the excep- 

 tion that the propellers of the Fulton had no rake. All the propellers were 

 cast and had the surfaces smoothed but not planed ; as is customary for such 

 propellers there was some thickness near the edge which was rounded on the 

 back to the edge. The propellers, which were made by the Hyde Windlass 

 Company of Bath, Maine, were closely correct to pitch; the pitch-ratios are 

 so nearly correct that variations can have little, if any, effect on our results. 



The hull of the Fulton was built in the shops of the Massachusetts 

 Institute of Technology; it had double sawed oak frames spaced 15 inches 

 apart, oak keel, keelson, stem, stern-post, and beams, and was single- 

 planked w^ith |-inch white cedar. The construction and general arrangement 

 are shown by Plate 3.- Measurement after construction showed that the 

 form was fair and true to the lines. In order to reduce wind resistance the 

 boat was practically flush-decked, the midships being covered with light 

 hatches that could be opened for convenience in installing and running the 

 machinery. The boat was maneuvered from a cock-pit forward and was very 

 handy under our system of indirect electric propulsion. 



The machinery and apparatus used on the Froude in 191 1 were trans- 

 ferred to the Fulton and do not require description beyond that given in the 

 former paper. 



The tow-rope pull in both years was taken by the vertical arm of a bent 

 lever ; the horizontal arm of the lever pulled directly on a good spring balance, 

 a dash pot being used to reduce vibration. This device was found to be con- 

 venient and as delicate as conditions v/arranted. The points for a series of 

 tests came on a fair curve and appeared to have an error of not more than 

 one per cent. 



During the experiments of 191 1 the Froude towed a drag made of three 

 raihoad ties bolted together in a triangle and towed from the apex. During 

 the experiments of 191 2 the Fulton towed the Froude, which had a plank 

 bolted across the stem to augment its resistance. The drag used in 1 9 1 1 was 



