DATA ON HOG AND SAG OF MERCHANT VESSELS. 

 By T. M. Cornbrooks, Esq., Member. 



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



New York, November 18 and 19, 1915.] 



In a paper read before this Society in 191 3, Naval Constructor S. F. Smith 

 presented considerable data showing observations made on three navy colliers built 

 by the Maryland Steel Company, to which was added the data of the two colliers 

 built by the Newport News Company. 



Since that time two additional colliers have been constructed for the Panama 

 Canal. These colliers are of the same general dimensions as the Orion and Jason, 

 but of increased deadweight capacity. 



The Ulysses and Achilles, Panama colliers Nos. i and 2, are built from the 

 same lines as the Orion and Jason, but to secure the necessary capacity for coal the 

 machinery was moved aft 15 feet and the 'thwartship coal bunkers reduced 10 feet 

 in length, making the holds 25 feet longer. The contract for these vessels re- 

 quired that they should carry 12,000 tons of cargo, 1,200 tons of bunkers and 105 

 tons of stores, feed water, crew and effects, on a draught of 28 feet i inch. As a 

 matter of fact they drew 27 feet 8 inches when loaded with the above deadweight. 



Following the methods used in securing the data on the previous colliers, we 

 started by establishing a datum line by transit while the vessels were on the stocks 

 and supplemented this by readings taken immediately after launch, when machinery 

 was installed, when in dock, before loading and when fully loaded. 



These curves are shown on Plate 60. It will be noted that when fully 

 loaded the Ulysses sagged 2^^ inches and the Achilles 2^^ inches from the original 

 datum line, as compared with 3% inches on the Neptune, 2^f inches on the Orion 

 and 3i% inches on the Nereus. The difference in the amount of sag between the 

 Orion and Jason and Ulysses and Achilles can probably be accounted for by the 

 better distribution of cargo. 



It will be noted that two curves are shown of the Achilles, of the ship com- 

 pleted, i. e., May 10 and 20; these observations were taken under the dates noted to 

 determine the deflection while the forward oil tanks and double bottoms were filled 

 with water as itemized, in preparing for a test of the oil pumping capacity. 



The results show considerable hogging effect when compared with the Ulysses 

 when completed under date of March 15, which can be accounted for by the differ- 

 ent conditions of tank loadings. 



In addition to the curves taken on the Orion and Jason, observations on the 

 Achilles were taken, as shown by curves on Plate 61, for determining the deflection 

 of the hull in way of the forward oil holds, when under hydrostatic test. 



