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March, 1914 docked. She lay in fresh water at Camden, N. J., from the launch until July 26, during which time no ap- preciable fouling would take place. I also call attention to the printer's error, top of page 4, second line, for 1,500 read 1,750, which is confirmed by: reference to table No. 3. Howard C. Higgins contributed the following data confirming the ship's excellent performance: Attention is called to the small cargoes carried on several trips and the large average space (198 cu. ft.) taken up per ton. This is due to the business being largely a one-way movement, and the ship being gen- erally dispatched on _ schedule. re- gardless of the amount of cargo of-. fering. Had it been possible to obtain a full load each way, each trip, the per- formance as shown would have been much improved. Charles H. Peabody:--I congratu- late Mr. Rigg in presenting us with -a test of a merchant ship under fa- THE MARINE REVIEW tion on the after body lines nor upon the happy choice of revolutions for the propeller. While the complete lines of the hull govern the effective horsepower required to tow that particular hull at any given speed, the indicated horsepower necessary to be _ devel- oped by the propelling engines in order that this effective horsepower may be delivered depends directly upon the form of .the after body lines, upon the designed revolutions of and the permissible diameter of the propeller. In designing a pro- peller to deliver a _ given effective horsepower, and to realize the max- imum tank efficiency possible, a cer- tain diameter and a tip. speed cor- responding to this diameter are re- quired. In addition, the after body of the hull must be of such form as will permit the water from forward to flow to the screw and to enter it in a solid' unbroken stream. This I will designate as condition 1; it is met with in bodies having a long, ABSTRACT OF LOGS FOR NOVEMBER, 1913, OF S. S. TYLER Speed, Coal Mean Cargo, tons, Leaving statute (2,000 draught, (2,000 Per cent Port. Date. miles. R. P.M. lbs.) Mileage. ft, Ibs.) slip. S-NY Nov. a 12:73 86.76 41 339 16:2 2,329 10.9 N-PP Nov. 4 1342 86.73 80 328 1233, 0 825 9.2 S-NY Nov. 8 135t1 92.06 86 - 339 14 1 1,930 14.7 N-PP Nov. 11 13.48 87.85 86 328 15:0 1,554 6.8 S-NY Nov. 15 13476 89.90 84 339 ioe AT 1,875 Lae N-PP Nov. 18 13.10 - 82.30 84 "328 15 20 1,417 3.4 S-NY Nov. 22 12.67 83.90 Ze 339 16 10 2,125 8.4 N-PP Nov. 25 13.21 83.80 72 328 12.9 1,093 4.4 S-NY Nov. 29 2 13879 87.30 ee 339 13 1,426 Aol Averages and 118.97 780.60 363 3,007 ee 14,574 69.1 Totals Pae2e 86.73 40 334 1455 1,619 Lad Speed, knots "per show geg ot ocr eas eins ete Fa ne eee et es 11.48 Coal per trip, tons, (2,240 Ibs.); (including Loe Sere amineen) Oe Va Ne GR 35.71 Km otse per rip ose te as oti woe ae eet ease whe cosine ho okey cin calor 290 Tons. cargo, (2,240. 1bS.) "per stripy oc fee gh cs i i eee ie See ee teen 1,446 Tons knot, per trip, (including port CONSUMPtiON sie es See 419,340 Pounds coal per trip, Gncluding: pott.consumption) 4.5.5 iy.. es he ty 80,000 Tons cargo, one knot per one pound coal, (including port consumption) CL is 5.24 Cubic feet cargo space per ton (2,240 Ibs. s) Careo CaTRed | ace inde cia, oe uee ee a 198 Pounds coal' 'per knots cs ele ae cies ss sip tae ips ie cay ale cle eo ON pa sce n eieeie eee 276 Tons cargo carried per ton of coal consumed, (including port cuicumation) Era toe Average pounds per mile no deduction for port use.....-.-+eeeees eee r sees reece 249.5 Displacement 14 ft. 5 in: 37925 tons, vorable conditions, and I wish also to express my appreciation of the state- ment he makes that there is no se- rious difficulty about preparing mer- chant ships for such tests. I wish he would kindly inform us what methods were used in this case for producing such a load, because it has come to my knowledge that in many cases it is exceedingly difficult to get a merchant ship properly loaded for trial, that in many cases there is no.way of loading except by throwing cargo or ballast into the hold, and I believe that both of these performances, while possible, are fre- quently inconvenient. C.. W. Dyson (Communicated) :--_ In reading over the article prepared by Mr. Rigg, I note that he makes no reference either to the beneficial effect of the very full midship sec- fine after body and the propeller lo- cated well clear of the hull. For condition 2, the after body lines are such as to break up the col- umn of water flowing to the pro- peller, so that the propeller is work- ing in water more or less broken up by eddies and which may also con- tain considerable quantities of free air. This condition produces the loss that is ordinarily called "thrust de- duction", or "augment of resistance", and reduces the propulsive efficiency below the tank efficiency. | For condition 3 the diameter may be limited to a dimension smaller than that indicated by condition 1, while the revolutions remain the same. In this case the tip speed will be lower than in condition 1, the col- umn of water acted upon by the pro- peller will be smaller in cross-section- 101 al area, the velocity of flow of the water in the column will be increased, the indicated horsepower per revolu- tion will be increased from that of condition 1, but the apparent slip per revolution will be increased over that existing for condition 1, the pitch and surface of the propeller also being increased over that of con- dition 1, a net loss-in efficiency of propulsion resulting. By scanning the above conditions it fs seen that a propeller may op- erate under any one of the following conditions: 1. Under Condition 1--Maximum Efficiency. : 2.. Under Condition 2--Maximum Efficiency decreased by thrust ae tion. - 3. Under Condition 3--Maximum~ Efficiency decreased by diameter re- duction. 4, Combined Conditions 2 and: 3-- Maximum Efficiency decreased by both thrust deduction and diameter reduction. The greater number of single screw cargo steamers suffer the losses as in 4, and these losses are greatly aggravated where the midship_ sec- tion is fined down at the expense of the after body lines, and where the designed revolutions of the propeller are low, thus aggravating both sources of loss. In the case of the Tyler, the ef- fect of the full midship section was to reduce the thrust deduction to a minimum for that block coefficient, while an analysis of the propeller in-. dicates that the reduction in diameter of propeller was practically nil, thus escaping this latter serious source of loss. _ The vessel reflects great credit on both the naval architect who is re- sponsible for the design of the hull, and the engineer who designed the propeller and machinery. | E. H. Rigg!--Mr... Chairman and Gentlemen: In regard to Prof. Pea- body's question, as to how we got the ship loaded, I think the explana- tion is two-fold. The first part of the answer is the first two lines of the second paragraph of the abstract, which reads as follows: "In view of the endeavors being made today to improve the propulsion of vessels, it is refreshing to meet and do business with owners who are sufficiently keen to have models towed and _ proper trial run." That is one part of the difficulty settled--the kindness of the owners to do it, also, as well as the builders and designers. The other part of the answer, per- haps, needs a little explanation. I+