Ocean Steam Navigation and the Ocean Post Part 3

An intelligent gentleman who happened to know that we were using only one boiler, and consequently, but half the power, remarked to me that it was very strange that the ship was still going about eleven miles per hour, without any sail. He said: "It is strange, sir; two boilers of equal size drove us thirteen miles per hour; and here now but one boiler drives us nearly eleven miles, or nearly as fast; when common-sense teaches that the one boiler would drive us only six and a half miles per hour. How is that?" I then explained to him very clearly the natural law relative to power and speed, (_See Rule II., page 68_,) which he at once comprehended and admitted, but with the remark: "Indeed, sir, I would have testified that she ought with one boiler to have gone at only half the speed; or that going at six miles with one boiler, she would go twelve with two."

As it will be interesting to the general reader to examine the details of the increased consumption of fuel at increased rates of speed, I present the following elaborate table recently prepared by Mr.

Atherton for his new edition of "Steamship Capability," according to the formula above noticed, and the performance of the best type of vessel in the Royal Navy, the steamer "Rattler." Mr. A. found a higher efficiency in this vessel per horse power than any other in the Navy, and consequently based the consumption of coal in the table on the a.s.sumption that the mail and pa.s.senger vessels generally should be of as good contractive type as "Rattler." I shall present also another table showing a much larger consumption of fuel by an inferior type of vessel. I use these tables because they are thoroughly correct, and quite as perfect as any that I could construct on the same formula; and because they carry with them the weight of probably the highest authority in Great Britain.

COAL TABLE: No. I.

_Displacement,[B] Speed, and Fuel consumed per Day, for Mail, Pa.s.senger, and Freight Steamers, whose locomotive performance is equal to that of the best cla.s.s of ocean steam vessels; a.s.suming the consumption of fuel to be 4-1/2 lbs. per indicated horse power per hour, equal to 33,000 lbs. raised one foot in one minute. The quant.i.ty consumed is expressed in tons per day of 24 hours._

[B] Displacement refers to the number of cubic feet of water displaced by the hull; allowing thirty-five cubic feet to the ton.

KEY: A: SHIP'S DISPLACEMENT.

-----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+---- | SPEED PER HOUR.--NAUTICAL MILES.

A +----+----+----+----+----+----+----+----+----+----+----+----+----+----+---- | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 -----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+---- TONS.|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS -----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+---- 100|1.04|1.65|2.47|3.51|4.82|6.41|8.32|10.6|13.2|16.3|19.7|23.7|28.1|33.0|38.5 125|1.20|1.92|2.86|4.07|5.59|7.44|9.66|12.3|15.3|18.9|22.9|27.5|32.6|38.3|44.7 150|1.36|2.16|3.23|4.60|6.31|8.40|10.9|13.9|17.3|21.3|25.9|31.0|36.8|43.3|50.5 175|1.51|2.40|3.58|5.10|7.00|9.31|12.1|15.4|19.2|23.6|28.7|34.4|40.8|48.0|56.0 200|1.65|2.62|3.91|5.57|7.65|10.2|13.2|16.8|21.0|25.8|31.3|37.6|44.6|52.4|61.2 | | | | | | | | | | | | | | | 250|1.92|3.04|4.54|6.47|8.87|11.8|15.3|19.5|24.3|29.9|36.3|43.6|51.7|60.9|71.0 300|2.25|3.44|5.13|7.30|10.0|13.3|17.3|22.0|27.5|33.8|41.0|49.2|58.4|68.7|80.1 350|2.40|3.81|5.68|8.09|11.1|14.8|19.2|24.4|30.5|37.5|45.5|54.5|64.7|76.2|88.8 400|2.62|4.16|6.21|8.85|12.1|16.2|21.0|26.7|33.3|41.0|49.7|59.6|70.8|83.3|97.1 450|2.84|4.50|6.72|9.57|13.1|17.5|22.7|28.8|36.0|44.3|53.8|64.5|76.6|90.1|105 | | | | | | | | | | | | | | | 500|3.04|4.83|7.21|10.3|14.1|18.7|24.3|30.9|38.6|47.5|57.7|69.2|82.1|96.6|113 600|3.43|5.46|8.14|11.6|15.9|21.2|27.5|34.9|43.6|53.7|65.1|78.1|92.8|109 |127 700|3.81|6.05|9.02|12.8|17.6|23.5|30.4|38.7|48.4|59.5|72.2|86.6|103 |121 |141 800|4.16|6.61|9.87|14.0|19.3|25.6|33.3|42.3|52.9|65.0|78.9|94.6|112 |132 |154 900|4.50|7.15|10.7|15.2|20.8|27.7|36.0|45.8|57.2|70.4|85.4|102 |122 |143 |167 | | | | | | | | | | | | | | | 1000|4.83|7.67|11.4|16.3|22.4|29.8|38.6|49.1|61.3|75.5|91.6|110 |130 |153 |179 1250|5.60|8.90|13.3|18.9|26.0|34.5|44.8|57.0|71.2|87.6|106 |127 |151 |178 |208 1500|6.33|10.0|15.0|21.4|29.3|39.0|50.6|64.4|80.4|98.9|120 |144 |171 |201 |234 1750|7.01|11.1|16.6|23.7|32.5|43.2|56.1|71.3|89.1|110 |133 |159 |189 |223 |260 2000|7.66|12.2|18.2|25.9|35.5|47.3|61.3|77.9|97.4|120 |145 |174 |207 |243 |284 | | | | | | | | | | | | | | | 2500|8.89|14.1|21.1|30.0|41.2|54.8|71.2|90.5|113 |139 |169 |202 |240 |283 |329 3000|10.0|16.0|23.8|33.9|46.5|61.9|80.4|102 |128 |157 |191 |228 |271 |319 |372 3500|11.1|17.7|26.1|37.6|51.5|68.6|89.0|113 |141 |174 |211 |253 |301 |354 |412 4000|12.2|19.3|28.8|41.1|56.3|75.0|97.3|124 |155 |190 |231 |277 |329 |386 |451 5000|14.1|22.4|33.5|47.7|65.4|87.0|113 |144 |179 |221 |268 |321 |381 |448 |523 | | | | | | | | | | | | | | | 6000|15.9|25.3|37.8|53.8|73.8|98.3|128 |162 |203 |249 |302 |363 |431 |506 |591 7000|17.7|28.1|41.9|59.6|81.8|109 |141 |180 |224 |276 |335 |402 |477 |501 |654 8000|19.3|30.7|45.8|65.2|89.4|119 |155 |196 |245 |302 |366 |439 |522 |613 |715 9000|20.9|33.2|49.5|70.5|96.7|129 |167 |215 |265 |327 |396 |475 |564 |663 |774 10000|22.4|35.6|53.1|75.6|104 |138 |179 |228 |285 |350 |425 |510 |605 |712 |830 | | | | | | | | | | | | | | | 12500|26.0|41.3|61.7|87.8|120 |160 |208 |265 |330 |406 |493 |592 |702 |826 |963 15000|29.4|46.6|69.6|99.1|136 |181 |235 |299 |373 |459 |557 |668 |793 |933 |1088 20000|35.6|56.5|84.4|120 |165 |219 |285 |362 |452 |556 |675 |809 |961 |1130|1318 25000|41.3|65.6|97.9|139 |191 |254 |330 |420 |525 |645 |783 |939 |1115|1311|1529 30000|46.6|74.0|111 |157 |216 |287 |373 |474 |592 |728 |884 |1060|1258|1480|1727 -----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----

By the inspection of this table we can see in condensed form the coal-cost of any speed as high as twenty miles per hour, and for any size of vessel from one hundred tons to thirty thousand tons. Let us find in the left hand column a vessel of 2,500 tons displacement.

Pursuing the line along to the right we find in the second column 8.89 tons of coal, which a steamer of this displacement would burn in 24 hours, if running, as indicated at the head of the column, 6 Nautical miles per hour.

In the next column, under the head of 7 Nautical miles per hour, we find that she would burn in one day 14.1 tons; or one and a half times as much coal to gain one sixth more speed:

Again, at 8 miles per hour she burns 21.1 tons; nearly three times as much as at six miles:

At 9 miles she burns 30 tons: above twice as much as at 7, and nearly four times as much as at 6, although the speed is but half doubled:

At 10 miles per hour she burns 41.2 tons; about twice as much as at 8 miles, although the speed is increased only one fourth. At 10 she burns 34 per cent. more than at 9, although the increase of speed is only eleven per cent. (_See pages 67 and 68_):

At 11 miles per hour she will burn 54.8 or 55 tons; nearly three times as much as at 8 miles per hour, and six times as much as at 6 miles per hour:

At 12 miles per hour she will burn 71.2; about thirty per cent. more than at eleven miles per hour, although gaining but 9 per cent. in speed; nearly twice as much as at ten miles per hour, three and a half times as much as at 8, five times as much as at 7, and above eight times as much as at 6 miles per hour. It is here seen that to double the speed the consumption of fuel has increased eight-fold, which verifies my statements. .h.i.therto made on this subject. We have already seen that to gain two miles of speed on any stated speed, it was necessary to double the quant.i.ty of fuel used.

At 13 miles per hour she burns 90.5 tons. This is burning two and a fourth times as much coal as if she ran only 10 miles per hour. Now, at this speed, the steamer will reach Southampton or Liverpool in 10 days and 6 hours, which is equivalent to 10 days and 12 hours burning fuel, allowing six hours for heating and starting, and which would make an aggregate consumption of 950 tons of coal for the pa.s.sage of this steamer of 2,500 displacement or probably 3,000 tons register.

At 14 miles per hour she burns 113 tons. This is nearly three times as much as 10 miles per hour. At this speed the steamer would reach Southampton or Liverpool in 9 days, 12 hours, and 30 minutes, supposing the distance to be 3,200 miles from New-York, or say 9 days 18-1/2 hours coal-burning time, and would consume an aggregate of 1,104-1/2 tons. As this is but little above the distance from New-York to Southampton, and under that from Panama to California, and about the tonnage of the steamers running, the time being within eleven days generally, it will be seen how large is the cost of running the steamers of the Pacific Mail Steamship Company, those on the European routes, and also those between New-York and Aspinwall. As the route of the Havre and Bremen steamers is much longer, they are compelled to run slightly slower, or they would be filled up with their own fuel and power. Taking a Collins steamer of 3,000 tons, which we find in the line below, and we see that in running 14 miles per hour as they have frequently done, the consumption would be 128 tons per day, or 1,252 tons for the pa.s.sage. And yet, one of those steamers could make 12 miles per hour on 80.4 tons per day, or at 11 miles per hour on 61.9, or less than half that used at 14. But pursuing this table we see that,

At 15 miles per hour she would burn 139 tons, or three and a half times as much as at 10 miles.

At 16 miles per hour she would burn 169 tons, or precisely eight times as much as at 8 miles per hour. Here again doubling the speed is found to be an enormous expense.

At 17 miles per hour she burns 202 tons per day.

At 18 miles per hour the consumption is 240 tons per day.

At 19 miles per hour she burns 283 tons coal per day; and

At 20 miles per hour she burns 329 tons per day. At 20 miles per hour she would run 480 miles per day, a thing as yet wholly unheard of, and would consume on the voyage of 6 days and 16 hours, say 6 days and 22 hours, 2,276 tons of coal. It would be clearly impossible for her to carry her own fuel; as the immense boiler and engine power necessary to secure this speed would of itself fill a ship of this size, to say nothing of the fuel which also would nearly fill it. Then, we may never expect any such ship to attain any such speed as seventeen, eighteen, or twenty miles per hour on so long a voyage without recoaling.

Seeing thus the enormous increase in the consumption of fuel for a moderate increase in the speed, we are enabled the better to appreciate the large expense incurred in running ocean steamers sufficiently rapidly for successful mail and pa.s.senger purposes. We will further pursue these inquiries by examining in this table the consumption for vessels of 6,000 tons, which would make the displacement of the ship nearly 5,000 tons, such as the "Adriatic,"

the "Vanderbilt," and the "Niagara." It appears that at 8 miles per hour they would consume 33 tons per day; at 10 miles, 65 tons; at 12 miles, 113 tons; at 13 miles, 144 tons; at 14 miles, 179 tons; at 15 miles, 221 tons; and at 16 miles, 268 tons per day. This is supposing this speed to be maintained on an average across the ocean, in all kinds of weather, which this size of steamer could not do without more engine and boiler power than any of them have. With such additional power the ships noticed would have scarcely any available room for freight or any thing else. One thing is very clear from this table, that when steamers run at very moderately slow rates of speed, their consumption of fuel is very small; and that when they leave this low freighting speed, for that of the necessarily rapid mails and pa.s.sengers, the consumption increases to an extent and with a rapidity that would seem almost incredible at first view.

COAL TABLE: No. II.

_The following coal table is constructed in all respects as the preceding, but for a lower type of vessels, or those whose coefficient of Dynamic performance is inferior to that upon which the previous table is estimated. As a consequence, this style of vessel requires more fuel._

KEY: A: SHIP'S DISPLACEMENT.

-----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+---- | SPEED PER HOUR.--NAUTICAL MILES.

A +----+----+----+----+----+----+----+----+----+----+----+----+----+----+---- | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 -----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+---- TONS.|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS|TONS -----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+---- 500|3.95|6.28|9.37|13.4|18.3|24.3|31.6|40.1|50.2|61.7|75.0|89.9|106 |125 |147 600|4.46|7.10|10.6|15.1|20.6|27.5|35.7|45.3|56.6|69.8|84.6|101 |120 |141 |165 700|4.95|7.86|11.7|16.6|22.8|30.5|39.5|50.3|62.9|77.3|93.8|112 |134 |157 |183 800|5.41|8.59|12.8|18.2|25.1|33.3|43.3|55.0|68.7|84.5|102 |123 |145 |171 |200 900|5.85|9.29|13.9|19.7|27.0|36.0|46.8|59.5|74.3|91.5|111 |132 |158 |186 |217 | | | | | | | | | | | | | | | 1000|6.28|9.97|14.8|21.2|29.1|38.7|50.1|63.8|79.7|98.1|119 |143 |169 |199 |232 1250|7.28|11.5|17.3|24.5|33.8|44.8|58.2|74.1|92.5|114 |137 |165 |196 |231 |270 1500|8.23|13.0|19.5|27.8|38.1|50.7|65.7|83.7|104 |128 |156 |187 |222 |261 |304 1750|9.11|14.4|21.5|30.8|42.2|56.1|72.9|92.7|115 |143 |173 |206 |245 |290 |338 2000|9.95|15.8|23.6|33.6|46.1|61.5|79.7|101 |126 |159 |188 |226 |269 |316 |369 | | | | | | | | | | | | | | | 2500|11.5|18.3|27.4|39.0|53.5|71.2|92.5|117 |147 |180 |219 |262 |312 |368 |427 3000|13.0|20.8|30.9|44.0|60.4|80.4|104 |132 |166 |204 |248 |296 |352 |414 |483 3500|14.4|23.0|34.3|48.8|66.9|89.1|115 |147 |183 |226 |274 |329 |391 |460 |535 4000|15.8|25.1|37.4|53.4|73.2|97.5|126 |161 |201 |247 |300 |360 |427 |501 |586 5000|18.3|29.1|43.5|62.0|85.0|113 |147 |187 |232 |287 |348 |417 |495 |582 |679 | | | | | | | | | | | | | | | 6000|20.6|32.9|49.1|69.9|95.9|127 |166 |210 |264 |323 |392 |472 |560 |657 |768 10000|29.1|46.2|69.0|98.2|135 |179 |232 |296 |370 |455 |552 |663 |786 |925 |1079 -----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----

FREIGHT TABLE: No. III.

_Showing the mutual relation of Displacement, Power, Speed, Consumption of Coal, and capacity for Cargo of vessels of progressively increasing magnitude up to nearly 30,000 tons of Deep-draught Displacement, employed on a pa.s.sage of 3,250 nautical miles, without recoaling: showing also the prime cost Expenses per ton of Cargo conveyed._

KEY: A: Mean or Mid-pa.s.sage Displacement.

B: Speed.

C: POWER. Nominal H. P.

D: POWER. Indicated h. p.

E: a.s.sumed weight of Hull and Engines.

F: Pa.s.sAGE 3,250 N. M. DIRECT. Time.

G: Pa.s.sAGE 3,250 N. M. DIRECT. Coal.

H: Pa.s.sAGE 3,250 N. M. DIRECT. Cargo.

I: Pa.s.sAGE 3,250 N. M. DIRECT. Deep Displacement.

J: Pa.s.sAGE 3,250 N. M. DIRECT. Expenses per Ton of Cargo.

--------+-----+-----+-----+------+------+-----+------+------+---------- A | B | C | D | E | F | G | H | I | J Tons. |N. M.|H. P.|h. p.| TONS.| D. H.|TONS.| TONS.| TONS.| S. D.

--------+-----+-----+-----+------+------+-----+------+------+---------- {| 8| 109| 436| 1109| 16.22| 369| 1209| 2684| 2 1 10 {| 9| 155| 620| 1155| 15. 1| 466| 1112| 2733| 2 7 8 2,500 {| 10| 213| 852| 1213| 13.13| 577| 999| 2788| 2 16 11 {| 11| 284| 1136| 1284| 12. 7| 699| 867| 2849| 3 11 3 {| 12| 368| 1472| 1368| 11. 7| 830| 717| 2915| 4 14 5 | | | | | | | | | {| 8| 172| 688| 2172| 16.22| 582| 2537| 5291| 1 16 1 {| 9| 245| 980| 2245| 15. 1| 737| 2386| 5368| 1 19 7 5,000 {| 10| 336| 1344| 2336| 13.13| 882| 2223| 5441| 2 4 1 {| 11| 448| 1792| 2448| 12. 7| 1103| 2000| 5551| 2 13 1 {| 12| 581| 2324| 2581| 11. 7| 1311| 1763| 5655| 3 5 1 | | | | | | | | | {| 8| 276| 1104| 4276| 16.22| 934| 5257| 10467| 1 12 3 {| 9| 388| 1552| 4388| 15. 1| 1168| 5028| 10584| 1 13 10 {| 10| 536| 2144| 4536| 13.13| 1407| 4760| 10703| 1 16 9 10,000 {| 11| 712| 2848| 4712| 12. 7| 1753| 4411| 10876| 2 2 1 {| 12| 928| 3712| 4928| 11. 7| 2094| 4025| 11047| 2 9 4 {| 13| 1180| 4720| 5180| 10.10| 2458| 3591| 11229| 2 19 5 {| 14| 1472| 5888| 5472| 9.16| 2848| 3104| 11424| 3 14 3 | | | | | | | | | {| 8| 436| 1744| 8436| 16.22| 1476| 10826| 20738| 1 9 0 {| 9| 620| 2480| 8620| 15. 1| 1866| 10447| 20933| 1 9 11 {| 10| 852| 3408| 8852| 13.13| 2236| 10030| 21118| 1 11 4 20,000 {| 11| 1136| 4544| 9136| 12. 7| 2797| 9466| 21398| 1 14 9 {| 12| 1472| 5888| 9472| 11. 7| 3322| 8867| 21661| 1 19 1 {| 13| 1872| 7488| 9872| 10.10| 3900| 8178| 21950| 2 4 11 {| 14| 2340| 9360| 10340| 9.16| 4528| 7396| 22264| 2 13 1 --------+-----+-----+-----+------+------+-----+------+------+----------

Mr. Atherton gives this table, which shows the following facts:

That, as the various sized vessels named, increase in speed from 8 to 12, or from 8 to 14 miles per hour, their horse power, as well consequently as their coal, increases:

That, as the speed increases, so does the weight of the hull and engines:

That, as the speed increases, with the consequent increased coal and engine weight, the cargo decreases: and

That, as the speed increases, with the other necessary conditions noticed, the expense per ton of cargo also increases in a rapid ratio.

In the four cross columns ships of different sizes are considered; of 2,500, 5,000, 10,000, and 20,000 tons. There is also given the working or indicated horse power, and the nominal horse-power, or that of 33,000 lbs. raised a foot in a minute, which is the general basis of making contracts. It is a fact, however, that engines generally work up to three or four times their nominal horse power; so that the word horse power has no positive or useful meaning. Vessels called one hundred nominal horse-power have been known to work up to six hundred.

Let us take a ship of 5,000 tons. We find that at 8 miles per hour the horse power is 436; but at 12 miles it is 1,472, nearly four times as great. At 13 miles, it would be nearly 1800 horse, and at 14 it would be above 2100. So, also, with the weight of engines, boilers, etc. At 8 miles per hour they would weigh 1,109 tons; but at 12 they would have to weigh, to be large and strong enough, 1,368 tons. At 14 miles, they would weigh nearly 1,600 tons.

Now, see the columns "cargo" and "coal," and observe how rapidly that of coal increases, while that of cargo decreases in the inverse ratio of the coal, the engine, the boiler, and the hull weight combined. The cargo has come from 1,209 down to 717 tons; and if the speed were increased to 13 or 14 miles per hour, the cargo would be so reduced as to be unworthy of notice.

The next column shows how much greater the quant.i.ty of water displaced as the speed increases. This extra displacement requires extra power.

In the last column it is observable how rapidly the speed enhances the cost price of transporting cargo. At 13 miles per hour the cost would be about six pounds sterling per ton, and at 14 knots speed it would be higher than was ever paid a steamer in the most flush periods of even the best qualities of freights. Freights were about 8 per ton on the Cunard line before the establishment of the Collins; but they soon came down, and are not now 3, or $15, on an average. So with pa.s.sage. The "Great Western" charged 45, the "British Queen" 50; the Cunarders, until the Collins compet.i.tion, 40, 19_s._ The Collins steamers put the price down to 35, and have since reduced it to 30 homeward, and 24 outward. This is but little above half the fare of the Great Western, and something over two thirds of that formerly charged by the Cunard line. The Report to the House of Commons "on Steam Communications with India," No. 372 of 1851, second volume, page 395, says, that the average speed of the Cunard line was 10.443 knots, of the Collins line 11 knots, and of the Havre and Bremen lines 9.875 knots per hour. The Collins line had then just started, and has since made the average pa.s.sages one and a half days quicker than those of the Cunard line. This being the case, it is easy to estimate the gains of a steamer at such rates, when this column shows us that at 12 miles speed per hour and an average trip of 11 days, the actual prime cost of moving the freight is much above that which is received for it. It is therefore taken in small quant.i.ties only to a.s.sist in paying the running expenses of the steamer.

This table shows another thing very conclusively, that large ships running the same number of miles per hour, run cheaper and transport freight more cheaply than smaller vessels. It presupposes, however, that they go full both ways. The engine power and general outlay do not increase as rapidly as the tonnage of the vessel and her capacity for carrying. While a ship 2,500 tons at 12 miles per hour on a pa.s.sage of 3,250 miles would make the cost per ton for the transportation of freight $22.75, one of 20,000 tons, under the same conditions would reduce it to $9 per ton. Yet it is hardly probable that we shall ever profitably employ steamers of over 10,000 tons tonnage in the pa.s.senger, mail, and freight business.