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The Screw Propeller— Smith's Patent.
From The Journal of the Franklin Institute. Third Series. Vol. VII. January, 1844. Pages 90-94.
The complete success which has attended the application of the screw for the propulsion of vessels by steam, in every instance, induces us this week to lay before our readers some particulars connected therewith, and the performances of some of the ships which have during the past four years been fitted with it. Hitherto the vessels to which the screw has been applied have been of moderate tonnage, and it became a question, much canvassed among nautical and scientific men, whether it would have sufficient power to answer the expectations of the inventor in ships of extraordinary size and burthen; but the trial of the Great Northern down the river, on the 11th inst., when she accomplished ten and a half miles per hour without using any sales, has completely set the matter at rest, and proved the efficiency of the screw propeller for vessels of every size and description—and it is remarkable, that, although the propeller that has been applied to this monster ship is smaller in proportion to her tonnage than any other that has been yet fitted, her rate of speed under steam has surpassed the most sanguine expectations of all who have witnessed her performances.
The screw originally introduced into the Archimedes (the vessel on which the first really practical trial was made) consisted of one entire turn 8 feet in length and 7 feet in diameter; this, however, being found to large for the steam-power to drive with the requisite velocity, was gradually reduced to 5 feet 9 inches—subsequently it was divided into two half turns, which reduced it to half its length, while the superfices of the screw remained the same. Various propellers tried by Mr. Smith in small experimental boats, and subsequently in the Archimedes, have shown that the most effective form is one entire turn of the thread; this however, fr the sake of compactness, may be divided into two half, three thirds, or even four quarter turns, which renders the propeller considerably shorter, while its useful effect is in no way diminished.
The angle which the thread should make with the shaft has been closely experimented on, and it has been found that an inclination varying from sizty to seventy degrees at the circumference has produced the best result. The circumstances, however, which would determine the precise angle between the two, as also its diameter, depend on the form and description of vessel to be propelled—for instance, if a tug or heavily laden vessel, the latter angle would be most suitable; but in a vessel of fine lines and light draught of water, the former would be best adapted in order to obtain a high rate of speed.
On starting the vessel in a dead calm, a column of water in the shape of an inverted cone may bee seen thrown astern of the ship, from which it is inferred that the whole force of the screw is propellant in the direct line of its axis, while that of the paddle-wheels is partially lost in entering the water and raising it considerably above the level on leaving it, which produces the swell so much complained of in river steamers. The position of the screw is in the dead wood immediately before the rudder, the keel being continued along underneath it. One great advantage of the screw being placed in this position is, the transferring the whole weight of the propelling apparatus from the top sides of a vessel to the lowest part of the hull; and in the Great Britain (of 3600 tons), recently launched at Bristol, it has been ascertained that in applying the screw, instead of paddle wheels, as originally intended, 100 tons of superabundant weight have been removed from her upper works—a circumstance of immense importance to the safety of the ship when laboring in a heavy sea. The annexed engraving shows more clearly the principle and situation of the screw propeller.
Let us now proceed to give some particulars of the performances of those ships which have already adopted it.
(237 tons, 70-horse power.)
May 14, 1839.— Made the passage from Gravesend to Portsmouth in twenty-one hours, against a strong westerly breeze.
October, 1839.— Beat the Hon. East India Company's steamer Queen, of 220-horse power, upwards of three quarters of a mile in a run of eight miles.
April 18, 1840.— She was ordered to Dover for the purpose of trying her powers with her Majesty's packets at that station, on which occasion the fastest of them, the Widgeon, was beaten nine minutes between Dover and Calais, and five minutes on the return trip, which was done in one hour and fifty-three minutes—being the quickest passage ever made between England and France, by fourteen minutes. The Dover boats vary from 70 to 90 tons less, their engines from 5-horse to 10-horse power more, and the draught of water from four to five feet less than the Archimedes.
June 5.— Ran from Milford to Liverpool (200 miles) in nineteen and a half hours. Surpassed the swiftest boats on the Mersey; and on one occasion beat to windward up that crowded river with as much facility as an ordinary sailing ship. From Liverpool to the Isle of Man she beat the Mona's Isle packet (a vessel of superior power) nearly two hours—running the distance of seventy miles in seven hours and fifteen minutes.
August 1840.— She performed the passage from Plymouth to Oporto in sixty-eight and a half hours, and the homeward trip between those places in eighty-eight hours, with a wind a-head nearly the whole distance.
November, 1841.— During her passage from Bristol to London, made headway at the rate of three and a half knots per hour against a tremendous sea, whilst other steamers of much larger power bore up, as shown by the pilot's certificate.
(Steam-tug boat, on the screw principle, 45-horse power.)
After beating the fastest of that class of boats on the Tyne, performed a passage from that river to Brighton in forty-eight and a half hours, a distance of nearly 400 miles. She has towed out of Shoreham Harbor, at one time, two large brigs, agaisnt the wind, and tide setting in, at the rate of four miles per hour; on another occasion, towed out a brig, which carried away both topmasts immediately the steamer had cast off. This little vessel, also, went to sea with comparative ease, whilst the Dart steamer, of 120-horse power, was more than half an hour before she could accomplish the same object, owing to the sea and tide running at the time.
Sunday, Dec 25, 1842.— Sh. 5m. Weighed anchor from Cowes Roads, and put the ship on her course for London, under steam and canvass. 9 50 a.m. Massey's log put overboard; revolution per minute of engine, 18; rate per common log, 10 knots; Massey's log, 10 1/4 do. 11 50 a.m. Stopped engines abreast of the Ower's light-ship, and disconnected the screw; ship put on her course up channel, with sails only. Noon. Fresh breezes and cloudy. 2 30 p.m. Abreast of Beachy Head; ship brought to her course. 5 05 p.m. Massey's log hauled in. (Note—The distance run from the Ower's light-ship, by chart, sixty-six nautical miles, in five hours and two minutes.) Hove to, and fired guns for a pilot. 5 50 p.m. Took pilot on board; wind increasing. 7 50 p.m. Anchored in the Downs in eight fathoms water.
Monday, Dec. 26. — 4 a.m. The wind blowing a gale, down royal and top-gallant yards. 8 50. Changed pilots. Noon. Gale increasing, and a great number of ships running for the downs. Midnight. Weather about the same.
Tuesday, Dec 27.— 9 a.m. Gale suddenly moderated; steam raised to assist in getting the anchor. 11 40 a.m. Got under weigh, and proceeded through the Downs, setting fore and aft sail, wind being directly a-head. 5 17 p.m. Abreast of the Nore light. 9 p.m. Anchored nearly opposite the Chapman beacon.
Wednesday, Dec. 28.— 7 a.m. Got under weigh, steaming only; wind a-head. 9 05 a.m. Stopped off Gravesend and changed pilots. 9 17 a.m. Started for London agaisnt ebb tide and light wind. 12 a.m. Abreast of Woolwich. 12 20 p.m. Arrived at Blackwall, and moored ship, having stopped six minutes in Longreach to adjust machinery, thus accomplishing the run from Gravesend to Blackwall (twenty-one miles) in two hours and fifty-seven minutes, the mean rate of the tide being taken at two miles per hour.
Since the Great Northern's arrival at Blackwall, considerable improvement has bee neffected in her engines, by Messrs. Miller and Ravenhill, which was satisfactorily shown in her trials on the 11th instant, in the presence of a large party of gentlemen connected with science and the shipping interests. We subjoin the following particulars of her dimensions. —
| Ft. | In. | Ft. | In. | ||
| Extreme length | 247 | 0 | Diameter of screw | 11 | 0 |
| Extreme breadth | 37 | 0 | Length of screw | 5 | 10 |
| Length bet. perpendic. | 222 | 0 | Pitch of ditto | 14 | 0 |
| Depth in hold | 26 | 5 | Length of mainmast | 90 | 0 |
| Draught of water | 18 | 0 | Length of mainyard | 79 | 0 |
| Diameter of cylinders | 5 | 8 | Diameter of ditto | 1 | 10.5 |
| Length of stroke | 4 | 6 | Length of foremast | 83 | 0 |
| Immersed area of mid sec | 542 | 0 | Length of mizenmast | 61 | 0 |
| Area of screw propeller | 75 | 0 | Spread of canvas | 6700 yards. | |
| Burthen | 1515 tons. | ||||
It will be seen from the above extracts from her log, that the Archimedes, though not built for extreme speed, but more to show the practicability of uniting sailing and steaming qualities in one vessel, has succeeded in beating many vessels of superior power, built expressly for steaming. Her utmost speed under steam alone was nine and a quarter knots; with steam and sails combined, under the most favorable circumstances, it was upwards of eleven knots. This is particularly worthy of consideration, as showing the utility of a moderate steam-power on board sailing vessels in case of calms or contrary winds, while the expenditure of fuel need not be resorted to during favorable winds merely for the trifling gain above stated. Upon twenty out of thirty-two points of the compass a ship would be able to dispense with her steam power altogether.
The great superiority of the screw is most apparent in causing the ship immediately to answer her helm; the stream of water thrown astern by its action keeps the helm steadily amidships, and the slightest movement of the wheel is sufficient to govern her. In turning about, the effect of the screw is surprising; on the Archimedes putting the tiller hard over, she performs a complete circle in two and a half minutes, and two and three quarter minutes the second— the rudder acting as a drag on the stern, it takes longer time to make a second circle than the first, yet the space occupied is less, until the vessel seems to turn on a pivot—an entirely new manoeuvre in navigation.
Lond. Mining Journ.
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