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[United
337 Sturdee, A. 13 ., Royal Dockyard, Woolwich —Inventor.
Working model of a twin-stern steam ship, with aprotected propeller, prepared in 1848 at Bermuda by theinventor, to elucidate the advantages of his plan over theordinary mode of fitting screw steamers, of which thefollowing are the principal:—
First, as regards safety and speed
1. The propeller is entirely protected from accident byshot, floating ice, pieces of wreck, buoys, hawsers, sea-weed, fishing nets, and from a heavy sea. 2. Expense ofwear and tear of propeller is reduced. 3, In the case ofthe ship being driven on shore, the greater portion of thedead wood may be knocked away without injury to thepropeller. 4. The fluid thrown olf laterally by the pro-peller being reflected by the tunnel, vents itself aft withconsiderable force, like the stream of a rotatory pump,and acting against the after draught of the vessel, whichflows in the opposite direction, assists in propelling thevessel; while, in the ordinary construction, the powerexpended in driving the fluid laterally, is wholly lost.5. However much the form of the screw may be per-fected, the fluid thrown off laterally must always be con-siderable at starting. It will, therefore, be seen that thefirst revolutions of the screw will be much more effectivein the twin-stern steamers than in vessels of the ordinaryconstruction, and a great advantage to be thus gained inextricating the ship from difficult situations. 6. A more jdirect flood, and a more free passage for the water to thepropeller, the line of current being direct with the axisof the propeller.
Second, as regards construction;—
1. The stem-frame of the ship is much stronger than |that of an ordinary sailing vessel, has additional dis- jplacement, and dispenses entirely with ponderous over- |hanging quarters. 2. The stern-post is not, as now, Inearly severed by an enormous hole being bored throughit and the sternson knee, for the screw shafts. 3. Greaterstability is obtained, and the heavy rolling so muchcomplained of in the present screw ships greatly reduced.4. Vibration of stern, when under steam, is nearlyremoved. 5. The twin-rudder, which can be worked bya single tiller, acts with increased effect; but in case ofaccident to one, the remaining one will be found sufficientfor ordinary work, enabling the carpenter’s crew to effecta proper repair of the injured one, or to fit a temporaryrudder to the sister stern-post. A single rudder can,however, be adopted, if preferred. 6. On a foreignstation, or in the absence of a dock or slip, the ship maybe grounded abaft to effect any slight repairs to thepropeller shaft, &c.
Third, as regards the application of sails :—
l. The propeller can be housed without incommodingthe working of the ship or guns. 2. The lateral resist-ance is increased on the inclination of the ship, by theleeward keel having more immersion than when the shipis upright, thereby adding to her Weatherly qualities.
3. The form of the water sections being preserved beforeeach rudder, they have more power than that of thepresent screw ships, where the water from the leewardside of the vessel passes through the cavity for the screwto the weather side of the rudder. 4. In the case of theship getting on shore or striking abaft, and having aninclination or list at the time, by tacking or wearing, asthe case may require, she will immediately be broughtupright, and in many instances free herself, when in thatposition, as her draught of water abaft will then be lessthan at the moment she struck.
Lastly, as regards armament:—■
1. The propeller, and well for raising it when undercanvas, can be fitted clear of the pivot gun, both whenhoused and in action. 2. The additional strength andsupport to the stern-frame, already alluded to, and theabsence of quarters overhanging by many yards the sectionof load displacement, as in the case of the ordinary screwships, render the stern capable of sustaining much heaviermetal, and which can be better handled or worked from theincreased dimensions of the after part of the quarter-deck.
The illustration represents a quarter view of the ship,
with two stern-posts and two rudders to work simulta-neously. The space between the stern posts, regulatedby the diameter of the screw, forms a tunnel for the pro-peller to work in, which tunnel, extending towards thefore part of the ship, gradually resolves itself into theordinary form of the vessel near the mainmast, fromwhence the original model is preserved.
The sister keels which are substituted for the dispensed-with midship one abaft, are fixed at equal distances fromthe middle line, parallel to each other, forming bilg®keels amidships, and the foundation of the arched roof olthe tunnel abaft.
To the roof of the tunnel is given that form which willinsure the most effective delivery of that portion admittedof the displaced fluid, and the most free access of thewater to the screw.
The engines are placed and fitted in the ordinary way*and the ship may be built of either wood or iron.
Sturdce’s Working Model of a Twin-stern Steam Ship.
[In the event of a screw steamer fitted in the ordinarymanner being driven on shore, the first two or threeshocks would render the ship unmanageable, upon gettmooff again, both under steam and canvas, with the loss orudder and propeller, as in the case of a corvette on t| ieNorth American coast, in 1850. It is also said of m''“ Great Britain,” that, immediately after the first shooshe received on going on shore, the screw was jamm ’or locked, thereby preventing any hope of assistao®®from her engine of 1,000 horse power, which was there jrendered useless at the time it was perhaps most require
for the safety of the ship. j
The experience of nautical men and others conneewith the screw proves, that from its present exp°*oposition many instances have occurred of hawsers betaken up by, and coiled around, the propeller, complexchoking it, and endangering the engines as well asship, causing a detention of many days to cut thempiecemeal; in some cases it is not accomplished effectuawithout placing the vessel on shore, or in a dry d°ck*^^The eddy formed on starting the engines, beforeship gathers way, has, in more than one instance, drthe boats made fast astern into the propeller, which 1literally smashed and sunk them. „ j,y
The blades of the screw have also been knocked o jstriking against projecting shelves of rock, buoys, &c. *• ^
Drawings of the “Balsa” life-boat, in two l 10 ?, 1 ,* 1 thealso the mode of launching in a heavy surf, wi . g-carriage used for that purpose and transporting 3shore. Provisionally registered. (he
Sketches of a paddle-box boat, constr and
“balsa principle, showing her both undu *>•*■stowed in place.