Another great defect arising out of the present plan of constructing mercantile ships is, that the ends of the lower ribs or timbers, commonly termed the flit tocks, Fig. 3. B, are not continued across the keel C, so that no support is given in a transverse direction when the ship touches the ground; nor any aid to counteract the constant pressure of the mast. This great sacrifice of strength and safety, is made for no other purpose than that of giving a passage for the wa ter to the- pumps.
The floor timbers, which by this mode of construc tion are the only timbers which cross the keel, are also weakened for the same purpose, as shown at D in the figure last quoted. This mode, moreover, makes the conveyance of the water very uncertain, since the pas sage is not unfreguently choaked; and the pumps, from its not being practicable to continue them suffi ciently down, always leave from six to eight inches of water in the ship; so that these compartments con stantly contain a certain quantity of putrid bilge wa ter, offensive and injurious to the health of those on board.
The deficiency of strength causes also an alarming insecurity in the plank of the bottom, termed the gar board strake, as shown at E; and which consequently is in no other way connected with the general fabric, than its connexion with the keel at F, and a slight security at G. Hence it is obvious, that in the event of the keel being disturbed, the garboard strake, from its being attached to it, must share the same fate as the keel, and in that case the loss of the vessel would be inevitable.
To obviate these very serious defects, and to do that for our mercantile marine which he had already so successfully accomplished for ships of war, Sir Robert Seppings laid before the Royal Society in March 1820, a highly important paper, and which was printed in the Transactions of the same year. The principle may be comprehended by a reference to Fig. 4. in Which it will be seen, that the component parts of each rib arc of shorter lengths and less curvature, and conse quently less grain cut: that they are more firm and solid by the substitution (f cooks or dowels, for chocks or wedge pieces; and that the mode of connecting the lower timbers is better adapted, in the event of a ship ground ing, to give support and strength to the fabric, as will appear by the line ?narked IL That the frame of the Thunderer, (now Talavera,) built on this principle, is superior in point of strength, says Sir Robert Seppings, to a frame constructed on the common system, is fully established by a report from the officers of his majesty's yard at 'Woolwich to the Navy Board, who directed them to compare the strength of the frames so united with those of the Black Prince, constructed in the usual way with chocks or wedges.
In alluding to this interesting and important com parison, Sir Robert remarks, that " the frame of the Thunderer was composed of small timber, hitherto con sidered applicable only for the frames of frigates." "I was prompted," says this ingenious constructer, " to attempt the introduction of the plan on which she is built, from there being a surplus store of small timber in the yard; and from a conviction, that a bined number of small timbers ?night be made equal, if not superior, both in strength and economy, to the large, overgrown,and frequently grain-cut materials, made use of in constructing the frames of large ships; and the re sult has shown the correctness of the principle;* the adoption of which cannot fail to provi:rof great national advantage, in the application of sloop timber to thebuild ing of frigates, and of frigate timber to ships of the line, whenever larger timber cannot be procured. On this principle, also, may frigates and small ships of war, or merchant vessels, be built of straight fir, without the assistance of oak or elm, which were formerly employed to give the necessary curvature of the sides." The principles here laid down by Sir Robert Sep pings, are of vast importance, and we earnestly hope will speedily and generally be adopted.
As it respects the general safety of the ship, it will be seen by a reference to Figure 5, Plate D. and Plate DI. that the timbers uniformly cross the keel; that the frame of the ship is filled so as to form one compact body to the height marked K; and that only certain internal strakes of planks, or thick stuff, as it is termed, are introduced, which are those on the joints of the timbers,for the purpose of giving strength where every alternate timber necessarily joins, as shown at L. The rest of the inner planking may be omitted, and dunnage battens brought in a perpendi cular direction upon the timbers between the plank, as shown at M, forming regular spaces between each, as is usual at present, upon the plank; thereby giving an increase of stowage in proportion to the thickness of the plank omitted. Water courses, as shown by dotted lines at N, are to be left in the joints of the timber under the plank, for the purpose of conveying the water to the pumps; which, by this plan, will reach below the water, instead of being some inches above, as is the case with the present mode, before described. Consequently, by the proposed system, no stagnant water will remain; and farther, the limber passage, or water course, will be one smooth uniform channel, which can be cleared with ease, should it be required, whenever the hold is unstowed; whereas at present it is inaccessible in places, and forms com partments for putrid water, without there being any means of removing it.