In regard to the mode of constructing and fastening steamers, much diversity of practice exists; but, generally speaking, strength and durability are not sufficiently studied; and, although improvements are taking place in this respect, much remains to be done. In order to give a general notion of this branch of the subject, we shall insert some extracts from the specification of a steamer of 600 tons burthen, built for the City of Dublin Steam Packet Company. It was furnished by C. W. Williams, Esq., the managing director of the Company; and the improvements recommended are those which, from the long experience of the Company, will admit of no doubt of their efficacy.
Mr. Williams recommends generally -
1. That the hull be divided into at least five separate compartments, by four iron-plate water-tight bulkheads, or partitions, so as to confine the water or fire to the compartments in which either may have originated.
3. The addition of banging iron knees, properly constructed, with stays under the main and middle deck beams, wrought and fitted with care, according to prepared drawings; also, a continuous connexion of iron staple knees, by which the entire series of deck beams are firmly bound together, and to the sides of the vessel.
4. The adoption of an improved garboard strake, cut from a solid baulk, and fitted to the rabbet of the keel. Mr. Lang has lately done much towards introducing this valuable improvement.
5. The attaching the sister kelsons and sleepers, on which the engines and boilers are placed, firmly to the bottom of the vessel, by a proper system of bolts, passed through the flooring and bottom planking, and by lateral stayings; these sister kelsons passing the entire length of the vessel. This mode of strengthening a steamer is very little in use.
6. The introduction of powerful longitudinal wrought-iron stay-bolts, four at least, and from 1 1/2 to 2 1/2 inches diameter, running the entire length of the main-deck, and through all the main-deck beams, properly secured to each with washers and cotters on the fore and after side ofeach beam; so that each deck-beam be not only thus tied together, but that each shall bear its due proportion of any strain of the vessel endways in a heavy sea. These iron longitudinal bolt-stays have been introduced with great advantage into several steamers, which had previously worked considerably in a sea-way.
7. The introduction of an inner lining of sheet lead under the lining of sheet iron, and next to the skin of the vessel, to prevent the desiccation and charring of the timber bottom and sides, which the excessive heat and the decomposition of the fine powder of the coal in the neighbourhood of the engines and boilers frequently occasion. This under-sheeting of lead has been found an effectual remedy.
8. The use of iron in the various hatchways, ceilings, and scuttles, instead of timber, which latter weakens the deck of a vessel, whereas the former strengthens it.
9. The introduction of longitudinal cast-iron beams in lieu of wood, the entire length of the boiler hatchways, and to which is attached a wrought-iron deck-plate, the full size of the boiler hatchway. These iron beams secure that vulnerable part of the deck from contraction, sinking, or fire. The wood beams and deck usually adopted over the boilers contract instantly, and thus admit water to the top of the boiler.
10. The preparing the entire timbering, planking, decks, etc. on Kyan's or other anti-dry-rot principle, thus securing the greatest durability to the hull. This steeping process is effected in the builder's yard, and under the especial superintendence of a competent individual on the part of the owners.
Fig. 1 exhibits a plan of the solid floor, timber, and futtocks, with cogues and polts; the black parts denote spaces which are to be filled in solid, and the dotted lines denote the bolts.
Fig, 2 is a section of the keel and garboard strake with bolts.
The following engraving is a horizontal section of a portion of the frame at the main deck, with staple knees, and longitudinal iron stay bolts.
a a are the deck beams; b b, an iron stay bolt, 2 1/2 inches diameter, running the whole length of the vessel; there are four of these bolts; they pass through every beam, and are raised up on each side of the beam, and the beams being laid close enough to support the decks, carlings are not required; c c, the horizontal staple knees, secured to the sides and beams with screw bolts and nuts.
Subjoined is shown a vertical section of the hanging knee and stay, which supports the outer end of the main deck beam.
a is the main deck beam; b, the longitudinal stay bolt; c, the staple knee; d, the hanging knee bolted by serew bolts to the side and to the main deck beam; e, the diagonal stay to the knee; f, the shelf piece; g, the inner planking.