The angle iron is bent to cross the keel ; fitted between the floor throats thus formed is an oak chock (c Fig. 23), which rests on the angle iron and keel, and on this the bolt through lead and wood keel is fastened with nut and screw, so that the angle iron will not be weakened by being pierced for through bolts.
The angle iron floors will be secured to the wood keel with coach screws. The oak floor arms will project about a foot above the angle iron, and to these the timbers will be scarphed. The intermediate timbers run from gunwale to gunwale. Most of the intermediate timbers will be steamed, but where extra strength is required larger worked timbers will be put in.
It would be difficult to say which plan is to be preferred, as each is used where some special object is in quest. For instance, in Fig. 18 we see a vessel with an abnormally broad wood keel, and the keel is so broad solely because she should carry a considerable weight of metal under it ; it is manifest that no hogging piece is required here to prevent sagging or hogging, and such an addition to the structure would only be taking up space which would be much better occupied by ballast. Then, as the keel is so broad in its siding, too much or unnecessary displacement might be the result if the heels of the timbers were butted to the side of the keel ; hence the heels rest on the top of the keel, and the strength of the structure is insured as shown. In striking the ground there would not be the least possibility of the keel being driven up through the vessel, and all wrenching or twisting strains are amply provided for by the iron knees and transverse plates. So far as Fig. 21 goes, the hogging piece and main keel can be regarded as all one piece, strength and rigidity being supplied in depth instead of by breadth, as an object existed in having the lead keel deep in proportion to its breadth. Any chance of the keel going up through the bottom of the vessel is met by the heels of the frames being joggled into it, and by the garboards being rabbeted into it lower down ; beyond this there are the iron knee floors, which would have to be crushed or broken, or unfastened, before the keel could make an entry into the hold of the vessel. Next we come to the plan of half
joggling the heels of the frames to the top of the main keel ; and it is obvious that this plan, if the heels are at all cross-grained, is a very insecure one. The plan of having a hogging piece of less siding than a keel, so as to admit of a stepping line for the heels of the timbers, has no advantages over the plan shown by but is one that might very well be adopted where the hogging piece is of metal.
The plan of butting the heels of timbers to the sides of a keel without any joggles or stepping line whatever has been objected to, because there is a probability of the garboards, in case a vessel got ashore and bumped heavily, being driven out of the rabbets. In a vessel with a flat floor this assuredly would be the case, as the iron knees would most likely part in their angles at the first heavy bump ; in fact, they would have to bear the brunt of the shock. But even with a great rise of floor, the garboards may be crushed out of the rabbets, if the heels of the timbers are not butted into the keel ; in fact, a case occurred in 1877 where a vessel of some 120 tons weight got on some rocks, and her garboard strakes were split and forced out of the rabbets. The smallest movement of the heels of the timbers down the side of the keel would. serve to wrench the garboards away from their fastenings or crush them; whereas if the heels were properly butted into the keel they could not shift, and no undue strain would come on the garboards in case of bumping.
Fig. 24 illustrates the old-fashioned orthodox structure of a vessel's floor : a is a grown floor, sometimes joggled as shown, and sometimes not, to the main keel k. The keelson is shown by s and garboard by g, bolted through the keel. The keelson floor and keel are bound together by through bolts, as shown by b. The strength of these wood floors is mainly dependent upon the grain in the throat running as shown in Fig. 24. If the grain in the throat is vertical, the chances are that the through keel bolt would split the floor.