In large ships, beams are composed of two, three, and sometimes four, pieces, and are allowed to be stronger than in one. Beams so made, have scarphs tapering towards the top to about four inches, allowing the thickness of the tables, and the seat of those scarphs are to be sawed straight and out of winding.
Beams in two pieces have a scarph one-third of the whole length of the beam, like the fore and aftermost beams shewn in the Plan of the Gun-deck, Plate 5. Beams in three pieces have the middle pieces and end pieces each half of the length of the whole beam, the middle piece having a scarph each way to take the arms, as shewn by the midship beams in the Plan of the Gun-deck above mentioned. Beams made of four pieces have two middle pieces, each similar to the former; the arms and middle pieces are each to be of three-sevenths of the whole length, as the twelfth beam from forward, shewn in the Plan of the Gun-deck.
The general method of scarphing beams together is, to table them; the lengths of the tables being about once and a half of the moulding or depth of the beam. The tables are divided in the middle of the depth; and, where the wood is taken out on the upperside it is left on the lowerside, and so alternately, taking the wood out on the upperside of the scarph at the table next to the butt end, as it will be better hang and support the lip. At each lip, beyond the tables, is a coak about six inches long, and next to it is a straight lap of the same length.
Scarphs taken out in this manner are liable to retain water if the deck should leak, which must be the means of rotting the beams: but, if the beams were tabled together in dovetails, and taken through from the upper to the underside, putting tar only between them, which hardens the wood, the water then would have a free passage, and the beams would dry again. This method is not inferior in point of strength to that of tabling the beams just described.
The scarph which is thus tabled is to be laid upon the scarph it is to fay to; each piece to be kept straight sideways and out if winding, and well to the round-up mould: the butts of the tablings and coak may then be rased upon the scarph to be fayed; then a parallel mark with compasses, is to be taken at the greatest opening, which may be pricked off at every butt, and rased across at the ends of the lips. The piece may then be lined to those spots, and the tables, &c. trimmed out as before. The scarphs are now to be well dried, by burning reeds or shavings on them, then paid with tar, and set close together and bolted at every eighteen inches distance, at about three inches down from the edges; and the lips fastened with two small bolts or nails. The bolts are to be driven each way from each lip.
The beams, when put together, are cut to their lengths, thus: Stretch a line across the ship at the station or order upon the side; then, with a sliding staff or two staffs (confined together by nails or gimlets) take the length across the ship in the direction of the line. Thus may many lengths be taken, marking a line across the battens with a pencil, and numbering the beams in order. The bevellings are then taken from the said line, thus: Fix the tongue of the bevel against the side well with the beam line, and open the stock to range well with the line across the ship, which gives the fore and aft bevelling; the up and down bevelling is next taken, by fixing the tongue to the side, and opening the stock till it is out of winding with the line athwartships. These several bevellings may be marked on board, marking their respective sides, and number of the beam. To set off the length and bevellings, as taken, strike a straight line upon the same side of the beam as the line was fixed to in the ship, and along this line apply the staff with the length, and from that length set off the bevellings as taken; this is the true length when the beam has its proper round-up or nearly so. But the truest method of taking the length of a beam is, to set back from the station a four-inch sirmark on each side, on the beam line, in the centre of which stretch a line to each side. Then take the length and bevellings as before, and set off this length straight on the beam mould, and open the battens to that length on the round of the mould, there confining them. Then, from a straight line ranged along the side of the beam that the length was taken from, set back, upon the upperside, the four-inch sirmarks, parallel with the line, one in the middle and one at each end: then, laying the battens to the sirmarks, set off the last length taken, which gives the true length of the beam, whether it has its round-up or not. The bevellings are set off as before.
Observe, before the lengths are taken, and when the beams are to be let down, that the lips are kept as much from the order or station on the side as may keep them athwartships, or square from the middle line, and clear in the hatchways: and, likewise, that the upperside of the beam is out of winding with the beam line at the side.
The ends, after they are sawed off, are snapped back on the underside one-fourth more than the siding of the lodging knees, or so as to let them down in the clamps according to the dimensions. The ends are then mouthed, or a mortise is cut, through the heart, about two inches wide, and one inch and a half within the clamp, wearing off on the upperside that air may come to the heart at all times: or, the heart may be bored out with an inch and a half auger about eighteen inches in, and another hole bored up from the underside, to come into the former at about one inch within the clamp, with an auger of half the size, to admit air to the heart. The ends are then burnt very dry, and a hot bolt thrust into the heart once or twice till it is cold.
Transcribed by Lars Bruzelius
Copyright © 1996 Lars Bruzelius.