Shifts and expedients of camp life, travel & exploration

by William Barry Lord; Thomas Baines

DOUBLE BOAT OF IRON OR COPPER CONVERTIBLE INTO A SINGLE BOAT WHEN NEEDED.

In the first place, we had decided on the use of sheet metal, plain or galvanised iron in sheets of 6ft. by 2ft., or copper of 4ft. by 2ft., with screwed bolts and nuts in either case of exactly the same metal as the sheets, so that any galvanic action should be impossible. Next, the framework must be of wood; and as to form, it was absolutely necessary that the boat should have beam and buoyancy enough to launch, without fear of submersion through any rapid that had water enough to bear her clear of rocks, and was not steep enough to be considered as a waterfall. We purposed to put the materials together on the spot; and, therefore, their weight only, and not the dimensions of the boat, were taken into consideration with regard to waggon carriage.

For the mere purpose of passing from the head of the river navigation to the sea, and thus proving that such navigation was possible, nothing more than a single boat would be required. But for observing, mapping, sketching, or otherwise improving to some useful result the various opportunities of the journey, sufficient room must be provided for the voyager to work comfortably on deck instead of sitting cramped up in the stern-sheets, and we, therefore, decided on making ours capable of being used as a double boat when the breadth of the river permitted it.

The advantage of being able to use each part when separate, as an independent boat, so that the sharers in the voyage might trace separate branches of the river, had to be balanced against the disadvantage of having to take each of these singly through rapids, which their dimensions might not insure their passing in safety, and also against the fact that if the “double” is formed of two perfect boats, they cannot attain great speed either in sailing or rowing, from the fact that the volume of water admitted between the stems, which may be, for example, 8ft. apart, must be compressed as it passes the midship section, to 4ft. or 5ft., according to the breadth of beam of the boats, and will again have to expand as it passes the gradually increasing space between their “run,” or after section. And the loss of power thus expended in “heaping up water,” although imperceptible at a low speed, would become enormous if a higher rate were attempted. Therefore we made our model so that when not required as a double, she should become one single yawl or whale boat of 30ft. in length, and 6ft. beam, with 2½ft. internal depth in midships, rising to nearly 4ft. at either end to enable her to shoot a tolerably strong rapid without shipping water; the two sections were therefore each made like half a whale boat, the outer sides having their proper curve and the inner being perfectly flat, so that when used doubly the water might pass without resistance between them, and when singly they might be clamped together as one boat by screwed bolts through the keel, stem, stern posts, and the inner gunwales.

Our first care was to seek out a block of soft, fair grained wood, 30in. long and 3in. wide, and to shape this truly to the form required for one half section of our boat. We next provided a sufficiency of planking, ribbands, &c., also on a scale of 1in. to the foot, and then cut out from the thinnest tin case linings, forty pieces of 6in. by 2in., to represent our sheets of iron.

The dimensions of our boat had been previously so arranged that in the midship section the depth of nearly 2 ft. on the flat side should leave rather more than 4ft. of the iron available to form the curve on the outer, necessary to give a half beam of 3ft.

In building our model we adopted slightly different plans with each of the two sections. In that intended for the starboard side we laid along the flat or inner side of our block or wooden mould a batten, 1/4in. square (representing one of 3in.) and 24in. long (each inch being understood to represent 1ft.); to this we fitted the stem and stern post, each 6in. in length, both exactly alike, curving and raking forward and aft like those of a whale boat, so as to have an actual height, before the keel was added, of 3¾in. We then laid along the top of the flat side the inner gunwale 1in. deep, but as this would be an impediment to the rowers when the sections were clamped together to form a single boat, we cut out a piece (marked A, p. 106) ¾in. deep and 18in. long, so as to be removable at pleasure, the remaining quarter then forming the stringer on which the thwarts would afterwards be laid, the bottom of the three-quarter piece (A) having checks cut in it to allow it to fit over them. We then took the piece of tin representing the midship sheet, and drawing a line across it, 1½in. from its edge, bent it over the keelson, bolting the short end to the thwart stringer, and bringing the longer one of 4½in. round the curve to the outer gunwale; nine sheets were required aft and nine forward of this, and the only difference in laying them was that, as we proceeded forward, the edge of each sheet overlapped by nearly 1/4in. the one behind it, while in working aft, the edge of each had to be inserted beneath that which lay before it. When the curves of the stem and stern were reached, the sheets had to be cut to the required form instead of being bent, and were bolted in their proper places. The outer gunwale, ⅛in. thick and ¾in. deep, was now laid on and bolted to the metal sheets; another batten, ½in. wide, was laid from stem to stern along the bilge, and the keel, ¼in. thick and deep, was fitted in its proper place and bolted through the metal to the keelson.

Our half boat was now sufficiently firm to be taken off the mould. A short stringer of 18in. was laid internally upon the floor, and another the whole length along the inside on which to lay the outer end of the thwarts; and timbers, ¼in. thick, were bolted in with their heads projecting 1in. above the gunwale, so as to receive cross-beams of ½in. in thickness and 15in. long, by which the sections were kept apart when used as a double boat. We considered it better to secure the beams by cross-lashings than by bolts, which, if the boats worked much in troubled water, would probably rend the parts they served to connect. Along the gunwales, at short intervals, we intended to use lighter cross-beams, probably of bamboo, that is if it were procurable; but having carried out our model sufficiently to establish the general efficiency of our principle, we did not think it needful to spend time in completing every little detail, and this called forth the free but friendly criticism of Mr. Charles Bell, the Surveyor-General of the Cape colony, whose valuable and practical advice we take the liberty of giving (see [p. 115]).

The only difference of plan adopted in building the other or port section was that we built the whole of the inner or flat side of plank ⅛in. thick, by which we were enabled to cut 1½in. off each sheet, and this method in building a full-sized boat would have enabled us to use copper sheets of 2ft. by 4ft. instead of iron of 2ft. by 6ft.