DOUBLE BOAT OF IRON OR COPPER CONVERTIBLE INTO A SINGLE BOAT WHEN NEEDED.
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 tothe 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 (seep. 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.
THE SECTIONS CLAMPED TOGETHER AS A SINGLE BOAT, OR USED WITH CONNECTING BEAMS AS A DOUBLE.
THE SECTIONS CLAMPED TOGETHER AS A SINGLE BOAT, OR USED WITH CONNECTING BEAMS AS A DOUBLE.
Full-sized platform boat.
In building a full-sized boat on this model, our plan would beto make the flat side all of ¾in. plank, with the stem, stern post, and keelson all fast in their proper positions, and the keel left slightly apart, so as to allow the sheets of metal, whether iron or copper, to be inserted between it and the keelson. Then, laying the whole flat on its side, we would cross cut with a fine tenon saw our wooden model into eight pieces of equal length, and carefully enlarging the section of each length would make as many temporary frames, and set them upon the flat side, cutting checks in them to let in the stringers, which when bent down to the flat at either end would very effectually give the form of the boat. We would then fit the ribs, keeping them as light as possible with due regard to strength, cutting them, if requisite, out of wood selected with the proper natural curve; or, preferably, using flexible wood, such as ash, in pieces 2in. broad, and ½in. in thickness, and placing them not quite 2ft. apart, so that the overlapping edges of the sheets might coincide with the ribs, and the bolts might pass through them and also through the inner stringers, and the outer ribbands and gunwales at all their points of intersection. The ends of seven of these ribs, at nearly equal distances (as at sheets 2, 5, 8, 10, 13 and 16, on p. 106), we would leave standing six or eight inches above the gunwale, and about four inches from each we would set up another of equal height, so that the cross-beams might lie between them when required, and be secured by lashings passing down to the firststringer (p. 110), or so that when the two parts were connected as a single boat they might serve as rowlocks. Short struts from the foremost pair of these would give great additional stability to the masts.
In laying the deck, we should by all means endeavour to avoid injuring the planks by boring needless holes in them, as they might on an emergency be required for building a smaller boat. We should, therefore, lash them with raw hide to the foremost and aftermost crossbeams, and then laying lighter beams across near two or more of the intermediate ones, fasten them down where requisite by strips of the same material (p. 110).
For connecting the two sections, so as to form a single boat, we should use screwed bolts ½in. thick, and 7in. long, passing at intervals of about 16in. through both keels, stems, stern posts, and inner gunwales, thus firmly clamping both the flat sides together. The two removable portions of the inner gunwale (marked A) previously mentioned would, in this case, be unshipped to allow the oars free play, as in illustration on opposite page, and onpage 106.
Copper is the only metal we should wish to use or recommend to others, and all fastenings used with it must be of the same metal. We recommend in this case, screwed bolts and nuts, presuming that the boat would be built for a journey, the exigencies of which might oblige the traveller frequently to take her to pieces and rebuild her; but as our own means were at that time inconveniently limited, we made a calculation of the comparative cost of plain and galvanised iron and of wood.
The mode of setting the sails, spreading the awning, &c., will be sufficiently clear from the engraving (p. 106).
Our little model, when tried upon the flooded flats at Walvisch Bay, sailed “like the wind,” but had a tendency to bury the lee-bow, which was easily remedied by ballasting the weather quarter; an oar was the readiest and most convenient means of steering.
Estimate of material if the boat be built of copper, the flats or inner sides being of plank:—
All the bolts, screws, nails, and other fastenings, must be of plain iron, and none of them must be galvanised.
Galvanised iron would not be much cheaper than copper, and would be very intractable in working. We should not recommend it to a traveller who intends to build his own boats in the wilderness and expects to have to take them to pieces and rebuild them two or three times.
Tinned charcoal iron would be nearly as expensive as copper, and the fastenings would also have to be tinned.
Plain iron is the only metal on which any saving could be effected, even at the cost of additional labour. In this case, perhaps, three times the amount of paint should be taken.
A mixture of red and white lead, with half boiled and half raw linseed oil, should be used rather thickly for painting the inside of every joint, and all the bolts, screws, or nails, should be thrown into boiled oil, then taken out and allowed to drain and dry before they areused. The boat must be thoroughly well painted after completion, and the paint allowed to harden before she is put into the water.
If the boat is built of wood the same size—
Two deals and a half, as before, for keels, keelsons, stems, and stern posts.
Four deals, each to be cut into four ¾in. planks, for flat sides, gunwales, and stringers.
Five deals, each to be cut into six ½in. planks, or equal to 230 running feet of plank, to stand, when cleaned, not less than ⅝, and 630 feet not less than ⅜.
If the traveller can afford to carry two or four good 12ft. ash oars and one of 14ft., by all means let him do so. Nothing is equal to them for pulling or steering, but let him carefully preserve his treasures, and not put them to any use that will twist or warp. If he engages natives as a permanent crew, they may be taught to pull very well; but if he hires temporary helps, let them bring their own paddles, and they will make the boat go well enough.
For the connecting beams, the masts, yards, &c., we should prefer bamboo, as being exceedingly strong in proportion to its weight. In the Indian islands we have seen oars made of bamboo poles, with a disk of wood about as large as a dinner plate lashed on the outer end, and the men pulled very well with them. If bamboo cannot be obtained, poles may generally be cut in the vicinity of a river; but the traveller in Africa or Australia must not expect to find any wood that will possess all the valuable qualities of good red deal, therefore we would say take as much of this as you can carry, without inconveniently incumbering your vehicles. The battens we were able to take to the Zambesi astonished the natives there, they had never seen wood so light, so strong, and so even of grain throughout its length; whilethe fresh smell it gave out when cut was their constant theme of wonder.
In 1864 Mr. Charles Bell, the Surveyor-General at Cape Town, who has built and used double boats since 1850, favoured us with the subjoined description of his method of construction:—
“My boats are only 12ft. long by 9in. wide, and 9in. deep, and 12ft. by 14in. I have never made them more than 15ft. long, with a bearing power of about 800lb. I have now built or directed the building of about five good boats on the principle, easy and swift under oars or before the wind under sail, and not very faulty even on a wind without any false keel, but you can never sail quite close without one. Mine were built to go through heavy surf all fore and aft, so that the wave could strike nothing except sharp edges, and in surf they are first-rate.
“Iron is objectionable both on account of weight for carriage, and liability to oxidisation in heat and moisture; nothing like canvas. A bolt of No. 3, 2lb. of tin tacks, and a few needles and hanks of twine, would be all I would bother myself to carry a mile. My first boat had not an ounce of metal in her barring rowlocks and rowlock sockets, and she cost me 17s.6d.and some old plank, and carried me safely through wall-sided breakers that would have troubled a whale-boat’s crew. Say you want a pair of 30ft. boats of 3ft. beam and depth, tolerably safe even against snags and rocks. For each take a 30ft. batten, 3in. by 2½in. for keel; strut and erect on it knees’ planks and stem pieces as in Figs. 5 and 6, and section in Fig. 2 (p. 116).
“Trust greatly to lashing the frame; let the knees diminish in beam from the centre to each end as in Fig. 1 (p. 116): draw in your side pieces and planks, or rather press them down to your vertical side laid on a flat surface, and you will have lines that will astonish you. Of course you can raise stem and stern for the look of the thing, as I have done, but it gives more trouble than it is worth. If you want to make a safe lifeboat, tack tight over each knee-frame a piece of canvas (Fig. 3,p. 116), leaving an edge loose and broad enough to be sewn on to the outer canvas, loosely (so as not to interfere with the lines it will naturally take), and be tacked to boards and battens where they come in contact with it. I should have first said cover bottom and sides withtightly-stretched canvas, in which operation a cobbler’s pinchers are most useful, but any others will do, then grease outside and in. If you prefer tar and have it, well and good; then cover the deck in the same manner, stitching knee-piece canvases as you go. You will thus, if the workmanship be perfect, have in each half boat ten watertight compartments, which it will be no easy matter to damage; snags will be your worst enemies, and they cannot damage more than one at a time under ordinary circumstances, whereupon the first landing and a crooked needle with patch of canvas, twine, and grease, will make all right. In the deck of each such compartment you should pierce a marlinspike hole, button-hole the edges, and fit a plug, and as a large boat cannot be so easily turned upside down as ours, you may have a pipe, and any simple means of sucking out such bilge water as may get in. Next as to connection of the boats. If you wish it sliding, so as to increase or diminish the width between them when necessary, make it on the lattice girder or rafter principle, and avoid weight, as in Fig. 7; each not more than 6ft. from the centre. Stay and strut them to points near the stem and stern, and they will be quite strong and firm enough to support the mast and the awnings, with the other fittings. The knee-pieces may be left projecting when required to meet the sliding rafter; 1ft. between the boats will be quite enough, so 10ft. of rafter will be quite enough. The sail may be a long low lug, split if you like, to let it pass the mast when on a wind (Fig. 4). An oar will steer, and easily control the extra face of sail on one side whenbefore the wind with the yard squared. But on a wind you must have a keel, one that will slide over sunken rocks, and not be damaged even when it takes them side on. It may fix with free play in the front beam, and lay loose in cleats on the after one with a projecting arm to be held upright by rope, as in Fig. 8.
“Of course there must be an opening between the deck planks, to allow of its rise. Such a boat will carry at least a ton and a half of cargo, if made sufficiently flat in the bottom, and it will require a very stiff breeze and large sail even then to submerge the lee boat. There is this advantage, too, that it cannot be done so quickly as to prevent the remedy by luffing up or otherwise with ordinary vigilance. Your goods and tarpaulins will be quite safe 6in. above the gunwale.
“Yours very truly,“Charles Bell.”
Just before returning from South Africa we found that the clever author of “A Painter’s Camp in the Highlands” had also gone through nearly the same course of experiments, and had arrived, like us, at the conclusion that the double form of boat was the most safe, convenient, portable, and roomy on deck; and also that it was objectionable to have the inner sides rounded, for the reasons before given. He therefore finally adopted the flat inner side, and making his boats 30ft. in length and 4ft. apart at the stem, increased the width to 4ft. 1in. aft, so as to let the inclosed body of water glide away more easily. He found, however, that after working out his own idea for his own use, he was served with a notice for infringing a patent of which he had not previously heard; and in like manner, after our return from Africa, a description of a patent tubular life raft was submitted to Captain George, at the Royal Geographical Society, and he immediately saw that this was nearly identical with our own plan.
Making inflatable boats safe.
About 1853, a friend in Graham’s Town, with whom we left our model of the inflatable boat, subsequently used in Australia (seep. 48), made one for his own amusement, on a small river. He had but two tubes, each of them with a flat side toward the centre, with a small platform between raised on crossed struts, one pair of which on each sidewere very ingeniously made to carry the rowlocks, as in the next sketch (Fig. 9). And, as he was doubtful of keeping the canvas of his boats sufficiently air-tight, he either filled them, or proposed to do so, with the bladders of oxen previously inflated, so that, even were air to escape from the tubes which formed the boats, they could not collapse. This, in itself, would be a hint which a traveller, who must either shoot game or kill domestic animals for his followers, would do well to bear in mind.
Skiff of iron or copper.
Iron, whether plain or galvanised, is sold in sheets of 2ft. by 6ft., while those of copper are 2ft. by 4ft. We recommend only the copper; but economic or other reasons may very possibly compel the traveller to use iron.
We have, for facility of construction, chosen the form of a Norwegian praam, or wherry, with both ends alike. A semicircular section slightly flattened at the bottom, without a keel, and rising with an easy sheer to a sharp point at either end.
Eleven sheets of iron would be required; the central one being left of its original shape and size, while the five at either end are cut to the forms shown by the outer lines, and to the dimensions indicated by the figures marked along the lower edge: thus, in No. 1, from the centre there is no perceptible curve along the 6-foot side, but the ends are sloped off, with straight although diagonal lines, so that the side nearest the centre remains 6ft., while the farthest is reduced to 5ft. 9in.
In the next sheet, or No. 2, the side nearest the centre curves very slightly; the segment taking off only one inch at either end, the curved side (supposing we are now working from the centre forward) overlaps the edge of No. 1 two inches, and it is therefore cut, not to 5ft. 9in., but to 5ft. 10in., as No. 1 would be of that breadth, a couple of inches back; the front side is left straight, but is reduced in breadth to 5ft. 5in., and the after side of No. 3 is so much more curved that the segment cuts off three inches. The figures in the diagram will render the progressive diminution to the end sufficiently plain. It will be seen that the end remains one foot wide; this is usually filled in with a semicircular piece of plank, being quite sharp enough for all practical purposes, and affording room for a rowlock for a steering or sculling oar, or for a hole through which the boat’s painter may bepassed. But, if desired, another piece of iron, which may be called sheet No. 6, may very easily be let in to continue the curve quite up to a point, as in the dotted end of Fig. 2. The half section is given on the side marked iron of Fig. 3, the outer line standing for the two edges of the central sheet, where the skiff is 4ft. wide and 1ft. 10in. deep. The next line, 1½in. smaller all round, is the section at the overlap of sheets Nos. 1 and 2; the third line, two inches within the last, is at the edges of Nos. 2 and 3; the fourth, three inches smaller, is at the contact of Nos. 3 and 4; the fifth, six inches less, is at Nos. 4 and 5; and the sixth, diminishing by nine inches, is the end of No. 5, which is filled in by a semicircle of plank about five inches in diameter.
skiff of iron or copper
The eleven sheets laid side by side would, of course, present a length of 22ft., but the overlap and the segment of the curve cut from those near the ends would reduce the length of the boat to 19ft.
Our diagram is on a scale of a quarter of an inch to a foot, but this is somewhat small for the needful accuracy; therefore if anyone intends to build, we would advise him to copy it on a scale of at least one inch to a foot, in which case the halves will represent six inches and the quarters three, and if he has a rule divided to one-twelfths, his work will be much facilitated.
It would be better to make, as we have done in preparing this description, a model block on which to test his work; indeed we would advise this in all cases of intended boat building. If the boat is tohave a bow and stern distinct from each other, the model must be of the whole length, but may be of only half the breadth. If both ends are to be alike, it may be half the length and breadth, or one quarter of the boat.
sawing deal
In the present instance, take a piece of deal, as clean and straight-grained as possible, 19in. long (or 21in. if you wish the ends to come to a point), 4in. wide, and 3in. deep. Having smoothed this, draw a line along the centre of the top and bottom, connecting them by perpendiculars at the two ends; then on the top set off the line of one-quarter of the gunwale, or outer line, taking the breadths from the section in Fig. 3 (p. 119), and their distances from the centre, from the elevation in Fig. 2 (p. 119), bearing in mind that the centre means not either of the edges, but the middle of that marked as the central sheet. It will save trouble to cut out a piece of card to the size of this quarter, and trace the corresponding ones on the top and bottom of your block; then copy the elevation given in Fig. 2, and trace this, as before, on both sides. Now fix the block, with one end up in a bench vice, and with a narrow frame saw cut along the gunwale lines nearly to the centre, but do not cut them quite off, or you will lose your elevation lines (if a friend helps you by guiding the other end of the saw to the line on his side, you will be more certain to cut truly); then turn the block one-quarter round, and cut the line at top and bottom. Now place the other end uppermost, and repeat the process; and lastly, finish the cuts, and detach the superfluous pieces.
Take a piece of card or thin stuff, and draw on it the midship section, and cut this away, leaving a corresponding hollow; round off the edges of your model until she fits this hollow, and of this size 2in. of the centre must be left. Do the same with the diminishing sections, forward and aft; then cut eleven sheets of card 2in. by 6in., mark a central line across each, and also along the bottom of the model; lay onesheet uncut across the midship section, and tack it there; mark each of the others after the outlines given in the diagram (Fig. 1,p. 119), but test them in their places before cutting them. Take care also that as you go forward each sheet overlaps that which is behind; but as you work aft, insert the front edge under the one before it. You may think this operation would be tedious; but having once gone through it, you will build your full-sized boat with confidence. And let us again assure you that time spent in obtaining a preliminary certainty of your plan is saved over and over again when you come to actual work.
The sheets having been cut to the proper shape, set the two points of the gauge ¼in. apart, and so that the centre of the space between them shall be exactly 1in. from the shoulder, and gauge these lines all round the sheets, then, commencing from the centre of the longest side, mark off spaces of 3in., and with a flat-ended punch, and a dolly or matrix, or, in lack of that, a hard block of end wood, drive ¼in. holes on all the sides except those which are cut with a curve. Then lay the centre sheet on the rib or mould, which, like the rough frame on which bricklayers construct an arch, gives it its proper curve, and, under one edge, lay the curved edge of the next sheet. Mark where the holes should come; remove it and punch them, and fasten the two sheets together temporarily with three or more of the screw bolts. Do the same with the successive sheets towards each end, and you will find that the copper shell, even without ribs or strengthening of any kind, will assume its proper form and will be tolerably stiff. If the sheets are truly cut, the result may be attained, even without a mould, by driving one hole in the centre of the curved side, bolting it to the straight edge of the other sheet, and then bending both round till the curved edge coincides with the straight one. In this condition you may decide on increasing the width of your boat by forcing the sides farther apart; this will increase her sheer or elevation at either end, and will diminish her depth, or you may incline to reduce her beam, which will give her greater depth and will reduce the sheer till the elevation of the gunwale presents nearly a straight line. It would be better, however, if circumstances permitted, to adhere very nearly to the form given in the drawing, and set up such a frame for working on as is shown in the illustration on the next page.
aligning the sheets
Drive as many rough stakes into the ground as the number of sheets in your intended boat requires. Let these near the centre be three and a half or four feet high, and these at the ends slightly lower. Stretch a chalk line fore and aft, and see that all their centres are in true alignment and 1ft. 10in. apart. The line should be fastened to two posts in the same line as, but beyond these required for, the boat. Let it come low enough just to touch the central posts, then measure downwards from the line the amount necessary to be cut off those towards the ends, so as to give the proper sheer. Next, commencing from the centre, face off with a saw, or otherwise, as much of each post as is needful to let each frame lie truly against it, noticing that as the bottom of each is farther from the next than the top or part near the gunwale, it is more convenient to face that side of the post which looks towards the centre; then, with any rough slabs or planks, form two moulds the exact size and form of your midship section, just as bricklayers would do if they were building an arch. Nail these to their proper supports, and on them bend the strips, 2in. broad by 1/4in. thick, you intend for ribs, letting only one edge rest on the mould, while the other projects so far that you may have clear space to bore through the centre the holes for your screw-bolts. Do the same with all the others towards the two ends, confining them with a temporary ribband where the gunwale is afterwards to be; or, still better, leaving their ends 6in. too long, so that this ribband may not interfere with the completion of the boat. Have a chalk line stretched near the ground, along either side, parallel with the centre one above, so that any deviation from the proper form can be measured and corrected. Then lay on the sheets, insert the bolts, and screw them up, adding a keel or centre batten, bilge streaks, and gunwales, externally, and bottom boards to prevent the occupant treading on the copper, andstringers for the thwarts inside. The projecting ends of the ribs can be left where required for rowlocks, or cut off where they are not.
The same process, with attention to the different dimensions, will make you a copper boat, consisting of nine sheets, 2ft. by 4ft.; and this will be 16ft. long, 3ft. 3in. wide, and 10in. deep; but if the gunwales were made of plank, 4½in. wide, or half the width of a deal, the skiff would be quite deep enough to carry three or four persons in moderately smooth water.
If you wish to build the same boat of wood, ⅜in. planks (not more than 4in. wide) will be stout enough. The lines radiating from the centre in the sectional drawing are given for the purpose of showing the progressive diminution of the planks in width, from the central section towards each end. These should be tested by cutting strips of card and tacking them, like planks, on the block that serves as your model.
This would be a very handy form for a dingy for the traveller’s personal use, as it might be taken to pieces, and the sheets laid flat, occupying a space of 2ft. by 4in. in extent, and less than 1in. in depth, or they might be rolled up in three bundles, of which each must weigh less than 24lb., as the weight of the whole nine sheets of copper before being cut would be only 72lb. The screw-bolts would weigh probably more than the sheeting, but they could be divided into packets of any convenient weight for carriage by native porters or otherwise; and we should think that half a day would be quite sufficient to put the whole together when wanted, or take it apart when done with. The boat would pull or paddle, and would sail well enough off the wind, but would not compete with a keeled boat close hauled; if the iron sheets were used, she would, of course, be larger and heavier, and the material would be less portable.
In the boat built for Mr. E. D. Young, for use on the Shire river and Lake Nyassa, thin sheets of steel were at first proposed, but as these could not be readily obtained, the best iron was used, and the edges of these being turned upward and inward, formed the ribs of the boat, each sheet being connected by bolts passing through this inward edge to the next sheets before and behind it. This form of construction combines all the elements of lightness, simplicity, andstrength; but we do not recommend it to a traveller who has to work up his own material, because none but a skilled workman could turn inward a broad segment of a sheet of metal, the outer surface of which has to present a curve. If anyone doubts this, let him try it by folding half an inch of the edge of a sheet of paper to a right angle with the other part, he will then find it impossible for him to impart a curvature to the sheet without tearing the upturned edge if he bends it outward, or wrinkling it if he gives the contrary curve. If he wished to adopt this form of joining the parts, his plan would be to cut up his sheets of copper into planks 4ft. long, and 8in. broad, then gauging a line all round 2in. within the edge, cut out the squares at the four corners and turn up the borders all round, he would thus have out of one sheet of copper 4ft. by 2in., three planks 4in. wide, and 3ft. 8in. in length, a waste of material that hardly any circumstance could justify.
Metal boats.
In 1858 we made a model of a metal boat, about thirty feet long, by six feet beam, to carry a crew of sixteen men, each of whom, when it was taken to pieces, should not find his share of the load to exceed 50lb. each of the thwarts; and the bow and stern sheets were continued downward so as to form a water-tight box, the lower outline of which coincided with the section of the boat, so as to supply the place of ribs and convert her into a lifeboat. Indeed, we would advise that in all metal boats some such portions should assume the form of lockers or of reservoirs of air, so that, should the boat be swamped or become leaky, she might not sink even when filled with water.
Our model was approved by Captain Washington, R.N., the Secretary at that time of the Lifeboat Institution, and the builder to whom we submitted it estimated the weight of the sheet copper and bolts of the same to be employed in the hull at 260lb. and the cost at 60l., while the internal fittings, somewhat less in weight, would cost 40l.This expense Dr. Livingstone considered to be too great; but, when we reached the Zambesi, it was a matter of frequent regret that we had not some form of boat portable enough to be carried over rough country to rivers we wished to explore.
BOAT BUILDING ON THE LOGIER RIVER.
BOAT BUILDING ON THE LOGIER RIVER.
One of the most beautiful little vessels we ever saw was built bythe wrecked crew of a French steamer. She was 40ft. long and 8ft. or 10ft. beam, clinker-built, with thin and narrow planks, without a joint in their whole length, sawed out of the mainmast, and flexible ribs about a foot apart and not more than one inch in breadth or thickness. Her deck beams were, of course, somewhat more rigid, to sustain the weight of the men who crowded her. She was said to have sailed eleven knots.
Wattled boat.
Our friend, Mr. Wilson, an experienced African traveller, recommends a wattled or basket-work boat, and in a country where rattans, osiers, or flexible twigs, or green reeds, are obtainable, such a boat would be both light and durable; but it would be open to objection on the score of unavoidable roughness, and inequality of outer surface, which would impede its progress through the water, and expose parts of the canvas covering to constant liability to chafe whenever it touched the ground. Even if a traveller intends to purchase or hire native canoes, it is indispensable that he should have some small portable boat of his own, sufficient at least to show the natives that he is not totally helpless on the water and dependent on them.
In the case of our copper boat, illustrated atpage 53, we have already remarked that the difficulties of the road, and the mortality among Mr. Chapman’s cattle, obliged us to leave behind eight of the sections. The method we adopted with the other four is shown in our full-page illustration, representing boat-building on the Logier River.
On account of the danger from the tsetse, or poisonous cattle fly, our friend’s waggons could not be taken to the banks of the Zambesi, and everything had to be carried by the Damara servants and hired natives to Logier Hill, about eighty miles below the Victoria Falls, which we had selected as the first place from which continuous downward navigation was possible.
The building of the house will come more properly under its own heading, and we will now only treat of what concerns the boat.
About the 3rd of October, or towards the close of the dry season, we cut down a motchicheerie tree, which divided a little above the ground into two tolerably straight logs of manageable dimensions. These were first notched with the axe on the side we intended to “fall”them; the cross-cut saw was then “put in” as far as it would go without nipping from the pressure of the wood, and a notch being made on the other side, the saw was used freely, the weight of the tree on the “falling” side opening the cut as the work proceeded.
Fresh reports, however, caused us much uncertainty whether the Falls of “Moambwa,” or the rocks, were not still below the station, and some time was therefore spent in exploring the river down to Sinamane’s Island, when, having ascertained that the rapids and other difficulties appeared not quite impracticable, we set up the bow and stern sections of one boat, connecting them by the ribbands of red deal we had been able to carry up, and fitting at short intervals a series of frames on central posts, as described atp. 122, and further supported by shorter posts on either side, in a line with the gunwale streak, testing the accuracy of all parts where correctness was required with plumb line and level, and leaving the rest rough.
Our bench consisted of ten stakes, nearly 3ft. high, driven into the ground, and two long straight poles laid fore and aft in their forks; smaller poles were laid across these as closely as possible, and lashed with the inner bark of the young branches of the “kookomboyon”—a kind of stercuhia, which, while still moist, answers very well, but becomes brittle in drying. The large smith’s vice was firmly lashed to the stoutest upright with raw hide, and forked poles were set diagonally to resist the forward strain to which the bench was subject when wood was being planed up.
It was just possible to get thin poles that would bend, but none were sufficiently flexible to take the true curve required for the ribs, and at the same time strong enough to bear the strain when they became dry. Therefore we had to cut crooks out of the motchicheeries, the wood of which looked something like coarse short-grained cedar; and first burning away the light stuff from the tree cut down a month ago, we found a great many available forks and curves.
We had great difficulty in selecting wood of a suitable size for plank; trees too small, or too crooked, or of unsuitable wood, were in abundance; while those of the wood we wanted were mostly too large and unmanageable. Sometimes, at a distance, one would appear to be small enough, but when we came near it would prove three or fourfeet thick and sixty or eighty feet high, and had only seemed small by comparison with those around it. One group of motchicheeries had grown to maturity, throwing a wide-spread shadow around them; and a young sapling had shot straight up from near their roots towards the air and light; this was 9in. thick at the base, and 4in. at nearly 30ft. up; it proved impossible to “fall” the top outward, and it was very difficult to clear from the other trees. We would have saved labour by floating it down stream to our building-yard, but the wet season was coming on, and the sap had by this time risen in the wood, so that a small piece sunk when thrown into the water. The labour of sinking a saw-pit would have been great, and besides this the expected rains would have kept it always wet. We therefore erected trestles of primitive construction; two triangles of forked poles, 6½ft. long, supported the ends of a stout cross-beam, firmly lashed to them with buffalo hide, and for greater security lashed also to the stem of a tree. The second trestle was destitute of this support, and therefore had to be shored by longer poles, the forks of which took the necks of the opposite triangles, while their hands were stopped by wedges driven into the ground; for additional firmness, lashings were passed at the points of intersection. Two stout poles were laid fore and aft upon the trestles, and shorter pieces across served to rest the log upon; there was some difficulty in lining the lower side, but by cutting notches in the cross-pieces large enough to let the chalk line pass freely, and “springing” it only by short lengths at a time, this was accomplished. It was difficult to teach a young Dutch lad, strong as an ox, and nearly as stolid, to saw with us; but at length the “sapling” was cut, and one of the larger logs lifted gradually up by forming an inclined plane with strong poles, and supporting it whenever we gained a few inches of elevation by forks of various lengths lying ready for that purpose. This having been felled before the sap was up proved much easier to saw, and we had so far overcome the difficulties in our way, that we had commenced laying the bottom plank of the first boat, when the difficulty of providing food, owing to the retreat of the wild animals to the pools which the rainy season was filling all over the desert, and the fever among the people, seven Damaras, mostly women and children, having died in Chapman’scamp, and one of the most useful men in ours, obliged us, for the sake of saving the rest, to retreat to the highlands of the desert, and on the 3rd of February, 1863, we hauled down our colours at Logier Hill, and commenced our return journey.