INLAND NAVIGATION.

MODELLING SAIL VESSELS FOR THE LAKES.

To achieve utility in the production of any class of shipping, it is necessary to consider carefully at least three grand governing conditions, which seem to demark the main outline of adaptation to commercial purposes. These elementary points may be defined as the nature of the trade and cargo to be carried ; the extent and depth of the waters to be navigated ; and the mode of propulsion adopted. Other considerations of detail will [p. 10]likewise enter into the theoretical design, and the points are not few which should be definitely settled with regard to the manner of building, rigging, and manoeuvring the vessel, before the model is undertaken ; for we should never lose sight of the basis of all success in ship-building, to wit : that the ship, like a watch or a locomotive, is a unit in itself; one part must be studied with reference to another, and the performance with reference to them all. The strongest built and most costly finished ship is, after all, best prepared to carve her fortunes on the deep, when the designing mind and executing hand have been united in the same person directing the operations from keel to truck ; and, we may add with emphasis, that the commander's duty is to develop those designs in using the ship.

Having arranged our investigations to our mind, we shall discover the corresponding model looming up to our inner vision, and appearing in all its proper proportions and true shape. It is with our mental eye we should first view our incipient architecture afar off, and examine it well before we conclude to tow it into port. After we have submitted the distant ideal vessel to the ordeal of nautical criticism, as an intruding stranger advancing to receive our sympathy and paternal regard, we are prepared to adjust its form to the measure of capacity required. The work of "making the model" is now fairly under way, and we should grasp its configuration fast before our mind's eye, until the labors of the hand have produced it tangibly before us. Our task is not merely to fashion a block of wood into the likeness of something that floats the commercial element, but to produce the exact counterpart of the living shapes which genius has configured in the "lofts" of the mind.

By means of calculations, which, if not familiar to the modeller, may be found explained in Griffith's Treatise on Marine Architecture, it is by no means difficult to approximate the requisite capacity for cargo, or space for passengers. Tonnage, by dimensions, is no guide to determine the freighting capacity, being a mere romance of legislation ; the displacement must be the basis of our approximation. We will leave some remarks on this subject to another article, adding only that it is best not to be trammelled by dimensions, arbitrarily fixed, before the [p. 11] model is begun. The length, breadth, and height of load-line may be so determined that it shall contain the necessary buoy- ancy to float the vessel and cargo at any given exponent of capacity. Beyond this, we should have ample scope for the eye and the instrument.

With this brief sketch of our manner of producing models, we will take a trip to the lakes, and proceed to consider some of the peculiar points of vessels adapted to commercial purposes on the inland seas. On these waters, by far the most interesting of any basins on the globe, the chief staples of trade are furnished by the agriculturist and the lumber manufacturer, and consequently demand a natural fitness in the build of vessels suitable for the transportation of each commodity, or, in other words, a model adapted to the trade. Thus, lumber, being a cargo which can safely be carried on deck, requires for its transportation a shoaler craft, or one with less depth, relatively, than a cargo of produce, which must be stowed under decks ; and neither demands so much depth as vessels require which are engaged in freighting cotton or light goods. There can be no wisdom in loading lumber vessels with height of topside sufficient to stow all the cargo in the hold, for we would thereby impair the carrying properties, and lose in sea-worthiness. Low- deck vessels are, therefore, most profitable for this trade, and may carry a large proportion of their cargo on deck. Cargoes which require to be protected from the weather may be classed as heavy and light freights; the former requires displacement, and the latter space or stowage. High-decked vessels, of larger capacity, are found best calculated for heavy freighting, and we do not hesitate to state that our observation intimates that the most profitable sail vessel built for freighting oats, or other light cargoes of perishable goods, would be constructed with two decks -- a main-deck and a spar-deck. The main-deck, at the height of the load-water line, and the spar-deck seven or eight feet above, with light topsides, flush spar-deck, with cabins on the main-deck lighted from the sides. At present, the sail craft on these lakes have but one deck.

But the draught of water ought, perhaps, to exercise the greatest influence in the designs of lake shipping. Many of the [p. 12] harbors and rivers afford the navigator no more than eight feet of water, and but few can command ten feet, or more, over the bars; and on the noted "St. Clair Fiats," the channel varies in depth from eight to eleven feet from year to year, and in the lowest stages of the lakes, the water has been known to stand even below six feet. Among the most dangerous incidents in the history of lake navigation, the inland mariner classes the "making" of those shallow harbors, "pounding over the bar," with a heavy sea running between two breakwaters, or piers, entering often literally the very jaws of destruction. A light draught of water is, therefore, one of the most important points to secure in this class of vessels.

But, strange to say, rare have been the instances in which measures have been taken to accommodate the displacement of vessels to so plain a necessity. Immense sums are expended every year, together with a ruinous loss of time, where navigation is open but eight months in the year to "lighter" vessels over the "flats," that ought to pass clear. We may account for this in the prevailing notion that depth of hold and freighting capacity are the same terms, which is a mistake. The hope of receiving the aid of the General Government to build, dredge, and maintain suitable harbors on the Northern Lakes, has, no doubt, deterred the adoption of shoaler models.

It is, however, true that the relative length has been extended quite to the verge of practical limits, in some cases, partially to secure the advantages of light draught ; and this feature, in connection with the general adoption of centre lee-boards, with very little outstanding keel, constitutes the distinguishing characteristics of the shipping on the American Lakes. There are schooners, and, indeed, every variety of rig here, the largest about one hundred and forty feet long, twenty-six to twenty-eight feet beam, and from ten to twelve feet hold. A few vessels are wider, relatively. The unparalleled length of these vessels endows them with remarkable fleetness, when compared in their performances with shorter vessels of the same shaped ends. But while still greater advantages of light draught may be obtained, by increasing the breadth, as well as the length, it should not be forgotten that the lateral resistance will be diminished, [p. 13] and the vessel will require more strength in construction. This follows, because in such case the vessel will have increased stability, and consequently carry more sail; the absolute resistance will be diminished, and, of course, the speed will be improved; but, remember, the lateral resistance having been diminished by lessening the draught of water, (unless a compensating surface of centre-board is provided,) you will gain nothing in oblique courses, or, in other words, beating to windward.

It will be vain to expect that the qualities of speed by the wind will prove to be connmensurate with the vessel's high character in free courses, or with leading winds. We say, then, that long, wide, and shoal vessels require enormous centre-boards to enable them to sustain their reputation when working to windward. The feat of sailing by the wind is a problem of the least possible amount of absolute resistance, combined with the greatest possible amount of lateral resistance, and the largest capacity for sail. It is doubtful whether it will pay for freighting vessels, otherwise properly adapted to the navigation of riiallow waters, to be qualified in the highest degree to contend with head-driving gales. Vessels built for pleasure may well claim to dispute this privilege.

In case it be not designed to increase the speed materially, when adopting a liberal breadth of beam, the exponent of dis- phcement may be enlarged, or, in other words, the buoyancy Biay be augmented to advantage. But the mode of propulsion, or the application of sail, must be duly consulted before deter- Buning the outlines of proportion and shape, in order that the model may be adapted to the peculiar evolutions required at sea. This is a point seldom or never attended to; but we contemplate a live craft, and consider the rig as a very material instrument in developing her points at sea.

First, as regards the vessel, and her mode of propulsion or application of sail in adapting the one to the other, it may be inferred that we will assume the stability and velocity, in connection with the lateral or side resistance, to determine the basis of adjustment or choice. Thus it will be found that the sloop which is the simplest of all rigs, requires the most stability; the fore-and-aft two-masted schooner comes next, then the [p. 14] three-masted, and last the various rigs of square-sails, in the order of diminished beam or stability. Brigantines and topsail schooners require a large share of stability. This discrimination in favor of square-sails with moderate stability, and fore-and-aft canvas demanding greater beam, is principally with a view to the ease and safety of working ship, and to the fact that in the fore-and-aft rig the weight of canvas and spars must be borne to leeward, and consequently the wind exerts a greater depressing effort on such sails ; whereas, in the case of square-sails, in their rotation around the masts, the weight of propulsory power is very little moved to leeward, and the depressing effort is the smallest possible.

If the reader is conversant with the evolutions of the fore-and-aft and square rig at sea, especially before the wind, he will discover no difficulty in assenting to the distinction here laid down; and if the nature of the navigation requires one kind of rig rather than another, it should be furnished with the corresponding model. Thus sloops appear best adapted for river navigation, and they require great beam, flat bottoms, round sides, and large lee-boards. The expansive basins of the North American Lakes seem particularly inviting to the fore-and-after, and the various modifications of the schooner rig, while the more hardy seas are reserved for stately ships.

There is a fulness in all this that is pleasing to contemplate, so we feel sure we are right, and consequently go ahead.

Sloops are not to be met with in our lake waters, and the fore-and-aft two-masted schooner has long been the favorite rig for vessels under 300 tons ; and though we have seen fore-and-afters above 400 tons, with proportionate beam, this rig becomes too heavy ; and vessels over 300 tons had better be built longer, and then adopt the three-masted rig. Of these there are various modifications, and the best has not yet been generally fixed upon. But it will be conceded by most judges, that square-rigged foremasts, especially for the larger class, must continue to command a large share of nautical approbation. It may be inferred that such great length as this rig requires is unfavorable to celerity of movement in stays, but let it be remembered that it furnishes great lateral resistance, with diminished absolute [p. 15] resistance, and far head-reaching qualities. In addition, they are furnished with two centre-boards, the after one to be raised, if necessary, in tacking ship. The adoption of two boards has followed partly as a necessity, and partly as an experiment, in adding the third mast. We may remark that they cost more than one board, and are not so effective. This rig requires fine light ends, high, sharp bow, long midship body, with increasing sheer towards the head and stern, and accumulated strength amidships. It will yet be found necessary to introduce diagonal trussing of iron on the inner surface of the frame, as upon the larger vessels on the sea-board, in lieu of the arched strakes that are now worked over the ceiling in the hold. To facilitate the evolutions of such models at sea, it is not wise to be over-anxious in securing a superabundance of lateral resistance on the ends beneath water, as this will impede the working ; better depend on that furnished by the side and the centre-board. But we must apprise the builder, that the fore-and-aft rig, whether on two or three masts, requires great lateral resistance, and shape for velocity, inasmuch as this rig is peculiarly well adapted for oblique courses, and oblique courses demand velocity, in order to make it pay to contend with adverse winds. We would prefer the square rig (or full vessels, or those which do not hold on well, for this reason, were there no other: fore- and-aft sails are best calculated for close-hauling, and close- hauling demands great side resistance, with speed; and, on the other hand, the yard will not come so close as the boom, and is more in place on a vessel whose hull itself will not stand so close to the line of its course.

Vessels intended for brigantines require their main-breadth carried well forward, and the bulk of displacement contained in the fore-body. The bow should be furnished with great lifting power, and strongly built to withstand the great leverage of head-sail, and the increased shock of the sea. The lifting power, to which we refer, is developed in the shape of the immersed fore-ship, and is consequent on presenting to the fluid the exte- rior plane of the bow, inclined upward and forward, by which it has a tendency to. lift above the line of the depressive effort of propulsion. Thus the angle of anterior resistance may be [p. 16] made to accomplish what buoyancy and raking of masts cannot do. The brigantine has been a favorite rig, for a certain description of vessel, to which it seemed well adapted. There are such brigs on these waters, 135 feet long, having a fore-yard 66 feet, carrying, at the same time, a fore-spencer and a main stay-sail to the deck, without interfering.

The topsail schooner rig requires less preponderance in the bow and fore-body, may have finer lines, and with proper shape and management is quite a match for any other style of craft, when all the points of efficiency are fairly tested. And we desire to say, for the benefit of any whom it may concern, that if the lateral resistance lies chiefly in the board, and the vessel comes quick hi stays, it is an erroneous manoeuvre to bring the topsail aback, and pay off on the other tack with the due decorum of a ship of the line ; it is not required, and time is lost. Let go and haul as soon as it is fairly to the mast, and the schooner will be about and under way by the time the yards are sharp up. We have seen bows so long and sharp under water that they could not be paid off without gathering stemway, and it is plain that either the model or the manoeuvre was wrong ; other conditions must decide which, inasmuch as both are right in their place. Thus it may be seen, that from the market boat to the queenly clipper, the ship is a chain of a thousand links, to be forged with systematic skill.