Nothing, in the construction of a ship, requires more attention, than the fastenings; upon the sufficiency of which the strength of a ship as much depends, as it does upon the sufficiency in the dimensions of the timbers, planks, and other of its components parts. The fastenings should always be of a strength, proportioned to the parts united and secured by them: so that the one should hold till the other breaks. Fastenings should, moreover, be of the strongest and toughest materials, in order to be of as small a size as possible; for, when the fastenings are large, they require large holes, and these weaken the parts secured.
Tree-nails are a very inferior fastening: the material is too weak; they generally soon decay; and it is round about the tree-nail holes that the timbers go first to decay. Moreover, the tree-nail holes wound and weaken timbers very much; and, from their large size, render a larger scantling needful, than would be required, if bolts were introduced. Three-nail holes should never be bored in the timbers, in the ranges of the fastenings of the different decks. The latter fastenings are quite sufficient for the outside and inside plank, with a few additional bolts. It sometimes happens, that the most important timbers in those parts (and upon which the strength of the upper-works depends), is so perforated and weakened with tree-nail and bolt-holes, as to be scarcely strong enough to bear their own weight. Tree-nail holes should be kept dry, both before and after the tree-nails are driven. Whatever tree-nails are used, should be made of wood of the toughest, closets grain, and be always seasoned under cover. Pitch-pine tree-nails (which have been used in some of our men of war), are extremely weak. Under the torrid zone there is a choice of tough, close-grain woods. Persons might be sent abroad to make tree-nails from them: a ship-load of which would last the navy a considerable time. The Spanish and Portuguese rarely use tree-nails, and their ships are durable.
Bolts are certainly a more secure fastening; and they should be driven through both the inside and outside planks; and the points well secured, either by a clinch, by a ring and forelock, or nut and screw. — The screw-bolt is frequently used by the Dutch and the French. La Legurienne, a French brig of war, of sixteen guns, taken by the Petterell, in March, 1800, was fastened th[r]oughout with screw-bolts. A vessel was put up in France, by order of Bonaparte, which was fastened with screw-bolts, taken to pieces again, and stowed in one of the ships that accompanied him in his expedition to Egypt, with a view of being put together again in that country. The Spaniards use the spike-pointed bolt, and turn the end into the wood. The different modes of fastening, have each of them their advantages, according to local situations and circumstances. Where the strain tends, in a particular manner, to draw out the bolt, the forelock upon a plate is the strongest fastening of all. The clinch does very well for the lower fastenings of a ship, where the wood is not apt to shrink; and the screw-bolt is to be preferred above the water, where the parts secured require to be kept close together, but are liable to shrink. A ring, or plate, should always be introduced at the point of the bolt, for the nut to press against. These several fastenings should be used where best adapted.
The tree-nail is, in every respect, the most inferior fastening, with regard either to security, durability, or economy. In our woods, copper fastenings are the most durable, of the most permanent strength, and the least destructive to the timbers. In the end they are the cheapest fastening also that can be used in our ships. Their durability is such, that the same bolts will do for two or three successively, and lastly, for frame-bolts; and after their service is over, they will be worth nearly half as much as they cost at first. The only objection to copper-bolts is, that they are sometimes liable to loosed and start, from the straining of the ship; they should, therefore, be particularly well secured at the points.
The use of iron bolts and nails should be discontinued as much as possible, for the sea-water and the acid of our oak corrode and destroy the iron, and this in its turn decays the wood. There are but few woods with which iron agrees: in timber of an oily nature, such as teak, or live oak, iron will last for many years, without much rust from sea-water. In such woods, iron is unquestionably the best fastening. The teak will preserve iron some time from the corrosion even of copper; but in out woods, iron is highly pernicious in itself, and is of little durability. The Romans used brass, or copper, hardened, in building their galleys; but never iron, (the ancients had some method of rendering their copper hard, as out iron is hardened into steel); nor do the Chinese use iron in their vessels. The fastenings of the bottom and upper work, and fastenings of all the masts, should be of copper, and not of iron; in short, as few as possible of iron bolts or nails should be used in our ships; and particularly care is required that iron and copper fastenings should never come in contact in wood, for if the wet penetrates those parts, the wood will be destroyed, by the corrosive operation of the two metals on each other. The frame-bolts should all be of copper.
Isaac Blackburn: A Treatise on the Science of Ship-Building; with observations on the British Navy; the extraordinary decay of the men of war; and on the causes, effects, and prevention, of the dry rot; also on the growth and management of timber trees; The Whole, with a View to Improve. the Construction and Durability of Ships; James Asperne, London, 1817. pp 179-181.
Transcribed by Lars Bruzelius
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