A Few Notes on Timber for Shipbuilding

Jack [surveyed] the harbour as a naval base – a fine roomy naval base, with fresh water just at hand, deep-water repairing docks, and any amount of timber, capital Valona oak. – The Ionian Mission by Patrick O’Brian

It seems fairly obvious to say that ships in Jack and Stephen’s day were made out of wood… Of course they were. But it’s easy to forget, yet impossible to overstate, the importance of the quality of the timber used in ship construction. Wood from the wrong kind of tree, or wood that hadn’t been properly seasoned, could lead to major disasters. These notes on timber are from a bit later than our period (1857), but the points still hold true (well, everything except the bits about machinery changing how timbers are bent but that’s not the point).

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The Timber chiefly used in the construction of a ship is oak, elm, fir, teak, larch, and mahogany. Timber is purchased by the load, a measure which contains 40 feet of rough timber, averaging in weight about one ton. An 80-gun ship consumes as many as 2000 trees, averaging about two tons each. Timber is divided into three sorts, viz., square, which is the full size of the tree, having only its sides squared off “thick stuff” which is square timber cut into different thicknesses from 4½ inches to 10, but the whole depth of the tree; and plank, which runs from 4 inches down to 1½ ; all under that size being called board.

Deals occur in lengths of 10,12, and 14 feet, varying in thickness from 3 inches to ½ inch, and averages 9 inches in breadth. Those which are ½ inch thick, are flat deals; 1¼ inch are whole deals. Kyanising and Burnettising are somewhat similar processes, by which timber, canvass, and cordage are so readily seasoned as to be preserved from the injurious effects of dry rot, mildew, &c., and premature decay. In the former of these, the article is steeped for a certain length of time in a solution of corrosive sublimate and water. In the latter, as used in Her Majesty’s dockyards, canvass and cordage are immersed for 48 hours in a solution of chloride of zinc and water, in a wooden tank, in the proportion of 1 pound of the chloride to 4 of water.

Timber is placed in a wrought iron chamber, which contains about 20 loads at once; and after the air is exhausted from both timber and chamber, by means of an air pump which is worked by a steam engine, the solution is forced into the timber by a Bramah’s forcing pump, which exerts a pressure upon it equal to 150 pounds on the square inch for eight hours. Unless wood is previously well seasoned, to char or paint it accelerates decay by preventing the natural escape of the juices; seasoning requires from two to eight years.

The difficulty and expense involved in procuring suitably curved timber for ship-building purposes, as well as the labour and waste incurred by “conversion,” seem about to be diminished by timber-bending machines. In these, straight timber, having gone through a process of steaming, is bent into the desired form; not only increasing its value, but economising time, and avoiding that impairment of strength which is consequent on cutting wood against the grain. We are told, for instance, that in one of these machines a piece of straight oak, 14 feet long and 16 inches square, whose value is about £3., after being bent into the requisite angle is enhanced to three times its value, and that ten such pieces may be thus shaped in as many hours.

MECHANICAL PROPERTIES OF MATERIALS USED IN CONSTRUCTION – TIMBER Timbers are joined; together by scarphing, morticing, halving, dovetailing, &c. and when great strength is required, it is usual to make use of coakings, bolts, and iron bracings. The strength of timber is variable, being affected nut only by its place of growth, but degree of seasoning. Trees that have been grown on mountainous districts are stronger than those grown on plains. Roots and trunks are stronger than branches.

Source : A Manual for Naval Cadets By John McNeill Boyd c. 1857.

Courtesy of P. Benyon.
Image: A Small Shipyard on the Thames by Francis Holman. With heartfelt thanks to Collin Cillis for the information!

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1 Comment on A Few Notes on Timber for Shipbuilding

  1. This is a great topic. Not only am I a naval history buff, I’m also a forester. Its been argued that one of the reasons leading up to the Revolutionary War was that the king considered all of New England as Crown Land. Surveyors would blaze a tall straight tree suitable for making a ships mast with three hatchet slashes known as the Kings Broad Arrow. Any colonist who cut it down could be hung. A brief but interesting read on the topic is here:

    http://www.nelma.org/files/File/Monographs/Broad%20Arrow.pdf

    Keep in mind that by the 1700’s much of the forests of England had been cut down and regrown several times. You can see this in the architecture of buildings that survive from the 18th and 19th century. The availability of long beams was limited leading to buildings that utilized spliced support beams and the need for ship masts to come from the colonies. Forests in the new world were older and had closer growth rings making them very strong. Much of the USS Constitution was old growth Live Oak a very strong, dense wood that grows in the southern states.

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