Copper bolts and sheathing of ships
In 1761 the Royal Navy began to experiment with the sheathing of wooded ships with copper. The frigate Alarm was the first to be so treated. The idea was to construction an outer layer on the underwater parts of a ship’s hull to protect it from damage, fouling and attack by various pests. The initial trails suggested that the copper sheathing was “very neat, not heavy or expensive” and as it remained clean it gave greater speed at sea, much longer periods at sea between repairs and less time for repairs in dock yards.
One of the ships that was sheathed with copper was Nelson’s flagship the Victory which was built in 1785.
These features gave considerable advantage to the British ships during the war of American independence, the French Revolution and Napoleonic wars. An act of parliament was passed to allow the government to prohibit the export of copper, to ensure that it’s Navy could be fully supplied with copper sheathing.
However, by 1782 copper sheathing was about to be abandoned due to the loss of a number of ships. In 1780 HMS Royal George was at anchor in Portsmouth Harbour. Suddenly the ship’s hull parted in the area of the water line. The 900 people on board all lost their lives. the inquiry that followed decided that the Iron bolts used to hold the copper sheathing to the wood had rusted by a reaction between the Iron and copper. This in turn had rotted the timbers underneath.
Thomas William, realizing that a large market for copper was in danger of being lost encouraged several people to investigate the problem. The work of Westwood in hardening and shaping bolts by the use of rollers with graduated groves of reducing size and the use of cooling water during the annealing process and Collins in the actual bolt manufacture, lead to a new patented bolt being offered for sale by Williams in 1784.
In August 1783 the Admiralty decided on further trails for copper sheathing using the Westwood copper bar and Collins bolt production process. The trails were so successful that in 1784 the Admiralty ordered that all new ships were to use the patented copper bolts. In addition, the iron bolts of old ships were also to be replaced with copper. The patent meant that only Thomas William’s yards could supply the copper bolts and it made sense for them to supply the copper sheathing at the same time. By 1784 a contract for 25,000 bolts were week was obtained by Thomas Williams who was actually supply 40,000 per week.
At Holywell copper cake from the Ravens head smelter was rolled between the rollers of a cast iron mill. each roller was 18” in diameter and 4’6” long. the water wheels used to turn the mills also drew out the copper bolts. After preheating in a reverbatory furnace the copper for sheathing was passed thought the rollers repeatedly with a smaller gap between each time. Eventually the copper emerged as a thick ribbon 6 times its former length. It was then cut with water driven shears. The bolts were rough cut by hand and then finished off with a water driven tilt hammer. A 10-foot bolt could be made perfectly round in around 1 minute.
However, Thomas Williams was also after other orders, he had sales teams in Europe and soon sold to the French, Dutch and Spanish navies.
It has been estimated that a typical ship at the time would use around 11 tons of copper sheathing, 1 ton of nails and 20 tonnes of copper bolts. This amounted to around 34 tonnes per ship. The navy had upwards of 700 ships which required re-sheathing every 4 years.
In addition, soon merchant ships also required the same sheathing techniques especially if they were sailing to tropical waters were wood clinging and boring pests made copper sheathing and fastening even more economical. It has been estimated that copper sheathing could result in a saving of £2000 per voyage. Most of this saving came in quicker speed, less time in dock for repairs and a reduced journey time from West Africa to West Indies. This reduced the number of slaves lost in the journey which again improved profits.
By 1800 Thomas Williams agents were responsible for sheathing 105 ships per year at Liverpool. In addition, he had 30 to 40 ships carrying copper ore and sheathing from Amlwch Port to Holywell and Liverpool.