The practice of deliberately extending a vessel's life beyond its normal economic span. Motives may be religious, as with the Egyptian Cheops sepulchral ship; historical or patriotic, as with HMS Victory or USS Constitution; or utilitarian as with the 1897 river steamer Melik, now the headquarters for the Khartoum Sailing Club.
Without human intervention, ships decay steadily because of the hostile environment in which they usually operate. Sun, rain, and humidity are all hostile to a ship's structure, as is electrolytic action afloat. The Cheops ship has survived for more than 4,000 years thanks to the dry atmosphere of the tomb in which it was enclosed; and the almost original condition of the 1824 frigate Unicorn, now displayed at Dundee, can be put down to the roof which covered her weather deck for most of her life. However, Drake's Golden Hinde, perhaps the earliest example of ship preservation for patriotic reasons, soon decayed when displayed in the open air at Deptford following his circumnavigation of 1577–80. The fact is that a wooden ship open to the weather will require progressive replacement of its various timbers as they age and decay, so that, arguably, all that remains after many years is a replica ship of what was originally preserved. To avoid this fate, Amundsen's exploration vessel Fram has been totally enclosed in an exhibition building near Oslo, and other large museum ships may have to be similarly protected from the weather if they are to survive for posterity.
As a natural biocide, salt may actually extend the life of a wooden ship. During construction, merchant ships sometimes had rock-salt packed between their frames to deter rot. An old wooden ship will often survive longer if it can be kept working gently, so that its decks are sluiced regularly by salt water—in which rot-causing organisms cannot live—and fresh air is able to circulate below decks to deter dry-rot. Regular use also reveals any leaks or structural defects more quickly than when a vessel remains tied up for months or even years.
Vessels displayed alongside a quay for extended periods should be turned annually to equalize the exposure of each side to sun and wind. Rainwater encourages wet-rot in wooden decks, particularly where the vessels being exhibited are stationary, and there is no natural rolling to throw off the water. At Mystic Seaport Museum in Connecticut, vessels exhibited afloat benefit from a daily sluicing with salt water across their upper works to deter rot and shrinkage of timbers.
Steel corrodes steadily in a salty environment. Even with regular painting, the service life of a steel ship is about twenty years because of structural corrosion. Sacrificial anodes fitted to the external hull may inhibit electrolytic degradation if they are replaced regularly, but the waterlines of metal ships, where chlorides can combine with oxygen, are particularly affected by destructive corrosion. Wrought-iron ships fared better, and before the Bessemer process made steel widely available from the 1870s, wrought iron was frequently used in shipbuilding. Among the largest iron ships was Brunel's Great Eastern, still so strong when scrapped in 1888–90 that the labour of dismantling almost bankrupted her Merseyside shipbreakers. HMS Warrior, whose massive wrought-iron armour has contributed to her longevity, is another remarkable testament to the resistance of wrought iron to salt-water corrosion, and Brunel's earlier iron ship Great Britain survived nearly 50 years beached on the Falkland Islands, thanks to the durability of her riveted wrought-iron plates. But the ambient humidity within the dry-dock where she is now displayed in Bristol must be controlled if it is not to accelerate corrosion deep within her hull plates, where chlorides have penetrated over more than 150 years. A glass ‘roof’ is therefore being erected over her which will exclude rainwater from the dry-dock and help to inhibit further damage.
Subjects: Maritime History.