Thursday, May 28, 2015

The Hamilton Graving Dock & Caisson

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Some time ago I wrote a piece about a Chapple Family trip to see the SS Nomadic in Belfast (short answer: Go! You’ll love it!). At the time I had wanted to mention a few other aspects of the site, but rather than shoehorn them in, I decided to leave them for another post.

The Hamilton Caisson in its cradle, awaiting restoration
I did mention that the SS Nomadic is now on display at the Hamilton Graving Dock, where she was most likely fitted out when she was first built during 1910 and 1911. However, what I did not mention was the apparently ugly, rusting … thing ... that shares the graving dock with Nomadic. I’d driven past here numerous times and had frequently noticed the rather grubby looking pile of metal at the north-eastern end of the dock. It looked like one of those medieval drawings – borderline caricatures – of ships that seem to have all the right parts, but in all the wrong proportions … and this was way too small to be a functioning ship. As we walked over towards it, we could see that the upper deck of decaying, moss-covered wood was home to a veritable tribe of pigeons. It was definitely very rusty, and partially splattered in tar. A sign on the side said ‘Harland & Wolff 1867’ and below it (which should have given it away) ‘Graving Dock Side’. I remained in my ignorance for a while longer until I got to see the information panels on the far side and found out that it was a caisson. After a number of increasingly extravagant attempts to pronounce the word ‘caisson’, I was eventually instructed by the SS Nomadic tour guide: thus.

The hull plate
In the oldest form of graving docks, entry was controlled via large hinged gates. While eminently practical, they did restrict the size of the vessel that could be accommodated. A caisson was essentially a form of gate to a graving dock that could be floated into position, and then flooded with water to sink it and close the dock. Once securely in place, the water in the graving dock could be pumped out, leaving a dry dock, and sufficient room to work on the exterior hull of a ship that would normally be submerged. Once the works were complete the graving dock was re-flooded and then the caisson was emptied and floated out of position. It was a simple, and extremely elegant solution to the problem!

The Alexandra Caisson in place (image borrowed from onsite signage)
The Hamilton is the oldest graving dock in Belfast and was named for Sir James Hamilton, JP (1815-1882) former Chairman of the Belfast Harbour Commissioners. The excavation and building of the dock cost £40,000, and work began in early 1864. A further £1,200 was spent on the pumping equipment, purchased from the well-known firm B. Hick and Sons, based at the Soho Ironworks in Bolton. The work on the graving dock was completed by February 1867, and was flooded through the adjacent Abercorn Basin in May of that year.

The Hamilton Caisson and the SS Nomadic
Not surprisingly, Harland & Wolff fabricated the caisson, identifying it as hull No. 50 on the company's internal registers. The ‘keel’ – which fits into a dedicated groove at the mouth of the graving dock and provides the watertight fit – was constructed of Greenheart wood (Chlorocardium rodiei) from South America, and was chosen as it is remarkably resistant to marine boring organisms, fungal growth, and all forms of decay. The wooden top deck, today so weathered and covered in pigeon droppings, was constructed of stout oak planking. The caisson was finished in July 1867, though it would have been completed sooner if they did not have to wait on the delivery of brass control valves from England.

The Hamilton Caisson with the Titanic Belfast and the
Harland & Wolff drawing offices in the background
Quite apart from being a fantastic piece of marine engineering, this caisson is believed to be the single oldest surviving Harland and Wolff hull. True, its iron is rusty, its wood is rotting, and it’s probably well on the way to being Northern Ireland’s premier guano accumulation, but it’s still pretty amazing. For now it sits in its purpose built cradle awaiting restoration. Even in its current condition it’s well worth a visit as part of your trip to see the SS Nomadic. Did I mention that it’s a great day out? You should really go & see it!

Detail of the stonework on the Hamilton Graving Dock
If you have the need (and the cash) Harland and Wolff will still make you a caisson: brochure