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Black Water Tanks

I am currently designing a narrow boat that has a cross-passage around midships, hoping to utalize the space under the steps leading to the side doors as holding tanks, can thease be part of the superstructure or am i asking for future problems?

Asked by: a pumfrett  | 8.01pm, Wednesday 11 November

WW says:

As with so many things, opinion is divided on this one. Some argue that the contents of the holding tank are very corrosive. This is serious enough if the tank is free-standing but, if it is an integral part of the shell, it could result in pitting on the hull sides or even holes forming.
On the other hand, one well known boatbuilder once reported that he had cut a boat in half to lengthen it and found that the integral holding tank was the best preserved part of the whole boat. He reckoned it had been pickled by the contents. Nevertheless, I would tend to err on the side of caution and make the tanks free-standing.
Placing the tanks under the steps may seem an ingenious solution but there is a lot to be said for keeping things simple if you can. A single, rectangular tank at low level will be easier to construct, easier to pump out and has one set of connections. It also ensures that the centre of gravity is as low as possible.

Graham Booth  | 2.06PM, Saturday 14 November

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