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thickness of hull etc.

Can someone who knows tell me the exceptable thickness of a narrow boat hull,sides etc. I am aware the magic 10-6-4 but what is acceptable? Thanx in advance.

Asked by: Andy Durler  | 5.59pm, Monday 6 January

WW says:

The minimum thickness for the underwater surfaces of a narrowboat is 6mm; but most builders usually use thicker steel than this, especially for the bottom. The extra weight of a thick bottom plate also reduces the ballast requirement.
With the cabin sides as with most things there are compromises to be made; thicker steel gives nice smooth sides as it does not buckle, but too much weight high up in a boat will make it rock more, so 4 or 5mm is generally used as 3mm tends to show ripples. The roof can be 3mm as the curvature gives good strength.
Thicker steel under the water gives more resistance to pitting, but there is no substitute for a decent coat of paint at regular intervals.

Rupert Smedley  | 8.17PM, Monday 6 January

Thicker bottom plates (anything up to 25mm) can reduce ballast and reduce rolling, especially in finer-shaped hulls. However, they require far more expertise to weld correctly and so are rarely done.
Too thick a plate for the superstructure can make a boat top-heavy and prone to rolling, which is exacerbated if the cabin height is tall, and the underwater draught is shallow.

Mark Langley  | 12.09PM, Tuesday 7 January

Readers say:

Thanx Rupert very helpful answer yet again

Andy Durler  | 9.07PM, Monday 6 January

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