Michael, You might get a few blank stares if you mention shipbuilding Grade 'A' steel, especially for inland waterway (narrowboat?)...
As always - your design will depend on the end use. Will the spuds be used to anchor, or to locate the vessel in mid-river say, or do you need to...
Are you sure the hull is steel? More likely to be rivetted wrought iron construction if your estimate of age is right
Don't just focus on the strength of the hull. Keep the practical / operational aspects in mind as well. Your main concern will be the thickness of...
I agree - cure the leak, it will be cheaper in the long run. If you do need to make structural repairs at a later date, after foaming a space,...
