Wet Room question

[MunkeyBoy]

A boat I am considering buying has a wet room in it but the seller has said the box steel framing was removed from the shell to accomodate this wet room!

Am I right in thinking the box sections are part of the hulls structrural integrity and should not have been removed?

thanks.

[Paul C]

Yes, if its actually the box sections which make up the hull structure. It doesn't mean its necessarily less safe or strong though. For example campers have elevating roofs fitted which involves removing the roof struts, but the frame put in place restores the strength lost. Its not possible to say in a simple fashion what kind of frame would restore the strength of removed parts, but it would involve detailed engineering calculations.

[Neil2]

What sort of boat is it?

[MunkeyBoy]

Its a steel narrowboat.

[Neil2]

You wouldn't normally see square tube used in narrowboat "framing", maybe on the cabin sides, or the roof, - is that where it's been removed?

 

A lot of the structural strength of a narrowboat is in the plating itself, verticals and longitudinals are often there as much to support internal fixings as for structural strength, particularly with the heavy plating used these days. With an older more lightly built boat it might be different.

[MunkeyBoy]

Its been removed in the sides and base.

[Grace and Favour]

Its been removed in the sides and base.

I would be very cautious.

[Neil2]

I suspect the reason you're not getting many replies is because there are very few people who have a good grasp of the technical aspects of steel boat building. I wouldn't claim to be an expert but it is almost certainly the case that every narrowboat ever created was "overbuilt" and for one simple reason - weight is not an issue. With yachts and ocean going cruisers getting the weight right is very important, but even then there is a lot of discussion and disagreement about how much framing is actually necessary, and some boats are built with none at all.

 

The steel plating on most narrowboats is massive compared to other steel boats, and the only time you really have to be careful is if you plan to cut bits out of the hull/cabin eg if fitting a new window or hatch. I reckon most boats, certainly those built in the last 25 years or so, could lose quite a lot of their "framing" and it wouldn't make a scrap of difference. But I remember looking at a NB where at some point two side hatches had been cut directly opposite each other and the cabin sides and the roof were distinctly wavy, almost corrugated. Strangely the owner didn't seem to have noticed.

 

I've been on a few older boats that have this wet room arrangement, where the water drains into the bilge or a sump, Hancock and Lane boats typically had them though they were of course built like that from scratch.

[Paul C]

I suspect the reason you're not getting many replies is because there are very few people who have a good grasp of the technical aspects of steel boat building. I wouldn't claim to be an expert but it is almost certainly the case that every narrowboat ever created was "overbuilt" and for one simple reason - weight is not an issue. With yachts and ocean going cruisers getting the weight right is very important, but even then there is a lot of discussion and disagreement about how much framing is actually necessary, and some boats are built with none at all.

 

The steel plating on most narrowboats is massive compared to other steel boats, and the only time you really have to be careful is if you plan to cut bits out of the hull/cabin eg if fitting a new window or hatch. I reckon most boats, certainly those built in the last 25 years or so, could lose quite a lot of their "framing" and it wouldn't make a scrap of difference. But I remember looking at a NB where at some point two side hatches had been cut directly opposite each other and the cabin sides and the roof were distinctly wavy, almost corrugated. Strangely the owner didn't seem to have noticed.

 

I've been on a few older boats that have this wet room arrangement, where the water drains into the bilge or a sump, Hancock and Lane boats typically had them though they were of course built like that from scratch.

 

I'll half agree with you. I've heard stories of long (ie 65' or more) boats having minor issues with interior fittings when they're lifted out with a tractor/trailer. But then, if it were an issue longer boats would be plated on their bottoms with slightly more than 10mm, and shorter boats correspondingly less than 10mm.

[Neil2]

 

I'll half agree with you. I've heard stories of long (ie 65' or more) boats having minor issues with interior fittings when they're lifted out with a tractor/trailer. But then, if it were an issue longer boats would be plated on their bottoms with slightly more than 10mm, and shorter boats correspondingly less than 10mm.

That's true, but sort of reinforces what I was saying. Narrowboats are routinely lifted out of the water all the time yet when you consider that very few are built with keels/keelsons, there must be tremendous inherent strength in the plating to allow them to stand up to this.

 

Having said this, I remember when Hancock and Lane launched their "Norseman" design, there was a demonstration boat that was built with a full length keel because the boat was going to be moved around a lot by road and they were worried about hull flexing. I think if you wanted a boat to cope with this sort of treatment you might well opt for something similar.