Convertible catamaran widebeam

[Tacet]

4 hours ago, Steilsteven said:

I've often mentally toyed with is idea in the past but realised that there is no great advantage to be had.

It amounts to creating a vessel with the disadvantages of both a narrow boat and a wide beam.

 

Keith

Two narrow boats joined by RSJ at the stem and stern (bolted though the cants?) would be an aid to stability for those adventurous trips we all toy with.  Less chance of a total engine failure too.

Unbolt when you get to the continent.

[Ray T]

[MtB]

8 hours ago, BoatFortress said:

can you take two 6ft width narrowboats and convert them into a 12ft width convertible catamaran?

 

I'll be impressed if you can find two 6ft width narrowboats. They are normally 6ft 10in, which takes you to 13ft 8in. 

 

I think I know of one, a historic....

 

Apologies if this point ha been made before. I had a quick scan through the thread but didn't notice it. 

 

 

[Bacchus]

Hull speed in knots = 1.35 x the square root of the waterline length in feet

 

so for a 65' narrowboat or widebeam, 1.35*8.06  = 10.88

for the 65' twin hull 1.35*11.40 = 15.39

 

So the cat could go faster, or should use less fuel at the same speed?

 

(obviously i am not advocating cruising at 15 knots (18mph) on the canals...)

[Sea Dog]

For the first few posts here I was wondering why folk were responding to what was clearly a wind up. I'm starting to think it might not be...! 

[blackrose]

1 hour ago, Tacet said:

Two narrow boats joined by RSJ at the stem and stern (bolted though the cants?) would be an aid to stability for those adventurous trips we all toy with.  Less chance of a total engine failure too.

Unbolt when you get to the continent.

 

I asked the question before, but what's the point of bolted joints? If you want to breast two boats together why not just use ropes? Seems a lot simpler and easier.

Edited December 11, 2022 by blackrose

[blackrose]

3 minutes ago, Sea Dog said:

For the first few posts here I was wondering why folk were responding to what was clearly a wind up. I'm starting to think it might not be...! 

 

I don't think it's a wind up because when I lived on a narrowboat 25 years ago I had the same idea. Then I realised it was a silly idea.

[Jerra]

12 minutes ago, blackrose said:

 

I asked the question before, but what's the point of bolted joints? If you want to breast two boats together why not just use ropes? Seems a lot simpler and easier.

Surely that would mean you had to have two licences but a rigid joint which couldn't be quickly and easily undone might count as a single boat.

[Sea Dog]

11 minutes ago, blackrose said:

Then I realised it was a silly idea.

Hence why I thought it was a wind up...

[David Mack]

4 hours ago, BoatFortress said:

 

 

 

The vast majority of narrowboats have flat bottoms, with the internal floor only a few inches above. So the internal floor is usually below water level, meaning the cross-boat platform would have to be quite a lot higher than the internal floor.

[Murflynn]

we're waiting for your response about the extent your experience of a narrowboat on the canals, if any. 

the plan and cross section drawings that you provided suggest that you don't even know the shape of a narrowboat. 

[MtB]

4 hours ago, Murflynn said:

we're waiting for your response about the extent your experience of a narrowboat on the canals, if any. 

the plan and cross section drawings that you provided suggest that you don't even know the shape of a narrowboat. 

 

Let alone how wide they actually are.

 

 

[Jess--]

as others have pointed out the majority of narrowboats are flat bottomed, this means that your floor height inside the boat will be anywhere between 1 & 2 feet below the water line (depending on type of boat).

For current boat safety regs any hull opening should be a minimum of 10 inches above the waterline, this means that your access between the 2 boats would involve climbing over a barrier somewhere between 2 & 3 feet tall.

Even if you go ahead you may find that your boats start to buckle around the area of the access because you have cut away part of the hulls, the gunwales (the step at the bottom of the cabin side) isn't just there to walk along, it provides a substantial part of the structural strength to a narrowboat hull.

 

In all seriousness my advise to you is just buy a widebeam, in the long term it will save you money as you won't have to license, insure, and maintain 2 boats and at some point in the future when you decide to sell the boat (whether to get something different or leaving the water) you will have one "normal" boat to sell rather than 2 unusually modified boats that have to stay together and will get raised eyebrows for any buyers survey.

 

In the pic attached the internal floor would probably be at the height of the top of the grey section

anything in the red section would be underwater

the lowest point you could cut the hull would be around the height where you can see the 2 round outlets.

 

Edited December 12, 2022 by Jess--