Capsize Safety

[steelaway]

Hi All

 

Does any one know what angle is acceptable for narrowboat to tilt left/right - front/back before it is in danger of capsizing.

Is there a degrees of angle test for stability, from what angle should it right itself.

I realise the height of drains and the bow are a factor.

 

Alex

[Hairy-Neil]

I would be inclined to say that with the low centre of gravity the concrete ballast gives you, you're fairly safe from capsise full stop. There would always be an angle at which water would enter the vessel through deck well drains, engine cooling vents and fridge flues, causing it to take on water and eventually sink......

 

I have known boats be hoisted out of the water by a lock sill till you could see the underside of the baseplate with no untoward damage or great risk of sinking.

[blackrose]

I would be inclined to say that with the low centre of gravity the concrete ballast gives you, you're fairly safe from capsise full stop. There would always be an angle at which water would enter the vessel through deck well drains, engine cooling vents and fridge flues, causing it to take on water and eventually sink......

 

I have known boats be hoisted out of the water by a lock sill till you could see the underside of the baseplate with no untoward damage or great risk of sinking.

 

I don't understand Hairy? Surely most sorts of vessels will capsize given adverse conditions beyond which they were designed for? However, you're probably right that a NB would sink due to water entering before it would capsize.

 

The RCD Annexe 3 Declaration than came with my widebeam sailaway states that the hull was not designed to encounter wave heights of more than 0.5m. I've taken it through bigger waves than that on the Thames in central London - I think they were probably about 0.8m, and I certainly wouldn't want to be in anything bigger than that.

[DHutch]

Interesting question.

- Gary posted a presentation explaning the basics of stablity calculations, center of gravity, metacentric height, etc. Although im not sure that stated an angle.

 

Its true that naterally narrowboats can be considered supprisingly stable given there shape. Partiularly the deeper draughted ones.

 

However its still got to be well worth considering is, as you are, the calcs where done on emilyanne and tested ater she was built.

 

 

 

Daniel

[Chris Pink]

Hi All

 

Does any one know what angle is acceptable for narrowboat to tilt left/right - front/back before it is in danger of capsizing.

Is there a degrees of angle test for stability, from what angle should it right itself.

I realise the height of drains and the bow are a factor.

 

Alex

 

'ere go, bedtime reading;

 

http://en.wikipedia.org/wiki/Metacentric_height

http://www.fas.org/man/dod-101/navy/docs/s...ca/stg4-01.html

[steelaway]

'ere go, bedtime reading;

 

http://en.wikipedia.org/wiki/Metacentric_height

http://www.fas.org/man/dod-101/navy/docs/s...ca/stg4-01.html

 

 

 

Thanks for that Chris but I nodded of reading it all!

 

Could you be so kind as to work it all out for me, cant seem to keep my eyes open.

6'10" wide 50' swim 26" drought ect ect

 

I actually thought some might have an angle for a standard (?) narrowboat - 25degrees - 35 degrees - 45 degrees

 

Silly me

 

Thanks again Chris

Alex

[Hairy-Neil]

I don't understand Hairy? Surely most sorts of vessels will capsize given adverse conditions beyond which they were designed for? However, you're probably right that a NB would sink due to water entering before it would capsize.

 

Didn't notice any mention that the OP was planning on going to sea in his narrowboat.....

 

I understand the term capsize to mean overturn, turn upside down. I can't see this happening to a narrowboat on inland waters as, being heavily ballasted at the bottom, they are always goint to right themselves until such times as they take on water to the point that the shipped water outweighs the ballast.

[ChrisPy]

I understand the term capsize to mean overturn, turn upside down. I can't see this happening to a narrowboat on inland waters as, being heavily ballasted at the bottom, they are always goint to right themselves until such times as they take on water to the point that the shipped water outweighs the ballast.

.... exactly.

 

the RCD considers the risk is associated with 'downflooding' - water entering through openings in the hull, which is the first point at which the innate stability of a ballasted boat is compromised.

 

the other factor is that the ballast may shift to a point that the boat will never come upright again. That depends on how much the boat is shaken about and how well the ballast is secured.

 

I would set the limit at 'just before water enters the engine space vents', or whatever is the lowest opening. So you must work it out for yourself!

Edited February 20, 2008 by chris polley

[blackrose]

Didn't notice any mention that the OP was planning on going to sea in his narrowboat.....

 

I didn't notice any mention in my reply about going to sea in a narrowboat either.....

 

Of course if you use any vessel in conditions within its design capabilities there's no reason it would capsize.

Edited February 20, 2008 by blackrose

[Gary Peacock]

There is a short presentation on the subject below-

 

Powerpoint version

 

PDF version

 

Narrowboats have lots of issues when it comes down to compliance with the RCD (They just don't fit the envisaged mould!) and stability is one of the issues we had to alter are basic design to give a better margin.

 

You really need the software to look at stability prior to the build or a copy •ISO-12217-1 and then do a Offset-load test. (It is a bit more involved than it sounds and is a bit like closing the stable door after the horse as gone if it fails though!)

[dove]

Thanks for that Chris but I nodded of reading it all!

 

Could you be so kind as to work it all out for me, cant seem to keep my eyes open.

6'10" wide 50' swim 26" drought ect ect

 

I actually thought some might have an angle for a standard (?) narrowboat - 25degrees - 35 degrees - 45 degrees

 

Silly me

 

Thanks again Chris

Alex

 

When the Sea Otters were in the prototype stage a chap called Andrew Linall did a computer calculation with some software he had. The angle came out at 120deg. I'm sure it would sink before it got to that. I don't think it matters what the calculated angle it's where the lowest hole is! that will give you the angle.

 

Andrew

[WJM]

We learned it all in kindergarten - Weebles wobble but the dont fall down!

 

If you could seal a narrowboat up and secure the ballast then it will right itself from a totally inverted position.

[Chris Pink]

Could you be so kind as to work it all out for me, cant seem to keep my eyes open.

 

From reading the Coastguard stuff, I understand that they have tables for that kind of thing with different types of warship shape, so if you find me the tables.......

 

And I've have a couple of experiences that imply that the stability of a narrow boat is not a given. And there is a wonderful picture that i have been searching for of a family stood on the side of their horse boat in a gauging dock because they put the weights in wrong.

 

So I agree with Gary, it is an issue. But if you copy an existing design/loading/ballast configuration then all should be well. Worth noting that coal bags or logs on the roof make a large difference.

 

If you could seal a narrowboat up and secure the ballast then it will right itself from a totally inverted position.

 

Someone's not taking this seriously. (and hasn't read the Wiki entry)

Edited February 20, 2008 by Chris Pink

[dove]

From reading the Coastguard stuff, I understand that they have tables for that kind of thing with different types of warship shape, so if you find me the tables.......

 

And I've have a couple of experiences that imply that the stability of a narrow boat is not a given. And there is a wonderful picture that i have been searching for of a family stood on the side of their horse boat in a gauging dock because they put the weights in wrong.

 

So I agree with Gary, it is an issue. But if you copy an existing design/loading/ballast configuration then all should be well. Worth noting that coal bags or logs on the roof make a large difference.

Someone's not taking this seriously. (and hasn't read the Wiki entry)

 

Well, I havent seen a narrow boat floating upside down yet, anybody else?

 

best thing to do is a tank test, I'm not into design theory

 

Andrew

Edited February 20, 2008 by dove

[Hairy-Neil]

And I've have a couple of experiences that imply that the stability of a narrow boat is not a given. And there is a wonderful picture that i have been searching for of a family stood on the side of their horse boat in a gauging dock because they put the weights in wrong.

 

There's also the case of the town class motor, Yeoford? that was fitted with round tanks with the intention of carrying lubricating oil for Duckhams. As the tank was filled the vessel became unstable and the boat capsised. I also recall a case that resulted in an inquest, where a small plastic cruiser was overloaded with a serious amount of additional passengers sitting on the roof, causing it to capsise

 

And there is a wonderful picture that i have been searching for of a family stood on the side of their horse boat in a gauging dock because they put the weights in wrong.

 

Try 'Historic Waterway Scenes, London and South East England', Martyn Denney.

Edited February 20, 2008 by Hairy-Neil

[Neil@CanalVoyagers]

Why not go along to one of the remaining CBA Stability Testing Days and find out more? They've been running for the last couple of weeks; 'Stability Consultant' Andrew Blythe provides a demonstration and teaching session followed by a Q&A. £55 per person.

 

Remaining courses:

 

27th February – Napton Narrowboats, Napton Marine, Stockton, Southam, Warwickshire, CV47 8HX

Demonstration sessions will run from 2pm – 3:30pm & 3:30pm – 5pm

 

28th February – JD Boat Services, The Wharf, Watling Street, Gailey, Staffordshire, ST19 5PR

Demonstration sessions will run from 3:30pm – 5pm

[blackrose]

Why not go along to one of the remaining CBA Stability Testing Days and find out more? They've been running for the last couple of weeks; 'Stability Consultant' Andrew Blythe provides a demonstration and teaching session followed by a Q&A. £55 per person.

 

Remaining courses:

 

27th February – Napton Narrowboats, Napton Marine, Stockton, Southam, Warwickshire, CV47 8HX

Demonstration sessions will run from 2pm – 3:30pm & 3:30pm – 5pm

 

28th February – JD Boat Services, The Wharf, Watling Street, Gailey, Staffordshire, ST19 5PR

Demonstration sessions will run from 3:30pm – 5pm

 

Sounds like a great day out - fun for all the family!