Draft and depth of Counter

[Gregarious]

The stern on our narrowboat is about 5" lower in the water than intended by Hull manufacturer. The counter sits 7" below the water and the draft is 28". Does this matter?

[nicknorman]

It means there will be more drag from the counter than necessary, slowing the top speed of the boat. Which probably doesn’t matter on canals, but might do on a river.

 

Also you need to check the water level in the weed hatch, it could be perilously close to the top. Ditto for any hull openings at the back, bilge pump, exhaust outlets etc.

 
How has this come about? 5” is a lot!

[Gregarious]

Thanks for that, it's a new boat, so we are trying to get sorted, but Hull manufacturer is blaming fitter out for not removing ballast, and fitter out is blaming Hull manufacturer, so we're getting nowhere, and not sure of how big a book to throw at fitter out (point of sale) !

[nicknorman]

16 minutes ago, Gregarious said:

Thanks for that, it's a new boat, so we are trying to get sorted, but Hull manufacturer is blaming fitter out for not removing ballast, and fitter out is blaming Hull manufacturer, so we're getting nowhere, and not sure of how big a book to throw at fitter out (point of sale) !

Hmmm doesn’t sound good, 5” is a lot of draft to add in a fit out! But maybe it’s a pivot thing, perhaps the boat is nearly out of the water at the front and adding some ballast at the front will level it, taking the stern up?

 

Be aware that there are rules in the RCD about vertical distance between hull outlets and the water line, can’t remember exactly what it is but needs to be right.

 

If it were me I’d want it properly sorted before parting with my cash.

[Gregarious]

Unfortunately the bow is quite low as well, but I haven't investigated that much yet!

[Alan de Enfield]

From the BSS :

 

 

To reduce the risk of your boat sinking if it keels over or is excessively weighed down, it's a good idea for privately owned boats to only have openings which are at a height of at least 250mm (10ins) above the waterline. Where openings are necessary below this level this risk can be reduced by ensuring that these openings are permanently and securely connected to ducts or pipes, which are watertight up to that level.

Self-draining cockpits may not be able to meet the 250mm (10ins) recommendation but, for privately owned boats, it's a good idea to stop water getting into other parts of the hull by incorporating non-return valves in the drains and/or having bulkheads or cills up to a height of 150mm (6ins).

A weed hatch, if not properly secured, can allow water into the bilges of a boat, which could ultimately cause it to sink. It's advisable for privately owned boats to have a secure and watertight weed hatch which reaches to at least 150mm (6ins) above the waterline, when the boat is loaded up as normal. [10.3]

 

 

 

 

From the RCD guidance notes :

 

Through-hull openings :

 

Different editions of the Recreational Craft Directive harmonised standard ISO 12217 (Stability and Buoyancy) have included minimum downflooding heights. Various factors influence the minimum downflooding height, but as a rule the minimum equivalent height (above a fully laden waterline) is 400mm

Edited November 5, 2021 by Alan de Enfield

[MtB]

58 minutes ago, Gregarious said:

Thanks for that, it's a new boat, so we are trying to get sorted, but Hull manufacturer is blaming fitter out for not removing ballast, and fitter out is blaming Hull manufacturer, so we're getting nowhere, and not sure of how big a book to throw at fitter out (point of sale) !

 

Did you instruct these two firms yourself, and separately? Or did the hull manu subcontract out the fitting to the fitter?

 

If the former then I think this makes you "the boat builder", and the responsibility for considering ballast is yours rather than either of the other two parties. 

 

If the latter, then responsibility lies with whichever is/was the main contractor.

 

[nicknorman]

27 minutes ago, Gregarious said:

Unfortunately the bow is quite low as well, but I haven't investigated that much yet!

I would want to check the height of the gas locker drains above water, assuming it has gas in a bow locker.

Anyway, it sounds like ballast needs to be removed, which shouldn’t be that difficult especially in hidden floor areas such as under beds, cupboards etc.

 

When we got our new boat, it was level. But most of the cupboards/storage is on the port side, so by the time we had loaded all our “stuff” it was flying left wing low. The builder took out some ballast on the port side to level it up.

[Bee]

If it was fitted out on dry land it can be hard to know where a boat will settle when craned in but 5" is a lot, o a 70` working boat that will be 5 tons or so, on a 6` 10" boat that is likely to be even more so there is no point in dragging that lot around the canal system. Getting rid of some ballast SHOULD be easy, just lift up the floor and chuck some out. If the floor is sheets of ply just screwed down and everything built on top then whoever did that should be condemned to cutting out panels with a blunt breadknife so he / she learns that this is a boat and not a small bungalow and boats' floors need to come up.

[Tam & Di]

For interest, what is the size of boat and the nature of the ballast? It does seem to be ridiculously low in the water from what little you say.

 

Tam

[Alan de Enfield]

Just now, Tam & Di said:

For interest, what is the size of boat and the nature of the ballast? It does seem to be ridiculously low in the water from what little you say.

 

Tam

 

 

It does seem odd that even when sat 7" too low in the water it still only has a draft of 28".

Trimmed correctly that could make it only 21" draft and would be very sensitive to wind, people moving about and even steering could be a problem.

[nicknorman]

3 minutes ago, Alan de Enfield said:

 

 

It does seem odd that even when sat 7" too low in the water it still only has a draft of 28".

Trimmed correctly that could make it only 21" draft and would be very sensitive to wind, people moving about and even steering could be a problem.

It’s 5” too low, counter is normally 2” under, making it 23” nominal. Modern Narrowboats can be very shallow drafted, I don’t think 23” is abnormal.

Edited November 5, 2021 by nicknorman

[MtB]

 

The swim height (i.e. height of the uxter plate above the baseplate) on all three of my current boats is 24". On my first two narrowboats it was 18". 

 

I suspect yer average bargain basement Collingwood shell with a little Beta engine is gonna be 18". A better quality shell will prolly be 24" in order to fit in a sensibly large propeller. But for any boat to be 5" too low in the water on first launching seems like a terrible mis-judgement on the part of the builders. Any builder who has done a fair few boats will know roughly what to put in to get it right, so the question has to be, who decided what ballast should be put in there at the build stage? 

 

If this is a 70ft boat and 5 tonnes of ballast needs removing, that is going to be no easy task. There probably isn't 5 tonnes in there in the first place.  

[MtB]

 

2 hours ago, Gregarious said:

The counter sits 7" below the water and the draft is 28".

 

^^^This^^^ suggests the swim height on this boat is 21".

 

Depends on how exactly the 28" draft has been measured though. Is it with a tape hooked under the baseplate, or to the bottom of the skeg? 

[David Mack]

2 minutes ago, MtB said:

 

If this is a 70ft boat and 5 tonnes of ballast needs removing, that is going to be no easy task. There probably isn't 5 tonnes in there in the first place.  

A 70 ft shell + engine + fitout with no ballast is going to be a hell of a lot shallower draft than 28", so there must be a lot of ballast in there.  Whether enough of it is accessible to be removed without wrecking the interior is another matter!

[MtB]

Just now, David Mack said:

A 70 ft shell + engine + fitout with no ballast is going to be a hell of a lot shallower draft than 28", so there must be a lot of ballast in there.  Whether enough of it is accessible to be removed without wrecking the interior is another matter!

 

Yes I agree. 5 tonnes of ballast is a massive volume of bricks and somehow I doubt that is what's in there. Or if it's steel then the cost would have been massive instead! 

 

Something seems wrong here making me think this is not a 'normal' narrowboat. Perhaps the OP could fill in some of the missing details please. 

[Tracy D'arth]

Shorter the boat = More sensitive to ballasting.   What is the boat?

[Mike Tee]

1 hour ago, MtB said:

 

Did you instruct these two firms yourself, and separately? Or did the hull manu subcontract out the fitting to the fitter?

 

If the former then I think this makes you "the boat builder", and the responsibility for considering ballast is yours rather than either of the other two parties. 

 

If the latter, then responsibility lies with whichever is/was the main contractor.

 

I don't think we ever got an answer to this ^^^

If it were me, I'd be tempted to invest a few hundred quid and get an experienced surveyor in to get a professional opinion - a new boat these days is an awful lot of money to be not right.

I know its well and truly after the stable door has been shut, but anyone having a new boat built (who doesn't have lots of boat experience) would be well advised to get a surveyor in to monitor the build at various stages.

[MtB]

21 minutes ago, Mike Tee said:

I don't think we ever got an answer to this ^^^

If it were me, I'd be tempted to invest a few hundred quid and get an experienced surveyor in to get a professional opinion - a new boat these days is an awful lot of money to be not right.

I know its well and truly after the stable door has been shut, but anyone having a new boat built (who doesn't have lots of boat experience) would be well advised to get a surveyor in to monitor the build at various stages.

 

I suspect we are not getting an answer because the OP is actually "the builder" going by the rules of the RCR, so neither the shell builder nor the fitter is responsible. The OP is. I suspect he has already been told this by both the hull builder and the boat fitter and there is no need to employ a surveyor to find this out. 

 

My reading of the situation is perhaps the shell builder actually built the shell and supplied it as a "sailaway" with engine fitted, ballast laid, floors down, spray foamed and lined, ready to launch. But then the OP then employed a boat fitter to fit it out before launch, which has turned out to be a Big Mistake and now he is looking for someone to "throw the book at".

 

All just a guess though, and would be interesting if the OP could clarify the details please. The board could then go on to explore some solutions.

 

Edited November 5, 2021 by MtB
Spelling, and to add a bit.

[Alan de Enfield]

For the sake of completeness here is the relevant extracts for downflooding heights to comply with the RCR.

 

Canal boats are generally "Cat D" craft, so the 400mm is standard, irrespective of hull length

 

Point "C" in the text allows for any watertight piping from the fitting to an increased height inside the hull to be included in the Downflooding height measurement.

 

 

 

[David Mack]

So the RCR requires downloading protection to 400mm above normal loaded water level (whereas the BSS specifies 250mm and accepts that self draining cockpits may be less than that).  So how does any new narrowboat with a self draining cockpit comply with the RCR?

[ditchcrawler]

5 minutes ago, David Mack said:

So the RCR requires downloading protection to 400mm above normal loaded water level (whereas the BSS specifies 250mm and accepts that self draining cockpits may be less than that).  So how does any new narrowboat with a self draining cockpit comply with the RCR?

I didn't know it was a BSS requirement at all 

[Alan de Enfield]

2 minutes ago, ditchcrawler said:

I didn't know it was a BSS requirement at all 

 

Only for commercial boats, it is a recommendation for private boats.

This can be one reason why a private / pleasure boat can struggle to be adapted to meet the requirements to achieve a hire boat BSS / Licence.

10 minutes ago, David Mack said:

So the RCR requires downloading protection to 400mm above normal loaded water level (whereas the BSS specifies 250mm and accepts that self draining cockpits may be less than that).  So how does any new narrowboat with a self draining cockpit comply with the RCR?

 

I don't write the rules.

 

Is it just another example of an RCR declaration being falsely (fraudulently) made ?

[Iain_S]

13 minutes ago, David Mack said:

So the RCR requires downloading protection to 400mm above normal loaded water level (whereas the BSS specifies 250mm and accepts that self draining cockpits may be less than that).  So how does any new narrowboat with a self draining cockpit comply with the RCR?

Could be done by raising the threshold of the front doors.

[ditchcrawler]

15 minutes ago, David Mack said:

So the RCR requires downloading protection to 400mm above normal loaded water level (whereas the BSS specifies 250mm and accepts that self draining cockpits may be less than that).  So how does any new narrowboat with a self draining cockpit comply with the RCR?

The same way as the navigation lights and diesel tank inspection hatches