My boat rocks too much!

[Boatman Al]

Hi everyone.

 

This is my first post in a while as I have been off the water for a year. Found myself back on a boat again at present. I have been refitting and refurbishing the interior over winter. One thing that is bothering me daily is the amount the boat rocks and leans when weight moves around.

 

A few factors that are worth noting. The build is a curious bespoke design. The bow is built in an inspection launch style. Very straight pointed bow. Almost like a ships front. The hull and cabin sides are steel. 6/6/4 with section on baseplate at front being 10.

 

However the most curious part of its build is the roof (not including cabin sides) is made of 18mm marine ply with solid hardwood beams running through the cabin inside. This apparently is how the original owners requested it to be built. It also has a very high cabin. Well over 6ft standing room.

 

A final factor as part of my refurb I removed a standing pump out tank which initially almost cause a capsize when re floated. A lot of slabs were used under subfloor to correct it.

 

Now my only thought is it needs more ballast but my front deck drains are about 2 inches at most from the water line. So I'm concerned about bringing it lower into water.

The draft is about 18 inches upfront and 20 inches at back.

 

It's like a pendulum when I step off the boat. Rocks so much. And it leans when turning.

 

I guess my question is how much of worry is this? How normal is it? And how much would additional ballast help the problem baring in mind I can't go much deeper into the water?

 

Any input might help me rest east at night! Thanks in advance.

[Ex- Member]

Seems to suggest top heavy then. Any n/b I get in rocks, then I'm 20 stone

 

That's why we're in a wide beam.

 

Don't know what to suggest though, if the roof has been done in quality ply, it will be heavy. I wouldn't like to comment on weather it's safe though.

 

It might just come down to. Can I live in a rocky boat?

 

Just out of interest, is the roof insulated, or is this ply part on the internal finish? I ask as you mentioned hardwood beams, they'll be heavy too.

Edited March 2, 2014 by Julynian

[bigste]

Not much use I suppose but instability is usually insufficient ballast, bad design or both.

[Neil2]

Just for clarification - this is a narrowboat right?

 

Is the hull bottom flat or "chined" and so do you know how wide it is? They do vary.

 

Are your water and fuel tanks empty/full/part full and is the water tank on the "floor" or does it sit at deck height?

 

6' head room isn't unusual, and the ply roof will be lighter than a steel roof.

 

Sounds to me like the drains are too low anyway but that is no big deal - there are ways to sort that without major structural works.

 

When you say it's like a pendulum, presumably you mean it rocks from side to side and takes a while before it settles, or does it heel right over and then right itself quickly?

 

 

[Grace and Favour]

This is the Hancock and Lane boat you bought a year or so ago, is it (and brought it down from Dewsbury?)

 

How did it handle on the journey - - ??

[Paul's Nulife4-2]

I was going to say, 'Change to Country then' buttthat's not very helpful.

 

I thiink it could be a case of a combination of Top Heavy,To much Windage and or not enough ballast as well, EG a simple combination of More Coal,Logs on roof, Empty Water,Fuel Tanks & Less Beer & Tinned food than usual will make a difference

Just think it through.

[Boatman Al]

Yh it's a narrowboat flat bottomed. Not the Hancock and lane I used to have. That handled like a solid tank. This is a one off build as far as I know.

 

Someone has speculated to me that 18mm marine ply would weigh more than 4mm steel over the space of the roof.

 

When I was re flooring I noticed there wasnt loads of ballast in there. I added about 26 slabs when I removed waste tank.

 

The boat is 45 ft. 1997 build.

 

Here a pic - https://www.dropbox.com/s/kwittm254uiwz61/Photo%2002-03-2014%2015%2015%2030.jpg

[Neil2]

Yh it's a narrowboat flat bottomed. Not the Hancock and lane I used to have. That handled like a solid tank. This is a one off build as far as I know.

 

Someone has speculated to me that 18mm marine ply would weigh more than 4mm steel over the space of the roof.

 

When I was re flooring I noticed there wasnt loads of ballast in there. I added about 26 slabs when I removed waste tank.

 

The boat is 45 ft. 1997 build.

 

Here a pic - https://www.dropbox.com/s/kwittm254uiwz61/Photo%2002-03-2014%2015%2015%2030.jpg

That's nonsense. Steel weighs ten times as much as ply, Even at 18mm I reckon your ply roof its at least half the weight of a 4mm steel roof.

[saxplayer]

The boat rocks too much ?

sorry for being flippant......but is she complaining !!!!!!

shaun

[Paul G2]

That's nonsense. Steel weighs ten times as much as ply, Even at 18mm I reckon your ply roof its at least half the weight of a 4mm steel roof.

 

4mm steel weighs 31.4kg/m2

 

18mm plywood comes in at about 11 - 12kg/m2

[Grace and Favour]

So - with a light roof, the boat still wallows too much when you're walking around her..

 

I wonder how thick the baseplate is?

 

and

 

I suggest she's insufficiently ballasted

 

It may very well be that as a 'one-off' build the designer/builders were insufficiently experienced, and it may be that a good once-over from more experienced eyes/surveyor would give the optimal recommendations?

[saxplayer]

Seriously a vessels stability gets very technical. if i remember my learning days its all about the "metacentric height" which is the distance between a ships centre of bouyancy and its centre of gravity.

[Paul's Nulife4-2]

Seriously a vessels stability gets very technical. if i remember my learning days its all about the "metacentric height" which is the distance between a ships centre of bouyancy and its centre of gravity.

Absolutly,,

Or Coal on the roof & lack of Ballast !.

 

[Naughty Cal]

Ours is a bit tippy as well but it's down to hull shape and bring a light boat. You get used to it after a while.

 

We find the slow lumbering movements of our friends narrowboats a bit off putting after being on NC who moves a lot but quicker.

[Leo No2]

I have about 3/4 of a ton to a ton of iron ballast available in Stoke Bruerne to the OP (or anyone in fact) who would care to make a donation to The Friends of the Canal Museum (http://www.friendsofcanalmuseum.org.uk) which is currently sitting on the uxter plate of Sculptor but needs to come off as Sculptor has been re ballasted - providing Mr Fincher doesn't want it as he has first refusal and I would honour that offer to him. You can get a vehicle alongside Sculptor if needs be. If anyone is interested please PM me.

[The Lockie]

Could it be the shallow draft. Our first boat had a 12mm baseplate and weighed in at just over 20 ton, however she only drew 19 inches and whilst great for getting round Tue shallow bits she bounced around like a good 'in and was a bugger to handle in windy weather, my mate has just boughtva Hudson with 34" draft and it's really solid in the water even going side to side inside to make it rock,is hard work!!!

[Arthur Marshall]

Mine has the whole of the front of the boat under the deck as the water tank, which is about eight foot long (tapering obviously at the front), as wide as theboat and a couple of foot deep. That's a lot of water to swish around and if you start it rocking it goes on for a while. I know some boats like this have a spoiler in the middle of the tank to slow the movement down.

[Mike Jordan]

It may be that the clue is in the reference to an inspection boat replica, often built with slim lines and chine hulls with long entry and exit to get swift and easy movement through the water. You can get a considerable improvement in movement by just reducing the width of the base plate but this is at the cost of stability. What is the underwater shape and size like when compared to the standard square box shape with sharp corners?

[Bee]

Pretty boat, It is very fine at the bow and probably has a long swim, bit like a destroyer. Coupled with a plumb stem and no flare the buoyancy will not increase much as it heels. The proportion of the boat that is full width is a lot less than a tubby, blunt boat.I would think that adding ballast would slow the roll down but i doubt if theres much else you can do.

Mike is right, we crossed in the post

Edited March 2, 2014 by Bee

[PhilR]

The boat is of an unusual design by narrowboat standard, although it is still rather attractive IMHO. The single curvature bow section is very fine but doesn't provide much self righting bouyancy. Is there a long underwater swim at the stern too?

 

I'm not surprised that the boat is *rocky*, but it probably moves very smoothly through the water? More ballast should improve stability, but I note your concerns about the 2 ins freeboard at the front deck drains. One ton of extra (evenly placed) ballast would probably take the drainage holes below water......... unless most of that ballast is placed towards the stern. But is there a weedhatch and what freeboard does it have?

 

Personally, I would be quite happy with a *rocky* boat. And some people prefer rocky boats to floating cottages :-)

[Neil2]

Seriously a vessels stability gets very technical. if i remember my learning days its all about the "metacentric height" which is the distance between a ships centre of bouyancy and its centre of gravity.

 

The metacentric height is actually the difference between the CoG and the Metacentre which is a point determined by the boats centre of buoyancy as it heels over.

 

It's complicated, but it explains how the rolling characteristics of a boat are determined by how much of it is in the water and how high the centre of gravity is.

 

With most narrowboats there is usually enough of the boat in the water which with a low CoG resists rolling pretty well, but as other have said, this boat seems thin, maybe a little tall, and possibly a bit narrower than the normal 6'10"?

 

The ply roof suggests the builder was aware the design of the boat might make her a little "tender" so he tried to keep the high up weight down.

 

Personally I wouldn't worry about it. Most boats do roll, and if she swims and handles well, unless she's dangerously unstable, which I very much doubt, I wouldn't bother messing with it.

 

You do get heavy deep draughted boats that feel like they are set in concrete when you step aboard but Yongala (have you googled it by the way...) wasn't designed to be that type of boat so don't try and make her something she isn't,

[Boatman Al]

Thanks for all the informative responses. Sounds like it could just be symptomatic of the design and build.

 

I'm only second owner of the boat and I've been told that it was designed and built and spent all of its life to date on the Thames. So would the design be a river design? When I had it out the water the prop was huge. Much bigger than needed for the boat size on the cut.

 

It's been one hell of a project. The inside was very badly fit out with MDF floor throughout. Which I replaced as had turned to mush. That may of also affected it I guess.

 

The toilet was a flush which drew raw water in from beneath the boat and was decrepit and out of use. The engine was raw water cooled and under water. Safe to say it's now keel cooled and all tip top. Toilet removed too which took 4 blokes to lift out the tank. It had been on an end of garden mooring on the river and pretty much not maintained since 1997. Shame cause it's a lovely craft. Bring it back to glory tho.

 

I feel a little better about the rolling now

[Naughty Cal]

Nowt wrong with raw water cooling. Far more efficient than whatever skin tank you have added.

Edited March 2, 2014 by Naughty Cal

[FadeToScarlet]

Nowt wrong with raw water cooling. Far more efficient than whatever skin tank you have added.

...but a lot more susceptible to plastic bags and general canal muck. Good with a proper mud box and strainer, but I.shan't be taking my.skin tank out and replacing the raw water cooling fittings any time.soon.

[Theo]

Your boat is too tender for your preference. As said before the metacentric height (GM) is too little. I doubt very much that it is likely to be dangerous fi you have adequate freeboard. GM will rapidly reduce if a deckedge is immersed and or you start taking in water through hull openings. In this case you could be in danger of capsizing. Have a look around the hull and see if there is any likelihood of her heeling so much that you start taking on water. If there is danger of things falling about in the boat then that could affect stability but that sounds rather extreme. Slack tanks can have an effect but you won't have any way of controlling that. YOu can't keep the fuel and water tanks permanently full!

 

As has said before: the only control that you are likely to have over the stability is to ballast the bottom more heavily. Cast iron is more dense than the usual concrete.

 

N