Ballast

[embis]

Hi,

We are having some work done on our narrowboat; pullman dinette and a cross bed adding. This makes me wonder whether the end result will mean that the boat ends up being slightly out of trim. We have kitchen units, & pullman dinette on the same side of the boat

I will be having a trap added so I can access the bilge and was wondering about how feasible it is to redistribute ballast if I can reach it from the trap?

If I take some ballast out from one side of the boat, should I secure that remaining somehow so it doesn't shift?

 I notice that we have some concrete bricks piled in the lockers fore and aft I assume these are correcting trim and assume that the ballast in the bilges will also be concrete bricks.

[dmr]

Not much chance of removing the main ballast. Most likely need to take up a lot of floor rather than just making an access trap.

There are steel cross members every few feet on the baseplate so you will only get access to one section of the ballast. It might be complete paving slabs so not easy to get out through an access trap. Removing a few of those concrete bricks will likely be enough.

...............Dave

[embis]

3 minutes ago, dmr said:

Removing a few of those concrete bricks will likely be enough.

...............Dave

Thanks Dave,

Unfortunately the concrete bricks in the lockers fore and aft are on the  side I will have to add ballast to... maybe i just have to accept having less room in the lockers and add a few more bricks there!

Edited April 20, 2017 by embis

[john6767]

4 minutes ago, embis said:

Thanks Dave,

Unfortunately the concrete bricks in the lockers fore and aft are on the  side I will have to add ballast to... maybe i just have to accept having less room in the lockers and add a few more bricks there!

Swap the bricks for steel ballast, more dense, so you you will get more mass in the same volume.

[dmr]

2 minutes ago, john6767 said:

Swap the bricks for steel ballast, more dense, so you you will get more mass in the same volume.

I was just saying that but you got in first!!

Steel is about three times as dense as concrete. You could get some 56lb weights but they are becoming costly antiques these days. I think somebody often advertises steel blocks in the canal magazines, these will pack together quite nicely. Railway track is also common but does not pack (tesolate) that well

...............Dave

[WotEver]

11 minutes ago, dmr said:

does not pack (tesolate) that well

I've played that!

[system 4-50]

Some 56lb steel weights have a big hole in the middle which reduces their overall density but they pack very nicely in sets of 4 in my bilge spaces. To move them around easily without risk of strain thread a strap or rope through the handles so you can lift them while standing up. I put mine in Waitrose self-sealing plastic bags which fit exactly, but I am not sure why I did it.

I find that high weight has a bigger effect than weight at floor level in upsetting my trim. Leaving a few broads resting against the side of the cabin has a suprisingly large effect.

Some tractor (fork lift??) balancing weights have smaller holes and look as if they would work well.

Ed. I wondered about stopping the ballast moving around. In the end I decided that it couldn't move very far, not more than a couple of inches, before hitting the sprayfoam, and that it would not be a problem as long as I don't go to sea.

Edited April 20, 2017 by system 4-50

[dmr]

8 minutes ago, system 4-50 said:

Some 56lb steel weights have a big hole in the middle which reduces their overall density but they pack very nicely in sets of 4 in my bilge spaces. To move them around easily without risk of strain thread a strap or rope through the handles so you can lift them while standing up. I put mine in Waitrose self-sealing plastic bags which fit exactly, but I am not sure why I did it.

I find that high weight has a bigger effect than weight at floor level in upsetting my trim. Leaving a few broads resting against the side of the cabin has a suprisingly large effect.

Some tractor (fork lift??) balancing weights have smaller holes and look as if they would work well.

Ed. I wondered about stopping the ballast moving around. In the end I decided that it couldn't move very far, not more than a couple of inches, before hitting the sprayfoam, and that it would not be a problem as long as I don't go to sea.

Take them all out and replace with simple steel blocks or even bits of 10mm baseplate offcuts so no air holes. Give the 56lb weights a nice coat of black paint, pick out the lettering in red or gold and sell them as antiques. Have seen them going for £60 each.

............Dave

[Neil Smith]

I bought 1/2 a ton of steel bar and plate from man buck steel to level out my new build, it went under the kitchen units and under a section of floor.

Neil

[embis]

Thanks all, I will lookout for some hefty bits of scrap steel, I have already found  2 x 28lb weights lurking in my Dads garage so I am on the way, might even be able to get rid of a few of those bricks if I find some more..such an obvious solution!

[Chewbacka]

To give you an idea about the amount of ballast you might need.  My boat is 56ft long and after fitting out had a lean of about 5.5 degrees which is annoying.  I got some tractor weights to put along the side of the boat and needed almost 200kg to be level.

[Richard10002]

6 x 20kg bags of coal on the starboard side of my roof levels me up. 

[embis]

On 22/04/2017 at 18:10, Chewbacka said:

To give you an idea about the amount of ballast you might need.  My boat is 56ft long and after fitting out had a lean of about 5.5 degrees which is annoying.  I got some tractor weights to put along the side of the boat and needed almost 200kg to be level.

Wow, I hope it doesn't come to that!.. now I wish I had weighed, or calulated the weight, of everything before it started going in.

[Jen-in-Wellies]

There are other ways of correcting trim than moving, or adding ballast that it may be worth looking at. I recently corrected a ballasting problem on my boat had by moving the house batteries from one side of the boat to the other. A 110AHr battery is around 25Kg. Moving something heavy across is equivalent to twice that weight being added to one side and you don't increase the draft either. Four house batteries moved over is the equivalent of adding 200Kg of new ballast. Books are surprisingly heavy. If you are a keen reader, then moving, or adding some book shelves can have an effect on trim. The same with water. Moving a calorifier can have an impact. 1 litre of water weighs 1kg, so a typical boat calorifier is a heàvy beast once filled. If you have an anchor for rivers, then the storage site for it and its chain can be moved to the high side. Some of these are potentially more work than adding some heavy steel or concrete, but worth thinking about.

Jenny

Edited April 28, 2017 by Jen-in-Wellies

[Murflynn]

1 hour ago, Jen-in-Wellies said:

There are other ways of correcting trim than moving, or adding ballast that it may be worth looking at. I recently corrected a ballasting problem on my boat had by moving the house batteries from one side of the boat to the other. A 110AHr battery is around 25Kg. Moving something heavy across is equivalent to twice that weight being added to one side and you don't increase the draft either. Four house batteries moved over is the equivalent of adding 200Kg of new ballast. Books are surprisingly heavy. If you are a keen reader, then moving, or adding some book shelves can have an effect on trim. The same with water. Moving a calorifier can have an impact. 1 litre of water weighs 1kg, so a typical boat calorifier is a heàvy beast once filled. If you have an anchor for rivers, then the storage site for it and its chain can be moved to the high side. Some of these are potentially more work than adding some heavy steel or concrete, but worth thinking about.

Jenny

does it help to relocate your wellies storage locker (assuming you are still in them ) ?

[Jen-in-Wellies]

15 minutes ago, Murflynn said:

does it help to relocate your wellies storage locker (assuming you are still in them ) ?

Me and my wellies have a depressingly significant effect on a boats trim. Heavy wellingtons don't  you know.

Jen

[ditchcrawler]

9 hours ago, embis said:

Wow, I hope it doesn't come to that!.. now I wish I had weighed, or calulated the weight, of everything before it started going in.

When I launched mine it was similar but also down at the stern. I started off by removing all the slab behind the engine room and then all on the starboard side and had a coffee table made of concrete in the lounge on the port side. I bought a ton of cast iron from a trawler being broken up in Lowestoft and swapped it for the conrete, being denser I could get it all under the floor.

[Sea Dog]

42 minutes ago, ditchcrawler said:

being denser I could get it all under the floor.

Don't run yerself down so much DC; I've always thought you come across as quite bright!

[ditchcrawler]

1 hour ago, Sea Dog said:

Don't run yerself down so much DC; I've always thought you come across as quite bright!

 Well done that man

 

[Ampen Spekersohn]

Can I please ask a technical question about ballast and weight distribution? Basically, because of the way the floor is going to be laid, it's going to be quite hard to access the ballast without a lot of extra work. So I'm keen to try and accurately predict the amount of ballast needed and where it needs to go (without ending up with the swims, lockers etc, full of concrete blocks and lumps of old iron!)

I'm basically trying to add up the total weights which will be distributed down each side of the boat, but it then occurred to me that location of that weight, relative to the centreline of the boat, is very important too.

The basics I can figure out... if I put in 200Kg of batteries hard up against the left side, it stands to reason that if I install 200Kg of ballast hard against the right side, it will balance out. But what if the 200Kg of ballast isn't located as close to the side of the boat as the batteries are? I.e. if that additional weight was spread evenly between the right side and the centre line. It stands to reason that more weight would be required, because the 'leverage' would be less.

Is there some sort of formula for working this out, does anyone know? My gut feeling is that you'd need to install 50% more weight if it was spread evenly over the opposite side - i.e. 300Kg slabs to offset the 200Kg batteries. But is that right? And what about if the batteries weren't hard up against the side, but say, 8" in? Is there a way of calculating the various effects? A bit like a balanced see-saw with different weights in different place.

This all gets more complicated when I try to work out what impact the cooking range will have! If it's installed with one edge on the centreline and the other against the wall and the total weight is 300Kg; 600 x 600 slabs weight 43Kg and would have a centreline 300mm in from the opposite side. This suggests to me that I wouldn't need as much as 300Kg of slabs to offset the cooker.

Then... if I were to offset the 900Kg engine by say, 100mm, what impact would this have?

If there is anyone out there who has any knowledge of these calculations, I'd be very grateful for a reply!

Thanks.

 

 

[ditchcrawler]

All I can say is I am glad I made my flooring removable, because I got it badly wrong and 2 days after launching a had a concrete coffee table at the front right hand side of the lounge and very little under the floor. The slabs were given away and a trailer full of iron purchased.

[Ampen Spekersohn]

Precisely the kind of scenario I want to try and avoid, if I possibly can!

The non-removable flooring is due to the design... the floor will be a sandwich of 18mm WBP, an insulation layer with embedded underfloor heating pipes, then an 18mm engineered oak top layer. Hence the 'difficult access'! The only area which will be easily accessible will be either side of the engine.

I have allowed sufficient space under the WBP to fit two 50mm concrete slabs plus a 25mm air gap. So in the 6' engine room, I could fit 6 slabs weighing 250-odd Kg with a weight centreline 300mm from the side of the boat, which would potentially make quite a difference.

With the hull builder, we have calculated that a total of 3 tonnes of ballast will be required. This equates to roughly 25 sq. metres of 50mm thick slabs. The main cabin is around 20sq. m, so I will have a total ballast capacity of  around 40 sq.m. So this should give me a fair bit of flexibility in terms of where to locate it. Just need to figure out where!

[nb Innisfree]

We calculated the ballast on the leverage principle, i.e. a given weight placed a certain distance one side of the c of g will have double the effect if it's also placed twice that distance the opposite side of c of g. 

Longitudally we eventually arrived at a figure of two thirds of ballast placed immediately ahead of c of g and one third immediately behind c of g. Intuitively that doesn't seem right and everyone I spoke to advised it was wrong but the calculations said otherwise. We went with our calculations and kept our fingers crossed. Just before launch a well established boat builder confirmed that principle which proved spot on when we launched much to our satisfaction and more than a little relief. So much for advice! 

We needn't have worried anyway as I had arranged all floors to be removable. 

ETA: Total ballast was 2.25 tons (60' nb @ 22" average draught)

 

Edited November 22, 2017 by nb Innisfree

[Richard10002]

On 22/04/2017 at 18:18, Richard10002 said:

6 x 20kg bags of coal on the starboard side of my roof levels me up. 

Over time water collected under the bags of coal and caused the roof to rust. Coal bags removed and roof sanded and painted. Boat leaned noticeably to port.

Just bought 3 x 56lb weights at £25 each and placed on the outboard starboard side of the cruiser stern, they have levelled things up. I'll need a couple more to account for a couple of coal bags and a gas bottle on the starboard side of the stern.

The plan is to glue a piece of carpet to the bottom of the weights, and place them in the space behind the sofa in the lounge.

[Ampen Spekersohn]

10 hours ago, nb Innisfree said:

We calculated the ballast on the leverage principle, i.e. a given weight placed a certain distance one side of the c of g will have double the effect if it's also placed twice that distance the opposite side of c of g. 

Longitudally we eventually arrived at a figure of two thirds of ballast placed immediately ahead of c of g and one third immediately behind c of g. Intuitively that doesn't seem right and everyone I spoke to advised it was wrong but the calculations said otherwise. We went with our calculations and kept our fingers crossed. Just before launch a well established boat builder confirmed that principle which proved spot on when we launched much to our satisfaction and more than a little relief. So much for advice! 

We needn't have worried anyway as I had arranged all floors to be removable. 

ETA: Total ballast was 2.25 tons (60' nb @ 22" average draught)

 

Thanks! Your first sentence describes what I was trying to say - a bit like one of those old-fashioned sack scales, where you slide the weights along. I don't quite understand the one third/two thirds theory though. Is that to offset the weight of engine, batteries, etc? In all honesty, I hadn't even really started thinking about the fore/aft trim, but it should be easier to trim the bow down, as I will have a lot of storage forward of the well deck. 

My 60' hull will have a 30" draught at the stern, so probably not much more than your 22" average.