Rebalasting, weight distribution?

[SilverComet]

Our boat was ballasted before we got it, since then a tongue and groove style flooring has been put over the top so I'm reluctant to start ripping up boards.

The thing is, before we owned the boat it was fitted out, but empty. Now the calorifier has water in it, the cupboards have pots, pans and cans and the 3 beds have mattresses. The layout of the entire boat almost is completely on one side.

We've tried to counter this by putting heavier items we don't use often in to the one spare bed on the "light" side. It hasn't been enough and we have quite a noticeable lean now to one side.

My question is this: our spare bed is half way down the boat, almost exactly. If I were to put a layer of bricks under it to add weight there, would I be doing something stupid? How do I know I'm not causing the boat to sit too low? Is it safe?

To me it seems the easiest and cheapest solution, with the benefit of being able to remove bricks if, for example we ever got a cassette toilet rather than a pump out. The only issue is I like to stay informed, and when you're fiddling with your life savings on water you don't really want to risk anything!

One day I swear I'll answer questions rather than ask them...

Thanks in advance.

[Jen-in-Wellies]

My boat had a similar problem. Solved it by moving the batteries from the heavy side to the light side. Is there some heavy stuff that can be moved? Moving say 100Kg from one side to the other is equivalent to adding 200Kg of new ballast. If you have lots of books, then bookshelves on the light side can be very effective. Paper is surprisingly heavy.

Adding water to say a 60l calorifier adds 60Kg, so you need the same weight adding to the other side, or 30Kg moved over from one side to the other. Adjust to suit the actual capacity of your calorifier.

 

If you do add extra ballast then keeping it low down in the boat is not going to make it unstable. 100Kg more on a 20 ton boat is a 0.5% increase in weight and hence draft.

Jen

Edited September 29, 2017 by Jen-in-Wellies

[Tony Brooks]

I found enough space between the inner lining and hull, between the strengthening ribs, to secure bits of paving slabs wrapped in bubble wrap against the hull. I also have boxing in for the central heating pipes on the light side so I cast some lengths of  lead weights (bought lead from a scrap yard) to secure behind the boxing.

[Richard10002]

What sort of things do people use as ballast and where would you put it if you don't want to cut holes in the floor.

I have a similar issues to the OP and found that 6 bags of coal on the starboard side of the roof levelled things out, (120kg), but let water collect under the bags and things got rusty.

Just painted the roof so need a more suitable solution than bags on the roof.

 

ETA: Typed this 2 hours ago, but only just sent it. Just seen Tonys post and like the idea of bubble wrap slabs, but don't really want to take the inner lining apart to find space.

Edited September 29, 2017 by Richard10002

[Tony Brooks]

I have given you two and there is also steel offcuts plus cast iron scale or tractor weights. If using lead it is probably bets to wrap it in polythene/bubble wrap to ensure it can not make electrical contact with the steel and cause corrosion.

[alan_fincher]

Not really mentioned, I think,  is whether the boat, after fitting out, and being loaded with all your wares, is not sitting at the right amounts in the water front to back, even if not listing to one side.

IMO it is important to keep (particularly) the back end in to about the right depth, which I generally find for a modern boat is with the uxter plate, (bottom of counter) sat more on less on the water line.

If you are in that lucky situation, then simply add trimming ballast as already described.

However if you are already at the point where the bottom of the counter is well submersed, I would say ideally you need to get excess ballast out from the "heavy" side, rather than adding more to the "light" side.  It's not generally a good idea to have boat ballasted lower than is necessary for the prop to get a good "grip" on the water, and if you keep draught as little as sensible, you will be able to moor close to banks where deeper boats fail.  You should also also be mindful of how high the lip of your wed hatch is above the water, and whether any vents or drains in the hull are sitting lower than is sensible.

[Sea Dog]

Keep any weight added as low down as possible so as to maximise stability. Weight placed under the floor is clearly the most effective but low profile weight placed on the floor will be just a few inches above the base plate. This will certainly be below the metacentric height (think balance point) so you'll be adding to the 'righting moment' and therefore increasing the 'stiffness', in other words the tendency for the vessel to spring upright. Weight added high up will act against this tendency and reduce stability, so your permanent ballast should only be low. However, as long as there is a sufficient ballast low down, there is likely to be enough reserve to allow for the odd bag of coal or other junk higher up - as a look along any canal will attest! 

I have some concrete blocks laid below the bed to compensate for the trim shift to starboard cause by removal of a port side washing machine. Concrete blocks aren't anything like as dense as lead or steel rail, etc, but they may well be enough to correct athwartships trim. Do correct this allowing for changeable loads though, e.g. have a half-full sewage tank. Fore and aft trim or changes in draught will need the heavy stuff and possibly quite a lot of it.

[blackrose]

18 hours ago, alan_fincher said:

Not really mentioned, I think,  is whether the boat, after fitting out, and being loaded with all your wares, is not sitting at the right amounts in the water front to back, even if not listing to one side.

IMO it is important to keep (particularly) the back end in to about the right depth, which I generally find for a modern boat is with the uxter plate, (bottom of counter) sat more on less on the water line.

If you are in that lucky situation, then simply add trimming ballast as already described.

However if you are already at the point where the bottom of the counter is well submersed, I would say ideally you need to get excess ballast out from the "heavy" side, rather than adding more to the "light" side.  It's not generally a good idea to have boat ballasted lower than is necessary for the prop to get a good "grip" on the water, and if you keep draught as little as sensible, you will be able to moor close to banks where deeper boats fail.  You should also also be mindful of how high the lip of your wed hatch is above the water, and whether any vents or drains in the hull are sitting lower than is sensible.

I always thought that the counter/uxter was supposed to be a few inches below the waterline rather than on it?

I'd say as long as any engine air vents, exhaust and drain holes are a sufficient height above the waterline after adding additional ballasting then you're fine. The engine vent height is particularly important and should be as high as practically possible. Drain holes should be at least 10".

Edited September 30, 2017 by blackrose

[manxmike]

I've been told that old window sash weights will fit under the base of a cupboard - a few inches above the base plate, very heavy but small in size, add or subtract to balance out the trim.

I've managed to get some from a local double glazing firm and will be trimming next week!

[Murflynn]

18 hours ago, Sea Dog said:

Keep any weight added as low down as possible so as to maximise stability. Weight placed under the floor is clearly the most effective but low profile weight placed on the floor will be just a few inches above the base plate. This will certainly be below the metacentric height (think balance point) so you'll be adding to the 'righting moment' and therefore increasing the 'stiffness', in other words the tendency for the vessel to spring upright.

no, you mean the centre of gravity.

the metacentric height is the height (above the centre of gravity) of a point where the line of the extended centreline of the boat drawn perpendicular to the waterline when the boat is trimmed level intersects with a vertical line drawn through the centre of buoyancy.  Said metacentre could be at ceiling height, plus or minus.

[Sea Dog]

I stand corrected Sir! My RN stability stuff was a while ago, so my metacentre appears to have dislocated due to lack of exercise (I wonder if my notes are still in the loft...?). Fortunately, the general advice remains pertinent.

[alan_fincher]

5 hours ago, blackrose said:

I always thought that the counter/uxter was supposed to be a few inches below the waterline rather than on it?

A few inches under ?

Not really, in my view, but of course not all boats are the same, and on many narrow bats that sit "bow high", there is not enough "kick up" on the uxter plate to compensate for the  fact that the hull isn't level in the water.  It's not unusual that for the lead edges of the uxter, at the front of the rear swim to sit about on the water level, the back of the uxter plate has to be an inch or two under.  In that case, I'd agree - it is not a good idea to have a gap at the front where air can get "sucked" in.

However, I run both our boats with the back of the uxter an inch or two out of the water - it varies a bit because of the amount of fuel in the very large tanks.  That is because under way the back end always pulls down by that amont or more, such that the uxter is either on the water, or just a bit below it  This avoids dragging around a moving draught of much over 3 feet.  If I had the back of the uxter a few inches under before I moved, I'd be bouncing over more crap in bridge hoes than I could possibly put up with.  It is of course less of an issue with a modern shallower draughted boat, (and your wide beam almost certainly will be in that category), but even so why put up with a boat that's deeper in the water than it needs to be?
 

[Murflynn]

9 hours ago, Sea Dog said:

I stand corrected Sir! My RN stability stuff was a while ago, so my metacentre appears to have dislocated due to lack of exercise (I wonder if my notes are still in the loft...?). Fortunately, the general advice remains pertinent.

actually to be more understandable we should call the CofG the centre of mass; 'centre of gravity' is a meaningless expression although it is universally used.

[SilverComet]

Thanks all. I really like the suggestion of putting the batteries on the correct side, seems obvious now you've suggested it. I recall in the chaos of buying the boat that the previous owner swapped them to the heavy side to avoid the drain (there is a 2 step staircase at the back of our boat).

I'll look at improving the drain and then move them. I was amazed just how much draining the tank out and filling with diesel helped, I think if we swapped the batteries that would probably sort the lean to some extent at least.

Annoyingly our pump out tank is metal and pretty much impossible to tell when it is full. I think next winter a plastic one is a necessity.

Thanks again all.

[ditchcrawler]

10 minutes ago, SilverComet said:

 

Annoyingly our pump out tank is metal and pretty much impossible to tell when it is full. I think next winter a plastic one is a necessity.

Thanks again all.

How will that help. is it a remote tank, most are fitted with level gauges. If its a drop though then just look down the hole. If like mine its off centre then judge buy the way the boat trims

 

 

[system 4-50]

I drilled a hole in the top of my 6mm metal waste tank and fitted a level sensor. It was easy.

[SilverComet]

Just hearing horror stories of the metal ones corroding and such makes me very uncomfortable about it! We have no view hole, it's just a huge metal tank. A sensor isn't a bad idea.

[system 4-50]

30 minutes ago, SilverComet said:

Just hearing horror stories of the metal ones corroding and such makes me very uncomfortable about it! We have no view hole, it's just a huge metal tank. A sensor isn't a bad idea.

Don't worry about that unless you have some clear indication of possible failure, just listen to my horror stories about metal hulls corroding! 

[cuthound]

1 hour ago, SilverComet said:

Thanks all. I really like the suggestion of putting the batteries on the correct side, seems obvious now you've suggested it. I recall in the chaos of buying the boat that the previous owner swapped them to the heavy side to avoid the drain (there is a 2 step staircase at the back of our boat).

I'll look at improving the drain and then move them. I was amazed just how much draining the tank out and filling with diesel helped, I think if we swapped the batteries that would probably sort the lean to some extent at least.

Annoyingly our pump out tank is metal and pretty much impossible to tell when it is full. I think next winter a plastic one is a necessity.

Thanks again all.

I fitted one of these to my waste tank,  because I didn't want to rely on the "tank full" indicator light. Took me a couple of hours,  but shouldn't take long if you have already identified the 12 volt power supply, cable route and gauge location.

http://mcsboatproducts.co.uk/portfolio/waste-water-gauge/

An unexpected benefit was finding that the "tank full" light came when the tank was just over half full, thereby halving my pump out costs.

All you do is measure the depth of the tank, cut a hole in it with a hole saw and push in a rubber bung before pushing the sensor unit into the rubber bung, cutting a hole for the gauge, inserting the gauge and wiring up.

[MtB]

Is your engine a 'Lister'?

If so this might explain why you have the problem...