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Bow locker - extra water storage?


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I was trying to find a recent post about someone wanting to repaint the inside of their water tank, but slow internet today has caused me to give up.

Anyway, a separate post might be more appropriate as what I am thinking of doing is turning my bow locker into a water tank.

It has two tiny drain holes that would need welding up, (they are only 2-3cm above the water line btw) and I expect I could fit a screw down access plate with filler hole, under the lift up hatch (so keeping the appearance). Interestingly, the locker seems to have its floor at exactly water level, so I wonder if it means a bow thruster could be easily added underneath the portion towards the well deck? I digress.

I could use the special paint on the inside of the locker. That or fit one of those bladder things. Ideally I'd fit a ss tank into the locker but it would waste a lot of capacity unless it was a special shape - though I could at least insulate it then. Getting it in through the hatch would be interesting.

Pros and cons of this? I'm concerned about freezing in winter, and also wondering whether it would connect to the ss tank I have or if I would use a pump when the main tank is low, to transfer it through.

My ss tank is I believe, 500l, the extra capacity could give me another 400 or 500l I reckon. I really need extra water for when I want to stay at a spot for the full 14 days without having to go into miser mode.

Thoughts?

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Don't see a big problem with the idea apart from the trim issue. The Ownerships boats mostly had the main water tank there (gas cylinders in a locker in the semi trad stern) and didn't bother with a plate under the hatch, you could just lift the hatch to check on the state of the tank.

Edited by BruceinSanity
Spillung
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An extra half tonne in the front will lower your bow (and you may want this), but it will also lift your stern - how much height can you 'give away' before your counter / prop is out of the water ?

You may end up adding another half a tonne of ballast to the stern to get it back into he water.

Stability will certainly be affected if the weight is added above the water line - remember the stability checks done to ensure RCD compliance will now be null & void and ideally should be done again.

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I would have thought you could test the effect by removing everything from the gas locker, then shaping some wood to fit over the drain holes and use silicone sealant to stick them in place. You should then have a water tight locker that you can fill with water and see what impact on trim and stability there is.

Edited by john6767
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Brilliant advice guys. I did not know it would tip the stern upward - that's not a problem, it is stern heavy and I have already moved all the ballast from under the floors towards the bow end, plus I really want to add a generator at the stern too! Looks like a win win for me :)

I could very easily do a test fill as john suggests.

Would I go for the special paint or what?

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47 minutes ago, Johny London said:

I did not know it would tip the stern upward

I had a bow water tank and the 'gauge' for re-filling was when the top of the rudder went below the water surface.

Full water tank, rudder several inches above the water, empty water tank, rudder just below the surface

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I like the idea of a water tank in the bow locker, I'd do it on my boat but there isn't anywhere to resite the gas bottles.  

As for what to coat it with, by rights you shouldn't use bitumen based products now and there was a thread on this quite recently.  I think the options are limited for a "new" integral tank, I'd use a liner you wouldn't need to block the drain holes then but it could be quite expensive having a bladder custom made.  

I know this is only anecdotal but those "Clipper" boats that Calcutt used to make have the water tanks up front, I used to know quite a lot of the owners of these and far from affecting stability they all used to say how well the boats handled, particularly astern.  That may be nothing to do with the position of the water tank of course.  

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24 minutes ago, nb Innisfree said:

Innisfree has a bow tank (600+ lts) minimal effect on handling and a cinch to paint, just lift the lid and climb in. Once a year we used to use a long handled brush and black the odd rusty patch or three from the lid. '

I think the issue (potentially) is that the boat already has a 'bow tank of 500 litres' it was designed and ballasted to accommodate that, now the OP is looking to add another  500 litres (doubling the size and weight) which have not been included in the design / ballast calcs.

The last NB we had, (Reeves 45 foot) had a 600 litre bow-tank with a big hinged lid (you could climb in if you wanted) and being designed for it, the only time it was a problem was when it was empty and the bow was 'light'

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3 minutes ago, Alan de Enfield said:

I think the issue (potentially) is that the boat already has a 'bow tank of 500 litres' it was designed and ballasted to accommodate that, now the OP is looking to add another  500 litres (doubling the size and weight) which have not been included in the design / ballast calcs.

The last NB we had, (Reeves 45 foot) had a 600 litre bow-tank with a big hinged lid (you could climb in if you wanted) and being designed for it, the only time it was a problem was when it was empty and the bow was 'light'

Yes I misunderstood. 

I ballasted Innisfree to float level when bow tank was full and stern diesel tank empty,  vice versa was fine. 

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Glad to see this idea is definitely a go'er. Any advice on the correct paint if I go that rout? Also we haven't touched on freezing. I presume so many boats have integral tanks which is effectively what this will be. Though the water in the tank will be just above the water in the canal so not sure if that means it is more or less likely to freeze? And if it did, how much of a problem that would be.

One more thought - could a plastic (suitable type for drinking water) tank be built in situ - ie panels placed inside then glued together?

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Will you be connecting both tanks together, one feeding the other, if so check that the overflow pipe on your existing tank is at the correct height when new tank is installed. Also if you have a water gauge fitted it may need to be recalibrated.  

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I don't know if I'll have both tanks connected or have a pump to re fill the ss from the bow. The ss tank has an air admittance valve but no overflow. Though one time the air valve allowed water out and made a right mess - as it vents to inside the boat. That happened while I was filling so I have to be careful to turn off the water once its full as excess pressure seemed to cause it.

I do have a water gauge (that is already becoming slightly erratic) it can be re calibrated easily.

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Our last boat had an integral tank in the bow, and always found the extra weight an asset.  It was filled by lifting the hatch, which also provided access to prepare and paint (potable bitumen). This was a job for the missus as I couldn't fit! 

Being your new tank would only add weight at the top, you could add a central baffle to prevent any potential rolling, if you are having the vents welded up it could be done at the same time. It might be an idea to make any baffle removable to make it easier to maintain the tank interior, a sheet of stainless would do.

In the 15 years we owned the boat i never saw more than a bit of cat ice on the surface of the tank, generally when half empty. 

Edited by BWM
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We have a bow tank on our 61ft Reeves that is accesed through the hatch aswell, weather ours is full or empty it makes absolutely no difference to how low the bow sits i tested it with marks on the waterline and it doesnt budge it does however bring the stern up we can only see the top of the rudder if it is over 2/3 full and when only about 1/4 full the fender starts to get wet! i like having the tank open through the hatch as it means you can actually see whats going on in there.

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I've found Tankguard DW from Jotun, a two part epoxy that sounds like it would really do the job. It needs good prep first though and might be something for a boatyard to do rather than diy (sandblasting the metalwork, getting rid of weld splatter, then applying to correct thickness with spray, and in a not too cold/damp environment). It's very pricey though as only seems to come in 15l. 210 =vat :(

Otherwise I saw Rylards old style bitumin stuff which I presume is easy to apply but not really up to modern day standards.

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3 hours ago, dm6045 said:

We have a bow tank on our 61ft Reeves that is accesed through the hatch aswell, weather ours is full or empty it makes absolutely no difference to how low the bow sits i tested it with marks on the waterline and it doesnt budge it does however bring the stern up we can only see the top of the rudder if it is over 2/3 full and when only about 1/4 full the fender starts to get wet! i like having the tank open through the hatch as it means you can actually see whats going on in there.

Someone needs to tell Archimedes.

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