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twotails

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Registered: Thu 20th Nov 2014

Posts: 271

Tanks Freezing?

Just a quickie. I am having Dogboat taken out of the water for the winter to do some work. I am a little worried about the tanks freezing and causing damage over the winter as I live aboard and it would be a real pain if I have to empty them. Does anyone have experience of any problems or am I just going to have bite the bullet and live out of plastic bottles and buckets for a few months

SeaDog Name (if owner or crew) Dogboat
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Graham
Oct 8, 2012 - 1:40PM
Re: Tanks Freezing?

Hi Louis,
When we kept Dougal in Gosport she was lifted out for the winter several times and stored in the yard near the harbour, we never bothered to drain the fresh water system and all was well.
The first year we lifted out at Rochefort (France) we had temperatures down to minus 17 degrees and the entire fresh water system froze solid. Various pipes burst but the tanks were not damaged. Last year we again forgot to drain the water system down and in the spring had to deal with several leaks including the immersion heater collar becoming separated from the calorifier.
We have put the difference down to Rochefort being effectively inland (up a river) and air temperatures are lower for longer periods.
We have always 'winterised' the engine (anti-freeze through the sea-water system) and the tanks in the bilge keel seem to have survived without damage.
hope this helps you decide.
Graham

SeaDog Name (if owner or crew) Dougal
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Louis Goddard
Oct 10, 2012 - 8:50AM
Re: Tanks Freezing?

Great, thanks for the information Graham.
I am spending this winter in Rye and I am hoping that the temperature doesn't get anywhere near minus 17! fingers crossed.
Probably just leave it then and see how it goes. The make shift tap in the yard will probably freeze up way before the tanks anyway.
Luckily Rye has somewhere near 15 drinking holes so I'm sure I will survive

SeaDog Name (if owner or crew) Dogboat
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Eric Richardson
Oct 12, 2012 - 1:07PM
Re: Tanks Freezing?

Hi Louis

The best answer I can think of for your problem is to ensure that your tanks are never full!

As you know water expands when freezing, if your tanks are solid full something will have to give. I accept that there is a slight amount of elasticity in fibreglass, but best not to trust that it will be sufficient. If you leave a space above the water level and the water freezes it will expand upwards without damage to the tanks. I think in practice there will be an air space due to trapped air when you fill, but as said best to only fill say 3/4 full.
This is easy when on the hard, just fill both tanks then drain a few gallons out of each tank and you should be ok.

Eric

SeaDog Name (if owner or crew) Ex Taliesin
Louis Goddard
Oct 15, 2012 - 9:13AM
Re: Tanks Freezing?

I like your thinking. Thanks for the advise Eric

SeaDog Name (if owner or crew) Dogboat
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Graham
Oct 15, 2012 - 10:17AM
Re: Tanks Freezing?

Eric,

It is very rare I disagree with you (in fact this may be a first :-)).

Around here where swimming pools are common there is a need for caution during the winter. With concrete pools in particular it is recommended that polystyrene floats are used around the outside of the pools as the expansion of the ice that forms can push the walls out horizontally. This would suggest that when ice forms it can push in both directions and would not just expand 'upwards'.
If you can persuade me that I have it wrong then a lot of people around here will save a lot of expense and messing about.
regards
Graham

SeaDog Name (if owner or crew) Dougal
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jim lloyd-davies
Oct 15, 2012 - 5:34PM
Re: Tanks Freezing?

i have had gabrielle b ashore in falmouth for the last 2 years. last year we had some of the lowest temp for 10 years plus and i was able to draw water for my much needed cuppa without any problems. granted falmouth may not be as cold as other parts of the u.k.

SeaDog Name (if owner or crew) gabrielle b
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Eric Richardson
Oct 16, 2012 - 1:53PM
Re: Tanks Freezing?

Hi Graham

No need to disagree, what you say is correct. Its just the way it works, water reverses its circulation below about 4deg C and ice forms from the top down. In a tank where it is restricted sideways it initialy just pushes the top layer of ice up. If the tank is strong enough, or tapers up to the top it carries on rising, even heaping up in the middle. However in a swimming pool constructed of concrete with low tensile strength you cannot afford to let it load the sides in that manner and have to allow something else to crush.
The Seadog tank with air above and a degree of elasticity will get away with small amounts of ice forming. If they were to freeze more than perhaps a couple of inches thick the ice would grip the tank sides and further expansion would probably burst the tank. Water expands roughly 10% on freezing so with an air gap above you have a fighting chance in addition to that the Seadog tanks do taper such that the surface area at the top is larger than lower down, encouraging the ice to push up. Think of it as a boat floating when the ice forms, a round bilge boat is pushed up by the ice. now invert your thoughts and the taper tries to help the ice slide up the tank sides.
Sorry to prattle on.

Eric

SeaDog Name (if owner or crew) Ex Taliesin
Graham
Oct 16, 2012 - 2:00PM
Re: Tanks Freezing?

Afternoon Eric,
I am so relieved, thanks to your excellent explanation I really do understand now. I can see that we are both right. I knew in my heart that you couldn't be wrong on something like this. The SeaDog tanks are much less likely to become damaged when freezing than a concrete swimming pool. Ye another example of great design by Reg Freeman :-)
regards
Graham

SeaDog Name (if owner or crew) Dougal
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JACK WOODFORD
Oct 28, 2012 - 11:06AM
Re: Tanks Freezing?

When I was down in Northney Marina at the begining of this year before sailing EMRA back to Faversham, I noticed DOGBOAT in a yard just before the causeway over to Hayling Island, so guess like me you have since brought her back to new moorings in Rye, but it was mentioned in our local sailing club, that DOGBOAT had been in Conyer Creek just up the SWALE from our moorings, have you since moved her? There are 4 Seadogs berthed in Oare Creek now. Good luck with living on board through the winter, how do you intend to keep warm?

SeaDog Name (if owner or crew) EMRA
Louis Goddard
Nov 5, 2012 - 9:08AM
Re: Tanks Freezing?

Hi Jack,

Yes I was previously moored in Conyer but unfortunately due to constant price increases from Swale marina it was time to seek fresh pastures. Saying that, the Swale and the east coast have some dear memories for me, some fantastic sailing! Rye is perfect for us at the moment with cross channel plans for next season.
My beautiful girlfriend is my best way of keeping warm this winter

SeaDog Name (if owner or crew) Dog Boat
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Louis Goddard
Nov 5, 2012 - 1:01PM
Re: Tanks Freezing?

From My Pictures

SeaDog Name (if owner or crew) Dog Boat