Ice on the water in the marina - when to start to worry?

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rolf.nielsen

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This is my first winter where I keep my boat in the water. It's now freezing and the first ice has come. For now it's only a couple of cm thick but it is already packed fairly tightly around the boat. When the boat bobs in the water it pushes gently against the ice as if I was moored without fenders and pushing against the pier. Apart from the occasional unusual sound (probably ice creaking against the water line) everything looks good and I am not yet worried. At what point, however, should I start to worry? Can the ice damage the boat at some point if it gets heavy and packed tight and hard against the boat? Or will it merely immobilize the boat and keep it in a firm but harmless grip until thaw sets in? The marina does have some deicing system (air bubbles I'm told) but they haven't activated it yet and I don't know if it is too late when the ice is already starting to build and in any case that system will protect the pier and is not extended out under and around my boat.
 
Where are you located, what kind of hull material.
GRP hulls can withstand some ice, but if the boat gets ice locked, a large moving ice floe can exert heavy forces on boat an mooring ropes.
 
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knuterikt said:
Where are you located, what kind of hull material.
GRP hulls can withstand some ice, but if the boat gets ice locked, a moving large moving ice floe can exert heavy forces on boat an mooring ropes.
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Denmark he says
Staying in the water all winter (freezing/Denmark)
this is my first winter as a boat owner and I'm planning to keep our Grand Banks in the water through the winter
Read more at http://www.ybw.com/forums/showthrea...g-Denmark)-how-to-heat-up#7mEC6e4wmm1IWkU4.99
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GRP I believe
 
My last boat, a 21' Westerly, lived in the Crinan Canal over the winter for several years. She was often frozen in - I walked round her once - but never suffered any damage.
 
I once wintered afloat in Halifax, Nova Scotia where they experience severe freezing.

The marina rigged a garden hose round the waterline, and in it they'd punched small holes. It was connected to a very small air compressor on the shore which bubbled air into the water. The result is clear water all around you for a couple of feet. All the boats had them.
There was no tidal flow though, so no danger of lumps of ice drifting down on you.
I also hired a 'snow clearer' - young lad with shovel - and when I asked if this was really necessary, they told me they sometimes get 2feet of snow in a night and that kind of weight does a boat no good.
 
oldvarnish said:
I once wintered afloat in Halifax, Nova Scotia where they experience severe freezing.

The marina rigged a garden hose round the waterline, and in it they'd punched small holes. It was connected to a very small air compressor on the shore which bubbled air into the water. The result is clear water all around you for a couple of feet. All the boats had them.
There was no tidal flow though, so no danger of lumps of ice drifting down on you.
I also hired a 'snow clearer' - young lad with shovel - and when I asked if this was really necessary, they told me they sometimes get 2feet of snow in a night and that kind of weight does a boat no good.
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The bubble hose need to be ballasted to keep it on the submerged to move the warmer water to the surface.
This is a video I shot last winter showing the bubble system at work.
 
That crunch, crunch, timely reminder that snow is coming, I'm sitting by a radiator it made me feel cold,what with the winter scene.
 
We moved to Holland in 1997, the last time there was extensive freezing over there and the 11 towns skating race was run. Our boat was still in UK but we visited Hellevoetsluis in the January to arrange a berth there. The ice was then 12 inches thick and skaters were all around boats in the marinas, which seemed to be pretty full. I subsequently asked the harbourmaster whether boats were damaged by the conditions and he responded by saying that he knew of not a single incidence. A couple of years later our boat was frozen in with ice around 2 inches thick. The most obvious difference was the strange ringing noise that solid ice makes inside the boat. We had drained down any water that might freeze and the boat itself did not suffer in any way.
 
I have heard of this problem and the bubbler solution but obviously it does not affect us. I would very much doubt that the marina is going to sort things out for you I would presume the protection of your boat is down to you. People I know of who sail in places where this is an issue (N America) buy small pumps that run on electric to do the bubbling and it seems to work. I would not want to take the risk of no protection as ever scrape and creak you hear must be some damage to the hull. I suspect after a couple of months it all adds up. I am sure other local boats to you can advise on where to purchase the equipment. I think it is something to do sooner rather than later as ice is easier to keep et bay than to remove.
 
pmagowan said:
I have heard of this problem and the bubbler solution but obviously it does not affect us. I would very much doubt that the marina is going to sort things out for you I would presume the protection of your boat is down to you. People I know of who sail in places where this is an issue (N America) buy small pumps that run on electric to do the bubbling and it seems to work. I would not want to take the risk of no protection as ever scrape and creak you hear must be some damage to the hull. I suspect after a couple of months it all adds up. I am sure other local boats to you can advise on where to purchase the equipment. I think it is something to do sooner rather than later as ice is easier to keep et bay than to remove.
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Lots of Scandinavian GRP boats are used during winter, ice scraping along the hull does not harm the gelcoat but it might remove some of the anti fouling.
 
vyv_cox said:
We moved to Holland in 1997, the last time there was extensive freezing over there and the 11 towns skating race was run. Our boat was still in UK but we visited Hellevoetsluis in the January to arrange a berth there. The ice was then 12 inches thick and skaters were all around boats in the marinas, which seemed to be pretty full. I subsequently asked the harbourmaster whether boats were damaged by the conditions and he responded by saying that he knew of not a single incidence. A couple of years later our boat was frozen in with ice around 2 inches thick. The most obvious difference was the strange ringing noise that solid ice makes inside the boat. We had drained down any water that might freeze and the boat itself did not suffer in any way.
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As I wrote the ice scraping along the hull is not a problem.
But in some places wind shifting a large piece of ice with a boat locked into it can cause secondary damage by pushing the boat into other solid objects.

Some years ago there was extremely cold on the Swedish west coast (an area where there is little ice in "normal" winters) with ice forming, later the wind and currents started pushing the ice and the ice locked boats underneath the fixed piers. Mooring lines could not withstand the large masses in movement. To avoid damages chain saws where used to cut he boats free of the ice.
 
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knuterikt said:
As I wrote the ice scraping along the hull is not a problem.
But in some places wind shifting a large piece of ice with a boat locked into it can cause secondary damage by pushing the boat into other solid objects.

Some years ago there was extremely cold on the Swedish west coast (an are where there is little ice in "normal" winters) with ice forming, later the wind and currents started pushing the ice and the ice locked boats underneath the fixed piers. Mooring lines could not withstand the large masses in movement. To avoid damages chain saws where used to cut he boats free of the ice.
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Yes, I have seen photographs of pack ice in Kiel, in which huge masses of ice were piled up to many metres. If any boats had been there they could not possibly have resisted the pressure of ice like this.
 
No personal experience of this, but it seems that if the ice is not moving or under pressure as in a marina, then there is little to worry about. Where there is tidal movement to break the ice up, and to shift it around, or the wind can shift it, then huge and damaging pressure will rapidly build up. The sea froze here in Chichester harbour during the big winter of 1062, and there were apparently several cases where the build up of ice was enough to actually bodily lift a boat complete with its mooring chain and sinker, or to so overload the mooring that it simply tore the sinker out the mud, and set the whole thing adrift as the tide rose!

Arctic and Antarctic exploration is full of accounts of ships caught in the pack ice, and in some cases being completely crushed by the pressure. There of course they can be subject to the pressure of an ice field many miles across, being carried by wind and current. The inertia of such a mass on the move even too slowly to be visible would be more than enough to crush any ship out of existence!
 
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oldharry said:
No personal experience of this, but it seems that if the ice is not moving or under pressure as in a marina, then there is little to worry about. Where there is tidal movement to break the ice up, and to shift it around, or the wind can shift it, then huge and damaging pressure will rapidly build up. The sea froze here in Chichester harbour during the big winter of 1062, and there were apparently several cases where the build up of ice was enough to actually bodily lift a boat complete with its mooring chain and sinker, or to so overload the mooring that it simply tore the sinker out the mud, and set the whole thing adrift as the tide rose!

Arctic and Antarctic exploration is full of accounts of ships caught in the pack ice, and in some cases being completely crushed by the pressure. There of course they can be subject to the pressure of an ice field many miles across, being carried by wind and current. The inertia of such a mass on the move even too slowly to be visible would be more than enough to crush any ship out of existence!
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Do you actually remember 1062?:)
 
Ice is rarely an issue in Denmark (including Greenland :). Biggest problem is if you want to move the boat or lift it our after ice closes around it.

If it gets really cold for extended periods, you may chop the ice away tfrom the hull to keep it floating.

Bubble systems most often are for protection of poles and bridges in the harbour - not for the boats.
 
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